The document discusses acoustic textiles and summarizes:
1. Nonwovens are preferred for use as acoustic materials due to their porous structure, large surface area, and low production costs.
2. Sound absorption in fibrous materials occurs through frictional losses as sound pressure causes air molecules to oscillate within material interstices, and through momentum and temperature fluctuation losses.
3. A fabric's sound transmission loss increases with frequency, weight per unit area, and air resistance, but decreases with thickness and fiber density. Fabric microstructure also influences transmission loss.
Use of Textile for noise absorption application is a cost effective method which does not required additional energy source and acts as passive medium.
The document discusses the three fundamental interactions of sound with solid surfaces: reflection, absorption, and transmission. It describes different types of reflective and absorptive surfaces and materials used in architectural acoustics. These include porous and panel absorbers made of materials like open-cell foam that absorb sound energy. Proper use of reflective, absorptive, and diffusive surfaces and materials is important for acoustic design and controlling reverberation in spaces.
1. The document discusses various methods of noise control and sound insulation in buildings, including locating rooms away from noise sources, using insulating barriers, and considering both airborne and structure-borne noise.
2. Key approaches to noise reduction include using massive, rigid partitions to attenuate airborne noise and decoupling lightweight materials to reduce structure-borne noise.
3. Effective sound insulation depends on factors like the transmission loss value, absorption coefficient, and the relationship between the barrier area and room absorption. Heavier, more massive walls provide better insulation against outside airborne sounds.
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.
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 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.
The document discusses various acoustical materials used in architecture to control sound, including acoustical wall fiber, grass sheet, grass board, acoustical curtains, fibreglass blankets and rolls, acoustical carpets, and acoustic ceiling tiles. These materials help absorb unwanted sounds through properties like thickness, foam backing, and material composition to improve sound performances in buildings.
The document discusses acoustic textiles and summarizes:
1. Nonwovens are preferred for use as acoustic materials due to their porous structure, large surface area, and low production costs.
2. Sound absorption in fibrous materials occurs through frictional losses as sound pressure causes air molecules to oscillate within material interstices, and through momentum and temperature fluctuation losses.
3. A fabric's sound transmission loss increases with frequency, weight per unit area, and air resistance, but decreases with thickness and fiber density. Fabric microstructure also influences transmission loss.
Use of Textile for noise absorption application is a cost effective method which does not required additional energy source and acts as passive medium.
The document discusses the three fundamental interactions of sound with solid surfaces: reflection, absorption, and transmission. It describes different types of reflective and absorptive surfaces and materials used in architectural acoustics. These include porous and panel absorbers made of materials like open-cell foam that absorb sound energy. Proper use of reflective, absorptive, and diffusive surfaces and materials is important for acoustic design and controlling reverberation in spaces.
1. The document discusses various methods of noise control and sound insulation in buildings, including locating rooms away from noise sources, using insulating barriers, and considering both airborne and structure-borne noise.
2. Key approaches to noise reduction include using massive, rigid partitions to attenuate airborne noise and decoupling lightweight materials to reduce structure-borne noise.
3. Effective sound insulation depends on factors like the transmission loss value, absorption coefficient, and the relationship between the barrier area and room absorption. Heavier, more massive walls provide better insulation against outside airborne sounds.
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.
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 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.
The document discusses various acoustical materials used in architecture to control sound, including acoustical wall fiber, grass sheet, grass board, acoustical curtains, fibreglass blankets and rolls, acoustical carpets, and acoustic ceiling tiles. These materials help absorb unwanted sounds through properties like thickness, foam backing, and material composition to improve sound performances in buildings.
This document discusses acoustics and sound insulation in buildings. It defines acoustics as the science of sound, including how sound is generated, propagated, and perceived. Sound insulation aims to prevent the transmission of noise between spaces. Key techniques for sound insulation discussed include using absorbing materials, double wall constructions with cavities or insulation, floating floors with resilient materials or air gaps, and suspended ceilings with air spaces above the floor. Proper insulation of walls, floors, ceilings, doors, and windows is necessary to control noise transmission in residential buildings.
This document provides information about acoustics, lighting, and noise. It defines acoustics as the science of sound, and discusses topics within acoustics like noise control, sonar, and bioacoustics. It also defines key terms like velocity, frequency, sound intensity, and sound transmission. Additionally, it discusses the effects of noise pollution on hearing and health, and lists various types of sound absorbent materials like hair felt, acoustic plaster, and compressed fiberboard.
Factors affecting acoustic of building and their remediesDhrupal Patel
The document discusses various factors that affect acoustic quality in buildings, including reverberation time, loudness, focusing, echo, echelon effect, resonance, and noise. It provides explanations of each factor and potential remedies. Reverberation time can be optimized through the use of sound absorbing materials on walls, ceilings, floors, and furnishings. Loudness can be made more uniform through strategic placement of absorbers and use of reflecting surfaces. Curved surfaces should be avoided or covered to prevent focusing effects. Echoes and echelon effects are remedied by covering reflective surfaces. Resonance is addressed by ensuring tight fittings. Noise is categorized as airborne, structure-borne, or inside noise, each with corresponding
Architectural acoustics, New engineering materials ,ultrasoniKunj Patel
This document summarizes a physics presentation given by 5 students - Patel Harsh, Patel Hetul, Patel Jaina, Patel Kinjal, and Patel Kunj. The presentation covered three topics: Architectural Acoustics, New Engineering Materials, and Ultrasonics. For Architectural Acoustics, the document defines acoustics and discusses sound classification, characteristics, intensity, absorption materials, and factors affecting building acoustics. For New Engineering Materials, it discusses metallic glasses, bio-materials, and energy materials like solar cells. For Ultrasonics, it defines ultrasonic waves, methods of production like magnetostriction and piezoelectric, and applications of
This document discusses various topics related to sound and architectural acoustics. It defines sound as vibrations that travel through air or another medium and can be heard. It explains that sound travels in wave patterns called sound waves, which move by vibrating surrounding objects. Sound can move through air, water or solids. It also defines key terms like longitudinal waves, transverse waves, sound intensity, frequency, speed of sound, time period, amplitude, density and more. The document discusses factors that influence architectural acoustics like geometry, materials, generation of sound. It also discusses types of materials used like sound absorbers, diffusers, barriers and reflectors.
The document discusses noise control in architecture. It defines noise as unwanted sound and explains how sound intensity level is measured scientifically using a logarithmic scale. There are two main sources of noise: airborne noise transmitted through air, and structure-borne noise transmitted through building materials. Noise control techniques in architecture aim to reduce transmitted sound levels by selecting appropriate sound insulating materials and redirecting sound paths away from receivers using barriers. Case studies demonstrate how architectural design integrates these approaches.
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 various topics related to acoustics:
1. It defines acoustics as the study of mechanical waves in gases, liquids and solids, including vibration, sound, ultrasound and infrasound. Architectural acoustics deals with designing spaces for optimal sound.
2. Sound is classified by frequency into infrasound, audible sound, and ultrasound. Pitch is related to frequency, loudness to intensity, and timbre to sound quality. Reverberation is the persistence of sound after the source stops. Reverberation time is the time for sound to fall below audibility.
3. Factors like reverberation time, loudness, focusing, echo, and resonance
Acoustics Material Study - Architectural Acoustics - NIT TrichySabarathinam Kuppan
This document discusses various materials used for acoustic treatment of noise, including acoustic foams, polyurethane foams, asbestos products, balsa wood, brickwork, clinker block, concrete, lightweight concrete, glass, foamed glass, glass fibre wool, gypsum, mineral wool, lead sheets, lead/foam sandwiches, lead-loaded plastic sheets, and leaded plastics. It provides details on the sound absorbing and insulating properties of these materials.
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
Sound absorption insulation uses materials with numerous holes and fissures to resist sound from reflecting into a room. Acoustical ceiling tiles and panels are the most common type of sound absorption insulation that contains many small holes to trap sound waves.
