1、 Reference number ECMA-123:2009 Ecma International 2009 ECMA-74 13th Edition / June 2015 Measurement of Airborne Noise emitted by Information Technology and Telecommunications Equipment COPYRIGHT PROTECTED DOCUMENT Ecma International 2015 Ecma International 2015 i Contents Page 1 Scope 1 2 Normative
2、 references 2 3 Terms and definitions . 3 3.1 General definitions 3 3.2 Acoustical definitions . 5 4 Conformity requirements 7 5 Installation and operating conditions . 7 5.1 Equipment installation 7 5.1.1 General . 7 5.1.2 Floor-standing equipment 7 5.1.3 Table-top equipment . 8 5.1.4 Wall-mounted
3、equipment 8 5.1.5 Rack-mounted equipment 8 5.1.6 Hand-held equipment 8 5.1.7 Sub-assemblies . 9 5.2 Input voltage and frequency 9 5.3 Equipment operation . 9 6 Method for determination of sound power levels of equipment in reverberation test rooms 10 6.1 General . 10 6.2 Measurement uncertainty . 10
4、 6.3 Test environment . 11 6.3.1 General . 11 6.3.2 Meteorological conditions 11 6.4 Instrumentation . 11 6.4.1 General . 11 6.4.2 The microphone and its associated cable 12 6.4.3 Frequency response of the instrumentation system . 12 6.4.4 Reference sound source. 12 6.4.5 Filter characteristics . 12
5、 6.4.6 Calibration 12 6.5 Installation and operation of equipment: General requirements . 12 6.6 Microphone positions and source locations 12 6.6.1 General . 12 6.6.2 Number of microphone positions, reference sound source locations and equipment locations . 13 6.6.3 Microphone arrangement . 13 6.7 M
6、easurement of sound pressure level 13 6.7.1 General . 13 6.7.2 Measurement time interval . 13 6.7.3 Corrections for background noise 13 6.8 Measurement of the sound pressure level of the reference sound source 13 6.9 Calculation of the mean time-averaged band sound pressure levels . 14 6.10 Determin
7、ation of sound power level . 14 6.10.1 Calculation of band sound power levels . 14 6.10.2 Calculation of A-weighted sound power level 14 7 Method for determination of sound power levels of equipment under essentially free-field conditions over a reflecting plane . 17 7.1 General . 17 7.2 Measurement
8、 uncertainty . 17 ii Ecma International 2015 7.3 Test environment 17 7.3.1 General . 17 7.3.2 Meteorological conditions . 18 7.4 Instrumentation . 19 7.4.1 General . 19 7.4.2 The microphone and its associated cable . 19 7.4.3 Frequency response of the instrumentation system 19 7.4.4 Reference sound
9、source 19 7.4.5 Filter characteristics . 19 7.4.6 Calibration . 19 7.5 Installation and operation of equipment: General requirements . 20 7.6 Measurement surface and microphone positions . 20 7.6.1 General . 20 7.6.2 Microphone positions on the measurement surface 21 7.7 Measurement of sound pressur
10、e levels . 21 7.7.1 General . 21 7.7.2 Measurement time interval 21 7.7.3 Corrections for background noise 21 7.8 Calculation of surface time-averaged sound pressure level . 22 7.9 Determination of time-averaged sound power levels . 22 7.9.1 Calculation of band time-averaged sound power levels 22 7.
11、9.2 Calculation of A-weighted sound power level . 22 8 Method for determination of emission sound pressure levels at defined operator and bystander positions 23 8.1 General . 23 8.2 Measurement uncertainty 23 8.3 Test environment 24 8.3.1 General . 24 8.3.2 Meteorological conditions . 24 8.4 Instrum
12、entation . 24 8.5 Installation and operation of equipment 24 8.6 Microphone positions 25 8.6.1 At the operator position(s) . 25 8.6.2 At the bystander positions 27 8.6.3 Microphone orientation 27 8.7 Measurement of sound pressure levels . 27 8.7.1 General . 27 8.7.2 Measurement time interval 28 8.7.
