Wind turbines produce noise from aerodynamic and mechanical sources. Aerodynamic noise from airflow over the blades is the largest contributor. The sound is amplitude modulated by blade rotation. Wind turbine noise is perceived as more annoying than constant noise due to its unpredictable nature. Noise levels decrease with distance from the turbine following laws of spherical spreading and atmospheric absorption. Low frequency noise and infrasound may be issues for some turbines operating downwind of towers. Regulations establish noise limits and setback distances to minimize community impact.
The document provides terminology definitions related to noise control and acoustics. It defines key terms like insertion loss, noise reduction coefficient, sound pressure level, sound intensity level, octave bands, and more. It also discusses fundamental noise control concepts like frequency, sound pressure, sound power levels, and subjective loudness changes. The document is an engineering guide for noise control that refers the reader to a Price Industries HVAC handbook for more information on the topic.
EXPONENTIAL HORN - DESIGN,COMPUTER MODELING, CONSTRUCTION, MEASUREMENTS AND D...Bert Chenin
Design, Advanced Computer Modeling, Measurements and Discussion of a high efficiency tri-amplified speaker consisting of a low frequency vented enclosure (Bass Reflex), a hybrid conical/exponential midrange horn and a compression tweeter. The bass enclosure is modeled using BassBox Pro. The horn is 3D modeled using Hornresp. The measurements are made with SoundEasy with a full MLS (minimum length signal) implementation using the Ground Plane method and the Near-Field method.
This document provides an overview of sound from a mathematical perspective. It discusses how sound is created through vibration, its propagation as a longitudinal pressure wave, and how frequency and wavelength are related through the speed of sound. The speed of sound varies according to the medium and environmental factors like temperature. Sound intensity decreases with the inverse square of distance from the source and is measured on the decibel scale. Common sources of sound production are also examined, including vocal cords, speakers, and musical instruments like the French horn.
Noise is unwanted sound that varies air pressure in ways detectable by human ears. Common sources of noise pollution include traffic, industrial equipment, construction, and crowds. Noise is measured in decibels and standards set maximum levels for different land uses and times of day. Noise can be mitigated by modifying sources, transmission paths, or protecting receivers.
The document discusses key concepts in acoustics including sound reflection, absorption, diffraction, standing waves, reverberation time, room modes, and the inverse square law. It explains how reverberation time can be calculated using the Sabine equation and lists common absorption coefficients for various materials. Finally, it defines binaural hearing and the differences between mono and stereo audio formats.
Absorption Coefficients
The Sabine Equation
Reverb Calculation Example 1
Estimating the Reverberation Time
Reverb Calculation Example 2
Correcting the Reverberation Time
Control of Interfering Noise
Absorbers
Recording Solutions
b. 3 to 1 Rule
c. Working in Mono
d. Comb Filtering
1. Hearing
2. Stereophonic Sound & The Man Who Invented Stereo
3. The Haas Effect
4. Binaural Recording
5. HRTF
6. Stereo Microphone Techniques
Coincident and Non-Coincident Configuration
a. AB
b. XY
c. Mid Side
d. Blumlein
e. ORTF
7. Further Research
The document provides terminology definitions related to noise control and acoustics. It defines key terms like insertion loss, noise reduction coefficient, sound pressure level, sound intensity level, octave bands, and more. It also discusses fundamental noise control concepts like frequency, sound pressure, sound power levels, and subjective loudness changes. The document is an engineering guide for noise control that refers the reader to a Price Industries HVAC handbook for more information on the topic.
EXPONENTIAL HORN - DESIGN,COMPUTER MODELING, CONSTRUCTION, MEASUREMENTS AND D...Bert Chenin
Design, Advanced Computer Modeling, Measurements and Discussion of a high efficiency tri-amplified speaker consisting of a low frequency vented enclosure (Bass Reflex), a hybrid conical/exponential midrange horn and a compression tweeter. The bass enclosure is modeled using BassBox Pro. The horn is 3D modeled using Hornresp. The measurements are made with SoundEasy with a full MLS (minimum length signal) implementation using the Ground Plane method and the Near-Field method.
This document provides an overview of sound from a mathematical perspective. It discusses how sound is created through vibration, its propagation as a longitudinal pressure wave, and how frequency and wavelength are related through the speed of sound. The speed of sound varies according to the medium and environmental factors like temperature. Sound intensity decreases with the inverse square of distance from the source and is measured on the decibel scale. Common sources of sound production are also examined, including vocal cords, speakers, and musical instruments like the French horn.
Noise is unwanted sound that varies air pressure in ways detectable by human ears. Common sources of noise pollution include traffic, industrial equipment, construction, and crowds. Noise is measured in decibels and standards set maximum levels for different land uses and times of day. Noise can be mitigated by modifying sources, transmission paths, or protecting receivers.
The document discusses key concepts in acoustics including sound reflection, absorption, diffraction, standing waves, reverberation time, room modes, and the inverse square law. It explains how reverberation time can be calculated using the Sabine equation and lists common absorption coefficients for various materials. Finally, it defines binaural hearing and the differences between mono and stereo audio formats.