This document discusses sound insulation and soundproofing. It defines key terms like sound, decibel, and reverberation. Sound insulation refers to reducing sound transmission through building elements like walls and floors. Different materials have varying abilities to absorb or block sound transmission. Common sound insulating materials include glass/rock wool, foamed plastics, quiet batts, and studio foam. Proper room arrangement, solid walls, planning for single-story structures, balcony placement, and courtyards can help reduce unwanted noise in buildings. Mass and rigidity help materials resist sound, while openings decrease sound blocking ability.
The document discusses various topics related to indoor acoustics, including:
1) It defines sound and acoustics, and describes how acoustics applies to many aspects of modern society.
2) It discusses acoustic treatment in recording studios to improve sound quality and accuracy for monitoring.
3) It describes different room types commonly found in recording studios, such as the live room, control room, and isolation booths.
This document discusses architectural acoustics and provides information on sound classification, characteristics of musical sound, intensity, absorption coefficient, sound absorbing materials, reverberation, and factors affecting building acoustics such as reverberation time, loudness, focusing, echo, echelon effect, and resonance. It also covers noise control and discusses remedies for improving acoustics issues in buildings.
Acoustics is the science dealing with mechanical waves, including sound. It involves the study of sound propagation, absorption, and reflection. Acoustics consultants provide services related to architectural acoustics, noise control, vibration analysis, and modeling of sound. The spectrum of sound ranges from infrasound to ultrasound. Sound is transmitted through materials as longitudinal or transverse waves. Key characteristics of sound waves include amplitude, frequency, wavelength, and the decibel scale used to measure intensity.
This document discusses various types of acoustical materials used to control sound, including sound absorbers, diffusers, barriers, and reflectors. It provides details on common sound absorbing materials like acoustical foam panels, fabric-wrapped panels, wall coverings, ceiling tiles, and baffles. These materials use porous materials like foam, fiberglass, and fabrics to absorb sound waves. The document also briefly mentions sound diffusers which scatter sound reflections instead of absorbing them.
This document provides information about acoustic panel false ceilings. It discusses the components of a false ceiling including acoustic panels made from glass fiber and a bio-based binder. The panels have a Class A fire rating and are installed by snapping metal channels together in a grid and dropping the lightweight acoustic panels into the grid. Benefits of acoustic ceilings include sound absorption, hiding pipes and wires, and increased light reflection. A market survey for different acoustic panel companies and their product specifications is also included.
This document discusses acoustics and sound insulation in buildings. It defines acoustics as the science of sound, including how sound is generated, propagated, and perceived. Sound insulation aims to prevent the transmission of noise between spaces. Key techniques for sound insulation discussed include using absorbing materials, double wall constructions with cavities or insulation, floating floors with resilient materials or air gaps, and suspended ceilings with air spaces above the floor. Proper insulation of walls, floors, ceilings, doors, and windows is necessary to control noise transmission in residential buildings.
This document provides information about acoustics, lighting, and noise. It defines acoustics as the science of sound, and discusses topics within acoustics like noise control, sonar, and bioacoustics. It also defines key terms like velocity, frequency, sound intensity, and sound transmission. Additionally, it discusses the effects of noise pollution on hearing and health, and lists various types of sound absorbent materials like hair felt, acoustic plaster, and compressed fiberboard.
Factors affecting acoustic of building and their remediesDhrupal Patel
The document discusses various factors that affect acoustic quality in buildings, including reverberation time, loudness, focusing, echo, echelon effect, resonance, and noise. It provides explanations of each factor and potential remedies. Reverberation time can be optimized through the use of sound absorbing materials on walls, ceilings, floors, and furnishings. Loudness can be made more uniform through strategic placement of absorbers and use of reflecting surfaces. Curved surfaces should be avoided or covered to prevent focusing effects. Echoes and echelon effects are remedied by covering reflective surfaces. Resonance is addressed by ensuring tight fittings. Noise is categorized as airborne, structure-borne, or inside noise, each with corresponding
Architectural acoustics, New engineering materials ,ultrasoniKunj Patel
This document summarizes a physics presentation given by 5 students - Patel Harsh, Patel Hetul, Patel Jaina, Patel Kinjal, and Patel Kunj. The presentation covered three topics: Architectural Acoustics, New Engineering Materials, and Ultrasonics. For Architectural Acoustics, the document defines acoustics and discusses sound classification, characteristics, intensity, absorption materials, and factors affecting building acoustics. For New Engineering Materials, it discusses metallic glasses, bio-materials, and energy materials like solar cells. For Ultrasonics, it defines ultrasonic waves, methods of production like magnetostriction and piezoelectric, and applications of
This document discusses various topics related to sound and architectural acoustics. It defines sound as vibrations that travel through air or another medium and can be heard. It explains that sound travels in wave patterns called sound waves, which move by vibrating surrounding objects. Sound can move through air, water or solids. It also defines key terms like longitudinal waves, transverse waves, sound intensity, frequency, speed of sound, time period, amplitude, density and more. The document discusses factors that influence architectural acoustics like geometry, materials, generation of sound. It also discusses types of materials used like sound absorbers, diffusers, barriers and reflectors.
The document discusses noise control in architecture. It defines noise as unwanted sound and explains how sound intensity level is measured scientifically using a logarithmic scale. There are two main sources of noise: airborne noise transmitted through air, and structure-borne noise transmitted through building materials. Noise control techniques in architecture aim to reduce transmitted sound levels by selecting appropriate sound insulating materials and redirecting sound paths away from receivers using barriers. Case studies demonstrate how architectural design integrates these approaches.
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 various topics related to acoustics:
1. It defines acoustics as the study of mechanical waves in gases, liquids and solids, including vibration, sound, ultrasound and infrasound. Architectural acoustics deals with designing spaces for optimal sound.
2. Sound is classified by frequency into infrasound, audible sound, and ultrasound. Pitch is related to frequency, loudness to intensity, and timbre to sound quality. Reverberation is the persistence of sound after the source stops. Reverberation time is the time for sound to fall below audibility.
3. Factors like reverberation time, loudness, focusing, echo, and resonance
Acoustics Material Study - Architectural Acoustics - NIT TrichySabarathinam Kuppan
This document discusses various materials used for acoustic treatment of noise, including acoustic foams, polyurethane foams, asbestos products, balsa wood, brickwork, clinker block, concrete, lightweight concrete, glass, foamed glass, glass fibre wool, gypsum, mineral wool, lead sheets, lead/foam sandwiches, lead-loaded plastic sheets, and leaded plastics. It provides details on the sound absorbing and insulating properties of these materials.
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
Sound absorption insulation uses materials with numerous holes and fissures to resist sound from reflecting into a room. Acoustical ceiling tiles and panels are the most common type of sound absorption insulation that contains many small holes to trap sound waves.
This document discusses sound insulation and soundproofing. It defines key terms like sound, decibel, and reverberation. Sound insulation refers to reducing sound transmission through building elements like walls and floors. Different materials have varying abilities to absorb or block sound transmission. Common sound insulating materials include glass/rock wool, foamed plastics, quiet batts, and studio foam. Proper room arrangement, solid walls, planning for single-story structures, balcony placement, and courtyards can help reduce unwanted noise in buildings. Mass and rigidity help materials resist sound, while openings decrease sound blocking ability.
The document discusses various topics related to indoor acoustics, including:
1) It defines sound and acoustics, and describes how acoustics applies to many aspects of modern society.
2) It discusses acoustic treatment in recording studios to improve sound quality and accuracy for monitoring.
3) It describes different room types commonly found in recording studios, such as the live room, control room, and isolation booths.
This document discusses architectural acoustics and provides information on sound classification, characteristics of musical sound, intensity, absorption coefficient, sound absorbing materials, reverberation, and factors affecting building acoustics such as reverberation time, loudness, focusing, echo, echelon effect, and resonance. It also covers noise control and discusses remedies for improving acoustics issues in buildings.
Acoustics is the science dealing with mechanical waves, including sound. It involves the study of sound propagation, absorption, and reflection. Acoustics consultants provide services related to architectural acoustics, noise control, vibration analysis, and modeling of sound. The spectrum of sound ranges from infrasound to ultrasound. Sound is transmitted through materials as longitudinal or transverse waves. Key characteristics of sound waves include amplitude, frequency, wavelength, and the decibel scale used to measure intensity.
