Visit https://alexisbaskind.net/teaching for a full interactive version of this course with sound and video material, as well as more courses and material.
Course series: Fundamentals of acoustics for sound engineers and music producers
Level: undergraduate (Bachelor)
Language: English
Revision: February 2020
To cite this course: Alexis Baskind, Room Acoustics
course material, license: Creative Commons BY-NC-SA.
Course content:
1. Time-Space perspective: Sound propagation in a room
Raytracing, example of a rectangular room, evolution from free field to diffuse field, initial time delay gap (ITDG), direct sound, first reflections, late reverberation, exponential decay of the pressure, definition of the reverberation time, T60, T30, T20, Schroeder curve, critical distance, flutter echoes, diffusion, effect of distance, effect of room size
2. Frequency-Space perspective: Room modes
Reminder: monodimensional standing waves, axial modes, tangential modes, oblique modes, eigenfrequencies, effect of room size on modal density, duration and bandwidth of modes, effect of absorption on modes, Schroeder Frequency
3. Time-Frequency perspective
Early reflections, modes and diffuse reverberation in an unified time-frequency perspective, waterfall view
4. Room acoustics design
prediction of the reverberation time, Sabine formula, frequency-dependent absorption, porous absorbers, effect of absorber’s thickness and air gap, resonant absorbers, membrane absorbers, Helmholtz absorbers
5. Room acoustics of listening rooms
importance of symmetry, need for a sufficient room size and controlled reverberation time, recommended reverberation time, need for controlling the early reflections, LEDE design, RFZ design
6. Spatial hearing in a room
perception of distance in a room, perception of the room size, clarity, apparent source width, envelopment, reverberation timbre
Explains basics about sound and what classroom issues are present due to sound effects which causes problem for students to hear teacher properly.
Explains concept of reverberation and other issues and suggests about its solution for better classroom sound efficiency
This document discusses various aspects of room acoustics, including how sound travels and interacts with surfaces. Sound can bounce off surfaces, be absorbed, diffracted, or interfere with itself. The properties of the room, including surface smoothness and materials, impact the behavior of sound. Absorptive materials can reduce reverberation time by transforming sound energy into heat. Diffraction causes sound to bend around objects. Experiments are described to understand reflection and diffraction. Different room designs, like amphitheaters and concert halls, influence the listener experience through focused or diffuse reflections.
Sound can propagate as longitudinal waves through air and solids, and as transverse waves through solids. The velocity of sound in air depends on temperature. Common units used to measure sound include decibels (loudness), hertz (frequency), and sone and phon (perceived loudness). Sound reflects off hard surfaces similarly to light, while diffraction causes bending around obstacles. The amount of sound absorbed versus reflected by a material is quantified by its absorption coefficient. Reverberation is the prolongation of sound after the source stops due to reflections, and reverberation time is used to characterize how long reflections are audible in a space.
WHAT IS ACOUSTICS? what is sound? AMPLITUDE AND VOLUME, FREQUENCY AND PITCH
LOUDNESS OR INTENSITY
LOUDNESS OR INTENSITY
LOUDNESS OR INTENSITY, TIMBRE
VELOCITY OF SOUND
AMPLITUDE
REFLECTION
The document discusses acoustics and sound. It begins by defining acoustics as the branch of physics dealing with sound generation, propagation, and analysis. It then discusses key acoustics terminology like amplitude, frequency, wavelength, absorption, and reverberation. The document explains how sound intensity decreases with distance according to the inverse square law. It also discusses how different materials can absorb or reflect sound to varying degrees, and how the reverberation time of a space is measured. In summary, the document provides an introduction to acoustics concepts including sound properties, behavior in enclosed spaces, and factors that influence sound absorption.
Acoustics is the scientific study of sound, including how it behaves and is perceived. It deals with properties of sound waves like reflection, refraction, absorption, and interference. Acoustics is important for learning environments and other spaces where noise can be distracting or carry too much. Good acoustics involve distributing sound well, creating a sense of intimacy, and having proper reverberation times. Factors like reverberation time, loudness, echoes, and sound reflections off surfaces can impact architectural acoustics. A variety of materials like sound absorbers, reflectors, and diffusers are used to control sound.
Explains basics about sound and what classroom issues are present due to sound effects which causes problem for students to hear teacher properly.
Explains concept of reverberation and other issues and suggests about its solution for better classroom sound efficiency
This document discusses various aspects of room acoustics, including how sound travels and interacts with surfaces. Sound can bounce off surfaces, be absorbed, diffracted, or interfere with itself. The properties of the room, including surface smoothness and materials, impact the behavior of sound. Absorptive materials can reduce reverberation time by transforming sound energy into heat. Diffraction causes sound to bend around objects. Experiments are described to understand reflection and diffraction. Different room designs, like amphitheaters and concert halls, influence the listener experience through focused or diffuse reflections.
Sound can propagate as longitudinal waves through air and solids, and as transverse waves through solids. The velocity of sound in air depends on temperature. Common units used to measure sound include decibels (loudness), hertz (frequency), and sone and phon (perceived loudness). Sound reflects off hard surfaces similarly to light, while diffraction causes bending around obstacles. The amount of sound absorbed versus reflected by a material is quantified by its absorption coefficient. Reverberation is the prolongation of sound after the source stops due to reflections, and reverberation time is used to characterize how long reflections are audible in a space.
WHAT IS ACOUSTICS? what is sound? AMPLITUDE AND VOLUME, FREQUENCY AND PITCH
LOUDNESS OR INTENSITY
LOUDNESS OR INTENSITY
LOUDNESS OR INTENSITY, TIMBRE
VELOCITY OF SOUND
AMPLITUDE
REFLECTION
The document discusses acoustics and sound. It begins by defining acoustics as the branch of physics dealing with sound generation, propagation, and analysis. It then discusses key acoustics terminology like amplitude, frequency, wavelength, absorption, and reverberation. The document explains how sound intensity decreases with distance according to the inverse square law. It also discusses how different materials can absorb or reflect sound to varying degrees, and how the reverberation time of a space is measured. In summary, the document provides an introduction to acoustics concepts including sound properties, behavior in enclosed spaces, and factors that influence sound absorption.
Acoustics is the scientific study of sound, including how it behaves and is perceived. It deals with properties of sound waves like reflection, refraction, absorption, and interference. Acoustics is important for learning environments and other spaces where noise can be distracting or carry too much. Good acoustics involve distributing sound well, creating a sense of intimacy, and having proper reverberation times. Factors like reverberation time, loudness, echoes, and sound reflections off surfaces can impact architectural acoustics. A variety of materials like sound absorbers, reflectors, and diffusers are used to control sound.
Room acoustics and sound absorption materialsPankaj Kumar
1) The document discusses different methods for calculating reverberation time in rooms and auditoriums, including based on room dimensions, materials, and total sound absorption.
2) It provides formulas for calculating reverberation time based on room volume, total absorption, and other factors. The optimal reverberation time for an auditorium with 5000 cubic meters volume is given as 0.8 seconds.
3) Different types of sound absorbing materials are described, including porous materials like fiberboards and mineral wools, non-perforated panel absorbers, and cavity/Helmholtz resonators. Examples and properties of each type are outlined.
This document discusses the calculation of reverberation time. It defines reverberation time as the time it takes for sound in a room to decay by 60dB. It provides the Sabine formula to calculate reverberation time: RT60 = 0.049 V/a, where RT60 is reverberation time, V is volume, and a is total room absorption. An example calculation is shown for a classroom with given dimensions, materials, and furnishings to find its reverberation time of 1.24 seconds, which is longer than expected. Reducing reverberation time is recommended through sound absorption methods.
Acousticsandsoundinsulationsby K R ThankiKrunal Thanki
This document provides information about building acoustics and sound absorption materials. It discusses characteristics of sound including pitch, intensity, wavelength, speed of sound in different mediums, reflection, refraction, interference, reverberation, and more. It then describes different types of sound absorption materials like foam panels, fabric wrapped panels, ceiling tiles, baffles, and gives specifications for each. The goal is to educate on acoustics and available soundproofing options.
This document discusses key acoustic factors to consider for effective communication in classrooms. It outlines that the distance between speakers and listeners, signal-to-noise ratio, reverberation, and physical barriers all impact sound transmission. Early reflections contribute positively to the effective speech signal while late reflections and background noise contribute to the effective noise level. The proportion of speech signal that exceeds the effective noise level allows an estimate of speech perception regardless of individual characteristics. Reverberation time determines the equivalent noise level from late reflections.
This document provides an overview of architectural acoustics. It discusses the classification of sound, characteristics of musical sound, types of sound absorbing materials, factors affecting building acoustics like reverberation time, and conditions for good acoustics such as uniform loudness distribution and avoiding echoes. The key topics covered include sound absorption, reverberation, noise control and designing buildings for optimal acoustics.
The document discusses the physics of sound. It defines sound as a pressure wave that travels faster through solids than liquids or gases. Sound waves are longitudinal waves that create compressions and rarefactions. The key characteristics of a sound wave are its frequency, amplitude, wavelength, and speed. Frequency is measured in Hertz and determines the pitch of a sound. Amplitude determines loudness. Wavelength is the distance between compressions or rarefactions. Sound waves can be reflected, transmitted, absorbed, or cause diffraction or reverberation when interacting with surfaces. The range of normal human hearing is between 20-20,000 Hz. Different materials are used to absorb sound like porous absorbers, panel absorbers, and resonators
1) Acoustics refers to vibrations that are audible to humans, ranging from 20-20,000 Hertz. All sounds originate from object vibrations.
2) Key characteristics of sound include requiring a medium to propagate, having a finite velocity, and traveling at different speeds in different materials. Sounds can be classified by pitch, timbre, and intensity.
3) Important factors that affect building acoustics include optimizing reverberation time, avoiding uneven loudness or focusing due to interference or resonance, and reducing echoes and noise. Absorbing materials and proper ventilation help address these factors.