Absorption Coefficients
The Sabine Equation
Reverb Calculation Example 1
Estimating the Reverberation Time
Reverb Calculation Example 2
Correcting the Reverberation Time
Control of Interfering Noise
Absorbers
Recording Solutions
b. 3 to 1 Rule
c. Working in Mono
d. Comb Filtering
1. Hearing
2. Stereophonic Sound & The Man Who Invented Stereo
3. The Haas Effect
4. Binaural Recording
5. HRTF
6. Stereo Microphone Techniques
Coincident and Non-Coincident Configuration
a. AB
b. XY
c. Mid Side
d. Blumlein
e. ORTF
7. Further Research
Sound is a vibration that propagates through a medium such as air or water. Humans can hear sounds between 20 Hz and 20 kHz. Sound is measured in decibels and moves through vibrations and reflections off surfaces. Dynamic microphones are used for live performances as they are ruggedly built to handle loud noises. They work through electromagnetic induction of a diaphragm, coil, and magnet. Condenser microphones are used in studios as they have better frequency response but are more sensitive. Types of microphones include lavalier, boundary, and cardioid microphones. Recording equipment includes Logic Pro, handheld recorders, acoustic cameras, and screen recorders. Multi-track recording captures multiple sources simultaneously like during
This document discusses noise pollution and its assessment. It defines noise and sound, and explains that decibels are used to measure sound power level, sound intensity level, and sound pressure level. It describes how sound is transmitted and the relationships between sound power, intensity, and pressure levels. It outlines the health effects of noise pollution and guidelines for controlling noise, including absorption, barriers, isolation, and personal protective equipment. It also discusses modeling noise propagation from mining complexes and measuring ambient noise levels.
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.
Sound is a vibration that propagates through a medium such as air or water. Humans can hear sounds between 20 Hz and 20 kHz. Dynamic microphones are commonly used for live performances as they are durable, while condenser microphones are commonly used in studios as they have better frequency response. Different types of microphones include lavalier, boundary, and cardioid microphones. Recording equipment includes digital audio workstations, handheld recorders, acoustic cameras, and screen recorders. Multi-track recording allows multiple sources to be recorded simultaneously.
The document discusses various concepts related to acoustics, including:
- Live rooms which bounce sound around in a pleasing way, such as auditoriums and bathrooms, versus dead rooms with high sound absorption like for recording vocals.
- Reverberation, which is the reflection of sound off surfaces that allows sounds to travel further and is used in theaters but can become "muddy" if excessive.
- Soundproofing, which reduces sound transmission between areas.
- Unwanted noise can be minimized through reducing electrical circuitry, editing out noise tails, and using windscreens for outdoor recording.
The document summarizes key aspects of different parts of the electromagnetic spectrum including radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, and gamma rays. It also discusses properties that apply across the spectrum such as all waves traveling at the speed of light, interference and diffraction effects. Additionally, it covers topics in waves and optics including reflection, refraction, lenses, sound waves, and seismic waves.
Business Energy Magazine 206-06 Edition - MIRATECH ArticleMehmood Ahmed
This document discusses solutions for sound attenuation and emission concerns from distributed power generation sources like generators, turbines, and engines. It describes how noise is created by these sources and discusses standards and regulations around noise pollution. It then outlines various mechanical methods that manufacturers use to provide sound attenuation, including enclosures, silencers, and spark arrestors from companies like Girtz Industries, Harco Manufacturing, and Miratech. These solutions help distributed power sources meet noise limits set by local codes and ordinances.
This document provides an overview of key concepts about sound waves including:
- Sound waves are longitudinal waves that cause fluctuations in air pressure.
- Pressure can be graphed against position or time to show variations from equilibrium.
- The speed of sound depends on properties of the medium like bulk modulus and density.
- In air, speed increases with temperature as density decreases.
- Wavefronts represent crests of high pressure spreading out from a source.
- Frequency determines pitch while amplitude determines loudness.
- The human ear detects sounds from 20-20,000 Hz and converts pressure waves to nerve signals.
This document discusses antennas and propagation. It begins by defining antennas and their use for transmission and reception of electromagnetic energy. It then describes common antenna types including dipole antennas and parabolic reflective antennas. The document discusses concepts like antenna gain, effective area, and the relationship between them. It also covers propagation modes including ground-wave, sky-wave, and line-of-sight propagation. Key challenges like multipath propagation, fading, and different types of noise are summarized. Finally, it discusses techniques to compensate for errors during transmission.
Preliminary Physics - World communicates 2Silvia Choi
This document discusses the properties and behavior of sound waves. It explains that sound waves are longitudinal waves that propagate through a medium by transmitting pressure variations. The speed at which sound travels depends on the properties of the medium, with denser and less compressible materials allowing for faster transmission. The document also describes how sound waves can be reflected, refracted, undergo interference and superposition, and how their amplitude and frequency determine the loudness and pitch we perceive.
Physics 3 notes: light and sound mechanics including eyes, ears, longitudina...Robin Seamon
Notes on Light and Sound waves including the mechanics of how we see and hear to the different pitches, frequencies, and sound quality explaining longitudinal & electromagnetic waves as they relate; optical illusions & color theory included as well as video links
Sound is produced by the vibration of objects and is classified as a longitudinal mechanical wave that requires a medium to propagate. It travels faster in solids than in liquids or gases due to the closer spacing of particles. The human ear can detect sounds between 20 Hz and 20,000 Hz, and instruments measure sound intensity in decibels. Ultrasound uses high frequency sound to generate images inside the body.
