Designation:E90–09
Standard Test Method for
Laboratory Measurement of Airborne Sound Transmission Loss of Building Partitions and Elements1
This standard is issued under thefixed designation E90;the number immediately following the designation indicates the year of original adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.A superscript epsilon(´)indicates an editorial change since the last revision or reapproval.
INTRODUCTION
This test method is part of a set for evaluating the sound-insulating properties of building elements. It is designed to measure the transmission of sound through a partition or partition element in a laboratory.Others in the set cover the measurement of sound isolation in buildings(Test Method E336),the laboratory measurement of impact sound transmission throughfloors(Test Method E492), the measurement of impact sound transmission in buildings(Test Method E1007),the measurement of sound transmission through building facades and facade elements(Guide E966),the measurement of sound transmission through a common plenum between two rooms(Test Method E1414),a quick method for the determination of airborne sound isolation in multiunit buildings(Practice E597),and the measurement of sound transmission through door panels and systems(Test Method E1425).
1.Scope
1.1This test method covers the laboratory measurement of airborne sound transmission loss of building partitions such as walls of all kinds,operable partitions,floor-ceiling assemblies, doors,windows,roofs,panels,and other space-dividing ele-ments.
1.2Laboratories are designed so the test specimen consti-tutes the primary sound transmission path between the two test rooms and so approximately diffuse soundfields exist in the rooms.
1.3Laboratory Accreditation—The requirements for ac-crediting a laboratory for performing this test method are given in Annex A4.
1.4This standard does not purport to address all of the safety concerns,if any,associated with its use.It is the responsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.
2.Referenced Documents
2.1ASTM Standards:2C423Test Method for Sound Absorption and Sound Ab-sorption Coefficients by the Reverberation Room Method C634Terminology Relating to Building and Environmen-tal Acoustics
E336Test Method for Measurement of Airborne Sound Attenuation between Rooms in Buildings
E413Classification for Rating Sound Insulation
E492Test Method for Laboratory Measurement of Impact Sound Transmission Through Floor-Ceiling Assemblies Using the Tapping Machine
E966Guide for Field Measurements of Airborne Sound Insulation of Building Facades and Facade Elements
E1007Test Method for Field Measurement of Tapping Machine Impact Sound Transmission Through Floor-Ceiling Assemblies and Associated Support Structures
E1111Test Method for Measuring the Interzone Attenua-tion of Open Office Components
E1289Specification for Reference Specimen for Sound Transmission Loss
E1332Classification for Determination of Outdoor-Indoor Transmission Class
E1414Test Method for Airborne Sound Attenuation Be-tween Rooms Sharing a Common Ceiling Plenum
E1425Practice for Determining the Acoustical Perfor-mance of Exterior Windows and Doors
E2235Test Method for Determination of Decay Rates for Use in Sound Insulation Test Methods
2.2ANSI Standards:
S1.6-1984(R2006)American National Standard Preferred Frequencies,Frequency Levels,and Band Numbers for
1This test method is under the jurisdiction of ASTM Committee E33on Building
and Environmental Acoustics and is the direct responsibility of Subcommittee
E33.03on Sound Transmission.
Current edition approved July1,2009.Published August2009.Originally
approved in1955.Last previous edition approved in2004as E90–04.
2For referenced ASTM standards,visit the ASTM website,,or
contact ASTM Customer Service at For Annual Book of ASTM
Standards volume information,refer to the standard’s Document Summary page on
the ASTM website.
Copyright©ASTM International,100Barr Harbor Drive,PO Box C700,West Conshohocken,PA19428-2959,United States.
Acoustical Measurement 3
S1.10Pressure Calibration of Laboratory Standard Pressure Microphones 3
S1.11Specification for Octave-Band and Fractional-Octave-Band Analog and Digital Filters 3
S1.40Specifications and Verification Procedures for Sound Calibrators 3
S1.43Specifications for Integrating-Averaging Sound-Level Meters 3
S12.51Acoustics—Determination of Sound Power Levels of Noise Sources Using Sound Pressure—Precision Meth-ods for Reverberation Rooms 32.3ISO Standards:
ISO 717Rating of Sound Insulation for Dwellings 3
ISO 3741Acoustics—Determination of Sound Power Level of Noise Sources—Precision Methods for Reverberation Rooms 3
2.4IEC Standards:
IEC 60942Electroacoustics—Sound Calibrators 4
IEC 61672Electroacoustics—Sound Level Meters—Part 1:Specifications 43.Terminology
3.1The following terms used in this test method have specific meanings that are defined in Terminology C 63
4.
