Sound Power Measurement


 Ashlyn Bruce
 3 years ago
 Views:
Transcription
1 Sound Power Measurement A sound source will radiate different sound powers in different environments, especially at low frequencies when the wavelength is comparable to the size of the room 1. Fortunately this difference is not very large for most sound sources, in particular mechanical sources, and we can always use the sound power radiated in the free field as an approximation. 1 Principle The sound power is defined as W = I ds = I n ds, (1) S where I = pu is the sound intensity vector and I n is the sound intensity normal to the surface S. The surface should completely enclose the sound source. Sound power level is then L w = 10 log W ( ) = W L S I + 10 log, (2) 0 S 0 where L I is the averaged normal sound intensity level and S is the area of surface enclosing the source. S 0 = 1 m 2 is the reference surface, and the reference sound power W 0 is defined through the reference intensity I 0 as W 0 = I 0 S 0. 2 Sound pressure method In practical situations, the relation between sound pressure level and sound power level or normal sound intensity level is very complicated, and one cannot get accurate estimation of sound power level by using sound pressure measurements. However, in two ideal cases free field and a diffuse field sound power is explicitly related to the sound pressure. Free field and reverberation room methods have been developed which can be used to estimate sound power level rather accurately. Engineering and survey methods with lower accuracy have also been developed for other environments and for in situ measurements. 1 More accurately, the mean free path ; the average distance a sound ray will travel between successive reflections. S 1
2 Free field In a free field there is only direct sound and no reflection exists. For a progressive wave, there is a unique relation between the meansquared sound pressure and the intensity in the direction of the wave propagation, I = p2 ρc. (3) Hence the normal sound intensity level over the surface can be expressed as L I = 10 log I I 0 = 10 log p2 ρci 0 = L p 10 log(c) (4) where C = I 0 ρc / p 2 0 = ρc/400. In room temperature (20 C) with an ambient pressure of 1 atm ( N/m 2 ), 10 log(c) = db and L I = L p db. Splitting the surface S into N different pieces S n, the discrete form of equation (1) becomes N free field N p W = I n S n 2 ns n ρc. (5) n=1 Sound power level is then estimated as L w = 10 log W W 0 = 10 log n=1 N n=1 p 2 ns n ρcw 0 db. (6) This can be expressed as by using averaged sound pressure level L w = L p + 10 log( S S 0 ) + 10 log( p2 0S 0 ρcw 0 ) db, (7) where S is the total surface in m 2 and L p = 10 log N p 2 ns n 1 s n=1 p 2 0 db (8) is the averaged sound pressure level. If the reference values of sound pressure and sound power are put into equation (7) the last term vanishes when ρc = 400. Equation (7) is the basic equation for sound pressure method in a free field. Diffuse field In a diffuse field the sound pressure level is essentially independent of the distance to the sound source. Based on the concept of mean free path, the relation between sound energy density E(t) and the sound power W radiated by the source can be obtained as E(t) = 4W cᾱs ( ( 1 exp cᾱs )) 4V t, (9) 2
3 where V and S are the volume and wall surface of the room respectively, and ᾱ is the mean absorption coefficient. The steadystate sound energy density can be obtained by letting t as E 0 = 4W cᾱs. (10) The steadystate sound energy density in above equation can also be expressed by the sound pressure as E 0 = p2 ρc 2. (11) Combining above two equations and rearranging them we can obtain the relation between sound power and sound pressure in a reverberation field W = p2 ρc ᾱs 4 = p2 ρc A 4 (12) where A = ᾱs is the equivalent absorption. The formula may also be expressed by using the reverberation time to replace the equivalent absorption as W = p2 ρc 13.8V ct, (13) since A = 55.26V. (14) ct Based on above formula one can calculate sound power levels from measured sound pressure levels if the parameters of the reverberation room are known. The sound power level of a sound source will then have the form ( ) ( ) W L w = 20 log = L A p + 10 log 6 + C. (15) W 0 The first three terms are obtained from (12), A 0 is a reference absorption of 1 m, and C is a term related to small correction factors for other influences such as air absorption, ambient pressure, temperature, and interface patterns formed near the room surfaces. ISO has suggested a few formulas for the correction term in ISO 3740 series of standards depending on the accuracy of the measurement methods. The details can be found in the corresponding standards. Field (in situ) In this case both direct and reverberation fields exist and the meansquared sound pressure can be written as ( p 2 Qθ = W ρc 4πr ), (16) R where W is the sound power, R = Sᾱ/(1 ᾱ) is the room constant and Q θ is the directivity of the sound source. In this situation it is difficult to measure sound power accurately by measuring sound pressure level. It is quite common to use comparison methods with reference sound sources or to introduce an environment correction K 2 to get more reliable measurement results. A 0 3
4 3 Direct method vs. comparison method Before intensity methods became widely used, it was common to find the sound power of a sound source using sound pressure measurements. Even nowadays, when sound intensity probes are commonly found and corresponding standards are published, sound pressure methods are still popular in practice. There are two main types of sound pressure methods used to evaluate sound power: Direct methods and comparison methods. Direct method In the direct methods, the sound power is calculated using the measured averaged sound pressure level with equation (7) for a free field and equation (15) for a diffuse field. When the diffuse field is a concern, the equivalent sound absorption should also be measured with the sound source in question through reverberation time measurements. For other nonideal situations, the relation between sound power and sound pressure is more complicated as indicated by (16). ISO suggests two parameters to describe environment corrections: K 1 for background noise correction and K 2 for environment correction. Those corrections should be included when evaluating the sound power level to take into account the effect of the environment and of background noise. It is the environment that determines which type of measurements should be performed and which accuracy level the measurement can reach. Comparison method As stated above, in order to calculate sound power from sound pressure level measured in a diffuse field, one needs to measure reverberation time when the sound source under test is mounted in the room. This may take longer time than the measurement of the sound pressure level radiated by the sound source under test. Furthermore, when measuring sound power level in situ, the environmental conditions may be so severe that the environment correction K 2 exceeds 7 db. In that case, no direct method with sound pressure level may be performed. In these situations, comparison