This document discusses various types of acoustical materials used to control sound, including sound absorbers, diffusers, barriers, and reflectors. It provides details on common sound absorbing materials like acoustical foam panels, fabric-wrapped panels, wall coverings, ceiling tiles, and baffles. These materials use porous materials like foam, fiberglass, and fabrics to absorb sound waves. The document also briefly mentions sound diffusers which scatter sound reflections instead of absorbing them.
This document provides information about acoustic panel false ceilings. It discusses the components of a false ceiling including acoustic panels made from glass fiber and a bio-based binder. The panels have a Class A fire rating and are installed by snapping metal channels together in a grid and dropping the lightweight acoustic panels into the grid. Benefits of acoustic ceilings include sound absorption, hiding pipes and wires, and increased light reflection. A market survey for different acoustic panel companies and their product specifications is also included.
This document provides details about the acoustics case study of the Jamshed Bhabha Hall at the National Centre for Performing Arts (NCPA) in Mumbai, India. It describes the location, founders, and neighboring sites. It also outlines the layout of the hall, including details about the main theatre space, experimental theatre, green rooms, doors, walls, ceilings, seating, floors, and lighting fixtures. The goal is to analyze the acoustics of the performance spaces through documentation of the physical design and construction features.
The document discusses various acoustic panel materials and their properties that can be used to improve acoustics in auditoriums. It describes acoustic panels made of sound absorbing cotton and aluminum frames that provide wide frequency sound absorption. It also mentions decorative acoustic wall panels that have both acoustic and decorative functions. Acoustic tiles, drywall, carpet, foam and eco-friendly absorption materials are outlined with their acoustic properties and applications in rooms where optimal sound is desired such as recording studios, theaters and meeting halls. Seating for auditoriums is also covered, describing molded foam, finishes and numbered/identified seats for ease of use.
Sound is a disturbance that passes through a medium as longitudinal waves, causing the sensation of hearing. The speed of sound differs depending on the molecular composition of the medium. When sound waves encounter barriers in an enclosed space, they can be reflected, absorbed, refracted, diffused, diffracted, or transmitted. Reflection occurs when the wavelength is smaller than the surface, causing the waves to hit the enclosure continuously until the energy reduces to zero. Absorption occurs when some of the wave's energy is lost through transfer to barrier molecules. Refraction is the bending of sound waves when passing between different media. [END SUMMARY]
Suspended ceilings are used to conceal structural features, pipes, ducts and provide acoustic and thermal insulation. Different types of grids are used including exposed, concealed and semi-concealed grids made of materials like metal, wood or gypsum board. Proper installation requires marking locations, installing perimeter trims and hangers before laying panels or tiles. Factors like fire resistance, lighting fixtures and sprinkler head clearance must be considered during installation and design of suspended ceilings.
Perfect relations at delphique 2010 compendium on social media discussionAnkit Khanna
Perfect Relations Digital recently shared their inputs on social media trends at MDI.They were the knowledge partners in the event conducted by the management school
The document describes the Volo Movable Wall system. It provides details on the extensive customization options for the walls, including a variety of material, lighting, and acoustic options. The walls can be configured to meet different privacy, branding, and space needs. They integrate seamlessly with other architectural elements and perform as well as or better than permanent walls. The walls are reusable and reconfigurable, allowing spaces to easily evolve over time without major construction.
C4706 Case Study - Acoustic Screen with Chevron LouvresChristian Senior
The document describes an acoustic screen project for an international construction company. An acoustic screen incorporating chevron louvres was designed, manufactured, and installed around existing roof-mounted cooling equipment to reduce industrial noise by 15dB and bring noise levels below ambient background levels. The screen was aesthetically designed to conform with architectural requirements and protect neighboring residential properties from noise as required by regulations.
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.
Susan Witterick Rosehill Case Study B S E CCapitaSymonds
Rosehill School conducted an acoustic case study to address the negative impacts of noise on children, especially those with special needs like autism spectrum disorder. Extensive research shows that noisy classroom environments can hurt children's memory, reading ability, motivation, attention, and learning outcomes. Rosehill created various quiet and sensory-controlled rooms to help children with auditory processing difficulties or sensory issues learn better in a low-noise setting tailored to their needs.
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.
Acoustic-The Way of Utilizing the Resource for Research and Technology Implem...ijtsrd
Acoustics is the study of small pressure waves or sound waves in air which can be detected by the human beings. The scope of acoustics is not limited and extended to lower and higher frequencies: ultrasound and infrasound. Acoustics now includes Structural vibrations and perception/travelling of sound is an area of acoustical research, for research purposes acoustics are considered, the propagation fluids like air and water. In such a case acoustics is a part of fluid dynamics. The outmost problem of fluid dynamics is that, the equations of motions are non-linear and this implies that an exact general solution of these equations is not available and need to be developed. Acoustics is a first order approximation in which non-linear effects are neglected. In classical acoustics the generation of sound is considered to be a boundary condition problem. The sound generated by a loudspeaker or any unsteady movement of a solid boundary are examples of the sound generation mechanism in classical acoustics. Turbulence is a chaotic motion dominated by non-linear convective forces but an accurate deterministic description of turbulent flows is not available, The famous Lighthill theory of sound generation by turbulence is used as an integral equation which is more suitable to produce approximations than that of a differential equation Next to Lighthill's approach which leads to order of magnitude estimate of sound production by complex flows. In this paper we produced the application of Acoustics, experiments, research done to utilize the benefits of the acoustics are reviewed much more in a better way to conceptually understand the concept and to deduce the equations of motion to build practical acoustics system and also concentration gone through the Acoustic refrigeration system. Prashanth H. K. | Keerthy Prasad B. | M. Gururaj Naik | Manjunatha G. D. | Murali G. E."Acoustic-The Way of Utilizing the Resource for Research and Technology Implementation to Domestic Equipments, An Introductory Overview" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-2 | Issue-4 , June 2018, URL: http://www.ijtsrd.com/papers/ijtsrd14599.pdf http://www.ijtsrd.com/engineering/mechanical-engineering/14599/acoustic-the-way-of-utilizing-the-resource-for-research-and-technology-implementation-to-domestic-equipments-an-introductory-overview/prashanth-h-k
PERFORMANCE OF TRANSMISSION LOSS ON HYBRID MUFFLER BY USING ROCK WOOL AND GLA...IJAMSE Journal
Muffler is categorized in two broad manners as absorptive muffler and reactive muffler. A Muffler
(silencer) is an important noise control element for reduction of machinery exhaust noise, fan noise, and
other noise sources involving the flow of gases. Reactive mufflers which reduce noise by reflecting sound
energy back to its source, and absorption mufflers, which absorb sound due to the energy dissipated in the
sound-absorbing material. The attenuation levels of these types of muffler are dependent on the frequency
of the noise source. Investigations on absorption mufflers have indicated that these have fairly good noise
attenuation over a relatively wide frequency band. The combination of both reactive and absorptive muffler
is termed as hybrid muffler. Hybrid muffler design may be expected to provide broadband high noise
attenuation and low pressure drop. Experimental Two load setup and Wave 1-D is used to predict the
transmission loss of hybrid muffler. Hybrid muffler generally includes the number of perforated tubes,
number of perforated baffles with absorptive materials like asbestos, rock wool, bensoil, powertex &
advantex etc. Transmission loss measurement using hybrid muffler is discussed in this paper. Various
sound absorption materials that are currently used for noise reduction are used. This paper shows the
acoustic performance of packed dissipative muffler with the variation in packing density of absorptive
material. Here easy available absorptive materials glass fiber & rock wool is used with same space. This
study is performed by taking four designs to observe the transmission loss performance by applying
different absorptive materials with different packing density.