NOISE REDUCTION & STUDY OF NOISE MEASURING EQUIPMENTSSony Madaan
Noise pollution is unwanted or disturbing sound produced by human activities that interferes with normal activities like sleeping or conversation. The document discusses methods of noise reduction like using absorptive materials and increasing transmission loss. It also describes common noise measuring equipment like sound level meters, octave band analyzers, and noise dosimeters that are used to measure sound pressure levels and exposure at various frequencies. The aim is to study techniques for noise reduction and understand how equipment is used to measure noise.
Frequency refers to the number of complete back-and-forth vibrations of a medium per unit of time. It is measured in Hertz, with one Hertz equaling one vibration per second. All particles in a vibrating medium oscillate at the same frequency, transferring sound waves that are detected by the ear at that frequency. Frequency can also refer to the number of compressions or rarefactions that pass a given point per unit of time in a sound wave.
This document provides guidance on selecting audible alarm signals and calculating their effective coverage distances. It discusses how sound level decreases with distance from the source, and is affected by background noise levels. The effective distance of a sounder is when its output exceeds the ambient noise level by at least 5dB. Lower frequencies and intermittent tones travel farther. Sound is also attenuated by doors and walls. The document provides examples of calculating sounder requirements for different sized areas and noise levels.
Sound waves are vibrational disturbances that transmit energy through a medium by compressing and rarifying the molecules of that medium. The frequency of a sound wave is measured in Hertz (Hz) and determines its pitch, with human hearing ranging from 20-20,000 Hz. Below 20 Hz are infrasonic sounds like some animal calls, and above 20,000 Hz are ultrasonic sounds like dog whistles. The fundamental frequency is the lowest (or basic) frequency that a sound source can produce.
Sound is produced by vibrating objects and travels as compressional waves through a medium such as air, which are sensed by the human ear. For sound to be produced, three things are required: a vibrating body, a medium such as air, and a receiver like the ear. Sound waves can be recorded and played back by converting vibrations to electrical signals that are stored and then used to recreate the original sound waves. The human ear can detect sounds between frequencies of 20-20,000 Hz.
This document provides an overview of time-based audio effects. It defines effects as ambient fields that dimension tracks. Common effects like reverb, delay, chorus, flanging and phasing are explained. Reverb is broken down into direct signal, early reflections and reverberation. Delay times are discussed in musical note values relative to tempo. Examples are given of classic songs that feature effects along with the specific effects used. The document also discusses how effects are applied using auxiliary sends and returns on mixing consoles and hardware effects units.
This document discusses various topics related to sound, including reflection of sound, reverberation, range of hearing, ultrasound, sonar, working of the ear, and applications of ultrasound like echocardiography. It provides definitions and explanations of key terms. For example, it defines an echo as the same sound heard again later after reflecting off an object, and defines reverberation as the persistence of sound in an enclosed space due to repeated reflections. It also discusses how sonar works using ultrasound to detect underwater objects, and how different parts of the ear detect and transmit sound waves.
The document provides an overview of basic acoustics concepts including quantification of sound through measurements of sound pressure, intensity, and power. It discusses acoustic variables such as sound pressure level and intensity level which are expressed on a logarithmic decibel scale. Key concepts covered include the inverse square law describing how sound pressure/intensity decreases with distance from a point source, effects of multiple sound sources, relationships between frequency and sound perception, and directionality of sound sources. Measurement techniques and standards are also summarized.
Sound is a vibration that propagates through a medium such as air or water. Humans can hear sounds between 20 Hz and 20 kHz. Sound is measured in decibels and moves through vibrations and reflections off surfaces. Dynamic microphones are used for live performances as they are ruggedly built to handle loud noises. They work through electromagnetic induction of a diaphragm, coil, and magnet. Condenser microphones are used in studios as they have better frequency response but are more sensitive. Types of microphones include lavalier, boundary, and cardioid microphones. Recording equipment includes Logic Pro, handheld recorders, acoustic cameras, and screen recorders. Multi-track recording captures multiple sources simultaneously like during
This document discusses noise pollution and its assessment. It defines noise and sound, and explains that decibels are used to measure sound power level, sound intensity level, and sound pressure level. It describes how sound is transmitted and the relationships between sound power, intensity, and pressure levels. It outlines the health effects of noise pollution and guidelines for controlling noise, including absorption, barriers, isolation, and personal protective equipment. It also discusses modeling noise propagation from mining complexes and measuring ambient noise levels.
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.
Sound is a vibration that propagates through a medium such as air or water. Humans can hear sounds between 20 Hz and 20 kHz. Dynamic microphones are commonly used for live performances as they are durable, while condenser microphones are commonly used in studios as they have better frequency response. Different types of microphones include lavalier, boundary, and cardioid microphones. Recording equipment includes digital audio workstations, handheld recorders, acoustic cameras, and screen recorders. Multi-track recording allows multiple sources to be recorded simultaneously.