methods can be an alternative. In comparison methods, the radiated sound pressure level of the sound source in question is compared with that radiated by a standard sound source. The sound power radiated from this reference sound source is precisely calibrated at the exactly the same environmental conditions. The sound power difference between the reference source and the source in question should then be the same as the difference between the measured sound pressure levels. The basic assumption of this method is that the environment influence (absorption, reflection, etc.) on the sound source under test should be the same as the reference sound source. This is usually a mechanical sound source with a stable output of sound power which is calibrated with high accuracy in a laboratory. It is used to find the influence of the environment which contributes in relating the sound power of the source to the resulting sound pressure level. This method is obviously suitable for mechanical sound sources with high internal impedance. Electrodynamic sound sources tend to have low internal 4
5 impedance and are thus more easily affected by the environment. Therefore, this method may not very suitable for this type of sound source. In the comparison method, one avoids measuring reverberation time, making sound power measurements much easier. The method is also commonly used to get the environment correction K 2 for special test environments. Since the comparison method compares the reflected or reverberant sound fields of a reference source and the source in question, it is clearly not suitable for a free field measurement. The more reverberant the sound field is, the higher accuracy this method can reach. We can get precision accuracy (grade 1) when this method is applied to a reverberation room and engineering accuracy (grade 2) when this method is applied to a field with the environment correction K 2 bigger than 7 db. For the case of K 2 smaller than 7 db, only survey accuracy (grade 3) can be reached. When the dimension of the sound source under test is much larger than the reference sound source or when the sound source has a strong directivity, the environment influence may not be same. Care must be taken in this situation. One solution is to measure the sound pressure level of the reference sound source when it is located at different positions and then the average is taken. The procedure is described in detail in corresponding ISO standards. 4 Sound intensity method This method directly measures the sound intensity instead of sound pressure level and hence it can in principle be used in free field measurements. The total intensity will be I = I direct + I diffuse. (17) In a diffuse field, waves propagate in random directions. Therefore, the intensity vectors of different waves have random directions and tend to cancel each other out, so that I diffuse 0. Thus, we are left with approximately only the intensity vector directly from the sound source, I I direct. Measuring intensity will thus give us the same intensity as if there were no reverberation. There are generally two methods to get averaged sound intensity level: Scanning method to get averaged sound intensity level by scanning over a hypothetical surface which completely encloses the noise source under test. Measuring at discrete points to get averaged sound intensity level by measuring at discrete points on the measurement surface which completely encloses the noise source under test. In principle, intensity methods can be applied to any environment but in practice they are restricted by instruments, background noise and the situation of the acoustic field. Measuring the normal intensity I n on each piece S i of the enclosing surface, the sound power component W i on that piece is W i = I n S i (18) 5
6 and the sound power level can thus be determined as ( N ) W i L w = 10 log. (19) W 0 5 Standards The above sections describe basic principles and procedures of measurements in different conditions. In practice many factors have to be taken into account in order to reduce errors and to make results more reliable and repeatable. The international standards for determination of sound power levels of machines and equipments are outlined in the ISO standard 3740:2000 where ISO 3741 ISO 3747 are sound pressure methods while ISO , ISO and ISO (not listed in ISO 3740) are sound intensity methods. They can be divided into three groups according to the measurement accuracy: Precision methods (grade 1), engineering methods (grade 2) and survey methods (grade 3). Consequently, they also have different requirements on environment and background noise level. In the followingm details on these standards are discussed with focus on precision laboratory methods (ISO 3745 and ISO 3741). Other in situ methods (ISO 3747 and 3746) will be discussed in the lab exercise. 5.1 Free field methods (ISO 3744, 3745 and 3746) For all three methods hypothetical surfaces over a reflecting plane are used with equation (7) to calculate the sound power. (The exception is ISO 3745, which uses no reflecting plane.) Direct measurements are always are used in these methods. The main differences among them are: 1. Accuracy 2. Required test environment 3. Background noise 4. Obtainable sound powers i=1 Here only ISO 3745:2003 will be discussed in detail. relevant standards. For others, see the Room The standards specify different kinds of requirements for the rooms to achieve different grades of accuracy. Background noise At least 10 db lower than the sound pressure level measured from the source under test in each frequency band. 6
7 Temperature Should be within the range 10 C to 30 C. Within this range the influence of humidity can be neglected. Instrumentation The accuracy of instruments should be consistent with the accuracy of the method. Installation of source Whenever a typical condition of mounting exists for the source, it should be used or simulated, if practicable. Radius of measurement sphere (or hemisphere) The radius of the test hemisphere should be equal to or larger than all of following: Twice the largest source dimension or three times the distance of the acoustic center of the source from the reflecting plane, whichever is larger (for a semianechoic room) The wavelength of the lowest frequency of interest 1 m Microphone positions One of the following four methods is used to obtain the average value of the mean squared pressure on the test sphere (or hemisphere). Any measurement point should be at least 1 m away from the absorptive surfaces of the room. Note that the averages must be performed on mean squared values instead of on db levels. a. Fixed microphone positions The standard recommends an array of microphone positions associated with equal areas on the measurement surface. In general, the number of measurement points is sufficient if the difference in decibels between the highest and lowest sound pressure levels measured in any frequency band of interest is numerically less than half of the number of measurement points. If this requirement is not satisfied using 20point array, an additional 20point array must be used. If the requirement is still not satisfied by the 40point, one might need to use microphone positions associated with unequal areas. In this case it should be taken into account when making average of sound pressure level. See ISO 3745 for details. b. Coaxial circular paths in parallel planes c. Meridional arc traverses d. Spiral path 7
