1、Report No. 54 A Technical ReportonOctober 1997 Recommended Methodsfor Measuring AcousticNoise EmissionPrepared byT1E1.8Working GrouponPhysical Protectionand DesignCommittee T1 is sponsored by the Alliance for Telecommunications Industry SolutionsAccredited by American National Standards InstituteCop
2、yright 1997 by Alliance for Telecommunications IndustrySolutionsAll rights reserved.No part of this publication may be reproduced in any form,in an electronic retrieval system or otherwise, without theprior written permission of the publisher.iForewordThis Technical Report (TR) has been produced by
3、Working Group T1E1.8 ( Physical Protectionand Design ) as part of Technical Subcommittee T1E1 ( Interfaces, Power and Protection ofNetworks ).Compatibility with the end-use environment is a primary concern for purchasers andmanufacturers of telecommunications equipment. An important compatibility is
4、sue is the amountof acoustic noise emitted by the equipment. This TR is intended to meet three primary needs ofpurchasers and manufacturers with regard to this issue: Recommendation of acoustic noise emission measurement methods Recommendation of a method for reporting acoustic noise emission Recomm
5、endation of a method for verification of declared noise emission valuesTo develop practical specifications and to have the capacity to make fair comparisons betweenequipment, it is essential to have a single, technically established method for the measurement ofacoustic emission. Therefore, this TR
6、recommends the use of sound power measurement and,more specifically, adopts ISO 7779 as the primary measurement reference document.Sound power levels can be used for direct comparison of noise emission for functionally similarequipment manufactured by different vendors, and/or in the calculation of
7、estimated soundpressure levels for spaces where the equipment is to be installed. The use of sound power level,instead of sound pressure level, as the specified quantity for product noise emission has clearprecedent within the international noise control community. Additionally, the EuropeanTelecomm
8、unications Standards Institute (ETSI) has recently adopted sound power as its primarydescriptor for noise emission.This TR recommends that manufacturers report measured A-weighted sound power values forequipment. Given that it is impractical and unnecessary to measure every manufactured unit, therep
9、orted sound power value should be one that all, or nearly all, units of a particular model willnot exceed. This means that, the reported value should take into account both productionvariation and the precision of the measurement method. ISO 9296 recommends methods thataddress these issues and is th
10、erefore recommended in this TR as the method for declaring soundpower values. ISO 9296 also recommends a method for verification of declared sound powervalues.In general, the noise levels associated with telecommunications equipment are well below thehealth and safety sound pressure limits required
11、by the Occupational Safety and HealthAdministration (OSHA). As discussed in Annex C, sound power data can be used to obtain anestimate of immission sound pressure levels when the appropriate environmental parameters areknown.iiContentsForeword1 Scope2 References3 Definitions4 Measurement methodology
12、5 Installation and operation of equipment5.1 Equipment installation5.2 Equipment operation “in-use”5.2.1 Variable emissions - standard temperature test5.2.2 Variable emissions - high temperature test6 Information to be recorded7 Information to be reported8 Verification of declared A-weighted sound p
13、ower levelsAnnex A (informative): Prominent discrete tonesA.1 ScopeA.1 Detection and reporting of prominent discrete tonesAnnex B (informative): Motivation for this reportAnnex C (informative): The relationship between sound power and sound pressureAnnex D (informative): Sound power measurement meth
14、odsD.1 Reverberation room techniqueD.1.1 ConceptD.1.2 Measurement procedureD.2 Free field over a reflecting plane techniqueD.2.1 ConceptD.2.2 Measurement procedureHistory1Recommended Methods for Measuring Acoustic Noise Emission1 ScopeThis Technical Report (TR) recommends methods for measuring, repo
15、rting and verifying thenoise emission of telecommunications equipment operated in a telecommunications networkfacility. The details of the methods are found in ISO 7779 and ISO 9296. The descriptor used toquantify acoustic noise emission is sound power level in units of bels. Measurements should bep
16、erformed on each equipment type or model.The recommendations contained herein apply only to the airborne acoustic noise generated byequipment during normal operation. That is, the document does not apply when the equipment isbeing serviced. Also, the document does not apply to equipment features whi
17、ch produce sound asan intentional aspect of their operation, e.g. alarm signals, attention signals and so on.2 ReferencesThis TR contains, by dated or undated reference, provisions from other publications. Thesereferences are cited at the appropriate places in the text, and are listed below. For dat