Visit https://alexisbaskind.net/teaching for a full interactive version of this course with sound and video material, as well as more courses and material.
Course series: Fundamentals of acoustics for sound engineers and music producers
Level: undergraduate (Bachelor)
Language: English
Revision: January 2020
To cite this course: Alexis Baskind, Psychoacoustics 1 – The ear, course material, license: Creative Commons BY-NC-SA.
Course content
1.What is psychoacoustics?
Psychophysics and psychoacoustics - Physical and perceptual attributes - Why is psychoacoustics important for music production?
2.The physiology of the ear
Inner ear, middle ear, outer ear - Inner hair cells - Corti organ
3.Hearing damages
Ear fatigue - ear damages
The document discusses acoustics and the theory of sound. It defines acoustics as the science dealing with the production, control, transmission, reception, and effects of sound. It also defines key terms like resonance, reverberation, and echo. The document discusses how sound is generated by vibrating bodies, and how sound waves propagate through the air in longitudinal compressional waves, requiring a medium to travel through. It notes that sound propagation means the movement of sound through a medium from a source to a receiver.
This document provides an overview of fundamental concepts in acoustics and audio fundamentals. It discusses the physics of sound, how sound is processed by the ear and brain, concepts of loudness and pitch, principles of sound measurement including decibels and meters, properties of sound waves like reflection and absorption, and applications in architectural acoustics. Key topics covered include the anatomy of the ear, function of the cochlea, psychoacoustics, principles of sound pressure, intensity and power levels, characteristics of VU and peak meters, and the inverse square law governing sound wave propagation.
Building service.ppt of neeru and aprajeetativar rose
This document discusses building acoustics and provides solutions for acoustic defects. It begins with definitions and characteristics of sound, including transmission, absorption, reflection, and reverberation. Common acoustic defects like echoes, reverberation, insufficient loudness, sound foci, and dead spots are described along with solutions. Various acoustic materials are presented with applications and coefficients. A case study of a hotel demonstrates acoustic design considerations for reception, doors, furniture, ceilings, floors, and glazing.
The document discusses key concepts in acoustics including:
1. Acoustics covers the properties and transmission of sound, and architectural acoustics applies these principles to buildings.
2. Important acoustic concepts include frequency, wavelength, amplitude, intensity measured in decibels, and reverberation.
3. A room's acoustics are determined by how sound waves propagate and are reflected off surfaces based on their material and shape.
4. Reverberation is the gradual decay of sound in a room after the source stops due to multiple reflections, and is measured by reverberation time.
This document provides an overview of architectural acoustics. It defines acoustics as the science dealing with the production, control, transmission, reception, and effects of sound. It discusses how different materials reflect, transmit, or absorb sound waves. Hard surfaces like tile and wood tend to reflect sound waves and cause echoes, while soft surfaces like textiles and insulation absorb sound waves. It then discusses some pioneers in acoustics like Pythagoras and how the early Greek civilization was concerned with acoustic design of theaters. Finally, it briefly touches on topics like resonance, standing waves, interference, and provides some examples of acoustic panels.
This document discusses acoustics and noise control. It begins by defining acoustics and describing the basics of sound, including properties like amplitude, frequency, wavelength. It then explains sound propagation principles such as reflection, refraction, diffraction and absorption. Different materials and their effects on sound are described. Noise control techniques like site planning, architectural design and sound barriers are discussed. Specific examples of architectural designs that enhance sound are provided.
Acoustical materials are designed to absorb sound that would otherwise be reflected. Foam panels and tiles made from materials like polyurethane and glass fiber are widely used as sound absorbers. They are applied in walls, ceilings and as freestanding panels. Fabric wrapped panels and acoustic wall coverings provide sound absorption while also decorating interior spaces. Baffles and banners hung from ceilings are an economical way to reduce reverberation in large spaces like auditoriums and gymnasiums. Porous materials like glass fiber and open cell foams absorb sound through both solid and gas phases as sound propagates through their structure.
This document discusses various topics related to sound and noise, including:
1. It defines key terms like wavelength, transverse and longitudinal waves, simple harmonic motion, velocity of sound waves, wave characteristics and properties.
2. It describes the characteristics of sound including intensity, pitch, quality and scales of measurement.
3. It discusses behavior of sound in enclosures, reflection, echoes, dispersion, and sound shadows.
4. It also covers topics like common indoor and outdoor noise levels, permissible noise exposure, sonometers, absorption coefficients, resonance absorbers, and reverberation time.
Acoustics is the study of sound waves and how they are generated, propagated, and received. When designing buildings, several acoustical factors must be considered, including reverberation, focusing of sound, echoes, unwanted resonance, interference, and extraneous noise. Reverberation is the persistence of sound after the sound source stops emitting sound, and the reverberation time depends on the size, surface materials, and absorption coefficients of the space. The Sabine formula relates reverberation time to the volume and absorption of a space. Proper acoustics in buildings ensures sound is uniformly distributed and factors like echoes, resonance, and interference are minimized.
This document discusses sound waves and room acoustics. It explains that sound travels as longitudinal waves through air and other substances. When sound waves hit surfaces in an enclosed space, they are reflected and create reverberation over time. The time it takes for reverberation to decay by 60dB is known as the reverberation time or RT60, which provides an objective measurement of room acoustics. Room reflections are important for both the direct sound picked up by microphones and the diffuse room tone, which conveys information about the size and surfaces of the space.
The distortion of sound we hear is due to "coloration" of the sound caused by reverberation - an invisible physical phenomenon. This presentation brings out the basics of reverberation.
Room acoustics and sound absorption materialsPankaj Kumar
1) The document discusses different methods for calculating reverberation time in rooms and auditoriums, including based on room dimensions, materials, and total sound absorption.
2) It provides formulas for calculating reverberation time based on room volume, total absorption, and other factors. The optimal reverberation time for an auditorium with 5000 cubic meters volume is given as 0.8 seconds.
3) Different types of sound absorbing materials are described, including porous materials like fiberboards and mineral wools, non-perforated panel absorbers, and cavity/Helmholtz resonators. Examples and properties of each type are outlined.
This document discusses the calculation of reverberation time. It defines reverberation time as the time it takes for sound in a room to decay by 60dB. It provides the Sabine formula to calculate reverberation time: RT60 = 0.049 V/a, where RT60 is reverberation time, V is volume, and a is total room absorption. An example calculation is shown for a classroom with given dimensions, materials, and furnishings to find its reverberation time of 1.24 seconds, which is longer than expected. Reducing reverberation time is recommended through sound absorption methods.
Acousticsandsoundinsulationsby K R ThankiKrunal Thanki
This document provides information about building acoustics and sound absorption materials. It discusses characteristics of sound including pitch, intensity, wavelength, speed of sound in different mediums, reflection, refraction, interference, reverberation, and more. It then describes different types of sound absorption materials like foam panels, fabric wrapped panels, ceiling tiles, baffles, and gives specifications for each. The goal is to educate on acoustics and available soundproofing options.
This document discusses key acoustic factors to consider for effective communication in classrooms. It outlines that the distance between speakers and listeners, signal-to-noise ratio, reverberation, and physical barriers all impact sound transmission. Early reflections contribute positively to the effective speech signal while late reflections and background noise contribute to the effective noise level. The proportion of speech signal that exceeds the effective noise level allows an estimate of speech perception regardless of individual characteristics. Reverberation time determines the equivalent noise level from late reflections.
This document provides an overview of architectural acoustics. It discusses the classification of sound, characteristics of musical sound, types of sound absorbing materials, factors affecting building acoustics like reverberation time, and conditions for good acoustics such as uniform loudness distribution and avoiding echoes. The key topics covered include sound absorption, reverberation, noise control and designing buildings for optimal acoustics.
The document discusses the physics of sound. It defines sound as a pressure wave that travels faster through solids than liquids or gases. Sound waves are longitudinal waves that create compressions and rarefactions. The key characteristics of a sound wave are its frequency, amplitude, wavelength, and speed. Frequency is measured in Hertz and determines the pitch of a sound. Amplitude determines loudness. Wavelength is the distance between compressions or rarefactions. Sound waves can be reflected, transmitted, absorbed, or cause diffraction or reverberation when interacting with surfaces. The range of normal human hearing is between 20-20,000 Hz. Different materials are used to absorb sound like porous absorbers, panel absorbers, and resonators
1) Acoustics refers to vibrations that are audible to humans, ranging from 20-20,000 Hertz. All sounds originate from object vibrations.
2) Key characteristics of sound include requiring a medium to propagate, having a finite velocity, and traveling at different speeds in different materials. Sounds can be classified by pitch, timbre, and intensity.
3) Important factors that affect building acoustics include optimizing reverberation time, avoiding uneven loudness or focusing due to interference or resonance, and reducing echoes and noise. Absorbing materials and proper ventilation help address these factors.
Visit https://alexisbaskind.net/teaching for a full interactive version of this course with sound and video material, as well as more courses and material.
Course series: Fundamentals of acoustics for sound engineers and music producers
Level: undergraduate (Bachelor)
Language: English
Revision: January 2020
To cite this course: Alexis Baskind, Psychoacoustics 1 – The ear, course material, license: Creative Commons BY-NC-SA.
Course content
1.What is psychoacoustics?
Psychophysics and psychoacoustics - Physical and perceptual attributes - Why is psychoacoustics important for music production?
2.The physiology of the ear
Inner ear, middle ear, outer ear - Inner hair cells - Corti organ
3.Hearing damages
Ear fatigue - ear damages
The document discusses acoustics and the theory of sound. It defines acoustics as the science dealing with the production, control, transmission, reception, and effects of sound. It also defines key terms like resonance, reverberation, and echo. The document discusses how sound is generated by vibrating bodies, and how sound waves propagate through the air in longitudinal compressional waves, requiring a medium to travel through. It notes that sound propagation means the movement of sound through a medium from a source to a receiver.