8 Measurement time For the frequency bands centered on or below 160 Hz, the measurement time must be at least 30 seconds. For Aweighted sound pressure levels and for the frequency bands centered on or above 200 Hz, the measurement time must be at least 10 seconds. Correction for background sound pressure levels Background noise correction is often denoted by K 1. If the difference of the sound pressure level when the source is in operation and the background noise level is between 10 db and 20 db for each frequency band, the influence of the background noise must be corrected. For frequency band i, the background noise correction is given by where K 1i = 10 log( Li ) db, (20) L i = L pi L pi is the difference in sound pressure level at the same measurement point and same frequency band with and without the source in operation. When L = 10 db, the factor K 1i is about 0.5 db. The corrected sound pressure level is then L pi = L pi K 1i db. (21) If the background noise is more than 20 db below the sound pressure level with the source under test, no correction is needed. Calculation of sound power level The sound power is calculated as where L w = L p + 10 log C 1 = 10 log B B θ ( S1 S 0 ) + C 1 + C 2 db, (22) and C 2 = 15 log B B θ (23) are small correction factors involving the ambient pressure B during the measurements, standard atmospheric pressure B 0 = Pa, and temperature θ (in C) during measurements. For an anechoic room, S 1 is equal to 4πr 2 where r is the radius of the test sphere. For a semianechoic room, S 1 is equal to 2πr Reverberation room methods (ISO 3741 and 3743) ISO 3741 is a precision method (grade 1) while ISO and ISO are engineering methods (grade 2). If frequencies above 300 Hz are included in the frequency range of interest, the volume of the test room should not exceed 300 m 3. 8
9 1/3 octave band center frequency Upper value of standard deviation of reproducibility σ R (db) (Hz) Anechoic room Semianechoic room a b Aweighted a: if the sound field is qualified b: if the instruments allows and if correction is made for absorption of sound by the atmosphere Table 1: Estimated upper values of the standard deviations of reproducibility of sound power levels determined in accordance with ISO 3745:2003 Bandwidth Center frequency (Hz) Upper value of standard deviation of reproducibility (db) /3 octave octave Aweighted 0.5 Table 2: Estimated upper values of the standard deviations of reproducibility of sound power levels determined in accordance with ISO 3741:1999 Lowest band of interest Minimum volume of the test room (m 3 ) 125 Hz (octave) or 100 Hz (1/3 octave) Hz (1/3 octave) Hz (1/3 octave) Hz (octave) or 200 Hz (1/3 octave) 70 Table 3: Minimum volume of the test rooms 9
10 Requirements for absorption of test room The absorption of the room can influence the minimum distance between the noise source and the microphone positions. It also influences the sound radiation of the source and the frequency response characteristics of the test space. Due to these reasons the absorption of the test room should be neither too large nor extremely small, requiring that α < 0.06 for the surface closest to the source, and that T > V/S. Location of the source Should be placed at least 1.5 m away from any wall of the room. Microphones The minimum distance between source and microphone is d min = C 1 V /T, where C 1 = 0.08, or 0.16 for a higher grade of accuracy. If the microphone is being moved during the measurement, it must move at constant speed over a path at least 3λ in length, where λ is the wavelength of the center frequency of the lowest frequency band (about 10 m if the lowest frequency band is 100 Hz). For an array of several microphones, the microphone positions must be spaced at a distance of at least λ/2 from each other and 1 m from the room surface. Number of microphone positions and source locations When fixed microphone positions are used, at least six microphone positions at different heights should be used. If the standard deviation for any frequency band is larger than 1.5 db, additional microphone positions must be used. See ISO 3741:1999 for details. Although a reverberation room represents a diffuse field, it is still far away from a real diffuse field where sound pressure is the same everywhere. That is the reason averaging over many microphone positions or over a long microphone traverse path is required. Radiation on discrete frequencies or narrow bands of noise If a source radiates narrow band or discrete frequency sound, a precision determination of sound power requires greater effort than that of a broadband sound source. The standard gives additional precautions which have to be observed for this type of sound source. The methods are often complex and time consuming for sources that mainly emit on discrete frequencies below 200 Hz. For such sources measurement in a free field described in ISO 3745 are likely to be more appropriate. 5.3 Environment correction K 2 Environment correction K 2 is a correction term to account for the effect of reflected or absorbed sound on the surface sound pressure level measured. It is 10
11 frequency dependent and is used in standards using an enveloping measurement surface such as ISO 3744 and Two methods can be used to determine the environment correction factor: An absolute comparison method or a method based on room absorption. For the absolute comparison method we need a calibrated reference sound source with characteristics which meet the requirements of ISO If we mount the reference sound source in the test room and then measure and calculate the sound power level according to the procedure described in 5.1 without any environment correction term, the environment correction term of the test environment can then be found as K 2 = L W L W r. (24) Here, L W is the uncorrected sound power level measured according to the procedure described previously for a free field and calculated by using (22), and L W r is the calibrated sound power level of the reference sound source. This procedure is actually exactly the same as the comparison method discussed before to use a calibrated reference sound source to estimate the influence of the environment. The other method to determine the environment correction is based on room absorption measured. In that case the correction term can be calculated as ( K 2 = 10 log S ), (25) A where A is the equivalent sound absorption area of the room and S is the area of the measurement surface. The problem in this method is that the sound absorption of the room has to be measured, which might be very time consuming. If only Aweighted sound power is required, one can use an approximate method to estimate the environment correction K 2A by using approximate values of the mean sound absorption coefficient of the room. In the lab exercise, we will use this method. 