acoustical barrier reverberation room airborne sound
sound absorption average sound pressure level sound attenuation background noise sound energy damp
sound insulation decay rate sound isolation decibel sound level diffraction
sound power diffuse sound field sound pressure
direct sound field sound pressure level flanking transmission sound transmission level level
sound transmission class
octave band sound transmission coefficient pink noise
sound transmission loss receiving room
source room reverberant sound field
unit
3.1.1For the purposes of this test method,transmission loss is operationally defined as the difference in decibels between the average sound pressure levels in the reverberant source and receiving rooms,plus ten times the common logarithm of the ratio of the area of the common partition to the sound absorption in the receiving room (see Eq 5).
N OTE 1—Sound transmission coefficient and sound transmission loss are related by either of the two equations:
TL 510log ~1/t !(1)t 510–TL /10
(2)
4.Summary of Test Method
4.1Two adjacent reverberation rooms are arranged with an opening between them in which the test partition is installed.Care is taken that the only significant sound transmission path
between rooms is by way of the test partition.An approxi-mately diffuse sound field is produced in one room,the source room.Sound incident on the test partition causes it to vibrate and create a sound field in the second room,the receiving room.The space-and time-averaged sound pressure levels in the two rooms are determined.In addition,with the test specimen in place,the sound absorption in the receiving room is determined.The sound pressure levels in the two rooms,the sound absorption in the receiving room and the area of the specimen are used to calculate sound transmission loss as shown in Section 11.Because transmission loss is a function of frequency,measurements are made in a series of frequency bands.
4.2In theory,it is not important which room is designated as the source and which as the receiving room.In practice,different values of sound transmission loss may be measured when the roles are reversed.To compensate for this,the entire measurement may be repeated with the roles reversed;the source room becomes the receiving room and vice versa.The two sets of transmission loss values are then averaged to produce the final result for the laboratory.
4.3Additional procedures that may be followed when testing doors are given in Test Method E 142
5.
5.Significance and Use
5.1Sound transmission loss as defined in Terminology C 634,refers to the response of specimens exposed to a diffuse incident sound field,and this is the test condition approached by this laboratory test method.The test results are therefore most directly relevant to the performance of similar specimens exposed to similar sound fields.They provide,however,a useful general measure of performance for the variety of sound fields to which a partition or element may typically be exposed.5.2In laboratories designed to satisfy the requirements of this test method,the intent is that only significant path for sound transmission between the rooms is through the test specimen.This is not generally the case in buildings where there are often many other paths for sounds—flanking sound transmission .Consequently sound ratings obtained using this test method do not relate directly to sound isolation in buildings;they represent an upper limit to what would be measured in a field test.
5.3This test method is not intended for field tests.Field tests shall be performed according to Test Method E 33
6.
N OTE 2—The comparable quantity measured using Test Method E 336is called the apparent sound transmission loss because of the presence of flanking sound transmission.
6.Test Rooms
6.1The test rooms shall be so constructed and arranged that the test specimen constitutes the only important transmission path between them.Laboratories must investigate their flank-ing limit and prepare a report as described in Annex A5.6.2The spatial variations of sound pressure level measured in the each room shall be such that the precision requirements in Annex A2are satisfied at all frequencies.
6.3Volume of Rooms —The minimum volume of each room is 80m 3.
3
Available from American National Standards Institute (ANSI),25W.43rd St.,4th Floor,New York,NY 10036,4
Available from International Electrotechnical Commission (IEC),3rue de Varembé,Case postale 131,CH-1211,Geneva 20,Switzerland,
www.iec.ch.
N OTE3—See Appendix X1for recommendations for new construction.
6.4Room Absorption—The sound absorption in the receiv-ing room should be low to achieve the best possible simulation of the ideal diffusefield condition,and to minimize the region dominated by the directfield of the test specimen.In the frequency range that extends from f=2000/V1/3to2000Hz, the absorption in the receiving room(as furnished with diffusers)should be no greater than:
A5V2/3/3(3) where:
V=the room volume,m3,and
A=the sound absorption of the room,m2.
6.4.1For frequencies below f=2000/V1/3,somewhat higher absorption may be desirable to accommodate requirements of other test methods(for example,ISO3741);in any case,the absorption should be no greater than three times the value given by Eq3.