This document reviews nonwoven acoustic textiles. It discusses how fiber parameters like size, type, and cross-section influence sound absorption properties. Process parameters like web formation and bonding methods are also important. Physical properties of nonwovens that impact sound absorption include thickness, density, airflow resistance, porosity, tortuosity, and the presence of an air gap behind the material. Fiber entanglement creates tortuous pathways that convert sound energy to heat through friction, improving absorption. Low density materials better absorb low frequencies, while denser structures perform better at high frequencies.
DYNAMIC RESPONSE RESEARCH OF U SHAPED PIPE WITH VISCOELASTIC DAMPINGVarakala Netha
1) The document analyzes the dynamic response of a U-shaped pipe with a viscoelastic damping layer to reduce vibration.
2) Finite element modeling is used to simulate the pipe with damping layer, accounting for cross-section deformation.
3) Experimental tests validate that the damping layer effectively reduces pipe vibration response by up to 79%, with positioning of the layer more influential than width.
Melamine Foam for Low Frequency Noise Control in UHV SubstationsSINOYQX
This paper conducts combined sound absorption experiments on melamine foam , micro-perforated plate, and foamed cement to obtain the sound absorption effects of different combination structures at different frequencies, which has important practical significance for practical engineering guidance.
This document summarizes an experimental and numerical study on controlling noise from a deep cavity with slanted walls at low Mach numbers. The study tested a rectangular cavity with a depth-to-length ratio of 1.5 and width-to-length ratio of 3 in a wind tunnel. Passive control using slanted front and rear walls was evaluated. Results showed that a slanted rear wall effectively suppressed tones by reflecting unsteadiness back into the shear layer, breaking up vortices. However, a slanted front wall enhanced tones by enlarging and accelerating vortices in the shear layer, intensifying impingement on the rear wall. Computational fluid dynamics simulations revealed the mechanisms of noise reduction and enhancement by the
HCL suggests solutions to reduce airborne noise being emitted by vacuum cleaners. It has been seen that blowers used in vacuum cleaners are the main source of airborne noise and blade wakes are unavoidable in turbo machines.Focus of this whitepaper is to understand how to reduce sound intensity of vacuum cleaners and studying its effects on human hearing. ERS division in HCL proposes the design of a spiral enclosure for the blower in the vacuum cleaner. HCL suggests solutions to reduce airborne noise being emitted by vacuum cleaners. ERS division in HCL proposes the design of a spiral enclosure for the blower in the vacuum cleaner.
Modeling ultrasonic attenuation coefficient and comparative study with the pr...IOSR Journals
Many phenomena can be responsible for the attenuation of sound through the suspensions depending on the nature of the particles of the fluid and the frequency range of interest. In particular we can make a distinction between the diffusion mechanisms corresponding to a geometric redirection of the incident wave and the dissipative phenomena, like the thermal and viscous losses. In this work, we are interested in propagation of the ultrasonic waves into suspensions of clay rigid particles with a size between 1 and 50 microns, for which the thermal phenomena and visco-inertial dominate. In this case the dipole diffusion of the wave induced differential motion between the dispersed phase (clay grain) and the continuous phase (distilled water) is coupled to the viscous dissipation in the matching motion of this brake. In this paper, we present the main theories known in calculating the ultrasonic attenuation and velocity coefficient. Such theories permit to take accounts all the orders of interaction, unlike the theoretical of multiple diffusion that remains limited to lower concentrations. Finally, the results calculated by the principal theories will be compared against earlier experimental results obtained from this work.
Underwater Sound Generation Using Carbon Nanotube Projectorschrisrobschu
The application of solid-state fabricated carbon nanotube sheets as thermoacoustic projectors is extended from air to
underwater applications, thereby providing surprising results. While the acoustic generation efficiency of a liquid immersed nanotube
sheet is profoundly degraded by nanotube wetting, the hydrophobicity of the nanotube sheets in water results in an air envelope
about the nanotubes that increases pressure generation efficiency a hundred-fold over that obtained by immersion in wetting alcohols.
Due to nonresonant sound generation, the emission spectrum of a liquid-immersed nanotube sheet varies smoothly over a wide
frequency range, 1-105 Hz. The sound projection efficiency of nanotube sheets substantially exceeds that of much heavier and thicker
ferroelectric acoustic projectors in the important region below about 4 kHz, and this performance advantage increases with decreasing
frequency. While increasing thickness by stacking sheets eventually degrades performance due to decreased ability to rapidly transform
thermal energy to acoustic pulses, use of tandem stacking of separated nanotube sheets (that are addressed with phase delay) eliminates
this problem. Encapsulating the nanotube sheet projectors in argon provided attractive performance at needed low frequencies, as
well as a realized energy conversion efficiency in air of 0.2%, which can be enhanced by increasing the modulation of temperature.
This document discusses industrial range measurement applications using acoustic level measurement technology. It provides an overview of the technology, noting that it works by measuring the time between sending a sound pulse and receiving an echo. It then discusses various challenges with the technology, such as how changes in the speed of sound can affect accuracy, and how factors like dust, pressure changes, obstructions, air currents, and target properties can impact performance. It provides details on how acoustic level measurement systems function and select operating frequencies.
Measurement of material volumes in a cylindrical silo using acoustic wave and...journalBEEI
This work presents an approach for measuring material volumes in a closed cylindrical silo by using acoustic waves and resonance frequency analysis of silo’s acoustic systems. With an assumption that the acoustical systems were linear and time-invariant, frequency responses of the systems were identified via measurement. A sine sweep was generated, amplified and fed to a loudspeaker inside the silo. Acoustic waves were picked up by a microphone and processed to yield the silo's frequency response. Resonance frequencies and wave mode numbers of standing waves in the frequency range below 900 Hz were analyzed and used for calculation of air-cavity lengths. With known silo's dimension, the material volume estimations were achieved. Sets of experiments for estimating volumes of sand, cement, water, rice grain, and stone flakes in a closed silo, were done. It was found that the approach could successfully estimate the volumes of sand, cement, and water with a satisfactory accuracy. Percent errors of the estimations were less than 3% from the actual volumes. However, the approach could not estimate the volume of rice grain and stone flakes, since their sound refractions were neither resulted in standing waves nor acoustical modes in the silo.
APPLICATION OF TAGUCHI METHOD FOR PARAMETRIC STUDIES OF A FUNNEL SHAPED STRUC...ijmech
In this paper, attempt has been made to minimize sound reflection from the wall by using Taguchi’s method and to find optimal structure for the suggested test-section inside the cavitation tunnel. The suggested structure which was added to the test-section is funnel-shaped with a performance like a check valve. In order to obtain approximate values of five independent parameters, three levels were taken into account for each parameter. By combining parameters of different levels, 27 tests were designed using Taguchi’s method and Minitab Software. Different acoustic analyses were conducted in COMSOL Multiphysics software, and defined parameter of general reflection coefficient was obtained for 21 observer points. Applying the general reflection coefficients to Minitab Software and drawing the SNR graph, approximate values of the parameters were obtained. However, these values did not produce enough accuracy to design the optimal structure. For this reason, five levels around optimal values, obtained from the previous analysis, were considered for each parameter. Same steps were repeated again for the parameters at five
levels and optimal values were obtained. Optimal structure was modelled and analyzed. Consequently, appropriate defined parameters of general and local reflection coefficients were extracted which represented an optimal structure for the intended test section.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Tympanometry measures the impedance of the middle ear by varying the air pressure in the external auditory canal and measuring the amount of sound reflected off the tympanic membrane. It does this using a probe with three apertures: one presents a probe tone, another measures the reflected sound, and a third varies the air pressure from +300 to -600 mm of water. By changing the air pressure, the stiffness of the tympanic membrane is altered, allowing the amount of reflected sound to be measured at different pressures and evaluating the impedance matching function of the middle ear.
The document discusses air permeability, which is a measure of how well a fabric allows the passage of air through it. It defines air permeability and lists common units of measurement. The standard test method used is the Shirley air permeability tester, which measures the volume of air passing through a fabric under a pressure differential. The document outlines factors that influence air permeability, such as fiber properties, yarn structure, weave, finishing treatments, and environmental conditions.