5.4 Intensity methods (ISO , and ) The relationship between sound intensity level and sound pressure level at any point depends on the characteristics of the source, the characteristics of the environment and distance of the measurement positions and the source. For the previously described sound pressure methods, many restrictions therefore have to be made for source characteristics and measurement environments in order to make the uncertainty of the sound power determination within acceptable limits. The procedures specified in the sound pressure methods are not always appropriate since it is not often possible to install and operate large equipment in costly facilities such as anechoic or reverberation chambers to make high accuracy measurements. These methods also can not be used in the presence of high levels of extraneous noise generated by sources other than the source under investigation. The intensity method is a complement of the sound pressure methods and can be used under less restricted test conditions. There are three standards of intensity methods differences in sampling methods and accuracies. ISO is based on discretepoint sampling of the intensity field normal to the measurement surface and can reach precision accuracy 11
12 (grade 1), engineering accuracy (grade 2) and survey accuracy (grade 3). Both ISO and ISO are based on scanning of the normal intensity over the measurement surface with the engineering and survey accuracy and precision accuracy, respectively. The uncertainties when determining the sound power using intensity methods stem from the characteristics of the sound sources, extraneous sound fields, the absorption of the source under test, the intensityfield sampling and the measurement procedure used. The standards also supply procedures to reach a desired grade of accuracy. When needed, one can consult the corresponding standards for details. Following terms with respect to Field indicators F 1 F 4 in the three standards are often used when describing an intensity field and the way to determine the sound power. In the discussion below we follow the symbols of ISO Temporal variability indicator This is defined as F 1 = 1 1 M ( ) 2, Ink Ī n M 1 Īn (26) where Īn is the mean value for M shorttimeaverage sample I nk. This is an indicator of the temporal variability of the sound field at the selected measurement position or surface. If the indicator is larger than a certain value, say 0.6, the sound field at the measurement surface is not stationary. It is always due to the influence of extraneous noise intensity. In order to increase the grade of accuracy one has to reduce the temporal variability or increase the measurement period. Surface pressureintensity indicator k=1 This is defined as F 2 = L p L In, (27) where L p is the surface averaged sound pressure level and L In is the surface averaged normal unsigned sound level, i.e., average of the magnitude of the sound intensity only, no matter what is the direction of the intensity. Negative partial power indicator This is defined as F 3 = L p L In, (28) The difference compared with F 2 is that here signed intensity is used. This is called negative partial power indicator. Field nonuniformity indicator This is defined as F 4 = 1 1 N ( ) 2, Iik Ī n N 1 Īn (29) i=1 12
13 This indicator specifies the field nonuniformity from segment to segment. In order to get a certain level of accuracy the condition L d > F 2 (30) must be fulfilled, where L d is a parameter of the measurement system, called the dynamic capability index. If a chosen measurement surface does not satisfy this criterion, some steps described in the standard have to be taken to improve the measurement accuracy. Otherwise the measurement accuracy grade has to be reduced. In the laboratory exercise, we use sound intensity method with scanning and follow standard ISO
Relationship between Sound Pressure and Sound Power Levels
Relationship between Sound Pressure and Sound Power Levels 4 W. T. W. CORY Chairman of the Eurovent WG 1 Fans If we wish to know the sound power transmitted through a fan and ducting system, it is preferable
More informationSound Intensity Testing Procedures for Determining Sound Power of HVAC Equipment
ANSI/AHRI Standard 230 2013 Standard for Sound Intensity Testing Procedures for Determining Sound Power of HVAC Equipment Approved by ANSI on April 15, 2014 IMPORTANT SAFETY DISCLAIMER AHRI does not set
More informationBasic Concepts of Sound. Contents: Definitions db Conversion Sound Fields db ± db
Basic Concepts of Sound Contents: Definitions db Conversion Sound Fields db ± db BA 766611, 1 Abstract This lecture introduces sound and sound measurements by describing sound pressure, sound level and
More informationEngineering Method of Sound Power Determination for Marine Engines
Engineering Method of Sound Power Determination for Marine Engines Minoru Ka1nata**, Hideo Ikeda***, Nobuhiro Baba*** The subject of this paper is the method to evaluate the sound power emitted from marine
More informationAcoustic Terms, Definitions and General Information
Acoustic Terms, Definitions and General Information Authored by: Daniel Ziobroski Acoustic Engineer Environmental and Acoustic Engineering GE Energy Charles Powers Program Manager Environmental and Acoustic
More informationWitold MIKULSKI. Central Institute for Labour Protection National Research Institute Czerniakowska 16, Warszawa, Poland;
ARCHIVES OF ACOUSTICS Vol. 38, No. 2, pp. 177 183 (2013) Copyright c 2013 by PAN IPPT DOI: 10.2478/aoa20130020 Method of Determining the Sound Absorbing Coefficient of Materials within the Frequency
More informationSound absorption and acoustic surface impedance
Sound absorption and acoustic surface impedance CHRISTER HEED SD2165 Stockholm October 2008 Marcus Wallenberg Laboratoriet för Ljud och Vibrationsforskning Sound absorption and acoustic surface impedance
More informationOptiffuser. Highperformance, high bandwidth lightweight 1D diffuser.
Optiffuser Highperformance, high bandwidth lightweight 1D diffuser. General product information The Optiffuser comes in packs of four panels. Two positives and two negatives (see page 5) per package.
More informationSound Power Level determination of AEG KM880 electrically operated food preparation appliance
Sound Power Level determination of AEG KM880 electrically operated food preparation appliance CHRISTER HEED AND ANDERS SÖRENSSON 4B1150 Stockholm March 2007 Marcus Wallenberg Laboratoriet för Ljud och
More informationVector Network Analyzer Techniques to Measure WR340 Waveguide Windows
LS296 Vector Network Analyzer Techniques to Measure WR340 Waveguide Windows T. L. Smith ASD / RF Group Advanced Photon Source Argonne National Laboratory June 26, 2002 Table of Contents 1) Introduction
More informationMultichannel Control Room Acoustics and Calibration
Multichannel Control Room Acoustics and Calibration After discussing control room layout, loudspeaker position and interaction of loudspeakers with room boundaries, Genelec s Christophe Anet highlights
More informationIntroduction to acoustic imaging
Introduction to acoustic imaging Contents 1 Propagation of acoustic waves 3 1.1 Wave types.......................................... 3 1.2 Mathematical formulation.................................. 4 1.3
