# ASTM C634-13e1

Designation: C634 − 13´1Standard Terminology Relating toBuilding and Environmental Acoustics1This standard is issued under the fixed designation C634; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (´) indicates an editorial change since the last revision or reapproval.ε1NOTE—Editorial corrections made throughout in October 2016.INTRODUCTIONIn some of the entries, those that are measures of physical quantities, the term is followed by severalitems: an abbreviation or a symbol, or both, the dimensions of quantities, the measurement units, andthe part of speech. The abbreviation, where applicable, indicates the term as typically referenced. Thesymbol stands for the magnitude of the quantity in mathematical expressions. The dimensions of aquantity express its measure in terms of three fundamental quantities: M for mass, L for length, andT for time. Speed, for instance, is the quotient obtained when the distance an object moves is dividedby the time involved. The dimensions are [LT−1], the negative exponent indicating division. Themeasurement units are consistently in SI, Le Système International d’Unités. Those still using the cgs(centimetre-gram-second) or the inchpound system of units are referred for most of the conversionfactors to IEEE/ ASTM SI 10. Some conversion factors are listed in Section 5 of this document forconvenient reference.The dimensions of a quantity are the same regardless of the units in which the quantity is measured.Speed has the dimensions [LT−1] whether it is measured in miles per hour, feet per second, or metresper second. Quantities with different dimensions are not the same. Flow resistance and specific flowresistance, for instance, are quantities of different kinds even though the names are similar. On theother hand, quantities with the same dimensions are not necessarily of the same kind. Sound energydensity, for instance, has the same dimensions as sound pressure, [ML−1T−2], but it is not a kind ofsound pressure. Nor is absorption with the dimensions [L2] a kind of area.1. Scope1.1 This terminology covers terms and definitions related toenvironmental acoustics. Only definitions common to two ormore standards under the jurisdiction of Committee E33 arelisted here. The purpose of this terminology is to promoteuniformity of key definitions. Definitions pertinent to only onestandard and exceptions to the definitions listed below arecontained in the individual standards and should be used whenfollowing those standards.2. Referenced Documents2.1 ASTM Standards:2C367 Test Methods for Strength Properties of PrefabricatedArchitectural Acoustical Tile or Lay-In Ceiling PanelsC384 Test Method for Impedance and Absorption of Acous-tical Materials by Impedance Tube MethodC423 Test Method for SoundAbsorption and SoundAbsorp-tion Coefficients by the Reverberation Room MethodC522 Test Method for Airflow Resistance of AcousticalMaterialsC635 Specification for the Manufacture, Performance, andTesting of Metal Suspension Systems for Acoustical Tileand Lay-in Panel CeilingsC636 Practice for Installation of Metal Ceiling SuspensionSystems for Acoustical Tile and Lay-In PanelsE90 Test Method for Laboratory Measurement of AirborneSound Transmission Loss of Building Partitions andElementsE336 Test Method for Measurement of Airborne SoundAttenuation between Rooms in BuildingsE413 Classification for Rating Sound Insulation1This terminology is under the jurisdiction of ASTM Committee E33 onBuilding and Environmental Acoustics and is the direct responsibility of Subcom-mittee E33.07 on Definitions and Editorial.Current edition approved Sept. 1, 2013. Published December 2013. Originallyapproved in 1969. Last previous edition approved in 2011 as C634 – 11. DOI:10.1520/C0634-13E01.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at service@astm.org. For Annual Book of ASTMStandards volume information, refer to the standard’s Document Summary page onthe ASTM website.Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1E477 Test Method for Laboratory Measurements of Acous-tical andAirflow Performance of Duct Liner Materials andPrefabricated SilencersE492 Test Method for Laboratory Measurement of ImpactSound Transmission Through Floor-Ceiling AssembliesUsing the Tapping MachineE557 Guide for Architectural Design and Installation Prac-tices for Sound Isolation between Spaces Separated byOperable PartitionsE596 Test Method for Laboratory Measurement of NoiseReduction of Sound-Isolating EnclosuresE756 Test Method for Measuring Vibration-Damping Prop-erties of MaterialsE795 Practices for Mounting Test Specimens During SoundAbsorption TestsE966 Guide for Field Measurements of Airborne SoundAttenuation of Building Facades and Facade ElementsE989 Classification for Determination of Impact InsulationClass (IIC)E1007 Test Method for Field Measurement of TappingMachine Impact Sound Transmission