The document summarizes an experiment that tested the effectiveness of different common materials for sound insulation. The materials tested included expanded polystyrene foam, stainless steel, wood, and paper. The experiment measured the sound reduction index and transmitted coefficient of each material at different frequencies. The results showed that stainless steel was the most effective at sound insulation, while expanded polystyrene foam and paper were the least effective. Common soundproofing techniques for homes using different materials were also discussed.
The document discusses several tests used to evaluate the properties of films and packages, including:
- Specular gloss measures the fraction of light reflected from a sample's surface.
- Haze measures the percentage of transmitted light that is scattered by a transparent sample.
- Transmittance measures the percentage of light transmitted through a translucent sample.
- Tear, tensile, and elongation tests measure a material's strength, flexibility, and resistance to tearing or breaking. Impact tests similarly evaluate a material's resistance to breaking from blows or impacts.
- Permeability tests like water vapor transmission measure how quickly gases pass through a material, important for evaluating moisture barriers.
Green Building Materials for Acoustics of an Auditorium - A Case Studyinventionjournals
ABSTRACT: In this paper we report the effectiveness of using coir mats – a green building material as an alternative to the less energy efficient and costly materials for acoustic absorption purposes. The most important parameter of the acoustic performance of an auditorium is the reverberation time(RT) which in turn depends on the sound absorption coefficient of materials layered on the floor, wall and ceiling. The present experimental case study carried out in auditoriums with coir mat fittings reveals that the coir mats are very effective in achieving the desired reverberation time for lecture and music concerts. Studies show a considerable reduction in the RT with the use of coir mats. An attractive feature of coir mats is its low cost, sustainable nature and indoor air quality without compromising the technical feasibility.
The experimental research at the University of California, Irvine Wind Tunnel Facility aims to understand how passive scalars are mixed by turbulent air flows. An electrically heated wire grid generates turbulence in the air, acting as a passive scalar. The decay of turbulence and approach to isotropy was analyzed by measuring velocity fields downstream of the grid. The power decay law was validated, with decay exponents of 1.504 and 1.389 for different turbulence intensities. A region of homogeneous isotropic turbulence was established, becoming isotropic farther downstream for higher flow speeds.
UiPath Test Automation using UiPath Test Suite series, part 6DianaGray10
Welcome to UiPath Test Automation using UiPath Test Suite series part 6. In this session, we will cover Test Automation with generative AI and Open AI.
UiPath Test Automation with generative AI and Open AI webinar offers an in-depth exploration of leveraging cutting-edge technologies for test automation within the UiPath platform. Attendees will delve into the integration of generative AI, a test automation solution, with Open AI advanced natural language processing capabilities.
Throughout the session, participants will discover how this synergy empowers testers to automate repetitive tasks, enhance testing accuracy, and expedite the software testing life cycle. Topics covered include the seamless integration process, practical use cases, and the benefits of harnessing AI-driven automation for UiPath testing initiatives. By attending this webinar, testers, and automation professionals can gain valuable insights into harnessing the power of AI to optimize their test automation workflows within the UiPath ecosystem, ultimately driving efficiency and quality in software development processes.
What will you get from this session?
1. Insights into integrating generative AI.
2. Understanding how this integration enhances test automation within the UiPath platform
3. Practical demonstrations
4. Exploration of real-world use cases illustrating the benefits of AI-driven test automation for UiPath
Topics covered:
What is generative AI
Test Automation with generative AI and Open AI.
UiPath integration with generative AI
Speaker:
Deepak Rai, Automation Practice Lead, Boundaryless Group and UiPath MVP
Maruthi Prithivirajan, Head of ASEAN & IN Solution Architecture, Neo4j
Get an inside look at the latest Neo4j innovations that enable relationship-driven intelligence at scale. Learn more about the newest cloud integrations and product enhancements that make Neo4j an essential choice for developers building apps with interconnected data and generative AI.
Climate Impact of Software Testing at Nordic Testing DaysKari Kakkonen
My slides at Nordic Testing Days 6.6.2024
Climate impact / sustainability of software testing discussed on the talk. ICT and testing must carry their part of global responsibility to help with the climat warming. We can minimize the carbon footprint but we can also have a carbon handprint, a positive impact on the climate. Quality characteristics can be added with sustainability, and then measured continuously. Test environments can be used less, and in smaller scale and on demand. Test techniques can be used in optimizing or minimizing number of tests. Test automation can be used to speed up testing.
Securing your Kubernetes cluster_ a step-by-step guide to success !KatiaHIMEUR1
Today, after several years of existence, an extremely active community and an ultra-dynamic ecosystem, Kubernetes has established itself as the de facto standard in container orchestration. Thanks to a wide range of managed services, it has never been so easy to set up a ready-to-use Kubernetes cluster.
However, this ease of use means that the subject of security in Kubernetes is often left for later, or even neglected. This exposes companies to significant risks.
In this talk, I'll show you step-by-step how to secure your Kubernetes cluster for greater peace of mind and reliability.
Essentials of Automations: The Art of Triggers and Actions in FMESafe Software
In this second installment of our Essentials of Automations webinar series, we’ll explore the landscape of triggers and actions, guiding you through the nuances of authoring and adapting workspaces for seamless automations. Gain an understanding of the full spectrum of triggers and actions available in FME, empowering you to enhance your workspaces for efficient automation.
We’ll kick things off by showcasing the most commonly used event-based triggers, introducing you to various automation workflows like manual triggers, schedules, directory watchers, and more. Plus, see how these elements play out in real scenarios.
Whether you’re tweaking your current setup or building from the ground up, this session will arm you with the tools and insights needed to transform your FME usage into a powerhouse of productivity. Join us to discover effective strategies that simplify complex processes, enhancing your productivity and transforming your data management practices with FME. Let’s turn complexity into clarity and make your workspaces work wonders!
In the rapidly evolving landscape of technologies, XML continues to play a vital role in structuring, storing, and transporting data across diverse systems. The recent advancements in artificial intelligence (AI) present new methodologies for enhancing XML development workflows, introducing efficiency, automation, and intelligent capabilities. This presentation will outline the scope and perspective of utilizing AI in XML development. The potential benefits and the possible pitfalls will be highlighted, providing a balanced view of the subject.
We will explore the capabilities of AI in understanding XML markup languages and autonomously creating structured XML content. Additionally, we will examine the capacity of AI to enrich plain text with appropriate XML markup. Practical examples and methodological guidelines will be provided to elucidate how AI can be effectively prompted to interpret and generate accurate XML markup.
Further emphasis will be placed on the role of AI in developing XSLT, or schemas such as XSD and Schematron. We will address the techniques and strategies adopted to create prompts for generating code, explaining code, or refactoring the code, and the results achieved.
The discussion will extend to how AI can be used to transform XML content. In particular, the focus will be on the use of AI XPath extension functions in XSLT, Schematron, Schematron Quick Fixes, or for XML content refactoring.
The presentation aims to deliver a comprehensive overview of AI usage in XML development, providing attendees with the necessary knowledge to make informed decisions. Whether you’re at the early stages of adopting AI or considering integrating it in advanced XML development, this presentation will cover all levels of expertise.
By highlighting the potential advantages and challenges of integrating AI with XML development tools and languages, the presentation seeks to inspire thoughtful conversation around the future of XML development. We’ll not only delve into the technical aspects of AI-powered XML development but also discuss practical implications and possible future directions.
Generative AI Deep Dive: Advancing from Proof of Concept to ProductionAggregage
Join Maher Hanafi, VP of Engineering at Betterworks, in this new session where he'll share a practical framework to transform Gen AI prototypes into impactful products! He'll delve into the complexities of data collection and management, model selection and optimization, and ensuring security, scalability, and responsible use.
In his public lecture, Christian Timmerer provides insights into the fascinating history of video streaming, starting from its humble beginnings before YouTube to the groundbreaking technologies that now dominate platforms like Netflix and ORF ON. Timmerer also presents provocative contributions of his own that have significantly influenced the industry. He concludes by looking at future challenges and invites the audience to join in a discussion.