More informationRobot Perception Continued
Robot Perception Continued 1 Visual Perception Visual Odometry Reconstruction Recognition CS 685 11 Range Sensing strategies Active range sensors Ultrasound Laser range sensor Slides adopted from Siegwart
More informationIntroduction to Error Analysis
UNIVERSITÄT BASEL DEPARTEMENT CHEMIE Introduction to Error Analysis Physikalisch Chemisches Praktikum Dr. Nico Bruns, Dr. Katarzyna Kita, Dr. Corinne Vebert 2012 1. Why is error analysis important? First
More informationLaboratory facilities for sound transmission measurements validation by measurement and simulation methods
Laboratory facilities for sound transmission measurements validation by measurement and simulation methods Marlon MEISSNITZER 1 ; Blasius BUCHEGGER 2 ; Heinz FERK 3 1, 2, 3 Graz University of Technology,
More informationNoise. CIH Review PDC March 2012
Noise CIH Review PDC March 2012 Learning Objectives Understand the concept of the decibel, decibel determination, decibel addition, and weighting Know the characteristics of frequency that are relevant
More informationComb Generator As a Reference Source AN104 CG
Comb Generator As a Reference Source AN104 CG What is a Comb Generator? We start with the discussion of what is a comb generator. It is an electronic device that produces a very fast (impulselike) pulse
More informationManual Analysis Software AFD 1201
AFD 1200  AcoustiTube Manual Analysis Software AFD 1201 Measurement of Transmission loss acc. to Song and Bolton 1 Table of Contents Introduction  Analysis Software AFD 1201... 3 AFD 1200  AcoustiTube
More informationTrans Bay Cable Project (400 MW) Preliminary Audible Noise Study
Page 1 of 5 Preliminary Audible Noise Study Pittsburg 10 th Street, NS Orientation Rev. Date Section Page Remarks Signature 0 17.11.06 all all first issue Page 2 of 5 1 Audible Noise Study 1.1 Basis The
More informationSound Pressure Measurement
Objectives: Sound Pressure Measurement 1. Become familiar with hardware and techniques to measure sound pressure 2. Measure the sound level of various sizes of fan modules 3. Calculate the signaltonoise
More informationDynamic sound source for simulating the Lombard effect in room acoustic modeling software
Dynamic sound source for simulating the Lombard effect in room acoustic modeling software Jens Holger Rindel a) Claus Lynge Christensen b) Odeon A/S, ScionDTU, Diplomvej 381, DK2800 Kgs. Lynby, Denmark
More informationACOUSTIC PERFORMANCES OF AN HEMIANECHOIC ROOM FOR ELECTROMAGNETIC COMPATIBILITY TESTS
ACOUSTIC PERFORMANCES OF AN HEMIANECHOIC ROOM FOR ELECTROMAGNETIC COMPATIBILITY TESTS Franco Cotana, Federico Rossi, Andrea Nicolini Università degli Studi di Perugia, Dipartimento di Ingegneria Industriale
More informationDirect and Reflected: Understanding the Truth with YS 3
Direct and Reflected: Understanding the Truth with YS 3 Speaker System Design Guide December 2008 2008 Yamaha Corporation 1 Introduction YS 3 is a speaker system design software application. It is
More informationTCOM 370 NOTES 994 BANDWIDTH, FREQUENCY RESPONSE, AND CAPACITY OF COMMUNICATION LINKS
TCOM 370 NOTES 994 BANDWIDTH, FREQUENCY RESPONSE, AND CAPACITY OF COMMUNICATION LINKS 1. Bandwidth: The bandwidth of a communication link, or in general any system, was loosely defined as the width of
More informationHVAC Acoustic Fundamentals
Application Guide AG 31010 HVAC Acoustic Fundamentals Decibel Sound Pressure Pascals 140 120 100 80 60 40 20 0 100 10 1.0 0.1 0.01 0.001 0.0001 0.00002 Barrier S1 BD BH R1 Measurement Point Path Length
More informationTesting laboratory HVAC. Test report No.: HP06525e
Testing laboratory HVAC Test report No.: HP62e Objective: Sound measurements on an air distribution box and an air inlet Client: RoomAir AG Thurstrasse 14 Postfach 81 Frauenfeld Date: 2662 This report
More informationSpectrum Level and Band Level
Spectrum Level and Band Level ntensity, ntensity Level, and ntensity Spectrum Level As a review, earlier we talked about the intensity of a sound wave. We related the intensity of a sound wave to the acoustic
More informationAirborne Sound Insulation
Airborne Sound Insulation with XL2TA Sound Level Meter This application note describes the verification of the airborne sound insulation in buildings with the XL2TA Sound Level Meter. All measurements
More informationAcoustical Analysis of Active Control in the Server Room of a C7 Data Centers Colocation Facility
Brigham Young University Acoustical Analysis of Active Control in the Server Room of a C7 Data Centers Colocation Facility Feasibility Report Advisor: Dr. Scott Sommerfeldt C7 Data Centers representative:
More informationThe infinite baffle loudspeaker measurement in half space by holographic near field scanning
The infinite baffle loudspeaker measurement in half space by holographic near field scanning 2015, Klippel GmbH The infinite baffle loudspeaker measurement in half space, 1 Comprehensive 3DDirectivity
More informationCALIBRATION HOW IT WORKS
PHOTO DETECTORS HIGH POWER SOLUTIONS POWER DETECTORS ENERGY DETECTORS At GentecEO, we understand that the essence of our business since 40 years has been delivering accuracy. There are no half measures:
More informationIntroduction... 2. Spatial Averaging... 15. Sound Pressure and Sound Power... 3. What about Background Noise?... 16. What is Sound Intensity?...
This booklet sets out to explain the fundamentals of sound intensity measurement. Both theory and applications will be covered. Although the booklet is intended as a basic introduction, some knowledge
More informationENGINEERING DATA. Fan Sound & Sound Ratings
Information and Recommendations for the Engineer ED300 ENGINEERING DATA Aerovent TC Ventco FiberAire Twin City Fan & Blower TC Axial Clarage Fan Sound & Sound Ratings Introduction Small, repetitive pressure
More informationMeasures to increase accuracy and precision of softwarebased noise prediction
Measures to increase accuracy and precision of softwarebased noise prediction Dr. Wolfgang Probst, DataKustik GmbH Gewerbering 5, 86926 Greifenberg, Germany ABSTRACT Following some similar national activities
More informationE190Q Lecture 5 Autonomous Robot Navigation
E190Q Lecture 5 Autonomous Robot Navigation Instructor: Chris Clark Semester: Spring 2014 1 Figures courtesy of Siegwart & Nourbakhsh Control Structures Planning Based Control Prior Knowledge Operator
More informationValidation for Smartphone Applications for Measuring Noise Méndez Sierra J.A. *, Vílchez Gómez, R., Rubio García, A.O.
Validation for Smartphone Applications for Measuring Noise Méndez Sierra J.A. *, Vílchez Gómez, R., Rubio García, A.O. Department of Applied Physics, Extremadura University, Cáceres, SPAIN *Email: jmendez@unex.es
More informationTuning a Monopole Antenna Using a Network Analyzer
11/21/11 Tuning a Monopole Antenna Using a Network Analyzer Chris Leonard Executive Summary: When designing a monopole antenna it is important to know at which frequency the antenna will be operating at.
More informationOuter Diameter 23 φ mm Face side Dimension 20.1 φ mm. Baffle Opening. Normal 0.5 Watts Maximum 1.0 Watts Sine Wave.