Through Floor-Ceiling Assemblies and Associated Support StructuresE1014 Guide for Measurement of Outdoor A-WeightedSound LevelsE1042 Classification for Acoustically Absorptive MaterialsApplied by Trowel or SprayE1050 Test Method for Impedance and Absorption ofAcoustical Materials Using a Tube, Two Microphones anda Digital Frequency Analysis SystemE1110 Classification for Determination of Articulation ClassE1111 Test Method for Measuring the Interzone Attenuationof Open Office ComponentsE1123 Practices for Mounting Test Specimens for SoundTransmission Loss Testing of Naval and Marine ShipBulkhead Treatment MaterialsE1124 Test Method for Field Measurement of Sound PowerLevel by the Two-Surface MethodE1130 Test Method for Objective Measurement of SpeechPrivacy in Open Plan Spaces Using Articulation IndexE1179 Specification for Sound Sources Used for TestingOpen Office Components and SystemsE1222 Test Method for Laboratory Measurement of theInsertion Loss of Pipe Lagging SystemsE1264 Classification for Acoustical Ceiling ProductsE1265 Test Method for Measuring Insertion Loss of Pneu-matic Exhaust SilencersE1289 Specification for Reference Specimen for SoundTransmission LossE1332 Classification for Rating Outdoor-Indoor Sound At-tenuationE1374 Guide for Open Office Acoustics and ApplicableASTM StandardsE1414 Test Method for Airborne Sound Attenuation Be-tween Rooms Sharing a Common Ceiling PlenumE1503 Test Method for Conducting Outdoor Sound Mea-surements Using a Digital Statistical Sound AnalysisSystemE1573 Test Method for Evaluating Masking Sound in OpenOffices Using A-Weighted and One-Third Octave BandSound Pressure LevelsE1574 Test Method for Measurement of Sound in Residen-tial SpacesE1686 Guide for Applying Environmental Noise Measure-ment Methods and CriteriaE1704 Guide for Specifying Acoustical Performance ofSound-Isolating EnclosuresE1780 Guide for Measuring Outdoor Sound Received froma Nearby Fixed SourceE2179 Test Method for Laboratory Measurement of theEffectiveness of Floor Coverings in Reducing ImpactSound Transmission Through Concrete FloorsE2202 Practice for Measurement of Equipment-GeneratedContinuous Noise for Assessment of Health HazardsE2235 Test Method for Determination of Decay Rates forUse in Sound Insulation Test MethodsE2249 Test Method for Laboratory Measurement of Air-borne Transmission Loss of Building Partitions and Ele-ments Using Sound IntensityE2459 Guide for Measurement of In-Duct Sound PressureLevels from Large Industrial Gas Turbines and FansE2638 Test Method for Objective Measurement of theSpeech Privacy Provided by a Closed RoomIEEE/ ASTM SI 10 Standard for Use of the InternationalSystem of Units (SI): The Modern Metric System2.2 ANSI Standard:ANSI S1.4 Specification for Sound Level Meters3ANSI S1.6 Preferred Frequencies, Frequency Levels, andBand Numbers for Acoustical MeasurementsANSI S1.11 Octave-Band and Fractional Octave-Band Ana-log and Digital Filters, Specifications for3. Terminology3.1 If the term sought by the user cannot be found in 3.2,itmay be found in 4.1.3.2 Definitions:acoustic impedance, Z[ML−4T−1], (mks acoustic ohm orPa·s/m3), n—of a surface, for a given frequency, the complexquotient obtained when the sound pressure averaged over thesurface is divided by the volume velocity through thesurface. The real and imaginary components are called,respectively, acoustic resistance and acoustic reactance.Z[R1jX (1)where:R = the real component of acoustic impedance, andX = the imaginary component of acoustic impedance.acoustical barrier, n—contiguous objects such as solid walls,buildings, or earthen berms that substantially block the directpath of sound between a source and receiver, and which, ifthey have an open edge or edges allowing diffraction around3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http://www.ansi.org.C634 − 13´12them, are sufficiently wide and high to cause significantreduction of the sound traveling from the source to thereceiver.acoustical material, n—any material considered in terms of itsacoustical properties. Commonly and especially, a materialdesigned to absorb sound.admittance ratio, yρc[dimensionless], n—the reciprocal of theimpedance ratio. The real and imaginary components arecalled, respectively, conductance ratio and susceptanceratio.ypc[gpc 2 jbpc (2)where:gρc = the real component of admittance ratio, andbρc = the imaginary component of admittance ratio.airborne sound, n—sound that arrives at the point of interest,such as one side of a partition, by propagation through air.airflow resistance, R[ML−4T−1], (mks acoustic ohm or Pa·s/m3), n—the quotient of the air pressure difference across aspecimen divided by the volume velocity of airflow throughthe specimen. The pressure difference and the volumevelocity may be either steady or alternating.airflow resistivity, ro[ML−3T−1], (mks rayl/m or Pa·s/m2),n—of a homogeneous