Sudheer Mechineni, Head of Application Frameworks, Standard Chartered Bank
Discover how Standard Chartered Bank harnessed the power of Neo4j to transform complex data access challenges into a dynamic, scalable graph database solution. This keynote will cover their journey from initial adoption to deploying a fully automated, enterprise-grade causal cluster, highlighting key strategies for modelling organisational changes and ensuring robust disaster recovery. Learn how these innovations have not only enhanced Standard Chartered Bank’s data infrastructure but also positioned them as pioneers in the banking sector’s adoption of graph technology.
Alt. GDG Cloud Southlake #33: Boule & Rebala: Effective AppSec in SDLC using ...James Anderson
Effective Application Security in Software Delivery lifecycle using Deployment Firewall and DBOM
The modern software delivery process (or the CI/CD process) includes many tools, distributed teams, open-source code, and cloud platforms. Constant focus on speed to release software to market, along with the traditional slow and manual security checks has caused gaps in continuous security as an important piece in the software supply chain. Today organizations feel more susceptible to external and internal cyber threats due to the vast attack surface in their applications supply chain and the lack of end-to-end governance and risk management.
The software team must secure its software delivery process to avoid vulnerability and security breaches. This needs to be achieved with existing tool chains and without extensive rework of the delivery processes. This talk will present strategies and techniques for providing visibility into the true risk of the existing vulnerabilities, preventing the introduction of security issues in the software, resolving vulnerabilities in production environments quickly, and capturing the deployment bill of materials (DBOM).
Speakers:
Bob Boule
Robert Boule is a technology enthusiast with PASSION for technology and making things work along with a knack for helping others understand how things work. He comes with around 20 years of solution engineering experience in application security, software continuous delivery, and SaaS platforms. He is known for his dynamic presentations in CI/CD and application security integrated in software delivery lifecycle.
Gopinath Rebala
Gopinath Rebala is the CTO of OpsMx, where he has overall responsibility for the machine learning and data processing architectures for Secure Software Delivery. Gopi also has a strong connection with our customers, leading design and architecture for strategic implementations. Gopi is a frequent speaker and well-known leader in continuous delivery and integrating security into software delivery.
Observability Concepts EVERY Developer Should Know -- DeveloperWeek Europe.pdfPaige Cruz
Monitoring and observability aren’t traditionally found in software curriculums and many of us cobble this knowledge together from whatever vendor or ecosystem we were first introduced to and whatever is a part of your current company’s observability stack.
While the dev and ops silo continues to crumble….many organizations still relegate monitoring & observability as the purview of ops, infra and SRE teams. This is a mistake - achieving a highly observable system requires collaboration up and down the stack.
I, a former op, would like to extend an invitation to all application developers to join the observability party will share these foundational concepts to build on:
Dr. Sean Tan, Head of Data Science, Changi Airport Group
Discover how Changi Airport Group (CAG) leverages graph technologies and generative AI to revolutionize their search capabilities. This session delves into the unique search needs of CAG’s diverse passengers and customers, showcasing how graph data structures enhance the accuracy and relevance of AI-generated search results, mitigating the risk of “hallucinations” and improving the overall customer journey.
Building RAG with self-deployed Milvus vector database and Snowpark Container...Zilliz
This talk will give hands-on advice on building RAG applications with an open-source Milvus database deployed as a docker container. We will also introduce the integration of Milvus with Snowpark Container Services.
For the full video of this presentation, please visit: https://www.edge-ai-vision.com/2024/06/building-and-scaling-ai-applications-with-the-nx-ai-manager-a-presentation-from-network-optix/
Robin van Emden, Senior Director of Data Science at Network Optix, presents the “Building and Scaling AI Applications with the Nx AI Manager,” tutorial at the May 2024 Embedded Vision Summit.
In this presentation, van Emden covers the basics of scaling edge AI solutions using the Nx tool kit. He emphasizes the process of developing AI models and deploying them globally. He also showcases the conversion of AI models and the creation of effective edge AI pipelines, with a focus on pre-processing, model conversion, selecting the appropriate inference engine for the target hardware and post-processing.
van Emden shows how Nx can simplify the developer’s life and facilitate a rapid transition from concept to production-ready applications.He provides valuable insights into developing scalable and efficient edge AI solutions, with a strong focus on practical implementation.
Let's Integrate MuleSoft RPA, COMPOSER, APM with AWS IDP along with Slackshyamraj55
Discover the seamless integration of RPA (Robotic Process Automation), COMPOSER, and APM with AWS IDP enhanced with Slack notifications. Explore how these technologies converge to streamline workflows, optimize performance, and ensure secure access, all while leveraging the power of AWS IDP and real-time communication via Slack notifications.
Threats to mobile devices are more prevalent and increasing in scope and complexity. Users of mobile devices desire to take full advantage of the features
available on those devices, but many of the features provide convenience and capability but sacrifice security. This best practices guide outlines steps the users can take to better protect personal devices and information.
2. a strong influence on the structure-borne wave are the
bulk stiffness and the structural loss factor.
Specific air flow resistance is measured by measuring
the pressure change from one surface of the material to
the other at a given flow speed, and is expressed in
Pa*s/m, or mks rayls. Flow resistivity is the specific air
flow resistance per unit thickness, and in this paper is
expressed in mks rayls/mm.
When, in an automotive application, absorption is
desired at lower frequencies, and thickness and weight
are limited, materials with different specific air flow
resistances can be used to achieve desirable results.
However, increasing or decreasing the specific air flow
resistance to achieve a result at low frequency also has
an effect (sometimes adverse) on performance at high
frequencies. This paper presents the results of a study
of several different materials that illustrate this behavior.
METHODOLOGY
When a sound wave strikes a surface, a fraction of the
acoustic energy is absorbed, and the remainder is
reflected. The ratio of absorbed energy to incident
energy averaged over all possible angles of incidence is
the Sabine absorption coefficient (or the random
incidence absorption coefficient) of the surface.
The absorption coefficient of a material is measured by
introducing a sound source into a reverberant room,
terminating the sound source, and measuring the
resulting sound field decay. The material is then placed
in the room and the measurement is repeated.
To minimize laboratory-to-laboratory variation, purpose
built reverberation rooms are used to make
standardized measurements. Large-size reverberation
rooms allow for longer wavelengths and therefore lower-
frequency measurements, but also require large
samples (generally 6 m2
or greater) that can be difficult
to obtain. For this reason, the Alpha Cabin
(manufactured by Rieter AG) is used by various
automotive OEMs. The Alpha Cabin has a total volume
of 6.44 m3
, making it one-third the size of a typical
large-size reverberation room. The Alpha Cabin was
used for this study.
The Alpha Cabin equipment tests the sample one-third-
octave band at a time. First, a burst of sound, band-
pass-filtered to a third-octave band, is introduced into
the room via three loudspeakers and measured at each
of five microphone locations. The sound field decay
rate is recorded. Then another burst of sound is
introduced, band-pass-filtered to the next third-octave
band, and the decay rate measurement is repeated.
This process is repeated for each third-octave band
from 250 Hz to 10,000 Hz. Results are presented above
250 Hz for this study , but the small size of the Alpha
Cabin does not allow enough modes at frequencies
below 400 Hz to represent a diffuse field (due to the
long wavelengths of sound at frequencies lower than
400 Hz). In other words, results at frequencies below
400 Hz are presented, but should be viewed with a
certain amount of caution. The average decay rate is
calculated from the individual decay rates at the five
microphone positions for each third-octave band.
The sound absorption of the material is given by the
following formula:
−=
01
11
163.0
TT
VS
[4] where S is the absorption of the material in metric
Sabines, V is the volume of the room in m3
, and T0 and
T1 are the 60 dB decay times of the room in seconds
without and with the material, respectively.
The absorption coefficient is calculated using the
following formula:
=
A
S
92.0α
where α is the absorption coefficient and A is the
surface area of the material sample. 0.92 is the
correction factor to account for the differences between
the results in an Alpha Cabin and a full-size
reverberation room [4].