The document discusses various concepts related to acoustics, including:
- Live rooms which bounce sound around in a pleasing way, such as auditoriums and bathrooms, versus dead rooms with high sound absorption like for recording vocals.
- Reverberation, which is the reflection of sound off surfaces that allows sounds to travel further and is used in theaters but can become "muddy" if excessive.
- Soundproofing, which reduces sound transmission between areas.
- Unwanted noise can be minimized through reducing electrical circuitry, editing out noise tails, and using windscreens for outdoor recording.
The document summarizes key aspects of different parts of the electromagnetic spectrum including radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, and gamma rays. It also discusses properties that apply across the spectrum such as all waves traveling at the speed of light, interference and diffraction effects. Additionally, it covers topics in waves and optics including reflection, refraction, lenses, sound waves, and seismic waves.
Business Energy Magazine 206-06 Edition - MIRATECH ArticleMehmood Ahmed
This document discusses solutions for sound attenuation and emission concerns from distributed power generation sources like generators, turbines, and engines. It describes how noise is created by these sources and discusses standards and regulations around noise pollution. It then outlines various mechanical methods that manufacturers use to provide sound attenuation, including enclosures, silencers, and spark arrestors from companies like Girtz Industries, Harco Manufacturing, and Miratech. These solutions help distributed power sources meet noise limits set by local codes and ordinances.
This document provides an overview of key concepts about sound waves including:
- Sound waves are longitudinal waves that cause fluctuations in air pressure.
- Pressure can be graphed against position or time to show variations from equilibrium.
- The speed of sound depends on properties of the medium like bulk modulus and density.
- In air, speed increases with temperature as density decreases.
- Wavefronts represent crests of high pressure spreading out from a source.
- Frequency determines pitch while amplitude determines loudness.
- The human ear detects sounds from 20-20,000 Hz and converts pressure waves to nerve signals.
This document discusses antennas and propagation. It begins by defining antennas and their use for transmission and reception of electromagnetic energy. It then describes common antenna types including dipole antennas and parabolic reflective antennas. The document discusses concepts like antenna gain, effective area, and the relationship between them. It also covers propagation modes including ground-wave, sky-wave, and line-of-sight propagation. Key challenges like multipath propagation, fading, and different types of noise are summarized. Finally, it discusses techniques to compensate for errors during transmission.
Preliminary Physics - World communicates 2Silvia Choi
This document discusses the properties and behavior of sound waves. It explains that sound waves are longitudinal waves that propagate through a medium by transmitting pressure variations. The speed at which sound travels depends on the properties of the medium, with denser and less compressible materials allowing for faster transmission. The document also describes how sound waves can be reflected, refracted, undergo interference and superposition, and how their amplitude and frequency determine the loudness and pitch we perceive.
Physics 3 notes: light and sound mechanics including eyes, ears, longitudina...Robin Seamon
Notes on Light and Sound waves including the mechanics of how we see and hear to the different pitches, frequencies, and sound quality explaining longitudinal & electromagnetic waves as they relate; optical illusions & color theory included as well as video links
Sound is produced by the vibration of objects and is classified as a longitudinal mechanical wave that requires a medium to propagate. It travels faster in solids than in liquids or gases due to the closer spacing of particles. The human ear can detect sounds between 20 Hz and 20,000 Hz, and instruments measure sound intensity in decibels. Ultrasound uses high frequency sound to generate images inside the body.
NOISE REDUCTION & STUDY OF NOISE MEASURING EQUIPMENTSSony Madaan
Noise pollution is unwanted or disturbing sound produced by human activities that interferes with normal activities like sleeping or conversation. The document discusses methods of noise reduction like using absorptive materials and increasing transmission loss. It also describes common noise measuring equipment like sound level meters, octave band analyzers, and noise dosimeters that are used to measure sound pressure levels and exposure at various frequencies. The aim is to study techniques for noise reduction and understand how equipment is used to measure noise.
Frequency refers to the number of complete back-and-forth vibrations of a medium per unit of time. It is measured in Hertz, with one Hertz equaling one vibration per second. All particles in a vibrating medium oscillate at the same frequency, transferring sound waves that are detected by the ear at that frequency. Frequency can also refer to the number of compressions or rarefactions that pass a given point per unit of time in a sound wave.
This document provides guidance on selecting audible alarm signals and calculating their effective coverage distances. It discusses how sound level decreases with distance from the source, and is affected by background noise levels. The effective distance of a sounder is when its output exceeds the ambient noise level by at least 5dB. Lower frequencies and intermittent tones travel farther. Sound is also attenuated by doors and walls. The document provides examples of calculating sounder requirements for different sized areas and noise levels.
Sound waves are vibrational disturbances that transmit energy through a medium by compressing and rarifying the molecules of that medium. The frequency of a sound wave is measured in Hertz (Hz) and determines its pitch, with human hearing ranging from 20-20,000 Hz. Below 20 Hz are infrasonic sounds like some animal calls, and above 20,000 Hz are ultrasonic sounds like dog whistles. The fundamental frequency is the lowest (or basic) frequency that a sound source can produce.