This document provides an overview of fundamental concepts in acoustics and audio fundamentals. It discusses the physics of sound, how sound is processed by the ear and brain, concepts of loudness and pitch, principles of sound measurement including decibels and meters, properties of sound waves like reflection and absorption, and applications in architectural acoustics. Key topics covered include the anatomy of the ear, function of the cochlea, psychoacoustics, principles of sound pressure, intensity and power levels, characteristics of VU and peak meters, and the inverse square law governing sound wave propagation.
Building service.ppt of neeru and aprajeetativar rose
This document discusses building acoustics and provides solutions for acoustic defects. It begins with definitions and characteristics of sound, including transmission, absorption, reflection, and reverberation. Common acoustic defects like echoes, reverberation, insufficient loudness, sound foci, and dead spots are described along with solutions. Various acoustic materials are presented with applications and coefficients. A case study of a hotel demonstrates acoustic design considerations for reception, doors, furniture, ceilings, floors, and glazing.
The document discusses key concepts in acoustics including:
1. Acoustics covers the properties and transmission of sound, and architectural acoustics applies these principles to buildings.
2. Important acoustic concepts include frequency, wavelength, amplitude, intensity measured in decibels, and reverberation.
3. A room's acoustics are determined by how sound waves propagate and are reflected off surfaces based on their material and shape.
4. Reverberation is the gradual decay of sound in a room after the source stops due to multiple reflections, and is measured by reverberation time.
This document provides an overview of architectural acoustics. It defines acoustics as the science dealing with the production, control, transmission, reception, and effects of sound. It discusses how different materials reflect, transmit, or absorb sound waves. Hard surfaces like tile and wood tend to reflect sound waves and cause echoes, while soft surfaces like textiles and insulation absorb sound waves. It then discusses some pioneers in acoustics like Pythagoras and how the early Greek civilization was concerned with acoustic design of theaters. Finally, it briefly touches on topics like resonance, standing waves, interference, and provides some examples of acoustic panels.
This document discusses acoustics and noise control. It begins by defining acoustics and describing the basics of sound, including properties like amplitude, frequency, wavelength. It then explains sound propagation principles such as reflection, refraction, diffraction and absorption. Different materials and their effects on sound are described. Noise control techniques like site planning, architectural design and sound barriers are discussed. Specific examples of architectural designs that enhance sound are provided.
Acoustical materials are designed to absorb sound that would otherwise be reflected. Foam panels and tiles made from materials like polyurethane and glass fiber are widely used as sound absorbers. They are applied in walls, ceilings and as freestanding panels. Fabric wrapped panels and acoustic wall coverings provide sound absorption while also decorating interior spaces. Baffles and banners hung from ceilings are an economical way to reduce reverberation in large spaces like auditoriums and gymnasiums. Porous materials like glass fiber and open cell foams absorb sound through both solid and gas phases as sound propagates through their structure.
This document discusses various topics related to sound and noise, including:
1. It defines key terms like wavelength, transverse and longitudinal waves, simple harmonic motion, velocity of sound waves, wave characteristics and properties.
2. It describes the characteristics of sound including intensity, pitch, quality and scales of measurement.
3. It discusses behavior of sound in enclosures, reflection, echoes, dispersion, and sound shadows.
4. It also covers topics like common indoor and outdoor noise levels, permissible noise exposure, sonometers, absorption coefficients, resonance absorbers, and reverberation time.
Acoustics is the study of sound waves and how they are generated, propagated, and received. When designing buildings, several acoustical factors must be considered, including reverberation, focusing of sound, echoes, unwanted resonance, interference, and extraneous noise. Reverberation is the persistence of sound after the sound source stops emitting sound, and the reverberation time depends on the size, surface materials, and absorption coefficients of the space. The Sabine formula relates reverberation time to the volume and absorption of a space. Proper acoustics in buildings ensures sound is uniformly distributed and factors like echoes, resonance, and interference are minimized.
This document discusses sound waves and room acoustics. It explains that sound travels as longitudinal waves through air and other substances. When sound waves hit surfaces in an enclosed space, they are reflected and create reverberation over time. The time it takes for reverberation to decay by 60dB is known as the reverberation time or RT60, which provides an objective measurement of room acoustics. Room reflections are important for both the direct sound picked up by microphones and the diffuse room tone, which conveys information about the size and surfaces of the space.
The distortion of sound we hear is due to "coloration" of the sound caused by reverberation - an invisible physical phenomenon. This presentation brings out the basics of reverberation.
This is a small presentation on Architectural Acoustics and Reverberation Time that i made for my coursework. it is not that detailed and explanatory (made for only 2 marks), but i thought sharing this might help someone with their study. So forgive me if u get disappointed, and feel free to reach me if u have any questions/complain or suggestion.
The document discusses acoustics in buildings and sound insulation. It covers topics such as sound absorption, transmission, reflection, and insulation. Proper acoustical design includes considering site selection, volume, shape, interior surfaces, reverberation, seating, and absorption to achieve optimum sound quality. Sound insulation can be improved through rigid wall and floor constructions, double walls, resilient materials, and isolating noise sources. The acceptable noise levels for different building types are also provided.
Notes for Architecture 4th Year subject Services. The topic is about Acoustic, how does it work for different places, how we can treat spaces according to acoustic and for better acoustic
ARCHITECTURAL SERVICES – V (ACOUSTICS) (RAR – 806)
MODULE-1 – BUILDING ACOUSTICS
(COMMON ACOUSTICAL DEFECTS AND
RECOMMENDED REMEDIES) Presented by Ar. Manish Kumar, Assistant Professor in
Architecture Department at Axis Institute of
Architecture
The document discusses various topics related to architectural acoustics including:
- The definition of architectural acoustics as the study of sound generation, propagation, and transmission in buildings.
- The importance of applying acoustic principles to improve quality of life through work and leisure environments.
- The need to both enhance desirable sounds like music, while reducing undesirable noise.
The document discusses acoustics in auditoriums. It defines acoustics and sound, and discusses topics like sound frequency and intensity, reflection of sound, defects due to reflected sound like echoes and reverberation, Sabine's equation for calculating reverberation time, absorbent materials used in auditoriums, acoustic design considerations for auditoriums including volume, shape, seating, and defects that can occur. It also covers noise mapping and sound insulation. The overall goal is to provide guidelines for designing auditoriums with good acoustics.
This document discusses key concepts in auditorium acoustics, including how sound propagates both in open and enclosed spaces. It explains the effects of different types of reflections - from flat, concave, and convex surfaces - on sound propagation. Key acoustic factors that determine the listener's experience are identified as direct sound, early reflections, and reverberant sound. The precedence effect and how it relates to localization is also summarized. The document provides an overview of how reverberation time is determined and measured, and the role of absorption properties in influencing reverberation time. It concludes with criteria for achieving good acoustics in an auditorium setting.
B.Tech sem I Engineering Physics U-V Chapter 1-SOUNDAbhi Hirpara
1. The document discusses various topics related to sound including how sound is produced, the difference between musical and noise sounds, factors that affect loudness and absorption, and Sabine's formula for reverberation time.
2. It also covers topics like sound absorption coefficient, factors that influence the acoustics of buildings like reverberation time, loudness, focusing, echoes, and different types of noise.
3. Remedies to improve acoustics by controlling reverberation time, loudness, focusing, echoes and reducing noise are also presented.
Classification and Characteristics of soundHarsh Parmar
Sound is a longitudinal wave that requires a medium and cannot travel through a vacuum. Sound can be classified as infrasound, audible sound, or ultrasound based on frequency. Within audible sound, musical sounds are periodic and have a pleasing effect, while noise is irregular and jarring. The key characteristics of sound are pitch (related to frequency), loudness (related to intensity), and timbre (related to quality). Reverberation is the persistence of sound in a room due to multiple reflections, even after the sound source stops emitting sound, and can be measured by reverberation time.
Visit https://alexisbaskind.net/teaching for a full interactive version of this course with sound and video material, as well as more courses and material.
Course series: Fundamentals of acoustics for sound engineers and music producers
Level: undergraduate (Bachelor)
Language: English
Revision: February 2020
To cite this course: Alexis Baskind, The Overtone Spectrum
course material, license: Creative Commons BY-NC-SA.
Course content:
1. What is the overtone spectrum?
Time and frequency representation of a sound, harmonic and inharmonic sounds, overtones, harmonic series, fundamental frequency, linear and logarithmic frequency scales
2. Physical generation of overtones
Tone generator, vibration modes, dependence on geometry
3. Shaping of the overtone spectrum in the instrument
resonator, resonance modes, dependence on geometry, formants, overtone singing
4. Designing the overtone spectrum by playing
harmonics glissandi, natural string harmonics, dependence of tone color on dynamics, decay, radiation patterns
5. Conclusion
1. The acoustical quality of a room is determined by its reverberation time, which is the time it takes for sound to decay 60 decibels after the source stops.
2. Reverberation time depends on the volume of the room and absorption of surfaces. Larger rooms and rooms with more reflective surfaces have longer reverberation times, while smaller rooms and rooms with more absorptive surfaces have shorter reverberation times.
3. Ideal reverberation times for concert halls range from 1.7 to 2.05 seconds, though the frequency response is also important for acoustical quality.
The document provides an overview of acoustics and architectural acoustics. It discusses key topics such as the physics of sound including amplitude, frequency, wavelength, velocity of sound and more. It also covers how sound behaves in an enclosed space through reflection, absorption, diffraction and other phenomena. The document outlines criteria for acoustic environments including reverberation time, speech intelligibility, and discusses echo and how to reduce it.
An auditorium is designed based on the function itself. For example: Dewan Agong Tuanku Canselor UiTM, that is a multi-purpose auditoria which indicates both functions; speech and also music purposes. It depends on the event that will be held in the auditorium. The design of the auditorium must comprises of both functions in order to have a good room acoustic. In addition, it must be work out for changes.