Note that measured Alpha Cabin absorption results can
exceed the theoretical maximum value of 1.0. This is a
result of the assumptions made in deriving the
absorption equation to calculate absorption from the
measured sound decay times. Sample edge diffraction
can also be a contributing factor.
The specific air flow resistance was measured using a
commercially available flow meter (Rieter CARE+
). This
meter is designed to provide a nondestructive
measurement of the specific air flow resistance of
materials and parts in the range 200 to 4000 mks rayls.
The CARE+
apparatus consists of a housing containing a
vacuum pump and instruments which measure pressure
and rate of flow. These instruments are connected to a
hand-held bell via two tubes. The bell consists of two
concentric cylinders through which air is drawn via a
vacuum pump. The unit measures the pressure
difference once the bell is placed directly over the
sample, and the specific airflow resistance of the
sample may then be calculated directly from this
pressure difference. The measurement differs from the
standard ASTM C522 measurement in that the air flow
is controlled rather than the pressure drop.
The edges of the sample are not sealed for such a test;
however, the use of concentric cylinders ensures an
essentially parallel airflow through the material beneath
the bell for most of the samples in question. The
apparatus includes a “check” to ensure that the pressure
3. difference measured in the outer cylinder and that
measured in the inner cylinder are similar; if the two
values are not close, it indicates that the airflow through
the material is not parallel (due, for example, to air
being drawn through the edges of the material), and that
the measurement is not reliable. This check was
employed for all of the samples tested, and parallel
airflow was present in all materials except those with
specific air flow resistance out of the range of the
CARE+
[5].
The thickness was measured using the Measurematic
thickness meter (manufactured by Randen
Technologies). The Measurematic measures thickness
of a material at a constant pressure between two parallel
plates.
STUDY
Ten manufacturers provided a total of 128 materials for
evaluation. The materials were supposed to range in
thickness from 5 mm to 25 mm; in reality, the thickness
ranged from 6.4 mm to 36.5 mm.
Several of the materials were needle punched blends of
cotton or plastic fibers (“shoddies”). Many of these
consist of post-industrial recycled fibers. Shoddies are
shown in Figure 1.
Figure 1. Shoddy
Several blown plastic fiber materials were tested as
well. Polyester and polypropylene are common plastic
materials used in absorbers. Plastic fibers are shown in
Figure 2.
Figure 2. Plastic Fiber
Some of the materials were lightweight microfibers.
These materials also consist of blown plastic fibers, but
have a higher loft and smaller fiber diameters. An
example of a microfiber material is shown in Figure 3.
Figure 3. Microfiber
Many of the samples were materials with no scrims or
embedded layers. However, many of them had scrim or
film layers. Some had layers of scrim or barrier
embedded inside the material. Several materials with
scrim-type layers are shown in Figure 4.
Figure 4. Materials with Scrims
Fiberglass materials were also tested, but not as many
of those as shoddy or PET as the former is not
commonly used for vehicle interior parts.
The materials are summarized in Table 1.
Suppl
ier
No. of
Materials
Material
Type
AFR
range
(mks
rayls)
Surface
Density
Range
(g/m2
)
Thickness
Range
(mm)
A 23 PET 21-2573 428-1748 8-26
B 9
Lightweight
Microfiber
279-
1643
179-670 7-24
C 17 Shoddy
124-
1426
708-1879 11-27
D 12 PET
139.5-
High
260-2428 10-27
E 14 PET
139.5-
1333
323-1068 7-21
F 16 PET 124- 696-1764 7-26
4. 2263
G 13 Fiberglass 62-682 255-634 6-23
H 7
Lightweight
Microfiber
124-
1054
250-667 10-32
I 4 Shoddy 155-320 672-1215 11-27
J 13 PET 83-816 204-684 7-37
Table 1. Material Descriptions
RESULTS
For brevity’s sake, the results of all 128 materials are
not given in detail. However, the results of the ten best
and ten worst performers are presented in Tables 2 and
3. The air flow resistivity (specific air flow resistance
divided by thickness), thickness and surface density
values are presented as well.
Material
Flow
Resistivity
(mks
rayls/mm)
Thickness
(mm)
Surface
Density
(g/m2
)
Scrim/Film
Average
alpha
D8 39.6 27 1998 Scrim* 0.942
B10a 68.6 24 670 Scrim 0.939
H7 33.3 32 666 Scrim 0.925
H5 33.5 31 667 Scrim 0.919
B8a 80.0 19 538 Scrim 0.909
D10 21.1 25 1455 Scrim 0.898
C17 35.0 27 1879 No* 0.897
H6 35.3 25 510 Scrim 0.891
D12 61.9 27 2428 Scrim* 0.886
B9a 38.3 20 508 no 0.873
*D8, C17, D12: Dual layer shoddy, scrim between layers (if applicable)
Table 2. Best Performers
Material
Flow
Resistivity
(mks
rayls/mm)
Thickness
(mm)
Surface
Density
(g/m2
)
Scrim/Film
Average
Alpha
A1 7.0 9 458 No 0.413
A5 6.6 9 473 No 0.419
E1 21.9 7 597 No 0.420
G3 10.7 9 259 No 0.451
A9 3.9 16 450 No 0.475
A3 34.6 8 1049 No 0.482
G1 38.6 6 317 No 0.484
JC 13.5 7 204 No 0.486
G9 5.2 12 255 No 0.494
A19 2.0 24 455 No 0.499
Table 3. Worst Performers
Typically, the noise reduction coefficient (NRC) is used
as a single index of absorption capability. The NRC is
an average of the absorption coefficients at 250 Hz, 500
Hz, 1000 Hz, and 2000 Hz. However, because the Alpha
Cabin only yields results down to 400 Hz, and because
high frequency performance is to be given detailed
consideration in the case of this study, the values at
each third octave frequency from 400 Hz and 10,000 Hz
are averaged to give a more accurate single-number
representation of the materials’ performance in the
Alpha Cabin.
A few initial observations can be made from Tables 2
and 3. No single material construction stood out as the
best (or worst) absorber. Plastic fibers can have very
good or very poor absorptive qualities. Several of the
best absorbers were lightweight fibers, and several of
the worst absorbers were fiberglass, but several of these
materials also ended up in the middle of the pack. A
similar observation can be made about surface density:
while the best performers had higher overall surface
densities than the worst performers, both sets contain
samples with a wide range of surface densities.
Eight of the 128 materials are discussed in greater detail
below. The specifications of these samples are given in
Table 3. These samples represent neither the best nor
the worst performers, but illustrate attributes that
contribute to the absorption performance.
Material Flow
Resistivity
(mks
rayls/mm)
Thickness
(mm)
Surface
Density
(g/m2
)
Scrim/
Film
Average
Alpha
E14 10.0 19 443 No 0.705
A19 2.0 24 455 No 0.499
B4a 18.3 10 279 Scrim 0.755
H1 11.7 11 250 No 0.531
F3 206.7 7 702 Scrim 0.601
E1 21.9 7 597 No 0.420
D11 168.0 28 1958 Scrim 0.650
F16 68.6 26 1001 Scrim 0.767
Table 3. Sample details
There is a strong trend where the thickest samples had
the highest absorption and the thinnest samples had the
lowest absorption. This is expected when the sound
absorption is dominated by the airborne sound wave as
described above. However, this trend was not hard and
fast. An example of an exception can be seen in Figure
1, which shows how sample E14, at 19 mm,
outperformed sample A19 at 24 mm.
Figure 5. Exception to Thickness Trend
5. It is noteworthy in the above example that the specific
air flow resistance of A19 was lower than that of E14.
This phenomenon indicates that both thickness and
specific air flow resistance must be taken into account
when considering the performance of a material.
As stated above, the specific air flow resistance in mks
rayls divided by the thickness in millimeters is the flow
resistivity, which for the materials in this study ranged
from 1.3 to 295 mks rayls/millimeter (as well as some
materials for which this coefficient could not be
calculated due to off-the-charts air flow resistance
values). The best performers were the thickest materials
that had a flow resistivity between 30 and 80.