N OTE4—For frequencies above2000Hz,atmospheric absorption may make it impossible to avoid a slightly higher value than that given in Eq 3.
6.5Unless otherwise specified,the average temperatures in each room during all acoustical measurements shall be in the range2265°C and the average relative humidity shall be at least30%.
6.5.1When testing specimens with temperature sensitive materials,such as systems that incorporate laminated glass,the average temperature of the specimen and in each room during all acoustical measurements shall be in the range2262°C. N OTE5—The sound damping properties of viscoelastic substrates between panels(glass,metal,etc.)and of viscoelastic materials used to mount glass often depend on temperature.This requirement minimizes any effects this has on measured sound transmission loss.
6.6During the sound pressure level and the corresponding sound absorption measurements,variations in temperature and humidity in the receiving room shall not exceed3°C and3% relative humidity respectively.Temperature and humidity shall be measured and recorded as often as necessary to ensure compliance.
6.6.1If a relative humidity of at least30%can not be maintained in the receiving room,users of the test
method shall verify by calculation that changes in the10log A0term(see 11.1)due to changes in temperature and humidity do not exceed0.5dB.
N OTE6—Procedures for calculating air absorption are described in Test Method C423.
7.Test Specimens
7.1Size and Mounting—Any test specimen that is to typify
a wall orfloor shall be large enough to include all the essential constructional elements in their normal size,and in a propor-tion typical of actual use.The minimum dimension(excluding thickness)shall be2.4m,except that specimens of doors,office screens,and other smaller building elements shall be their customary size.Preformed panel structures should include at least two complete modules(panels plus edge mounting elements),although single panels can be tested.In all cases the test specimen shall be installed in a manner similar to actual construction,with a careful simulation of normal constraint and sealing conditions at the perimeter and at joints within the field of the specimen.Detailed reporting and installation procedures for particular types of building separation elements are given in Annex A1.
7.2Offıce Screens—The minimum area of an office screen specimen shall be2.3m2.Testing an office screen according to this test method is only appropriate when the property of interest is sound transmission through the main body of the screen.Screens that incorporate electrical raceways may allow sound to pass through easily in this region.Such parts of an office screen shall be included as part of the specimen.For a complete test of the screen as a barrier,including the effects of diffraction and leakage,Test Method E1111is recommended.
7.3Operable Door Systems—Measurements may be in accordance with Test Method E1425to evaluate door systems in the operable and fully sealed state,and to measure the force required to operate the door.
8.Test Signal Sound Sources
8.1Signal Spectrum—The sound signals used for these tests shall be random noise having a continuous spectrum within each test frequency band.
8.2Sound Sources—Sound sources shall consist of one or more loudspeakers in an enclosure.
N OTE7—Sources should preferably be omnidirectional at all measure-ment frequencies to excite the
soundfield in the room as uniformly as possible.Using separate loudspeakers for high and low frequencies will make the system more omnidirectional.Aiming the loudspeakers into corners of the room can reduce the directfield from the loudspeaker system.An approximation to an omnidirectional speaker system can be obtained by mounting an array of loudspeakers on the faces of a polyhedron(cube,octahedron,dodecahedron,etc.).Sources in trihedral corners of the room excite room modes more effectively and laboratory operators mayfind that this orientation increases the low frequency sound pressure levels in the room.
8.3Multiple Sound Sources—If a laboratory chooses to use multiple sound sources at different locations in the room simultaneously,they shall be driven by separate random noise generators and amplifiers.
N OTE8—Measured values of sound transmission loss,especially at low frequencies,may change significantly when sound source position is changed.Multiple sound sources driven by uncorrelated noise signals have also been found to reduce the spatial variance of sound pressure level in reverberation rooms and thus make it easier to satisfy the requirements of Annex A2.
9.Instrumentation Requirements
9.1Microphones and analyzers are used to measure average sound pressure levels in the source and receiving rooms and sound decay rates in the receiving room.Various systems of data collection and processing are possible,ranging from a single microphone moving continuously or placed in sequence at several measurement positions to several microphones making simultaneous measurements(see Fig.1for two ex-amples).The measurement process must account for spatial and temporal variations of sound pressure level.