1. MODEL: 23CR08FH50ND 2 Dimension & Weight Outer Diameter 23 φ mm Face side Dimension 20.1 φ mm Baffle Opening 20.1 φ mm Height Refer to drawing Weight 4.0Grams 3 Magnet Materials Rare Earth Size φ 9.5
More informationIssues on inspection of audiometric room
Issues on inspection of audiometric room 1 Abstract 2 3 4 1 Abstract 2 3 4 1 Introduction of the audiometric room Application scope: The pure tone hearing test in CDC (Center for disease Control and Prevention)
More informationTrace Gas Exchange Measurements with Standard Infrared Analyzers
Practical Environmental Measurement Methods Trace Gas Exchange Measurements with Standard Infrared Analyzers Last change of document: February 23, 2007 Supervisor: Charles Robert Room no: S 4381 ph: 4352
More informationActive noise control in practice: transformer station
Active noise control in practice: transformer station Edwin Buikema 1 ; Fokke D. van der Ploeg 2 ; Jan H. Granneman 3 1, 2, 3 Peutz bv, Netherlands ABSTRACT Based on literature and extensive measurements
More informationThe Use of Computer Modeling in Room Acoustics
The Use of Computer Modeling in Room Acoustics J. H. Rindel Technical University of Denmark Abstract: After decades of development room acoustical computer models have matured. Hybrid methods combine the
More informationBuilding Design for Advanced Technology Instruments Sensitive to Acoustical Noise
Building Design for Advanced Technology Instruments Sensitive to Acoustic Noise Michael Gendreau Colin Gordon & Associates Presentation Outline! High technology research and manufacturing instruments respond
More informationThe Smith chart. Smith chart components. The normalized impedance line CHAPTER
26 CHAPTER The Smith chart The mathematics of transmission lines, and certain other devices, becomes cumbersome at times, especially when dealing with complex impedances and nonstandard situations. In
More informationDecember 14, 2004 Dear Valued Auralex Customer, Thank you for your interest in Auralex LENRDs. Before you review the attached test, we would like to
December 14, 2004 Dear Valued Auralex Customer, Thank you for your interest in Auralex LENRDs. Before you review the attached test, we would like to bring some important developments to your attention:
More informationBuilding Technology and Architectural Design. Program 4th lecture 9.009.45 Case studies Room Acoustics. 10.00 10.45 Case studies Room Acoustics
Building Technology and Architectural Design Program 4th lecture 9.009.45 Case studies Room Acoustics 9.45 10.00 Break 10.00 10.45 Case studies Room Acoustics Lecturer Poul Henning Kirkegaard 10102006
More information8. ACOUSTICS OF ROOMS AND ENCLOSURES
NOISE CONTROL Room Acoustics 8.1 8. ACOUSTICS OF ROOMS AND ENCLOSURES 8.1 Introduction This section covers the acoustics of enclosed spaces. Upon completion, the reader should have a basic understanding
More informationDOING PHYSICS WITH MATLAB COMPUTATIONAL OPTICS RAYLEIGHSOMMERFELD DIFFRACTION INTEGRAL OF THE FIRST KIND
DOING PHYSICS WITH MATLAB COMPUTATIONAL OPTICS RAYLEIGHSOMMERFELD DIFFRACTION INTEGRAL OF THE FIRST KIND THE THREEDIMENSIONAL DISTRIBUTION OF THE RADIANT FLUX DENSITY AT THE FOCUS OF A CONVERGENCE BEAM
More informationVIRTUAL SPACE 4D PROJECT: THE ROOM ACOUSTICAL TOOL. J. Keränen, P. Larm, V. Hongisto
VIRTUAL SPACE 4D PROJECT: THE ROOM ACOUSTICAL TOOL David Oliva University of Turku Department of Physics FIN20014 Turku, Finland. david.elorza@ttl.fi J. Keränen, P. Larm, V. Hongisto Finnish Institute
More information20110613. Acoustic design with wall acoustic solutions
20110613 Acoustic design with wall acoustic solutions Introduction A suspended ceiling is by far the most common acoustical treatment in a room. In most cases this is also a sufficient solution to create
More informationT = 1 f. Phase. Measure of relative position in time within a single period of a signal For a periodic signal f(t), phase is fractional part t p
Data Transmission Concepts and terminology Transmission terminology Transmission from transmitter to receiver goes over some transmission medium using electromagnetic waves Guided media. Waves are guided
More informationSOUND INTENSITY AND ITS MEASUREMENT AND APPLICATIONS
SOUND INTENSITY AND ITS MEASUREMENT AND APPLICATIONS Finn Jacobsen Acoustic Technology, Department of Electrical Engineering Technical University of Denmark, Building 352 Ørsteds Plads, DK2800 Lyngby
More informationDAAD: A New Software for Architectural Acoustic Design
The 33 rd International Congress and Exposition on Noise Control Engineering DAAD: A New Software for Architectural Acoustic Design Enis Ozgur a, Feridun Ozis b, Adil Alpkocak a a Dokuz Eylul University,
More informationAS COMPETITION PAPER 2008
AS COMPETITION PAPER 28 Name School Town & County Total Mark/5 Time Allowed: One hour Attempt as many questions as you can. Write your answers on this question paper. Marks allocated for each question
More informationSound Attenuation INTRODUCTION
INTRODUCTION In the broadest sense, a sound wave is any disturbance that is propagated in an elastic medium, which may be a gas, a liquid, or a solid. Noise is defined as any unwanted sound perceived by
More informationMeasurement of RF Emissions from a Final Coat Electronics Corrosion Module
Engineering Test Report No. 3780202 Rev. A Measurement of RF Emissions from a Final Coat Electronics Corrosion Module For : Canadian Auto Preservation, Inc. 390 Bradwick Drive Concord, Ontario CANADA
More informationEMC STANDARDS STANDARDS AND STANDARD MAKING BODIES. International. International Electrotechnical Commission (IEC) http://www.iec.