Some of the worst performers also had a flow resistivity
in the 30-80 range, but were so thin that they were not
able to absorb much sound across the frequency
spectrum. Likewise, some of the worst performers were
“typical” thicknesses used in automotive applications
(15-25 mm), but their flow resistivity was low (in the
case of A9 and A19, shown in Table 2, less than 10).
When all of the samples are examined, it is evident that
the thinner the sample, the higher the flow resistivity
required to yield high absorption. In fact, a flow
resistivity that might be too high in a thicker sample
yields desirable absorption results in a thin sample –
particularly when compared with a sample of similar
thickness but low flow resistivity, as shown in Figure 2.
Figure 6. Flow Resistivity vs. Thickness
To dissipate sound, a sound absorber must perform two
functions. First, it must admit the sound into the
material, and then it must dissipate the sound as it
travels through the material. The two functions
represent competing demands of the material. The first
function relates to the acoustic impedance of the front
face, because the impedance mismatch causes sound
to be reflected from the front face of the material. As
the material is made thinner, more flow resistivity is
required to dissipate the sound because the dissipation
must take place in a shorter distance. Thus, higher flow
resistivity becomes much more important as the
material is made thinner.
If a thicker sample is relatively thick (25 mm and above)
it might be able to overcome a low flow resistivity, but if
the resistivity is too high, the absorption will be
compromised at higher frequencies, as shown in Figure
3. (However, in some cases absorption at lower
frequencies is more of a priority.)
Figure 7. Effect of High Flow Resistivity
The overall trends for all 128 of the samples support the
conclusion that higher flow resistivity is required for
thinner samples, as shown in Figure 8, which plots flow
resistivity against average alpha for thin and thick
samples.
Figure 8. Flow Resistivity vs. Average Alpha: Trends
6. The optimal flow resistivity for a thinner material is in
the range of 50-80 mks rayls/mm, while the optimal flow
resistivity for a thicker material is between 25-40 mks
rayls/mm.
Figure 9 below shows the relationship between specific
air flow resistance and average alpha of all 128
materials.
Figure 9. Specific Air Flow Resistance vs. Average Alpha: Trends
It is clear that regardless of thickness, the specific air
flow resistance that yields the highest absorption is
around 1000 mks rayls. It is also noteworthy that for
thicker materials, a wider range of specific air flow
resistance can yield good results than for thinner
materials.
CONCLUSION
The results show that sound absorption performance of
the porous materials used in automobiles is not so much
a function of type of material (cotton shoddy, PET, or
fiberglass), as it is a function of how well the material
construction can be executed to achieve desirable
properties for sound absorption. For open faced
materials or materials with a porous scrim, the flow
resistivity is very important. Put another way, what a
porous material is made of is less important than how
economically it can be processed to have desirable
acoustic properties.
The best material properties are a function of the
application such as the material thickness and boundary
conditions. Thinner materials require significantly more
flow resistivity than thicker materials; therefore,
materials that are nearly optimal in one application may
not work well in another application. However, a specific
air flow resistance of around 1000 mks rayls can yield
good overall absorption regardless of the thickness of
the material.
Material properties may be adjusted to produce more
absorption in one frequency range than another. For
example, the flow resistivity of a material may be
increased to improve absorption at lower frequencies at
the cost of lower absorption at higher frequencies.
One common method of increasing flow resistivity is the
addition of a flow resistant scrim or film layer, which
increases the specific air flow resistance without adding
too much weight or thickness. It is also possible to
increase the flow resistivity by increasing the surface
density of the material (adding density without changing
the thickness); however, this method adds weight, which
may be an issue in automotive applications.
In general, there is a wide range of acoustical
performance of different materials available for sound
absorption in the interior of an automobile. As material
changes are made, the performance of the materials
needs to be carefully compared either by modeling,
material testing, and/or vehicle testing.
ACKNOWLEDGMENTS
The authors would like to thank Ed Green and Dick
Wentzel of Roush Noise & Vibration for their
contributions. The authors would also like to thank Ford
Motor Company for sponsoring this study, as well as
each of the suppliers who contributed material.
REFERENCES
1. Allard, J.F., Propagation of Sound in Porous Media,
Springer, 1993.
2. Shiau, Nae-Ming, “Multi-Dimensional Wave
Propagation in Elastic Porous Materials With
Applications to Sound Absorption, Transmission,
and Impedance Measurement”, Purdue University,
1991.
3. Bolton, J.S., “Cepstral Techniques in the
Measurement of Acoustic Reflection Coefficients,
With Applications to the Determination of Acoustic
Properties of Elastic Porous Materials”, University of
Southampton, 1984.
4. “Instructions for the use of the Alpha Cabin”,
Technical Report No. 848, Rieter (Interkeller SA),
1993.
5. “The Rieter Automotive Systems CARE+
: Apparatus
for the non-destructive Measurement of the Air-flow
Resistance of materials and parts”, Rieter
Automotive Systems, 2000.
7. The optimal flow resistivity for a thinner material is in
the range of 50-80 mks rayls/mm, while the optimal flow
resistivity for a thicker material is between 25-40 mks
rayls/mm.
Figure 9 below shows the relationship between specific
air flow resistance and average alpha of all 128
materials.
Figure 9. Specific Air Flow Resistance vs. Average Alpha: Trends
It is clear that regardless of thickness, the specific air
flow resistance that yields the highest absorption is
around 1000 mks rayls. It is also noteworthy that for
thicker materials, a wider range of specific air flow
resistance can yield good results than for thinner
materials.
CONCLUSION
The results show that sound absorption performance of
the porous materials used in automobiles is not so much
a function of type of material (cotton shoddy, PET, or
fiberglass), as it is a function of how well the material
construction can be executed to achieve desirable
properties for sound absorption. For open faced
materials or materials with a porous scrim, the flow
resistivity is very important. Put another way, what a
porous material is made of is less important than how
economically it can be processed to have desirable
acoustic properties.
The best material properties are a function of the
application such as the material thickness and boundary
conditions. Thinner materials require significantly more
flow resistivity than thicker materials; therefore,
materials that are nearly optimal in one application may
not work well in another application. However, a specific
air flow resistance of around 1000 mks rayls can yield
good overall absorption regardless of the thickness of
the material.
Material properties may be adjusted to produce more
absorption in one frequency range than another. For
example, the flow resistivity of a material may be
increased to improve absorption at lower frequencies at
the cost of lower absorption at higher frequencies.
One common method of increasing flow resistivity is the
addition of a flow resistant scrim or film layer, which
increases the specific air flow resistance without adding
too much weight or thickness. It is also possible to
increase the flow resistivity by increasing the surface
density of the material (adding density without changing
the thickness); however, this method adds weight, which
may be an issue in automotive applications.
In general, there is a wide range of acoustical
performance of different materials available for sound
absorption in the interior of an automobile. As material
changes are made, the performance of the materials
needs to be carefully compared either by modeling,
material testing, and/or vehicle testing.
ACKNOWLEDGMENTS
The authors would like to thank Ed Green and Dick
Wentzel of Roush Noise & Vibration for their
contributions. The authors would also like to thank Ford
Motor Company for sponsoring this study, as well as
each of the suppliers who contributed material.
REFERENCES
1. Allard, J.F., Propagation of Sound in Porous Media,
Springer, 1993.
2. Shiau, Nae-Ming, “Multi-Dimensional Wave
Propagation in Elastic Porous Materials With
Applications to Sound Absorption, Transmission,
and Impedance Measurement”, Purdue University,
1991.
3. Bolton, J.S., “Cepstral Techniques in the
Measurement of Acoustic Reflection Coefficients,
With Applications to the Determination of Acoustic
Properties of Elastic Porous Materials”, University of
Southampton, 1984.
4. “Instructions for the use of the Alpha Cabin”,
Technical Report No. 848, Rieter (Interkeller SA),
1993.
5. “The Rieter Automotive Systems CARE+
: Apparatus
for the non-destructive Measurement of the Air-flow
Resistance of materials and parts”, Rieter
Automotive Systems, 2000.