Sound is produced by vibrating objects and travels as compressional waves through a medium such as air, which are sensed by the human ear. For sound to be produced, three things are required: a vibrating body, a medium such as air, and a receiver like the ear. Sound waves can be recorded and played back by converting vibrations to electrical signals that are stored and then used to recreate the original sound waves. The human ear can detect sounds between frequencies of 20-20,000 Hz.
This document provides an overview of time-based audio effects. It defines effects as ambient fields that dimension tracks. Common effects like reverb, delay, chorus, flanging and phasing are explained. Reverb is broken down into direct signal, early reflections and reverberation. Delay times are discussed in musical note values relative to tempo. Examples are given of classic songs that feature effects along with the specific effects used. The document also discusses how effects are applied using auxiliary sends and returns on mixing consoles and hardware effects units.
This document discusses various topics related to sound, including reflection of sound, reverberation, range of hearing, ultrasound, sonar, working of the ear, and applications of ultrasound like echocardiography. It provides definitions and explanations of key terms. For example, it defines an echo as the same sound heard again later after reflecting off an object, and defines reverberation as the persistence of sound in an enclosed space due to repeated reflections. It also discusses how sonar works using ultrasound to detect underwater objects, and how different parts of the ear detect and transmit sound waves.
The document provides an overview of basic acoustics concepts including quantification of sound through measurements of sound pressure, intensity, and power. It discusses acoustic variables such as sound pressure level and intensity level which are expressed on a logarithmic decibel scale. Key concepts covered include the inverse square law describing how sound pressure/intensity decreases with distance from a point source, effects of multiple sound sources, relationships between frequency and sound perception, and directionality of sound sources. Measurement techniques and standards are also summarized.
The document discusses key concepts in acoustics including:
1. Acoustics is the science of sound, including its production, propagation, and effects. Sound is a wave motion consisting of compressions and rarefactions in an elastic medium.
2. For sound to be produced, there must be a vibrating body, transmitting medium, and receiving medium. The audible frequency range for humans is 20 Hz to 20 kHz.
3. Physical properties of sound waves include amplitude, period, frequency, wavelength, and velocity of propagation. The velocity of sound depends on the properties of the medium it is traveling through.
4. When a sound wave encounters an obstruction, it can be reflected,
This document provides an overview of fundamentals of noise. It defines sound as acoustic waves that propagate through a medium, with noise being unwanted or disturbing sound. Key concepts covered include:
- Sound is measured by properties like frequency, sound pressure level, intensity level, and power level.
- The decibel scale is used to quantify sound levels in a way that reflects human perception.
- Sound can be analyzed by its intensity or pressure levels across frequency bands like octave or one-third octave bands.
- The relationship between sound intensity, pressure, and power is explained. Combining sound from multiple sources is also addressed.
This document discusses radio frequency (RF) concepts including:
- RF refers to electromagnetic frequencies between 3 kHz and 300 GHz used in radio and radar. RF currents have special properties like flowing along conductor surfaces (skin effect) and radiating energy as electromagnetic waves.
- RF currents can cause burns but often do not cause a painful electric shock sensation due to their high frequency. Their ability to flow through insulating materials like capacitors decreases with increasing frequency.
- Factors that impact RF signals include free space loss as signals spread out, skin effect, absorption from the environment, and reflection from objects. Impedance matching is important to minimize signal reflections from impedance mismatches.
- Noise is an unwanted signal
Waves transfer energy and have characteristics like amplitude, wavelength, frequency, and period. The principle of superposition means waves can interfere and add or subtract from each other. Sound waves are longitudinal waves that propagate through air and other materials. The Doppler effect causes changes in the perceived frequency of sound waves due to the motion of the source.
This document discusses noise control for HVAC systems. It provides background on how noise is measured and perceived by humans. Common noise sources in HVAC systems are identified along with recommended noise level limits from ASHRAE. Methods for controlling airborne noise include duct liner, silencers, acoustic barriers and isolating noisy equipment. Proper location and integration of noise control elements into the overall system design is emphasized to prevent noise issues from arising.
This document discusses noise pollution and its measurement. It defines sound as pressure variations that propagate as waves. Frequency, amplitude, wavelength, and period are characteristics of sound waves. Sound is measured in decibels, with higher decibel levels indicating louder sounds. Common instruments for noise measurement include sound level meters, which can measure noise across different frequencies. Methods for noise control include reducing noise at the source, blocking its transmission, and protecting receivers with equipment.
This document discusses noise measurement and abatement. It defines sound and how it travels in waves. It explains how sound is measured in terms of pressure, frequency, intensity, bels, and decibels. It discusses common sources of noise pollution like transportation systems, and how noise affects human health. Solutions to noise problems include regulations, barriers, and selecting less noisy materials.
The document discusses noise pollution, including its measurement, sources, effects, and control. It defines sound and noise, and explains how sound is measured in units such as frequency, intensity, and decibels. Common sources of noise pollution like traffic, construction, and industrial activities are identified. The effects of noise on hearing, health, communication, and work are outlined. Standards for acceptable noise limits in different areas are provided. Finally, the document discusses approaches to control noise pollution through modifications to noise sources, transmission paths, and receivers.