EMC STANDARDS The EMC standards that a particular electronic product must meet depend on the product application (commercial or military) and the country in which the product is to be used. These EMC regulatory
More informationAs a minimum, the report must include the following sections in the given sequence:
5.2 Limits for Wind Generators and Transformer Substations In cases where the noise impact at a Point of Reception is composed of combined contributions due to the Transformer Substation as well as the
More informationYou will need the following pieces of equipment to complete this experiment:
UNIVERSITY OF TORONTO FACULTY OF APPLIED SCIENCE AND ENGINEERING The Edward S. Rogers Sr. Department of Electrical and Computer Engineering ECE422H1S: RADIO AND MICROWAVE WIRELESS SYSTEMS EXPERIMENT 3:
More informationINFLUENCE OF THE ACOUSTIC IMPEDANCE OF HEADPHONES
P26 INFLUENCE OF THE ACOUSTIC IMPEDANCE OF HEADPHONES 43.58.Bh, 43.38.Si, 43.38.Vk, 43.66.Qp, 43.66.Pn, 43.66.Yw Kleber, Jochen; Martín Cruzado, Carlos G. Institute of Technical Acoustics, Aachen University
More informationAntenna Properties and their impact on Wireless System Performance. Dr. Steven R. Best. Cushcraft Corporation 48 Perimeter Road Manchester, NH 03013
Antenna Properties and their impact on Wireless System Performance Dr. Steven R. Best Cushcraft Corporation 48 Perimeter Road Manchester, NH 03013 Phone (603) 6277877 FAX: (603) 6271764 Email: sbest@cushcraft.com
More informationUnderstanding Range for RF Devices
Understanding Range for RF Devices October 2012 White Paper Understanding how environmental factors can affect range is one of the key aspects to deploying a radio frequency (RF) solution. This paper will
More informationThe Nature of Electromagnetic Radiation
II The Nature of Electromagnetic Radiation The Sun s energy has traveled across space as electromagnetic radiation, and that is the form in which it arrives on Earth. It is this radiation that determines
More informationAffordable Sports Halls
Creating a sporting habit for life Appendix 5 Acoustics (To be read in conjunction with the main document) Speech Intelligibility with 40dBA Ambient Noise (BB93 Compliant) Affordable Sports Halls August
More informationRECOMMENDATION ITUR BS.708 *, ** Determination of the electroacoustical properties of studio monitor headphones
Rec. ITUR BS.708 1 RECOMMENDATION ITUR BS.708 *, ** Determination of the electroacoustical properties of studio monitor headphones The ITU Radiocommunication Assembly, (1990) considering a) that unified
More informationAntennas and Propagation. Chapter 3: Antenna Parameters
Antennas and Propagation : Antenna Parameters Introduction Purpose Introduce standard terms and definitions for antennas Need a common language to specify performance Two types of parameters 1. Radiation
More informationAcoustic design according to room shape
Acoustic design according to room shape The shape of the room defines the movement of the sound waves within the room. Placement of acoustic materials should be determined by the way the sound moves in
More informationAbsorption Coefficients and Impedance Daniel A. Russell Science and Mathematics Department, Kettering University, Flint, MI, 48504
Absorption Coefficients and Impedance Daniel A. Russell Science and Mathematics Department, Kettering University, Flint, MI, 48504 1 I. Introduction and ackground In this laboratory exercise you will measure
More informationUse the following image to answer the next question. 1. Which of the following rows identifies the electrical charge on A and B shown above?
Old Science 30 Physics Practice Test A on Fields and EMR Test Solutions on the Portal Site Use the following image to answer the next question 1. Which of the following rows identifies the electrical charge
More informationAntenna Measurements Using the Mirror Method with Gating in a Time Domain
58 H. BÁTÍK, MEASUEMENTS USING THE MIO METHOD WITH GATING IN A TIME DOMAIN Antenna Measurements Using the Mirror Method with Gating in a Time Domain Hynek BÁTÍK Dept. of Electromagnetic Field, Czech Technical
More informationMULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
Exam Name MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) A 660Hz tone has an intensity level of 54 db. The velocity of sound in air is 345 m/s.
More informationEffects of Different Diffuser Types on the Diffusivity in Reverberation Chambers
Effects of Different Diffuser Types on the Diffusivity in Reverberation Chambers Mélanie Nolan 1 Acoustic Technology, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark Martijn Vercammen Peutz
More informationA METHOD OF CALIBRATING HELMHOLTZ COILS FOR THE MEASUREMENT OF PERMANENT MAGNETS
A METHOD OF CALIBRATING HELMHOLTZ COILS FOR THE MEASUREMENT OF PERMANENT MAGNETS Joseph J. Stupak Jr, Oersted Technology Tualatin, Oregon (reprinted from IMCSD 24th Annual Proceedings 1995) ABSTRACT The
More informationState Newton's second law of motion for a particle, defining carefully each term used.
5 Question 1. [Marks 28] An unmarked police car P is, travelling at the legal speed limit, v P, on a straight section of highway. At time t = 0, the police car is overtaken by a car C, which is speeding
More informationApplications in EMC testing. Outline. Antennas for EMC Testing. Terminology
Antennas for EMC Testing Zhong Chen ETSLindgren 1301 Arrow Point Drive Cedar Park, TX 78613 Zhong.Chen@etslindgren.com Outline EMC Terms and Definitions Typical EMC Antennas Calibration of EMC Antennas
More informationIntroduction to acoustic phonetics
Introduction to acoustic phonetics Dr. Christian DiCanio cdicanio@buffalo.edu University at Buffalo 10/8/15 DiCanio (UB) Acoustics 10/8/15 1 / 28 Pressure & Waves Waves Sound waves are fluctuations in
More informationEstimation of Loudness by Zwicker's Method
Estimation of Loudness by Zwicker's Method Loudness is one category in the list of human perceptions of sound. There are many methods of estimating Loudness using objective measurements. No method is perfect.