This document discusses acoustics and reverberation time in rooms and auditoriums. It defines reverberation time as the time for sound to decay 60 dB from its original level. Ideal reverberation times are discussed for characteristics like liveness and intimacy. Formulas for calculating reverberation time are presented. Examples of reverberation times in famous concert halls like Vienna's Musikvereinsaal and Boston's Symphony Hall are provided to illustrate good ranges. Acoustical ceiling panels are mentioned as a way to produce balanced and blended sounds in performance venues.
This document discusses key concepts in acoustics including:
- Sound is reflected, transmitted, or absorbed depending on the material it encounters. Hard surfaces reflect more while soft surfaces absorb more.
- The decibel scale measures sound intensity logarithmically, with each 10dB increase representing a doubling of perceived loudness. Common sound levels are listed.
- An anechoic chamber absorbs all sound waves to eliminate echoes or reverberation.
- Acoustics involves the production and behavior of sound waves traveling through air or other media like walls. It also discusses the speed of sound versus light.
Fundamentals of Music Instrument AcousticsAlexis Baskind
Visit https://alexisbaskind.net/teaching for a full interactive version of this course with sound and video material, as well as more courses and material.
Course series: Fundamentals of acoustics for sound engineers and music producers
Level: undergraduate (Bachelor)
Language: English
Revision: February 2020
To cite this course: Alexis Baskind, Fundamentals of Music Instrument Acoustics
course material, license: Creative Commons BY-NC-SA.
Course content:
1. General Considerations about instrumental acoustics
Functions of the different parts of a musical instrument, exciter, oscillator, resonator, radiation
2. Woodwinds
Definition of a woodwind instrument, principle of reed instruments, resonance in bore, different kinds of reeds, airjets, bores, open and closed cylindrical bores (quarter-wavelength and half-wavelength tubes), conical bores, formant regions, role of the keys, role of the bell, examples of radiation patterns
3. Brass Instruments
Definition of a brass instrument, modes in a cylindrical bore for a brass, role of the bell, brassiness, shock waves, examples of radiation patterns
4. Strings
Subcategories (plucked, bowed, struck), transverse standing waves in strings, vibration modes of the body, role of the soundholes, examples of radiation patterns
5. Percussions
Subcategories (membranes, plates, idiophones, tubes…), most percussions are inharmonic, pitched percussions, examples of vibration modes (cymbal, snare)
https://alexisbaskind.net/teaching besuchen für eine vollständige, interaktive Version dieses Kurses mit Ton- und Videomaterial sowie mehr Kurs und -Material.
Kursreihe: Grundlagen der Akustik für Toningenieure und Musikproduzenten
Niveau: Bachelor
Sprache: Deutsch
Revision: Januar 2020
Diesen Kurs zitieren: Alexis Baskind, Raumakustik
Kursmaterial, Lizenz: Creative Commons BY-NC-SA.
Kursinhalt
1. Raum-Zeit-Betrachtung: Schallausbreitung in einem Raum
Raytracing, Beispiel eines rechteckigen Raumes, zeitliche Entwicklung vom Freifeld bis zum Diffusfeld, Anfangszeitlücke (ITDG), Direktschall, Frühe Reflektionen, Nachhall, exponentielle Abnahme des Schalldrucks, Definition der Nachhallzeit, T60, T30, T20, Schroeder-Kurve, Hallradius, Flatterechos, Diffusion, Einfluss der Entfernung, Einfluss der Raumgröße
2. Raum-Frequenz-Betrachtung: Raummoden
Erinnerung: eindimensionale stehende Wellen, axiale Moden, tangentiale Moden, oblique Moden, Eigenfrequenzen, Einfluss der Raumgröße auf die modale Dichte, Dauer und Bandbreite von Moden, Einfluss der Absorption auf Moden, Schroeder-Frequenz
3. Zeit-Frequenz-Betrachtung
Frühe Reflektionen, Moden und Nachhall in einer einheitlichen Zeit-Frequenz Sichtweise, Wasserfall-Darstellung
4. Raumakustik-Planung
Prognose der Nachhallzeit, Sabinische Formel, frequenzabhängige Absorption, Poröse Absorber, Einfluss von der Dicke des Absorbers und vom Hohlraum, Resonanz-Absorber, Membranabsorber, Helmholtz-Absorber
5. Raumakustik eines Regieraumes
Wichtigkeit der Symmetrie, Bedarf an genügender Raumgröße und kontrollierter Nachhallzeit, empfohlene Nachhallzeit, Bedarf an kontrollierten frühen Reflektionen, LEDE-Konzept, RFZ-Konzept
6. Räumliches Hören in einem Raum
Entfernungshören in einem Raum, Wahrnehmung der Raumgröße, Klarheit, Deutlichkeit, Wahrgenommene Schallquellenbreite, Einhüllung, Klangfarbe des Nachhalls
Visit https://alexisbaskind.net/teaching for a full interactive version of this course with sound and video material, as well as more courses and material.
Course series: Fundamentals of acoustics for sound engineers and music producers
Level: undergraduate (Bachelor)
Language: English
Revision: February 2020
To cite this course: Alexis Baskind, Psychoacoustics 4 – Spatial Hearing
course material, license: Creative Commons BY-NC-SA.
Course content:
1. Introduction
sound localization, lateralization, perception of height, perception of distance
2. Interaural level and time differences
head as acoustic shadow, ITD, ILD, frequency dependence, interindividual differences
3. Cone of confusion
ambiguity of ITD and ILD in the cone of confusion, front/back confusions, need for extra information (vision, previous knowledge, head movements, distance-based cues, spectral cues)
4. Estimating distance in a dry environment
use of absolute level and spectrum of the sound
5. Cocktail-Party Effect
selective attention based on spectral, spatial and time cues
6. Summing Localization
base of stereophony, phantom sources, influence of interchannel time and level differences, time-based, level-based and mixed stereophony, sweet spot
7. Precedence Effect
Haas effect / Law of the first wavefront, echo threshold, application in music production
Grundlagen der Akustik 2 - Phase, SchallquellenAlexis Baskind
https://alexisbaskind.net/teaching besuchen für eine vollständige, interaktive Version dieses Kurses mit Ton- und Videomaterial sowie mehr Kurs und -Material.
Kursreihe: Grundlagen der Akustik für Toningenieure und Musikproduzenten
Niveau: Bachelor
Sprache: Deutsch
Revision: Januar 2020
Diesen Kurs zitieren: Alexis Baskind, Grundlagen der Akustik 2 - Phase, Schallquellen
Kursmaterial, Lizenz: Creative Commons BY-NC-SA.
Kursinhalt
1. Die Phase
Sinuswelle, Phase und komplexe Signale, gleichphasige Signale, 90°-verschobene Signale, gegenphasige Signale, konstruktive und destructive Interferenzen, Kammfilter, Phasenumkehr, Phasenverschiebung
2. Ungerichtete Schallquellen (Monopolquellen)
Definition von ungerichteten Quellen, Abstrahlcharakteristik, Kugelwellen, Monopolquellen und Abstandsgesetz
3. Ebene Wellen, Nahfeld, Fernfeld
Definition von Ebene-Wellen, Nahfeld, Fernfeld
4. Dipolquellen
Definition von Dipolquellen, Abstrahlcharakteristik
5. Dipolquellen in Nah- und Fernfeld
frequenzabhängiges Verhalten von Dipolen in Nah- und Fernfeld
Fundamentals of Acoustics 2 - Phase, sound sourcesAlexis Baskind
Visit https://alexisbaskind.net/teaching for a full interactive version of this course with sound and video material, as well as more courses and material.
Course series: Fundamentals of acoustics for sound engineers and music producers
Level: undergraduate (Bachelor)
Language: English
Revision: February 2020
To cite this course: Alexis Baskind, Fundamentals of Acoustics 2 - Phase, sound sources
course material, license: Creative Commons BY-NC-SA.
Course content:
1. The phase
sine wave, phase, angle, phase and complex signals, signals in phase, signals in quadrature, signals in antiphase, constructive and destructive interferences, comb filter, phase inversion, phase shift
2. Omnidirectional sources (monopoles)
Definition of omnidirectional sources, radiation pattern, spherical waves, Omnidirectional sources and distance law
3. Plane waves, near field, far field
definition of a plane wave, near field, far field
4. Bidirectional sources (dipoles)
Definition of bidirectional sources, radiation pattern
5. Dipoles in near-field and far-field
frequency-dependent behaviour of dipoles in near and far field
Psychoakustik 3 - Wahrnehmung der Tonhöhe und der IntervalleAlexis Baskind
https://alexisbaskind.net/teaching besuchen für eine vollständige, interaktive Version dieses Kurses mit Ton- und Videomaterial sowie mehr Kurs und -Material.
Kursreihe: Grundlagen der Akustik für Toningenieure und Musikproduzenten
Niveau: Bachelor
Sprache: Deutsch
Revision: Januar 2020
Diesen Kurs zitieren: Alexis Baskind, Psychoakustik 3 - Wahrnehmung der Tonhöhe und der Intervalle
Kursmaterial, Lizenz: Creative Commons BY-NC-SA.
Kursinhalt
1. Was ist die Tonhöhe
Tonhöhe und Frequenz, Untere Grenze der Tonhöhenwahrnehmung, Tonhöhenklasse und Chroma
2. Kammerton
Entwicklung des Kammertons, Das « A 440 Hz »-Standard
3. Wahrnehmung der Intervalle
Intervalle und Frequenzverhältnisse, melodische Intervalle, harmonische Intervalle, Oktavspreizung, Schwebung, Rauhigkeit, Frequenzgruppen
4. Harmonizität und Konsonanz
Harmonik, die Naturtonreihe, Konsonanz – pythagoräische Definition, Reine Stimmung, Konsonanz – Moderne Definition
5. Stimmungen
Pythagoreische Stimmung, Zarlino Skala, Mitteltönige Stimmung, Wohltemperierte Stimmungen, Gleichstufige Stimmung
6. Komplexe Klänge
Komplexe Klänge, Residualton, Spektraltonhöhe, Tonhöhe von unharmonischen Klängen, Spreizung der Klavier-Stimmung
https://alexisbaskind.net/teaching besuchen für eine vollständige, interaktive Version dieses Kurses mit Ton- und Videomaterial sowie mehr Kurs und -Material.