18、edreferences, subsequent amendments to, or revisions of any of the publications apply to this TRonly when incorporated in it by amendment or revision. For undated references the latest editionof the publication referred to applies.1 ISO 7779 Acoustics - Measurement of airborne noise emitted by compu
19、ters and businessequipment.2 ISO 9296 Acoustics - Declared noise emission values of computer and business equipment.3 ANSI T1.304 Ambient temperature and humidity requirements for network equipment incontrolled environments.3 DefinitionsThe following definitions are intended to provide background in
20、formation for key quantitiesdiscussed in this TR. Except for the last two definitions, detailed definitions, along with relevantreferences, are found in ISO 7779 and ISO 9296.Sound power level (Lw), in units of bels: The logarithm (base 10) of the ratio of a given soundpower to the reference sound p
21、ower. The weighting network (A-weighting) or the width of thefrequency band used should be indicated. The reference sound power is 1 pW.Declared A-weighted sound power level (Lwad), in units of bels: A statistical maximum A-weighted sound power level for manufactured units, taking into account toler
22、ances of productionand measurement variance, described in ISO 9296. Typically, LWAdis 0.3 bels higher than the A-Technical Report 542weighted sound power level measured on an average manufactured unit. LWAdis used for allequipment classes and in the specification of noise emission limits.Sound press
23、ure level (LP), in units of decibels: Ten times the logarithm (base 10) of the ratio ofthe time-mean-square sound pressure to the square of the reference sound pressure. Theweighting network (A-weighting) or the width of the frequency band used should be indicated.The reference sound pressure is 20
24、mPa.A-weighting filter: Response characteristic of a filter used in acoustic measurement systemswhich attenuates low frequency and high frequency acoustic energy. This filter is used to providea frequency response characteristic similar to that of the human auditory system.The following definitions
25、are unique to this TR:High temperature A-weighted sound power level (HLWAd), in units of bels: A statisticalmaximum A-weighted sound power level for manufactured units, taking into account tolerancesof production and measurement variance. The method for determining the high temperature A-weighted so
26、und power level is similar to that used in the determination of declared sound powervalues, as described in ISO 9296. HLWAd is used for equipment whose operational noise varieswith temperature.High temperature limit: The high temperature limit specified can be found in ANSI T1.304.4 Measurement meth
27、odologyThe measurement methods specified in ISO 7779 should be used for determining the sound powerof products.In addition to the measurement of sound power, an indication of source directionality should beobtained by using only the bystander position sound pressure measurements specified in Section
28、 7of ISO 7779. That section should be adhered to in conducting the measurements, and in therecording and reporting of data.5 Installation and operation of equipmentThe installation and operation conditions specified in ISO 7779 should be used for determiningthe sound power of products. Where there a
29、re differences between this TR and ISO 7779, therecommendations contained herein should be followed.The equipment should be configured and operated according to its normal intended use. Withinthat constraint and the constraints specified below, the equipment should be configured andoperated to ensur
30、e worst case acoustic noise emission.Technical Report 5435.1 Equipment installationThe specific installation will depend upon the sound power measurement technique being used(reverberation room or free-field over a reflecting plane), and upon the normal installationrequirements of the equipment bein
31、g measured.5.2 Equipment operation “in-use”For telecommunication equipment whose operational noise varies with functional load, theelectrical input and load conditions of the equipment should be chosen to obtain full functionalutilization of the equipment under test. Dissipation should be maximized
32、by selection of supplypower and load conditions.Only the sound power of continuous, steady-state noise sources should be measured. Therefore,the equipment is to be operated such that intermittent sources are not active. Such sources include(but are not restricted to) alarms, attention signals, print
33、ing mechanisms, disk-drive seekingmechanisms and so on.For telecommunication equipment whose operational noise varies with temperature ( e.g.equipment using variable speed air moving devices ), the sound power will be measured with theequipment operating under the two conditions specified below:5.2.