The document discusses the key properties of sound:
Pitch refers to the highness or lowness of a sound and depends on the frequency of vibrations. Intensity refers to the energy of a sound wave and is measured in watts per meter squared. Loudness is a subjective measure of how loud a sound seems and is related to intensity, distance from the source, and condition of the transmitting medium. Quality or timbre distinguishes one sound from another by other characteristics beyond pitch and loudness. The document provides examples of the intensity and loudness of common sounds to illustrate these concepts.
Sound is a longitudinal wave that travels through a medium as a series of compressions and rarefactions. When sound waves reach the ear, they are converted into electrical signals that travel to the brain via auditory nerves. Microphones convert sound waves into electrical signals. Microphone placement depends on the sound source and microphone characteristics to capture sound with proper clarity, balance, and lack of feedback. The document discusses the nature of sound waves, microphone types and their uses, and considerations for microphone placement.
This document provides an overview of key concepts in antennas and propagation. It defines an antenna as a device that transmits or receives electromagnetic waves. It describes common antenna types like dipoles and parabolic reflectors. It also covers topics like radiation patterns, antenna gain, propagation modes (ground wave, sky wave, line-of-sight), factors that affect signal strength over distance like free space loss and multipath, and techniques to mitigate noise and fading like diversity and error correction.
The document discusses key concepts related to the propagation of sound waves. It defines that sound needs a medium to propagate through and discusses how sound waves are generated by vibrating sources and transmitted through different mediums. The speed of sound depends on the properties of the medium, not the frequency or amplitude of the sound. Sound intensity decreases with distance from the source according to the inverse square law.
Module 5 of ME 010 702 DYNAMICS OF MACHINESbinil babu
This document discusses acoustics and environmental noise control. It defines key acoustics concepts like sound propagation, decibels, Doppler effect, and acoustic impedance. It also discusses noise tolerance levels for humans and noise control strategies in industrial contexts, including controlling noise at the source, along transmission paths, and at receivers. An example problem calculates the total sound power level generated by four machines with different sound power outputs.
This document provides an overview of key concepts in antennas and propagation. It defines an antenna as a device that transmits or receives electromagnetic waves. It describes common antenna types like dipoles and parabolic reflectors. It also covers topics like radiation patterns, antenna gain, propagation modes (ground wave, sky wave, line-of-sight), free space loss, noise, multipath, and techniques to mitigate signal degradation like diversity and error correction.
Ultrasound uses high frequency sound waves to image internal structures. A transducer converts electrical pulses into ultrasound pulses and reflected sound waves back into electrical signals. Tissues reflect sound differently allowing visualization. Higher frequencies improve resolution but reduce penetration. Ultrasound has various medical uses like imaging fetuses, organs and detecting abnormalities by interpreting echo patterns. It provides real-time images without radiation unlike other modalities.
Sound is produced by air molecules vibrating in patterns called sound waves. Sound waves can be longitudinal or transverse. Characteristics of sound include pitch, determined by frequency; intensity, determined by amplitude; and quality, determined by the form of the waves. Musical sounds have a repeatable wave pattern while noise does not. Examples of low frequency sounds are lion roars and whale songs, while high frequency sounds include bird chirps and whistles. Intensity is measured in watts per meter squared and perceived loudness is measured in decibels. Tone depends on the combination of frequencies in the sound waves.
Sound is a longitudinal pressure wave that humans can hear if its frequency is between 20-20,000 Hz. The speed of sound depends on the medium, traveling fastest in solids and slowest in gases. Pitch is determined by frequency, with higher pitches having shorter wavelengths and higher energies. Loudness, measured in decibels, depends on sound intensity or amplitude. Quality or timbre distinguishes tones of the same pitch and loudness based on their waveforms. Sound waves can refract, diffract, interfere, and reflect, and technologies like sonar and altimeters utilize these properties.
Report on bass and trable - Analog ProectVatsal N Shah
This project report describes designing a bass/treble separator circuit to separate low and high frequency audio signals and output them to separate lines for a woofer and tweeter. The circuit uses a low-pass filter with 150Ω resistor and 10μF capacitor to output bass frequencies to the woofer, and a high-pass filter with the same components to output treble frequencies to the tweeter. The project was carried out by a student at Indus University for their 4th semester electronics course.
Similar to FUNDAMENTAL ACOUSTICS AND WIND TURBINE NOISE ISSUES (20)
2015 International Spatial Planning Symposium: Sharing Practical Solutions riseagrant
The document summarizes findings from a review of marine spatial plans around the world. It finds that most plans are implemented at smaller spatial scales than entire ecosystems. It also finds that few institutional changes are made to governing bodies to implement coastal and marine spatial planning, relying instead on existing agencies. Additionally, it notes that while formal decision support tools are used, informal expert judgment also plays a role. The main messages are that there is no single approach for marine spatial planning and that the value is in the planning process of engaging stakeholders as much as the final plan.
Five regional planning bodies have been established across the United States to coordinate ocean planning: the Northeast, Mid-Atlantic, Pacific Islands, Caribbean, and West Coast. The Northeast and Mid-Atlantic regions have established charters and are drafting regional marine plans to be completed in 2016. The Pacific Islands has a charter and is beginning to draft a plan, while the Caribbean is still finalizing its charter and the West Coast is working on one.