13、3 Corrections for background noise 28 8.8 Determination of emission sound pressure levels . 28 8.8.1 Calculation of band emission sound pressure levels. 28 8.8.2 Calculation of A-weighted emission sound pressure levels from band levels 28 8.8.3 Calculation of the mean emission sound pressure level a
14、t the bystander positions . 29 9 Information to be recorded and reported . 30 9.1 Information to be recorded 30 9.1.1 General . 30 9.1.2 Equipment under test . 30 9.1.3 Acoustical environment . 30 9.1.4 Instrumentation . 31 9.1.5 Acoustical data . 32 9.2 Test report . 34 Annex A (normative) Test acc
15、essories 35 Annex B (normative) Measurement surfaces 39 Annex C (normative) Installation and operating conditions for specific equipment categories . 45 Annex D (informative) Identification and evaluation of prominent discrete tones 91 Annex E (informative) Detection of impulsive noise 109 Ecma Inte
16、rnational 2015 iii Introduction ECMA-74 specifies methods for the measurement of airborne noise emitted by information technology and telecommunications equipment. Hitherto, a wide variety of methods have been applied by individual manufacturers and users to satisfy particular equipment or applicati
17、on needs. These diverse practices have, in many cases, made comparison of noise emission difficult. This Standard simplifies such comparisons and is the basis for declaration of the noise emission level of information technology and telecommunications equipment. In order to ensure accuracy, validity
18、 and acceptability, this Standard is based on the basic Standards for determining the sound power level and for determining the emission sound pressure level at the operator position(s) and bystander position(s). Furthermore, implementation is simplified by conformance with these International Stand
19、ards. In many cases free-field conditions over a reflecting plane are realised by hemi-anechoic rooms. These rooms may be particularly useful during product design to locate and to improve individual contributing noise sources. Reverberation test rooms may be more economical for production control a
20、nd for obtaining sound power levels for noise emission declaration purposes. The method for measuring the emission sound pressure level at the operator or bystander positions (based on ISO 11201) is specified in a separate clause, as this level is not considered to be primary noise emission declarat
21、ion information. The measurements can, however, be carried out in conjunction with those for sound power determination in a free field over a reflecting plane. For comparison of similar equipment it is essential that the installation conditions and mode of operation are the same. In Annex C these pa
22、rameters are standardized for many categories of equipment. The first edition of this Standard was issued in September 1981. It was contributed to ISO/TC 43 and formed the base for ISO 7779:1988, first edition. The second edition of ECMA-74 was issued in December 1987. The third edition was issued i
23、n December 1992 and was submitted to ISO for fast-track processing as a revision to ISO 7779 in the spring of 1993. The document was balloted by ISO from November 1994 to May 1995 and was approved with 18 of 20 P members in favour and 2 of 22 member bodies opposed. The fourth edition was issued in D
24、ecember 1996, taking into account most of the comments that accompanied the voting. The fifth edition was issued December 1997 to add a new equipment category CD- and DVD-ROM drives as C.19. ISO 7779, second edition, was published August 1st, 1999. The sixth edition of ECMA-74 was adapted to the fin
25、al wording of new ISO 7779 and also included additional provisions for CD- and DVD-ROM drives as C.19. Now C.19 with minor modifications was adopted as ISO/DIS 7779 Amendment 1. The C.19 changes that are in ISO/DIS 7779 Amendment 1 along with a revised Annex B and a revised Annex D are included in t
26、he seventh edition of ECMA-74, which was approved in December, 2002. The Annex B includes a provision allowing the use of a 0,5 m radius hemispherical surface for measuring the sound power emitted by small noise sources such as disk drives. Annex B also allows the use of a cylindrical measurement su
27、rface. The revised Annex D in the seventh edition includes prominence ratio in addition to tone-to-noise ratio, provides improved figures illustrating the tone-to-noise and prominence ratio calculations, and contains new criteria for prominent discrete tones. The new criteria are a result of a three
28、-year study by Ecma TC26 and ITI TC6. For the eighth edition, the reference list was updated and some text modified to account for the changes. The cylindrical measurement surface section of Annex B was re-worded to more closely follow the wording used in the draft of ISO 3744. Annex C contains addi