34、1 Variable emissions - standard temperature testFor the first test, the ambient temperature in the test environment should be 23 C*. Dataobtained from testing as specified in this paragraph is to be used in the determination of thedeclared A-weighted sound power level (LWAd ) for the equipment.5.2.2
35、 Variable emissions - high temperature testFor the second test, the sound power should be measured with the equipment operating as itwould in an ambient temperature equal to the high temperature limit (see below). Data obtainedfrom testing as specified in this section is to be used in the determinat
36、ion of the high temperatureA-weighted sound power level (HLWAd) for the equipment.This requirement can be satisfied using one of two methods. In the first method, the ambienttemperature in the test environment should be the high temperature limit.* In the second method,the ambient temperature in the
37、 test environment should be 23 C* but, the rotational speed(RPM) of air moving devices within the equipment under test should be set to the speed that thedevices will run at when the equipment is operating in an ambient temperature equal to the hightemperature limit.*Note: * indicates that the range
38、 for these values is +/- 2 C (per ISO 7779).Technical Report 5446 Information to be recorded1. The information to be recorded should be as specified in ISO 7779, including bystander soundpressure levels.2. For telecommunication equipment whose operational noise varies with temperature, the hightempe
39、rature A-weighted sound power level (HLWAd) should be recorded. HLWAdshould berecorded in bels, to the nearest 0.1 bels. Similarly, the high temperature limit and the test methodused per 5.2.2 should be recorded.7 Information to be reportedThe following information should be given in implementation
40、conformance statements:1. A statement that sound power levels have been obtained in full conformance with theprocedures of this TR.2. The declared A-weighted sound power level of the product, LWAd. The value LWAdshould bedetermined according to the method specified in ISO 9296 and using data obtaine
41、d as specified in5.2.1.3. For equipment whose operational noise varies with temperature, the high temperature A-weighted sound power level, HLWAd. The value HLWAdshould be determined according to themethod specified in ISO 9296 and using data obtained as specified in 5.2.2.Note: As described in ISO
42、9296, A-weighted sound power measurements are made on anumber of manufactured units and this data is used to obtain a declared sound power level or ahigh temperature sound power level for the production series or a portion thereof.8 Verification of declared A-weighted sound power levelsThis section
43、recommends a verification method for declared A-weighted sound power values,LWAd .The verification method specified in ISO 9296 should be used when verification of compliancewith this TR is required. When conducting sound power measurements, the equipment should beoperated as specified in this TR.Te
44、chnical Report 545Annex A (informative): Prominent discrete tonesOften the primary acoustic noise sources in telecommunications equipment are rotating machinerysuch as air-moving devices. Consequently, it is not unusual for the acoustic noise emitted byequipment to contain discrete tones. As the ton
45、es become more prominent, the likelihood that thenoise will be perceived as annoying increases. Unfortunately, unlike loudness, annoyance is aninherently difficult subjective response to accurately measure.A method for addressing the emission of prominent tones has been developed and included within
46、ISO 7779. However, given the nature of the problem, the information regarding the measurementand reporting of prominent tones is presented in a non-normative Annex of that document. Thisapproach has been adopted in this TR.A.1 ScopeThis Annex recommends a method for the detection and reporting of pr
47、ominent discrete tones.A.2 Detection and reporting of prominent discrete tonesAll relevant sections of ISO 7779 apply.Technical Report 546Annex B (informative): Motivation for this reportNew and emerging technologies are bringing about widespread changes in telecommunications.The impact of these cha
48、nges is dramatic and has affected all aspects of design including detailsrelevant to the generation of acoustic noise. In the past, telecommunication systems tended to becentrally located in isolated facilities where there was a limited amount of human activity. Morerecently, there has been a moveme
49、nt toward flexibility and decentralization in the design ofcommunication systems. As a result, equipment is often placed in close proximity to work orliving areas, and the noise generated by the equipment can have adverse effects on activities inthese areas. The primary concerns usually revolve around the effect of noise upon speechcommunication, task concentration and similar perceptual issues.Individual manufacturers and users have developed a variety of internal methods for measuringand recommending product acoustic noise. The lack of a standardized approach has been a sourceo