Kursreihe: Grundlagen der Akustik für Toningenieure und Musikproduzenten
Niveau: Bachelor
Sprache: Deutsch
Revision: Januar 2020
Diesen Kurs zitieren: Alexis Baskind, Das Obertonspektrum
Kursmaterial, Lizenz: Creative Commons BY-NC-SA.
Kursinhalt
1. Was ist das Obertonspektrum?
Zeit- und Frequenzdarstellung eines Klanges, harmonische und unharmonische Klänge, Obertöne, Naturtonreihe, Grundfrequenz, lineare and logarithmische Frequenzscala
2. Physikalische Ursachen der Obertöne
Tongenerator, Eigenmoden, Beziehung zur Bauform
3. Gestaltung des Obertonspektrums im Instrument
Resonator, Resonanzmoden, Beziehung zur Bauform, Formanten, Obertongesang
4. Gestaltung des Obertonspektrums durch das Spiel
Flageoletten, Eingluss der Dynamik auf die Klangfarbe, Ausklang, Abstrahlcharakteristik
5. Fazit
A workshop hosted by the South African Journal of Science aimed at postgraduate students and early career researchers with little or no experience in writing and publishing journal articles.
How to Manage Your Lost Opportunities in Odoo 17 CRMCeline George
Odoo 17 CRM allows us to track why we lose sales opportunities with "Lost Reasons." This helps analyze our sales process and identify areas for improvement. Here's how to configure lost reasons in Odoo 17 CRM
Exploiting Artificial Intelligence for Empowering Researchers and Faculty, In...Dr. Vinod Kumar Kanvaria
Exploiting Artificial Intelligence for Empowering Researchers and Faculty,
International FDP on Fundamentals of Research in Social Sciences
at Integral University, Lucknow, 06.06.2024
By Dr. Vinod Kumar Kanvaria
This presentation includes basic of PCOS their pathology and treatment and also Ayurveda correlation of PCOS and Ayurvedic line of treatment mentioned in classics.
Main Java[All of the Base Concepts}.docxadhitya5119
This is part 1 of my Java Learning Journey. This Contains Custom methods, classes, constructors, packages, multithreading , try- catch block, finally block and more.
How to Build a Module in Odoo 17 Using the Scaffold MethodCeline George
Odoo provides an option for creating a module by using a single line command. By using this command the user can make a whole structure of a module. It is very easy for a beginner to make a module. There is no need to make each file manually. This slide will show how to create a module using the scaffold method.
LAND USE LAND COVER AND NDVI OF MIRZAPUR DISTRICT, UPRAHUL
This Dissertation explores the particular circumstances of Mirzapur, a region located in the
core of India. Mirzapur, with its varied terrains and abundant biodiversity, offers an optimal
environment for investigating the changes in vegetation cover dynamics. Our study utilizes
advanced technologies such as GIS (Geographic Information Systems) and Remote sensing to
analyze the transformations that have taken place over the course of a decade.
The complex relationship between human activities and the environment has been the focus
of extensive research and worry. As the global community grapples with swift urbanization,
population expansion, and economic progress, the effects on natural ecosystems are becoming
more evident. A crucial element of this impact is the alteration of vegetation cover, which plays a
significant role in maintaining the ecological equilibrium of our planet.Land serves as the foundation for all human activities and provides the necessary materials for
these activities. As the most crucial natural resource, its utilization by humans results in different
'Land uses,' which are determined by both human activities and the physical characteristics of the
land.
The utilization of land is impacted by human needs and environmental factors. In countries
like India, rapid population growth and the emphasis on extensive resource exploitation can lead
to significant land degradation, adversely affecting the region's land cover.
Therefore, human intervention has significantly influenced land use patterns over many
centuries, evolving its structure over time and space. In the present era, these changes have
accelerated due to factors such as agriculture and urbanization. Information regarding land use and
cover is essential for various planning and management tasks related to the Earth's surface,
providing crucial environmental data for scientific, resource management, policy purposes, and
diverse human activities.
Accurate understanding of land use and cover is imperative for the development planning
of any area. Consequently, a wide range of professionals, including earth system scientists, land
and water managers, and urban planners, are interested in obtaining data on land use and cover
changes, conversion trends, and other related patterns. The spatial dimensions of land use and
cover support policymakers and scientists in making well-informed decisions, as alterations in
these patterns indicate shifts in economic and social conditions. Monitoring such changes with the
help of Advanced technologies like Remote Sensing and Geographic Information Systems is
crucial for coordinated efforts across different administrative levels. Advanced technologies like
Remote Sensing and Geographic Information Systems
9
Changes in vegetation cover refer to variations in the distribution, composition, and overall
structure of plant communities across different temporal and spatial scales. These changes can
occur natural.
A review of the growth of the Israel Genealogy Research Association Database Collection for the last 12 months. Our collection is now passed the 3 million mark and still growing. See which archives have contributed the most. See the different types of records we have, and which years have had records added. You can also see what we have for the future.
ISO/IEC 27001, ISO/IEC 42001, and GDPR: Best Practices for Implementation and...PECB
Denis is a dynamic and results-driven Chief Information Officer (CIO) with a distinguished career spanning information systems analysis and technical project management. With a proven track record of spearheading the design and delivery of cutting-edge Information Management solutions, he has consistently elevated business operations, streamlined reporting functions, and maximized process efficiency.
Certified as an ISO/IEC 27001: Information Security Management Systems (ISMS) Lead Implementer, Data Protection Officer, and Cyber Risks Analyst, Denis brings a heightened focus on data security, privacy, and cyber resilience to every endeavor.
His expertise extends across a diverse spectrum of reporting, database, and web development applications, underpinned by an exceptional grasp of data storage and virtualization technologies. His proficiency in application testing, database administration, and data cleansing ensures seamless execution of complex projects.
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Date: May 29, 2024
Tags: Information Security, ISO/IEC 27001, ISO/IEC 42001, Artificial Intelligence, GDPR
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বাংলাদেশের অর্থনৈতিক সমীক্ষা ২০২৪ [Bangladesh Economic Review 2024 Bangla.pdf] কম্পিউটার , ট্যাব ও স্মার্ট ফোন ভার্সন সহ সম্পূর্ণ বাংলা ই-বুক বা pdf বই " সুচিপত্র ...বুকমার্ক মেনু 🔖 ও হাইপার লিংক মেনু 📝👆 যুক্ত ..
আমাদের সবার জন্য খুব খুব গুরুত্বপূর্ণ একটি বই ..বিসিএস, ব্যাংক, ইউনিভার্সিটি ভর্তি ও যে কোন প্রতিযোগিতা মূলক পরীক্ষার জন্য এর খুব ইম্পরট্যান্ট একটি বিষয় ...তাছাড়া বাংলাদেশের সাম্প্রতিক যে কোন ডাটা বা তথ্য এই বইতে পাবেন ...
তাই একজন নাগরিক হিসাবে এই তথ্য গুলো আপনার জানা প্রয়োজন ...।
বিসিএস ও ব্যাংক এর লিখিত পরীক্ষা ...+এছাড়া মাধ্যমিক ও উচ্চমাধ্যমিকের স্টুডেন্টদের জন্য অনেক কাজে আসবে ...
2. Alexis Baskind
Room Acoustics
Course series
Fundamentals of acoustics for sound engineers and music producers
Level
undergraduate (Bachelor)
Language
English
Revision
January 2020
To cite this course
Alexis Baskind, Room Acoustics, course material, license: Creative Commons BY-NC-
SA.
Full interactive version of this course with sound and video material, as well as more
courses and material on https://alexisbaskind.net/teaching.
Except where otherwise noted, content of this course
material is licensed under a Creative Commons Attribution-
NonCommercial-ShareAlike 4.0 International License.