9.2Microphone Electrical Requirements—Use micro-phones that are stable and substantially omni-directional in
the
frequency range of measurement,with a known frequency response for a random incidence sound field.(A 13-mm (0.5-in.)random-incidence condenser microphone is recom-mended.)Specifically,microphones,amplifiers,and electronic circuitry to process microphone signals mu
st satisfy the re-quirements of ANSI S1.43or IEC 61672for class 1sound level meters,except that A,B,and C weighting networks are not required since one-third octave filters are used.All micro-phones used in testing according to this method shall be of the same type.
9.3Calibration —Calibrate each microphone over the whole range of test frequencies as often as necessary to ensure the required accuracy (see ANSI S1.10).A record shall be kept of the calibration data and the dates of calibration.
9.3.1Calibration checks of the entire measurement system for at least one frequency shall be made at least once during each day of testing.Make the calibration check of the mea-surement system using an acoustic calibrator that generates a known sound pressure level at the microphone diaphragm and at a known frequency.The class of Calibrator shall be class 1per ANSI S1.40or IEC 60942.
9.4Bandwidth —The overall frequency response of the filters used to analyze the microphone signals shall,for each test band,conform to the specifications in ANSI S1.11for a one-third octave band filter set,class 1or better.
9.4.1If filtering is applied to the source signals to concen-trate the available power in one test band or a few bands,the frequency range of the signal shall always be greater than the frequency range of the
microphone filter.
9.5Standard Test Frequencies —Measurements shall be made in all one-third-octave bands with mid-band frequencies specified in ANSI S1.11from 100to 5000Hz.For sound transmission loss measurements on building facades,exterior doors or windows,or other building facade elements where the
outdoor-indoor transmission class is to be calculated,the minimum frequency range shall be from 80to 5000Hz.
N OTE 9—It is desirable in any case that the frequency range be extended to include bauds below 125Hz.Many applications require information on low frequency transmission loss and laboratory operators are encouraged to collect and report information down to at least 50Hz where feasible.Note that larger room volumes are recommended when measuring at lower frequencies (see X1.2).
10.Measurement of Average Sound Pressure Levels and
Room Sound Absorption
10.1The microphone system used to obtain the average sound pressure level must satisfy the require
ments given in Annex A2.
10.2Measurement of Average Sound Pressure Levels,L S and L R —With the sound sources generating the sound field in one room,the source room,measure the space-and time-averaged sound pressure level in the source room,L S ,and in the receiving room,L R .
10.3Background Noise in the Receiving Room and Associ-ated Measurement System —With the sound sources not oper-ating,measure the background noise levels in the receiving room for each frequency band at the same microphone posi-tions used to measure L R .Make these measurements using the same microphone and analyzer gain settings as used for measurements of the received level.This accounts properly for residual noise and the dynamic range in instrumentation.At each measurement position corrections shall be made unless the background level is more than 10dB below the combina-tion of signal and background.(The signal is the sound pressure level due to transmission through the test specimen.)If the background level is between 5and 10dB below the combined level,correct the signal level using:
L a 510log @10L sb /10–10L b /10#
(4)
where:
L b =background noise level,dB,
L sb =level of signal and background combined,dB,and L a =adjusted signal level,dB.
10.3.1If the output of the sound sources cannot be increased so the combined level is at least 5dB above the background level,then subtract 2dB from the combined level and use this as the corrected signal level.In this case,the measurements can be used only to provide an estimate of the lower limit of the sound transmission loss.Identify such measurements in the test report.
N OTE 10—Noise measured by the microphone system in the receiving room when the sound sources are not operating may be due to extraneous acoustical sources or to electrical noise in the receiving system,or both.
10.4Determination of Receiving Room Absorption,A R —Measure the mean value of the receiving room absorption at each frequency in accordance with Test Method E 2235.The determination of A R shall be made with the receiving room in the same condition as for the measurement of L S and L R .Specifically,the test specimen shall remain in place so its effective absorption (which includes transmis
sion back to the source room)is included.Sound sources used for measuring A R shall be present during the measurement of L R ,so their absorption is present during both
measurements.
N OTE —This figure is not meant to be a design guide but is for illustrative purposes only.As an example,the room on the right has fixed microphones to measure average sound pressure level;the room on the left has a continuously moving microphone to measure average sound pressure level.Usually both rooms will have the same microphone system.The loudspeakers in the rooms generate the incident sound fields for the measurement of level differences or sound decay rates.