29、tional figures in section C.15 on personal computers and workstations. A new equipment category, C.20, for data projectors was added. Also Annex D was expanded with additional figures, equations and examples. iv Ecma International 2015 For the ninth edition, only Annex D was modified. Changes were m
30、ade in part to better define the critical band edges, including changing from geometric critical bands to arithmetic critical bands for frequencies below 500 Hz. Also, curves were fitted to the band edges for the lower and upper critical bands when calculating prominence ratio, thus eliminating the
31、need to use iteration for the calculations. Clarifications were added on frequency range of interest and elsewhere. The criteria for prominence did not change. For the 10th edition, changes were made to the main body of the Standard to be in agreement with upcoming changes in the underlying standard
32、s: ISO 3741, ISO 3744, ISO 3745 and ISO 11201. Two new equipment categories were added to Annex C: 1) multi-function devices (MFDs) and 2) hand-held computing and media playback devices. The addition of these categories included some changes in the main body of the Standard as well as some of the ot
33、her print-related categories. Annex D was revised to give clearer direction on determining the prominence of tones as well as introducing the concept of Threshold of Hearing when analyzing very low-noise equipment. For the 11th edition, changes were made to the Standard to align more closely with IS
34、O 7779:2010, 3rd edition. A new equipment category was added to Annex C, Digital media recorders and playback units for consumer use. Also the document was reformatted with the new Ecma standards template. For 12th edition, there were several updates as follows: In Clause 3, the wording of some defi
35、nitions was updated to be more consistent with the basic standards (ISO 3741, ISO 3744, ISO 3745, ISO 11201). In 7.3.1 and related sections, an expanded criteria on the environmental correction K2 was added to address its more detailed treatment in the basic standards. In Annex B, the minimum number
36、 of fixed microphone positions on the cylindrical measurement surface was made consistent with ISO 3744 Annex D. In Annex C, the clarity and consistency of procedures for imaging equipment under C.3, C.13, C.16 and C.21 were improved. Inkjet printers were categorized under C.16. Procedures for measu
37、ring idle mode noise were made uniform. The measurement of functional operations under C.13, C.16 and C.21 were aligned with one another and with the typical use prescription of C.1. The consistency of media use and reporting procedures across C.13, C.16 and C.21 was improved. Hand-held computing an
38、d media playback devices under C.22 having neither air moving devices nor a hard disk drive were generally exempted from reporting requirements. In Annex D, bibliographical references 18, 19 and 20 were replaced by ISO 2896129. For 13th edition, there were several updates as follows: In 6.4.6 and 7.
39、4.6, the microphone calibration procedures were amended to be consistent to those of the basic standards (ISO 3741 and 3744, respectively). In 7.3.1, the procedure for test environment qualification was amended to clarify that any frequency bands, typically low in frequency, not significantly affect
40、ing A-weighted sound power level need not meet the hemi-anechoic room qualification criteria for the purposes of determining A-weighted sound power level. In Annex B, B.2, a procedure for reducing the microphone positions on cylindrical measurement surface was introduced. This procedure is not prese
41、ntly in ISO 3744 but is expected in future versions of ISO 3744. In addition, editorial improvements were made, and equations were renumbered. In Annex D, some editorial improvements were made, and references to content within the annex were corrected (no technical changes). In Annex E, the method f
42、or detecting impulsive noise was removed. Because, by the recent update of IEC 61672-1:2013, the time-weighting I, which was the technical basis of the previous detection Ecma International 2015 v method in Annex E, had been removed. However, for historical reasons and also for the possibility of fu
43、ture development of another method detecting for impulsive noise, this informative Annex E remains with the same title, at least, in the 13th edition. This Ecma Standard has been adopted by the General Assembly of June 2015. vi Ecma International 2015 Ecma International 2015 vii “COPYRIGHT NOTICE 20
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