Room Acoustics
3. Alexis Baskind
Outline
1. Time-Space perspective: Sound propagation in a
room
2. Frequency-Space perspective: Room modes
3. Time-Frequency perspective
4. Room acoustics design
5. Room acoustics of listening rooms
6. Spatial hearing in a room
Room Acoustics
4. Alexis Baskind
Sound propagation in a room
• The time evolution of the sound propagation in a
room can be considered from the point of view of
sound rays, reflection, absorption and diffusion
surfaces
• Most of room acoustics simulation softwares uses
indeed among others raytracing algorithms
(similar to 3D image rendering algorithms)
• For this, let’s first consider a simple rectangular
room, with a sound source and one listener
Room Acoustics
5. Alexis Baskind
Sound propagation in a room
• The sound sources only emits a short impulse, for
example a hand clapping, or a gunshot (gunshots were
used a lot in the early ages to measure room acoustics)
Room Acoustics
Source: Charles Feilding
6. Alexis Baskind
Direct Sound
• The first information that reaches the listener is the direct sound
• Without any further reflections, this would correspond to the so-
called free-field (in an anechoic chamber)
Room Acoustics
Temporal
representation
Spatial
representation
Source: Charles Feilding
7. Alexis Baskind
Early reflections
• After a moment (called initial time-delay gap), the first reflected
waves reach the listener, with less level because of absorption and
the distance (inverse-square law)
Room Acoustics
Temporal
representation
Spatial
representation
In red: the initial
time delay gap
Source: Charles Feilding
8. Alexis Baskind
Early reflections
• The temporal density of reflections increases drastically with time
Room Acoustics
=> =>Direct sound
First-order reflections
(i.e. reflected once)
Second-order reflections
(i.e. reflected twice)
Source: Geoff Martin
9. Alexis Baskind
Late Reverberation
• After 20-100ms (depending on the room dimensions and on the
diffusion – see below), the reflections become dense and come
from every direction: the sound field becomes more and more
diffuse => late reverberation
Room Acoustics
Temporal
representation
Spatial
representation
Source: Charles Feilding
10. Alexis Baskind
Late Reverberation
Without flutter echoes or other late reflections, the sound pressure
decays on average exponentially with time during the late
reverberation process
Room Acoustics
Soundpressure(linear)
Room impulse response (schematic), linear representation
11. Alexis Baskind
Late Reverberation
Without flutter echoes or other late reflections, the sound pressure
decays on average exponentially with respect to time during the late
reverberation process
Room Acoustics
Sound
pressure
(Pa)
Time (ms)
in red: envelope of late
reverberation decay
Room impulse response (measured), linear representation
12. Alexis Baskind
Late Reverberation
Thus the sound pressure level (on a logarithmic scale) decays on
average linearly with respect to time
Same room impulse response (measured), logarithmic representationSound
pressure
level
(dB SPL)
time (ms)
in red: envelope of late reverberation decay
in blue: measurement noise
Room Acoustics
13. Alexis Baskind
Sound
pressure
level
(dB SPL)
Time (ms)
Reverberation Time
• The Reverberation Time (T60) is the time the sound pressure level
needs for a 60 dB decrease
• The reverberation time is the most well known measure to
characterize a given reverberation
60 dB
T60 = time
corresponding to a
60 dB decrease
Room Acoustics
14. Alexis Baskind
Sound
pressure
level
(dB SPL)
Time (ms)
Reverberation Time
• In practice, the reverberation time is measured thanks to an
estimation of the envelope (called „Schroeder-curve“), which is
much smoother as the impulse response.
In black: Schroeder-curve
60 dB
T60 = time
corresponding to a
60 dB decrease
Room Acoustics
15. Alexis Baskind
Sound
pressure
level
(dB SPL)
Time (ms)
Reverberation Time
• Since a dynamic range of 60 dB is almost impossible to achieve, the
reverberation time is calculated based on a decay of 30 dB or 20 dB, and
then doubled (for 20dB) or tripled (for 60dB), in order to stay coherent
with T60 => Those estimations are called T20 and T30.
• T30 is measured between -5 dB and -35 dB, and T20 between -5 dB and
-25 dB with regards to the maximum of the curve
T30 / 2
Max – 5dB
Max – 35dB
Room Acoustics
16. Alexis Baskind
Sound
pressure
level
(dB SPL)
Time (ms)
Reverberation Time
• Since a dynamic range of 60 dB is almost impossible to achieve, the
reverberation time is calculated based on a decay of 30 dB or 20 dB, and
then doubled (for 20dB) or tripled (for 60dB), in order to stay coherent
with T60 => Those estimations are called T20 and T30.
• T30 is measured between -5 dB and -35 dB, and T20 between -5 dB and
-25 dB with regards to the maximum of the curve
T20 / 3
Max – 5dB
Max – 25dB
Room Acoustics
17. Alexis Baskind
Free field / diffuse field
• The time evolution of the sound propagation in a room can
be considered as the evolution from a free field to a diffuse
field
– Direct sound = free field: the signals that reach the
microphones/ears are highly correlated
– Early reflections = the correlation between recorded signals drops
more and more down as new reflections reach the microphones
– Late reverberation = diffuse field:
1. The sound is coming from all directions with the same level
2. The correlation between sound pressures at different positions is close to
zero
3. The diffuse field has the same characteristics at all positions of the room
Room Acoustics
18. Alexis Baskind
Critical Distance
• The critical distance (or Room Radius) is defined as the distance to
the source where the energy of the direct sound equals the energy
of the reverberated sound
Room Acoustics
Distance from source
• Below this distance, the
energy mainly follows
the inverse square law
• Above this distance, the
energy is roughly always
constant whatever the
position is, and
corresponds to the level
of the reverberant field
19. Alexis Baskind
Diffusion
• Late reflections, even attenuated by absorption, are often
disturbing, since they may lead to audible echoes
• The worst case is flutter echoes between parallel surfaces
• Therefore, diffusive surfaces are often used as an
alternative to reflective surfaces: they help to reduce late
reflections without making the room dryer
• The more diffusive surfaces, the earlier the transition to
diffuse reverberation
Room Acoustics
22. Alexis Baskind
The effect of Distance
• How is the reverberation changed when the source gets
farther ?
Room Acoustics
timetime
The source is farThe source is close
23. Alexis Baskind
Effect of Distance
With increasing distance:
1. The direct sound and the early reflections come later
2. The initial time delay gap is smaller
3. The early reflections come less from the sides and more
from the front. According to the cocktail-party effect, they
are preceptually less easy to distinguish from the direct
sound => Coloration
4. The level of the direct sound decreases, but the level of
the diffuse reverberation remains more or less identical
=> the relative part of reverberation increases
Room Acoustics
24. Alexis Baskind
The effect of Room Size
• How does the reverberation depend on the size of the
room ?
Room Acoustics
The room is bigThe room is small
timetime
25. Alexis Baskind
The effect of Room Size
If the room is bigger:
1. The overall sound level decreases
2. The early reflections come later
3. The reverberation time is longer
This means that a relatively long reverberation time can be
achieved:
– In a small room which walls, ceiling and floor are not good
absorbers (like small echo chambers used in studios)
– In a very large room which walls, ceiling and floor are good
absorbers
=> the main difference between those two cases is that
early reflections come earlier in a small room (which is used
by perception to recognize if a room is small or big)
Room Acoustics
26. Alexis Baskind
Limits of the geometrical model
• The geometrical model makes only sense if the
wavelengths are short enough, so that reflections can
occur.
• This is a requirement in order to consider the reverberant
field as diffuse
• At low frequencies, surfaces and distances between them
are too small compared to the wavelength: the geometrical
model does not work any more, and must be replaced with
a modal model (i.e. standing waves)
Room Acoustics
27. Alexis Baskind
Outline
1. Time-Space perspective: Sound propagation in a
room
2. Frequency-Space perspective: Room modes
3. Time-Frequency perspective
4. Room acoustics design
5. Room acoustics of listening rooms
6. Spatial hearing in a room
Room Acoustics
28. Alexis Baskind
Room resonances
• Reminder: monodimensional standing waves between two walls
Room Acoustics
Wall 1 Wall 2
distance between walls
wavelength
29. Alexis Baskind
Axial modes only depend on 1 dimension Tangential modes depend on 2 dimensions
Room resonances
• In 3 dimensions, more complex combinations are possible:
Room Acoustics
Oblique modes (also
called diagonal)
depend on 3
dimensions
Image sources: mcsquared.com
30. Alexis Baskind
Room resonances
• In 3 dimensions, more complex combinations are possible:
Room Acoustics
Image source: gikacoustics.com
31. Alexis Baskind
Frequency distribution of modes
• Because modes are 3-dimensional, their frequencies
(called eigenfrequencies) are not distributed regularly (on
a harmonic series), contrary to the 1-D case
Room Acoustics
Example: simulated eigenfrequencies for a rectangular room with
dimensions: 4.6m x 3.75m x 2.34m
Hz
frequency
32. Alexis Baskind
Frequency distribution of modes
• The frequency distribution depends on the size of the
room: the bigger the room, the bigger the modal density
(i.e. the number of modes per frequency)
• The higher the frequency, the bigger the modal density
Room Acoustics
Example: simulated eigenfrequencies for a rectangular room with
dimensions: 9.2mx 7.5m x 4m
Hz
frequency
33. Alexis Baskind
Modes: Duration and Bandwidth
• The duration and the bandwidth of single modes, like for
every resonances (or like band-pass filters), are inversely
proportional with each other: the longer it lasts, the
narrower it is in the frequency spectrum
• Therefore:
– Modes in a room without any absorbing material are long, thus
very narrow in the frequency spectrum (= a high quality factor)
=> very clear resonances, holes between two modes
– Modes in a room with a proper acoustic treatment (i.e. enough
absorption at low frequencies) are short, thus wider in the
frequency spectrum (= a low quality factor) => the spectrum is
more flat, less obvious resonances
Room Acoustics
34. Alexis Baskind
Modes: Duration and Bandwidth
-0.10
0.00
0.10
Volts/Volts
0 100 200 300 400 500
Time (ms)
Impulse Response
-0.10
0.00
0.10
Volts/Volts
0 100 200 300 400 500
Time (ms)
Impulse Response
-0.10
0.00
0.10
Volts/Volts
0 100 200 300 400 500
Time (ms)
Impulse Response
Frequency Response Impulse Response (time)
lessresonant
(=lowQ-Factor)
moreresonant
(=highQ-Factor)
Room Acoustics
Behavior of a single mode with respect to frequency and time, depending on damping
35. Alexis Baskind
Modes: Duration and Bandwidth
Example: empty room (no treatment)
Source : Ethan Winer
Time
Frequency
Level
Room Acoustics
36. Alexis Baskind
Modes: Duration and Bandwidth
... With 12 thin absorbers: 703-FRK from Owens Corning
Source : Ethan Winer
Time
Frequency
Level
Room Acoustics
37. Alexis Baskind
Modes: Duration and Bandwidth
... With 12 thin absorbers: 705-FRK from Owens Corning
Source: Ethan Winer
Time
Frequency
Level
Room Acoustics
38. Alexis Baskind
Modes and frequency response
The overall frequency spectrum at low frequencies consists in the
overlapping of all modes.