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2Environmental Data Center
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*http://www.beachsamp.org/research/stormtools/
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FUNDAMENTAL ACOUSTICS AND WIND TURBINE NOISE ISSUES
1. FUNDAMENTAL ACOUSTICS
AND
WIND TURBINE NOISE ISSUES
Prof. Gopu R. Potty, Ph.D.
Department of Ocean Engineering
University of Rhode Island
Narragansett, RI 02882
potty@egr.uri.edu
4. Sound Waves
Sound is a pressure wave Intensity is the average amount
of sound power transmitted
Sounds have different frequencies through a unit area in a
Human hearing: 20 Hz to 20 kHz specified direction. The unit of
Less than 20 Hz - infrasound intensity is watts per square
meter.
5. Decibel
•The decibel (dB) is a
logarithmic comparison of
intensities.
•Named for Alexander
Graham Bell
⎧ Acoustic Intensity ⎫
Level = 10 log ⎨ ⎬
⎩ Reference Intensity ⎭
Reference acoustic intensity = 1x10 −12 W/m 2
7. Adding decibels
• Let’s say we had 3 sources of sound at 70, 80
and 90 dB each, what is the total level?
• We need to convert the individual levels into
raw intensities and add them
• The sum thus calculated (expressed in dB) in
this case is 90.5 dB
Two turbines produce 3 dB more than one turbine
8. Sound Pressure Level (SPL)
SPL= 20 log Pressure of an acoustic signal
reference pressure
The units of L are dB relative to the
reference pressure.
The reference pressure is
20 micropascals based on
hearing tests of 16 million men
in WW2.
This corresponds to an
Intensity of 1x10-12 W/m2.
9. Source Level SL
(Rogers et al., 2006)
SL is defined to be
20 log Pressure of source at 1 m
reference pressure
The units of SL are dB relative to
Reference pressure of 20 micropascals at 1 meter.
SL referenced at 1 meter
Quantifies the strength of the source !!!!
10. Acoustics at a distance
• We can predict the sound pressure level of an
acoustic signal at a distance.
L = SL - TL
L = Sound Pressure Level
SL = Source Level
TL = Transmission Loss
Nascar fans in the front row are exposed to more intense sound
than the fans in back row due to transmission loss.
11. Transmission Loss
• Transmission Loss TL (aka
propagation loss) describes
the weakening of sound
between a point 1 meter
from the source and a point
at a distance r meters.
• It is the ratio of intensity at
any range ‘r’ to intensity at 1 (Rogers et al., 2006)
m
Intensity at r meters
TL = -10 log
Intensity at 1 meter
12. Transmission Loss Components
Absorption coefft.
• Geometrical spreading expressed in dB/km or
• Absorption dB/m
• Scattering Absorption a function of
– Volumetric scattering, turbulence • Temperature
• Humidity
– Groundcover, trees, structures • Frequency
• Total loss = Geometrical Spreading +Absorption
+Scattering
13. Geometrical Spreading: Spherical
Weakening of the acoustic intensity due
to spreading
Related to the surface areas of spheres (or
hemi-spheres) at two ranges.
Doubling the distance to the
turbine reduces the SPL by 6dB
15. The Hearing Threshold Curve
From: Yost
The range of human hearing is
generally considered to be 20
Hz to 20 kHz, but it is far more
sensitive to sounds between 1
kHz and 4 kHz.
Listeners can detect sounds as low as 0 dB SPL at 3 kHz, but require 40
dB SPL at 60 hertz (an amplitude increase of 100)
16. A and C Weightings
• A weighting filters out the low frequencies
and slightly emphasizes the upper middle
frequencies around 2‐3 kHz. By comparison C
weighting is almost unweighted, or no
filtering at all.
• As a general rule, C weighting is used for
protection against very intense sounds while
A weighting is used for less intense sounds
and predicts annoyance fairly well.
http://www.e-a-r.com/pdf/hearingcons/FAQdba.pdf
17. Wind Noise
Wind turbines differ in several respects from other sources of community noises
Modern wind turbines mainly emit noise from turbulence at the trailing edge
of the rotor blades.
The turbine sound power level varies with the wind speed at hub height.
The sound is amplitude modulated with the rotation rate of the rotor blades, due
to the variation in wind speed with height and the reduction in wind speed near the
tower.
Amplitude-modulated sound is more easily perceived than is constant-level sound
and has been found to be more annoying
Sound that occurs unpredictably and uncontrollably is more annoying than
other sounds
18. Wind Noise
Wind turbines are tall and highly visible, often being placed in open,
rural areas with low levels of background sound.
Consequently, wind turbines are sometimes regarded as visible and
audible intruders in otherwise unspoiled environments.
Furthermore, the moving rotor blades draw attention, possibly
enhancing the perception of sound in a multi-modal effect
19. Wind Turbine Noise Sources
The sources of noise emitted
from operating wind turbines can
be divided into two categories:
• mechanical and
• aerodynamic.
The primary sources of
mechanical noise are the gearbox
and the generator.
The highest contributor to the
total sound power from a turbine
is the aerodynamic noise, which
is produced by the flow of air
over the blades.