More informationCorrelation between OATS, Fully Anechoic Room and GTEM Radiated Emissions
Correlation between OATS, Fully Anechoic Room and GTEM Radiated Emissions Stephen Clay Introduction: Just a few words about myself. My name is Steve Clay and I work for Nokia Mobile Phones, and it is my
More informationPUMPED Nd:YAG LASER. Last Revision: August 21, 2007
PUMPED Nd:YAG LASER Last Revision: August 21, 2007 QUESTION TO BE INVESTIGATED: How can an efficient atomic transition laser be constructed and characterized? INTRODUCTION: This lab exercise will allow
More informationDetermination of sound immissions from sources placed close to the ears  such as head and earphones. Abstract
The 2001 International Congress and Exhibition on Noise Control Engineering The Hague, The Netherlands, 2001 August 2730 Determination of sound immissions from sources placed close to the ears  such
More informationCABLES CABLES. Application note. Link Budget
CABLES CABLES radiating Link Budget 3. 1. LINK BUDGET The basic elements to calculate a link budget can be illustrated by considering the example shown in Figure 4. It involves a GSM 900 radio coverage
More informationFaçade acoustic design strategy Proposed residential development Irvin Avenue, Saltburn
strategy Proposed residential development Report Number: 1420.1 Version: A Date: 13 th October 2008 Prepared by: Checked by: Andrew Gibson Jack HarvieClark Apex Acoustics Limited Design Works William
More informationPART VIII: ABSORPTIVE SILENCER DESIGN
PART VIII: ABSORPTIVE SILENCER DESIGN Elden F. Ray June 10, 2013 TABLE OF CONTENTS Introduction 2 Silencer Performance 4 Flow Resistance and Resistivity 7 Flow Velocity 7 Baffle Attenuation Example 7 Silencer
More informationExhaust noise control case study for 2800 class locomotive
Exhaust noise control case study for 2800 class locomotive Briony CROFT 1 ; Steve BROWN 2 ; Aaron MILLER 3, Andrew PARKER 4 1 SLR Consulting (Canada) Ltd, Canada 2,3,4 SLR Consulting Australia Pty Ltd,
More informationAcoustics VTAF05. Content Kristian Stålne Engineering acoustics. Course introduction, administrative details. Foundations of acoustics
Acoustics VTAF05 Kristian Stålne Engineering acoustics Content Course introduction, administrative details Foundations of acoustics 1 Lärare Lectures: PhD Kristian Stålne, Vbuilding 4th floor (north)
More informationTECHNOLOGY RESEARCH AND DEVELOPMENT More Than Alarm Anna KołodziejSaramak
TECHNOLOGY RESEARCH AND DEVELOPMENT More Than Alarm Anna KołodziejSaramak The purpose of the voice alarm systems (VAS) is to inform people about hazards in a possibly efficient way (which, unfortunately,
More informationPrinted Omni Directional WiFi Antenna for 5.6 GHz Dragoslav Dobričić, YU1AW
Printed Omni Directional WiFi Antenna for 5.6 GHz Dragoslav Dobričić, YU1AW dragan@antennex.com Why printed antenna? Building antenna on SHF is associated with problems of manufacturing its parts with
More informationMinimum requirements for DVBT receiving antennas for portable indoor and portable outdoor reception
Deutsche TV Platform Minimum requirements for DVBT receiving antennas for portable indoor and portable outdoor reception compiled by Working Group: DVBT launch (a working group of the Deutsche TV Platform)
More informationTechnical Notes 5A  Sound Insulation  Clay Masonry Walls (Reissued August 2000) INTRODUCTION
Technical Notes 5A  Sound Insulation  Clay Masonry Walls (Reissued August 2000) INTRODUCTION The sound insulation or sound transmission loss of a wall is that property which enables it to resist the
More informationReference Sound Source Calibration at Different Temperatures and Altitudes.
Reference Sound Source Calibration at Different Temperatures and Altitudes. Angelo CampanellaDecember 2000 Campanella Associates Compensation for environmental variables in the calibration and the
More informationANALYZER BASICS WHAT IS AN FFT SPECTRUM ANALYZER? 21
WHAT IS AN FFT SPECTRUM ANALYZER? ANALYZER BASICS The SR760 FFT Spectrum Analyzer takes a time varying input signal, like you would see on an oscilloscope trace, and computes its frequency spectrum. Fourier's
More informationSolutions to Exercises, Section 5.1
Instructor s Solutions Manual, Section 5.1 Exercise 1 Solutions to Exercises, Section 5.1 1. Find all numbers t such that ( 1 3,t) is a point on the unit circle. For ( 1 3,t)to be a point on the unit circle
More informationCalibration i of ESD Generators According to IEC Edition 2.0:
Calibration i of ESD Generators According to IEC 6100042 Edition 2.0:200812 Presented by : Standards and Calibration Laboratory (SCL) Innovation and Technology Commission The Government of the HKSAR
More informationVectron International Filter specification TFS 1220N 1/5
Vectron International Filter specification TFS 1220N 1/5 Measurement condition Ambient temperature: 22 C Input power level: 0 dbm Terminating impedance: Input: 50 Ω Output: 50 Ω Characteristics Remark:
More informationDesign of an Uslot Folded Shorted Patch Antenna for RF Energy Harvesting
Design of an Uslot Folded Shorted Patch Antenna for RF Energy Harvesting Diponkar Kundu, Ahmed Wasif Reza, and Harikrishnan Ramiah Abstract Novel optimized Uslot Folded Shorted Patch Antenna (FSPA) is
More informationE6211.0211311R0 ACOUSTICAL PERFORMANCE TEST REPORT ASTM E90. Rendered to: TREX COMPANY, LLC. Series/Model: Trex Seclusion
ACOUSTICAL PERFORMANCE TEST REPORT ASTM E90 Rendered to: TREX COMPANY, LLC Series/Model: Trex Seclusion Type: Sound Barrier Fence Summary of Test Results Data File No. Description STC OITC E6211.01 Trex
More informationAntenna Measurements
Antenna Measurements Antenna Measurements Introduction Antenna range Radiation patterns Amplitude Phase Gain measurements Antenna polarization Scale model measurements Introduction Most of the methodology
More informationA Theoretical Model for Mutual Interaction between Coaxial Cylindrical Coils Lukas Heinzle
A Theoretical Model for Mutual Interaction between Coaxial Cylindrical Coils Lukas Heinzle Page 1 of 15 Abstract: The wireless power transfer link between two coils is determined by the properties of the
More informationA model noise declaration to satisfy the European Machinery and Outdoor Noise Directives
A model noise declaration to satisfy the European Machinery and Outdoor Noise Directives Paul BRERETON 1 Health and Safety Executive, United Kingdom ABSTRACT A forestry woodchipper has been used to produce
More informationTHE ACOUSTICS OF ROOMS
Killam 1 THE ACOUSTICS OF ROOMS Josiah Killam PHYS 193: The Physics of Music Prof. Steven Errede University of Illinois at UrbanaChampaign Killam 2 For my project for The Physics of Music, I decided to
More information