Example: calculated modes and frequency response in a rectangular room
(left: single modes, right overlapping = estimated frequency response)
Room Acoustics
Image sources: BBC Research Department Report, Low-Frequency Room Responses
39. Alexis Baskind
Modes and frequency response
Room Acoustics
Caution: the overlapping of modes leads not only to constructive
interferences, but also sometimes destructive
Holes in the frequency spectrum
Example (Simulation of room modes in the
Software “Room EQ Wizard”):
• The eigenfrequencies of the room modes
are shown als colored lines
• There are holes at ca. 44Hz and 52 Hz,
that result from the big frequency
distance between the closest modes as
well as from destructive interferences
between them.
• There is also a hole at 62 Hz although the
closest mode (63 Hz) is quite strong at
this position. This hole can only be
explained with destructive interferences
42. Alexis Baskind
The problem with room modes
When the modal density is too small at low frequencies
(i.e. for small rooms), the sound pressure level present
strong variations as a function of the position of the
source and of the listener.
Room Acoustics
Source: Thomas Görne, “Tontechnik”
Simulated position-dependent sound field in a rectangular room 3m x 3.40m x 2.40m
(Reverberation time ca. 0.5 s); sound pressure on the horizontal plane 1,2m above the floor at
80 Hz, 93 Hz, 109 Hz, 127 Hz; the level varies up to 40 dB as a fonction of position
43. Alexis Baskind
Modes and Modal Density: Summary
• Modes can also interfere in a destructive way
• The position of the loudspeakers and the listening position are
extremely important for the linearity of reproduction at low
frequency
So there are 3 possible causes for amplitude dips at low
frequencies:
1. The loudspeaker or the listening point is at a node of a room
mode
2. The frequency lies between 2 modes with a big frequency
distance between their eigenfrequencies
3. The frequency lies between 2 modes with a small
distancebetween their eigenfrequencies, but the two modes
interfere in a destructive way at the listening position
Room Acoustics
44. Alexis Baskind
Modes and Modal Density: Summary
• If the modal density is too small:
1. There will be amplitude dips between the eigenfrequencies
2. The amplitude varies a lot for a given position with respect to
position
• If the modal density is big enough:
1. The distance between the modes is smaller
2. The amplitude for a given frequency depends on several
modes => less influence of position, less destructive
interferences, the room sound field is more diffuse
The bigger the modal density, the better
• Room modes are especially problematic in small rooms,
for which the modal density is often too small at low
frequencies
Room Acoustics
45. Alexis Baskind
Schroeder-Frequency
• The Schroeder-Frequency provides an order of magnitude
of the frequency region above which the modal density is
big enough (>=3) to consider the room sound field as
diffuse
• It can be calculated as follows:
• This means:
– The bigger the room, the smaller the Schroeder-Frequency
– The drier the room , the smaller the Schroeder-Frequency
Small listening rooms must be dry in order to minimize linear
distortions at low frequencies
Room Acoustics
Fs» 2000
T60
V
(T60 is the reverberation time in this frequency region, V
is the room volume)
46. Alexis Baskind
Acoustics of Listening Rooms
The ITU-R BS.1116-1 recommendation suggests that:
• The average reverberation time, measured over
the frequency range 200 Hz to 4 kHz, should be:
… where V is the volume of the room in m3
RTm = 0.25
V
100
3 (s)
Room Acoustics
47. Alexis Baskind
Acoustics of Listening Rooms
The ITU-R BS.1116-1 recommendation suggests that:
• The reverberation time stays in the given limits:
RTm
Room Acoustics
48. Alexis Baskind
Outline
1. Time-Space perspective: Sound propagation in a
room
2. Frequency-Space perspective: Room modes
3. Time-Frequency perspective
4. Room acoustics design
5. Room acoustics of listening rooms
6. Spatial hearing in a room
Room Acoustics
49. Alexis Baskind
Time-frequency model of a reverberation
• Time and frequency approaches can be grouped in a single model:
Room Acoustics
Frequency (Hz)
Time (s)
Modes
Early reflections
Diffuse reverberation
50. Alexis Baskind
Waterfall View
• The Waterfall view is a time-frequency representation of a measured
room response:
Room Acoustics
Frequency (Hz)
Time (ms)
Level (dB)
51. Alexis Baskind
Waterfall View
• The Waterfall view shows very well the frequency
dependence of the late decay (see later)
• On small rooms, the low-frequency modes are also
quite visible
• It gives in general more information as the
frequency response (since it also shows thetime
evolution of the spectrum)
• But: the time resolution is very low. Among others,
it does not reveal the early reflections
Room Acoustics
52. Alexis Baskind
Outline
1. Time-Space perspective: Sound propagation in a
room
2. Frequency-Space perspective: Room modes
3. Time-Frequency perspective
4. Room acoustics design
5. Room acoustics of listening rooms
6. Spatial hearing in a room
Room Acoustics
53. Alexis Baskind
Room acoustics design
• The first step and requirement for the acoustic design of a
room is the stipulation of the desired reverberation time
• The required reverberation time depends on the usage of
the room (recording room, listening room, concert hall,
teaching room etc.). There are specific recommandation for
each kind of room: for instance, a listening room is
designed to be typically drier as a recording room
• Based on the reverberation time, the room dimensions and
the construction materials (concrete, dry wall, wood...), a
selection of absorbing, diffusive and reflective surfaces is
being made in order to reach the required reverberation
time and optimize the acoustics
Room Acoustics
54. Alexis Baskind
Prediction of the Reverberation Time
• Several (partly empirical) formulas provide an estimation of the
reverberation time. The most well known are from Sabine (1898)
and Eyring (1920)
=> Sabine Formula (for low absorptions coefficients): the surfaces
are categorized by their material, thus their absorption properties:
… with: V = Room volume in m3
αi is the absorption coefficient for the surface Si
The product αi.Si is called equivalent absorption area (unit =
Sabins).
• Since the absorption coefficient depends on frequency, the
reverberation time also depends on frequency
Room Acoustics
𝑇60 ≈ 0.161
𝑉
𝛼𝑖 𝑆𝑖𝑖
56. Alexis Baskind
Frequency-dependent absorption
• Reverberation time is typically bigger at low frequencies, since
most absorbers are not efficient for big wavelengths:
Room Acoustics
Example: Reverberation time as a function of frequency for 3 concert halls
57. Alexis Baskind
Sound Absorbers
• Absorbers are usually classified in 3 categories
Room Acoustics
. Porous absorber
(=velocity-based
absorber)
=> Used as wideband
absorbers if they are
thick enough
1/ Resonant absorbers (=pressure-based absorbers)
. Membrane absorbers
. Helmholtz-Absorber: with holes or slots
2/ „Tube traps“
(3/ active bass traps)
Absorptioncoefficient
High-frequency absorber mid-frequency absorber low-frequency absorber
Frequency
58. Alexis Baskind
Porous Absorbers
• Porous Absorber are velocity-based absorbers: they reach
a maximum of efficiency at positions where the sound
velocity is maximum
• The sound velocity is maximum at zeros of the sound
pressure (=nodes)
Room Acoustics
• This means for standing waves, that the
maximum of efficiency is reached for a
distance to the wall of λ/4, 3λ/4, 5λ/4,
etc.
blue: sound pressure
red: sound velocity
59. Alexis Baskind
Porous Absorbers
This means: the lower cutoff frequency of absorption
depends on the thickness of the absorber
Room Acoustics
red: sound velocity for standing waves with various wavelengths
gray: porous absorber
high frequencies: several maxima of the sound velocity in
the absorber => maximum efficiency
Lower cutoff frequency: the first maximum of sound
velocity is at the limit between absorber and air
Low frequencies: maxima of the sound velocity are
outside the absorber => lower efficiency
60. Alexis Baskind
Porous Absorbers
This means: the lower cutoff frequency of absorption
depends on the thickness of the absorber
Room Acoustics
Example: simulated absorption coefficient for two different thicknesses
(source: www.acousticmodelling.com)
61. Alexis Baskind
Porous Absorbers
Room Acoustics
High-frequency
absorber
High-frequency absorber with increased
absorption surface
Corner absorbers: often sold as als „bass traps“, but
typically efficient above 100-200 Hz and almost useless
at lowest frequencies
62. Alexis Baskind
Porous Absorbers
A possibility to increase the efficiency at low frequencies is to
place the absorber at a certain distance with the reflecting
surface => for instance usefull for ceiling absorbers
Room Acoustics
red: sound velocity for standing waves with various wavelengths
gray: porous absorber
High frequency Frequenzen: several maxima of the sound
velocity in the absorber => maximum efficiency (although
bigger dependence on the wavelength)
smaller (but not zero-) efficiency
Again good efficiency, since the first maximum of the
sound velocity is within the absorbing material
Air gap
63. Alexis Baskind
Porous Absorbers
Room Acoustics
Example: simulated absorption coefficient with and without air gap
(source: www.acousticmodelling.com)
Porous Absorber with air gap with reflecting surface
64. Alexis Baskind
Resonant Absorbers
• Resonant absorber are pressure-based absorbers: they
reach a maximum of efficiency at positions where the
sound pressure is maximum: this means against the walls
and room corners
• Resonant absorbers are harmonic oscillators and work like
spring-mass systems. This means:
– The absorption is achieved thanks to friction. Without friction,
the energy may actually be amplified instead of absorbed
– The resonance frequency:
• Increases with the spring constant (stiffness)
• Decreases with increasing mass
• Decreases with increasing friction
– The bandwidth increases with friction
Room Acoustics
65. Alexis Baskind
Membrane absorbers
Room Acoustics
Source: Heinrich Kuttruff,
“Room Acoustics”
• Membrane absorbers consist in a thin
oscillating rigid or soft membrane (typically
wooden) clamped with a spacing to the
ceiling or wall. The enclosure is airtight and
partly filled with absorbing (porous) material
• The mass is the masse of the membrane
• The stiffness depends on the volume of air
and absorbing material in the enclosure, and
partly also on the elasticity of the membrane
and clamping
• Friction takes place partly in the wood but
mostly in the absorbing material
66. Alexis Baskind
Perforated plates, slat absorbers
Room Acoustics
Source: Heinrich
Kuttruff, “Room
Acoustics”
• Perforated plates and slit absorbers work
as Helmholtz resonators: the panel does
not vibrate, but the air in the openings
(holes or slots)
• The resonance frequency depends on the
geometry (thickness and width of the
openings), width of the air volume.