FIG.1Illustration Showing Conceptual Arrangement of a Wall
Sound Transmission Loss
Suite
10.4.1Room Coupling —Because the two test rooms are coupled by the test specimen,it is possible that the decay rate measurements in the receiving room will be influenced by sound energy transmitte
d into the source room and then back again during the decay process (1).5Decay curves may be markedly curved or have two pronounced slopes.To ensure the effect will be small the product t S must be smaller than A S ,the absorption in the source room,or A R ,the absorption in the receiving room,or d S /d R ,the ratio of decay rates in the two rooms,must be larger than unity.The latter requirement may be met by adding absorption to the source room until no further effect is observed on the measured value of d R .
N OTE 11—Additional absorption in the source room is required only during measurement of receiving room absorption.It shall not be present during measurement of L S and L R .
10.5For estimates of the direction-averaged transmission loss it is necessary to repeat all measurements with the second room acting as the source.This results in four sets of average sound pressure levels and two sets of room absorptions corresponding to the two directions of sound transmission.11.Calculation
11.1For the chosen test directions),calculate the sound transmission loss at each frequency f from:
TL ~f !5L S ~f !–L R ~f !110log S /A R ~f !
(5)
where:
TL(f)=transmission loss,dB,
L S (f)=average sound pressure level in the source room,
dB,
L R (f)=average sound pressure level in the receiving
room,dB,
S =area of test specimen that is exposed in the
receiving room,m 2,and
A R (f)=sound absorption of the receiving room with the
test specimen in place,m 2(1).
11.2When measurements are made in both directions,the final value of transmission loss to be reported shall be calculated using:
TL ~f !5~TL 1~f !1TL 2~f !!/2
(6)
where TL 1(f)and TL 2(f)correspond to the two directions of measurement.
11.2.1If TL 1(f)or TL 2(f)is invalid (for example,because of excessive background noise)then the remaining valid measure-ment shall be used for TL(f).Identify in the test report transmission loss values that are not averaged as required in 11.2.
11.3If a laboratory chooses to use only one direction of measurement,then no averaging is required.
11.4This test method specifies the use of one-third octave bands for measurement and calculation of sound transmission loss.It does not allow measurement of octave band transmis-sion losses because these are very sensitive to the shape of the spectrum in the source room and to the details of the transmis-
sion loss characteristics of the test panel.In applications where octave band transmission loss values,TL oct ,are required,they shall be calculated using the expression:
TL oct ,f c 5–10log F 13(B 5B c 21
B c 11
102TL B /10
G
(7)
where:
f c =preferred octave band mid-band frequency as specified
in ANSI S1.6.
editor evaluating revision11.4.1The summation is made over three one-third octave band TL values:one at the frequency f c with band number B c and the adjacent one-third octave bands,with band numbers B c +1and B c –1.The octave band transmission loss values calculated from this expression approximate what would be measured if the spectrum in the source room had the same sound pressure level in each one-third octave band.
12.Report
12.1Include the following information in the test report:12.1.1A statement,if true in every respect,that the tests were conducted according to this test method and that detailed test procedures,data for flanking limit tests,repeatability measurements and reference specimen tests are available on request.
12.1.2A description of the test specimen in accordance with the requirements in Annex A1.The description must be sufficiently detailed to identify the specimen,at least for those elements that may affect its sound transmission loss,unless the test sponsor wishes to withhold information of a proprietary nature.A designation and description furnished by the sponsor of the test may be included in the report provided that they are attributed to the sponsor.If some details of the specimen construction are withheld at the sponsor’s request,the report shall state this.
12.1.3The dates of construction and testing.
12.1.4If the test specimen is a screen,include a statement,if true,that sound transmission through raceways and other penetrations are included in the evaluation.
12.1.5State clearly whether the transmission loss values are for a single direction of measurement or are averages of two directions.
12.1.6A table of sound transmission loss values rounded to the nearest decibel for the frequency bands required in 9.5and any other bands measured.These data may also be presented as a graph.
12.1.7Identify data affected by flanking transmission (An-nex A5)or background noise.
12.1.8The temperature and humidity in the rooms during the measurements.
12.1.9The volumes of the source and receiving rooms.12.1.10Single Number Ratings :
12.1.10.1Sound Transmission Class —If single number rat-ings are given,the sound transmission class described in Classification E 413shall be included.
N OTE 12—The weighted airborne sound reduction indexes described in ISO 717have a similar purpose to STC.These may also be given.
12.1.10.2Outdoor-Indoor Transmission Class —Where the test specimen maybe used as part of a facade of a building,the
5
The boldface numbers in parentheses refer to the list of references at the end of this
standard.
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