20. Portsmouth Wind Turbine
(July/Aug 2009)
Measured at a distance of 65 meters.
Units are dB re 20 μPa2 in a 1/3-octave band
21. Portsmouth Wind Turbine
Science Fair Project (Chitanya Gopu- SK High) At 0.5 km (Heather Rhodes)
Trial 1 Trial 2: Trial 3: Trial 4: Trial 5: Trial 6: 11/30 11/30 11/30 11/30 12/01
6:50 AM 10:31 3:30 8:30 5:30
59.27 59.30 59.40 59.12 59.36 59.41 AM PM PM AM
56.7 54.4 54.7 51.3 49.2
Simple hemispherical propagation model
100
90
80
B
70
SPL dBA
60
50
40
30
20
A
0 100 200 300 400 500 600 700 800 900 1000
distance from tower (m)
sound of the traffic from Rt. 24 was dominant !!!!
23. Low Frequency Noise
• Low frequency noise (20‐100 Hz)
and infrasound (less than 20 Hz)
are issues that are frequently
raised as concerns associated with
wind farm developments
• Usually G‐weighted
• Perceived a mixture of tactile and
auditory sensations
• Threshold of hearing at 10 Hz very
high (~100 dB G)
Sources for low-frequency noise are either
• Low frequency noise generation is of a natural origin, such as air turbulence
generally confined to turbines wind, thunder, ocean waves, volcanic
whose rotors operate downwind eruptions, and earthquakes or of human
origin such as heating, ventilation, air-
of the support tower – a conditioning systems, machinery, cars,
downwind machine. trucks, airplanes, and loudspeaker systems
24. Infrasound Measurements
Note the high
background
noise level
below 5 Hz
10 dB
From: Jorgen Jakobsen, journal of Low Frequency Noise, Vibration and Active Control, 24(3), 2005
26. ‘Swish’ Noise
• Swish‐swish sound is
amplitude modulation at
blade passing frequencies of
higher frequency blade tip
turbulence
• Does not contain low
frequencies
• Diminishes with distance
• Blurs with multiple turbines
Time
28. Wind Noise Regulations
Most international and various states in USA set a base
noise level for low wind speeds.
Many regulations specify a night time level of 35 dBA in a
rural location.
To prevent the adverse impacts from the increased noise of
wind turbine generators at high wind conditions, the
increased noise levels must also be compared to the
corresponding background noise at any location of interest.
For example some codes specify that the wind farm noise
doesn’t exceed the background noise by more than 5 dBA at
higher wind speeds.
29. Typical Guidelines for Pure Tones
A pure tone is defined to exist if the 1/3rd octave band sound pressure
level in the band, including the tone, exceeds the arithmetic average
of the two contiguous 1/3 octave bands by
•5 dBA for center frequencies of 500 Hz and above
•8 dBA for center frequencies between 160 Hz and 400 Hz
•15 dBA for center frequencies less than or equal to 125 Hz
Most of the codes penalize tonals. For example, Huron County, MI,
specifies that when steady pure tone is present, the standard for
audible noise shall be reduced by 5 dBA.
30. ISO 1996-1971 guidelines
Lower
night time
limits !!!
Gabrielson,
Acoustic Today,
2006 A temperature increase
(an “inversion”) with
altitude often occurs at
night and this causes
sound to be refracted
downward
On an expedition to Venezuela in 1899, Baron von Humboldt observed much better
sound transmission from a waterfall on the Orinoco River at night than during the day !!.
35. Study Plan
• Make repeated sound level measurements using sound
level meter (during day and night) near existing turbines
in RI.
• Compare this to sound level models
• Make ambient sound measurements at locations of
interest.
• Develop a weight to reflect noise considerations which
can be incorporated into TDI calculations
• Develop general guidelines on allowable sound level
thresholds
36. Dose-Response Relationship Studies
Dutch and Swedish
studies (Pedersen et
al., J. Acoust. Soc.
Am., Vol. 126, No. 2,
August 2009
Need to account
LDEN dB(A) for perception !!!
Annoyance towards wind turbine sound is enhanced by the
•high visibility of the noise source,
•swishing quality of the sound,
•its unpredictable occurrence,
•continuation of the sound at night.
40. Perception of Sound from Wind Turbines
Annoyance was highest in what was classified as built-up area (mostly
small towns and villages)
Could be interpreted as an effect of place attachment
In this view, new technical devices being deemed not beneficial for the
living environment induce a negative reaction .
This theory cannot, however, be confirmed from the present data set.
42. Perception of Sound from Wind Turbines
Noise from wind turbines was found to be more annoying than other
sources.
Percentage of people annoyed lies between noise from aircraft and from
shunting yards.
Like aircraft, wind turbines are elevated sound sources visible from afar
and hence intrude both visually and aurally into private space
Wind turbine noise (like shunting yard noise) ceases at night
48. Auditory Perception
• A 1 dB change in SPL is below the level of
human perception
• For a sound to double in loudness, an increase
of 10 dB is required
• A 3 dB change in SPL level is minimum level of
human perception (it is just barely noticeable)
• An SPL of 140 dB is the threshold of pain
From: Acoustic Analysis Dartmouth DPW Wind Project (Atlantic Design Engineers, LLC)