Source: topakustik.ch
67. Alexis Baskind
Perforated plates, slat absorbers
Room Acoustics
Perforated Panel with Porous Absorber
Properties of panel Display options
Panel thickness (tp) 6,0 mm 0,236 in Start graph at 62,5 Hz Eq 6.8
Repeat distance (D) 25,0 mm 0,984 in To see the graph in the standard
Hole radius (a) 10,0 mm 0,394 in analysis frequencies, select
Open Area ( ) 50,27% Show subdivisions of "Whole Octaves" and set the
Properties of cavity starting frequency to 62.5Hz
Cavity depth (d) 100,0 mm 3,937 in
Absorber thickness (ta) 10,0 mm 0,394 in
Air space in cavity (d - ta) 90,0 mm 3,543 in This is ignored for the "No Air Gap" plot. Cavity assumed to be filled with absorber.
Absorber flow resisitivity 10 000 rayls/m
This plot is a simplification of reality because it is only calculated for normal incident sound.
2 f
2 /
Eq 5.19
Eq 5.20
Eq 5.11
Eq 5.9
Eq 5.10
Eq 5.26
Eq 5.27
Eq 6.15
Eq 6.26
Eq 1.22
Eq 1.25
Eq 6.22
Eq 6.23
Eq 6.24
0,00
0,10
0,20
0,30
0,40
0,50
0,60
0,70
0,80
0,90
1,00
62,5
70
79
88
99
111
125
140
157
177
198
223
250
281
315
354
397
445
500
561
630
707
794
891
1000
1122
1260
1414
1587
1782
2000
2245
2520
2828
3175
3564
4000
4490
5040
5657
6350
7127
8000
8980
10079
11314
12699
14254
16000
Absorption
Frequency (Hz)
Normal incidence absorption Absorber against panel Absorber against backing No Air Gap
a/
b/
c/
• The absorption properties depend also on the
position and thickness of the material
68. Alexis Baskind
Outline
1. Time-Space perspective: Sound propagation in a
room
2. Frequency-Space perspective: Room modes
3. Time-Frequency perspective
4. Room acoustics design
5. Room acoustics of listening rooms
6. Spatial hearing in a room
Room Acoustics
69. Alexis Baskind
Acoustics of Listening Rooms
Room dimensions
• Most important: a listening room (and the position
of the loudspeakers) should have a symmetry
axis!
• It should be big
– Room modes are lower in frequency and the modal
density is bigger
– Reflections do not arrive too early (to avoid a “boxy”
sound)
100 m3 (it would correspond for example to 6m x 6m x
3m if it were rectangular) is the reference volume in
the ITU-R BS.1116-1 recommendation
Room Acoustics
70. Alexis Baskind
Acoustics of Listening Rooms
• A listening room should not be too dry
– Unnatural sound
– Tendency to add too much artificial reverberation in
the mix
– Need for a certain amount of short reverberation
(typically 0.25 – 0.3 s)
– Need for envelopment => late reflections
• But it should not be too live as well
– Lack of precision
– Spectral effects (because of early reflections)
Room Acoustics
71. Alexis Baskind
Acoustics of Listening Rooms
The ITU-R BS.1116-1 recommendation suggests that:
• The reverberation time stays in the given limits:
Room Acoustics
RTm
72. Alexis Baskind
Acoustics of Listening Rooms
For mid and high frequencies (> 200 Hz)
• There should not be flutter echoes => no parallel
walls (otherwise put absorbers or diffusors)
• The ceiling and the floor as well can create flutter
echoes => ceiling should not be horizontal
(otherwise put absorbers or diffusors)
Room Acoustics
73. Alexis Baskind
Acoustics of Listening Rooms
• Too loud early reflections (< 15ms) entail comb-
filtering and alteration of the stereo image
• The ITU-R BS.1116-1 recommendation suggests
that:
“Early reflections caused by the boundary surfaces of
the listening room, which reach the listening area
during a time interval up to 15 ms after the direct
sound, should be attenuated in the range 1-8 kHz by
at least 10 dB relative to the direct sound.”
Room Acoustics
74. Alexis Baskind
Acoustics of Listening Rooms
The fluctuations of the frequency responses are mostly
determined by the early reflections (comb-filtering)
Room Acoustics
Influence of the early reflections
Example:
measurement of a
listening room,
frequency response
for the direct sound
only
75. Alexis Baskind
Acoustics of Listening Rooms
The fluctuations of the frequency responses are mostly
determined by the early reflections (comb-filtering)
Room Acoustics
Influence of the early reflections
Example:
measurement of a
listening room,
frequency response
for the first 1.3 ms
76. Alexis Baskind
Acoustics of Listening Rooms
The fluctuations of the frequency responses are mostly
determined by the early reflections (comb-filtering)
Room Acoustics
Influence of the early reflections
Example:
measurement of a
listening room,
frequency response of
the whole room
response
77. Alexis Baskind
Acoustics of Listening Rooms
The ITU-R BS.1116-1 recommendation suggests that the
frequency response stays in the given limits:
Room Acoustics
Frequency response
78. Alexis Baskind
Example 1: LEDE
• LEDE-design (“Live-End-Dead-End”), proposed in
1979, aims at reducing the early reflections while
keeping enough late diffusion (for the
envelopment)
Room Acoustics
(Source: F.
Rumsey, Spatial
Audio)
79. Alexis Baskind
Example 2: RFZ
• With RFZ-design („Reflection-free zone“), proposed in 1984,
early reflections are not any more strongly absorbed but
deviated from the zone around the sweet spot
• Like with LEDE, the back wall is diffusive (and not
absorbing), so that the room does not become to dry
Room Acoustics
80. Alexis Baskind
Outline
1. Time-Space perspective: Sound propagation in a
room
2. Frequency-Space perspective: Room modes
3. Time-Frequency perspective
4. Room acoustics design
5. Room acoustics of listening rooms
6. Spatial hearing in a room
Room Acoustics
81. Alexis Baskind
Perception of distance
• As explained above, the perceived distance to the
sound source depends on:
– The direct-to-reverberant ratio: the softer the direct
sound with respect to reverberation, the farther the
source is localized
– The initial time delay gap: the smaller the ITDG, the
farther the source is localized
– The lateralness of the early reflections: the source is
localized farther if the early reflections come from the
front as if they come from the sides
Room Acoustics
82. Alexis Baskind
Perception of the room size
• Human Hearing uses two cues to judge the size of a
room:
– The reverberation time is the major parameter
– The time distribution of the early reflections are
considered to provide extra cues, but only in extreme cases
Room Acoustics
A reverberant chamber is a small
but very reverberant room. It’s
meant to simulate big halls, and it
works somehow well, even if the
early reflections are “too” early
83. Alexis Baskind
Clarity
• The Clarity of a room for a given seat is the ability to
understand the message (usually speech) driven by
the source
• Clarity is known to depend on three factors:
– The quantity of early reflections after the echo threshold
(typically 20-30 ms for percussions, 50-60 ms for speech,
80-100 ms for signals without clear transients): early
echoes can heavily damage the clarity of the sound !
– The direct-to-reverberant ratio: reverberation can partly
mask the direct sound and reduce clarity
– Reflections in the direction of the source damage the clarity
more than lateral reflections (see cocktail-party effect and
comb filtering)
Room Acoustics
84. Alexis Baskind
Clarity
• Examples (from David Griesinger)
Room Acoustics
• Dry speech
– Note the sound is uncomfortably close
• Mix of dry with early reflections at -5dB.
– The mix has distance (depth), and is not muddy!
– Note there is no apparent reverberation, just depth.
• Same but with the reflections delayed 20ms at -5dB.
– Note also that with the additional delay the reflections begin to be heard as discrete
echos.
• But the apparent distance remains the same.
• Same but with the reflections delayed 50ms at -3dB
– Now the sound is becoming garbled. These reflections are undesirable!
– If the speech were faster it would be difficult to understand.
• Same but with reflections delayed 150ms at -12dB
– I also added a few reflections between 20 and 80ms at a level of -8dB to
smooth the decay.
– Note the strong hall sense, and the lack of muddiness.
85. Alexis Baskind
Apparent Source Width
• The Apparent Source width corresponds to the
perceived size of the source
• A point source in a non reverberant room will be
perceived as very narrow (equivalent of a
monophonic pan-potted sound)
• The presence of early lateral reflections (before 80-
120ms) blurs the time and intensity cues and creates
a (often pleasant) widening of the perceived source
• The reflections have to be lateral to create this effect.
Frontal reflections only modify the tone color
Room Acoustics
86. Alexis Baskind
Envelopment
• Envelopment is the sensation of being surrounded by the
diffuse field
• This sensation corresponds to the proportion of late lateral
reflections (after 100-150ms)
Room Acoustics
until ca. 100 ms:
widening
ca. 100-200
ms:
Envelopment
Perception of the room
Time
Perception of the source
Soundpressure
Direct sound
Early reflections
Late reverberation
87. Alexis Baskind
Reverberation Timbre
• The timbre of the reverberation („dark hall“,
„warm room“, „bright stage“, etc.) depends on the
ratio between reverberation times at low, mid and
high frequencies:
– For a „dark“ room, the reverberation time is relatively
longer at low frequencies
– For a „warm“ room, the reverberation time is relatively
longer at low-mids than at low and high frequencies
– A „bright“ room has similar reverberation times at low
and high frequencies
Room Acoustics