material, the quotient of its specificairflow resistance divided by its thickness.ambient noise, n—the composite of airborne sound from manysources near and far associated with a given environment.No particular sound is singled out for interest.arithmetic mean sound pressure level, n—of several relatedsound pressure levels measured at different positions ordifferent times, or both, in a specified frequency band, thesum of the sound pressure levels divided by the number oflevels.DISCUSSION—The arithmetic mean sound pressure level is sometimesused to approximate the average sound pressure level. The accuracyof this approximation depends upon the range of sound pressure levels.average sound pressure level, L¯p[dimensionless], n—of sev-eral related sound pressure levels measured at different posi-tions or different times, or both, in a specified frequency band,ten times the common logarithm of the arithmetic mean of thesquared pressure ratios from which the individual levels werederived.DISCUSSION—1—An average sound pressure level obtained by aver-aging the A-weighted sound level continuously over a specified periodis called the time-average sound level.DISCUSSION—2—Since, by definition, a squared pressure ratio, pi2/p02, is equal to 10Li/10, average sound pressure level is calculated fromthe expression:L¯p5 10log10S1n(i51n10Li/10D(3)where:L¯p= average sound pressure level, dB,n = number of individual sound pressure levels,pi= rms pressure at an individual position or time, or both,Pa,p0= 20 µPa, reference sound pressure, andLi= an individual sound pressure level, dB.If conditions warrant, an integral expression may be used:L¯p5 10log10S1T*t1t2~p2~t!/p02! dtD (4)where:L¯p= average sound pressure level during a specified timeinterval, dB,T =t2−t1= a specified time interval, s, min, h, or day,p(t) = instantaneous sound pressure, Pa, andp0= 20 µPa, reference sound pressure.background noise, n—noise from all sources unrelated to aparticular sound that is the object of interest. Backgroundnoise may include airborne, structureborne, and instrumentnoise.cutoff frequency, n—of an anechoic wedge or set of wedges,the lowest frequency above which the normal incidencesound absorption coefficient is at least 0.990.damp, v—to cause a loss or dissipation of the oscillatory orvibrational energy of an electrical or mechanical system.decay rate, d[T−1], (dB/s), n—for airborne sound, the rate ofdecrease of sound pressure level after the source of soundhas stopped; for vibration, the rate of decrease of vibratoryacceleration, velocity, or displacement level after the exci-tation has stopped.decibel, dB[dimensionless], n—the term used to identify tentimes the common logarithm of the ratio of two likequantities proportional to power or energy. (See level, soundtransmission loss.) Thus, one decibel corresponds to apower ratio of 100.1and n decibels corresponds to a powerratio of (100.1)n.DISCUSSION—Since the decibel expresses the ratio of two likequantities, it has no dimensions. It is, however, common practice totreat “decibel” as a unit as, for example, in the sentence, “The averagesound pressure level in the room is 45 decibels.”diffraction, n—a change in the direction of propagation ofsound energy in the neighborhood of a boundarydiscontinuity, such as the edge of a reflective or absorptivesurface.diffuse sound field, n—the sound in a region where the soundintensity is the same in all directions and at every point.direct sound field, n—the sound that arrives directly from asource without reflection.dummy microphone, n—a microphone substitute which haselectrical characteristics identical to a functionalmicrophone, but which has essentially no sensitivity toincident sound pressure.field sound transmission class, FSTC[dimensionless],n—sound transmission class calculated in accordance withClassification E413 using values of field transmission loss.C634 − 13´13field transmission loss, FTL[dimensionless], n—sound trans-mission loss measured in accordance with Annex A1 of TestMethod E336.flanking transmission, n—transmission of sound from thesource to a receiving location by a path other than that underconsideration.impact insulation class, IIC[dimensionless], n—a single-number rating derived from measured values of normalizedimpact sound pressure levels in accordance with Annex A1of Test Method E492. It provides an estimate of the impactsound insulating performance of a floor-ceiling assembly.impedance ratio, z/ρc[dimensionless], n—the ratio of thespecific normal acoustic impedance at a surface to thecharacteristic impedance of the medium. The real andimaginary components are called, respectively, resistanceratio and reactance ratio.z⁄pc[r⁄pc1jx⁄pc (5)where:r/ρc = the real component of impedance ratio, andx/ρc = the imaginary component of impedance ratio.impulsive sound, n—a brief, intrusive sound, such as thatassociated with a tir