DIN EN ISO 3743-2-2009 Acoustics - Determination of sound power levels of noise sources using sound pressure - Engineering methods for small movable sources in reverberant fields -.pdf

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1、November 2009DEUTSCHE NORM English price group 12No part of this standard may be reproduced without prior permission ofDIN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,has the exclusive right of sale for German Standards (DIN-Normen).ICS 17.140.01!$Za 4 250 a

2、nd A-weighting 4 3 2 500 4 2 2 1 000 to 8 000 3 2 1 NOTE - For each Source Position, the mean-Square pressure should be determined. 7.5 Criteria for the presence of spectral irregularities The presence of irregularities in the spectrum of the emitted Sound tan be determined from the values of SM. Be

3、cause SM is only an estimate of the true stan- dard deviation 0, three broad ranges have been se- 14 EN ISO 3743-2:2009 (E) DIN EN ISO 3743-2:2009-11 lected to define the presence of discrete frequencies or narrow bands of noise: a) if SM 4 dB, a discrete tone may be present in the band in question;

4、 b) if 2,3 dB SM 4 dB, narrow-band noise com- ponents may be present in the frequency band in question; c) if SM 2,3 dB, the spectrum is probably broad- band in Character. The suspected presence of any narrow-band com- ponents or discrete frequencies in the spectrum of the emitted Sound shall be rep

5、orted. 7.6 Averaging technique with moving microphone 7.6.1 General The use of a moving microphone traversing a path in the test room at constant Speed will often be more convenient than the use of a number of fixed micro- phone positions. The path may be a line, an arc, a circle or some other geome

6、tric figure. 7.6.2 Path length for continuous averaging For continuous averaging, the minimum path length, Z, may be determined from the formula 1 ;1 Nm =- 2 if the path is a line or arc. If the averaging is made over a rectangular or circular area, the minimum area, A, may be determined from the fo

7、rmula If these formulae, ;1 is the wavelength of the Sound corresponding to the centre frequency of the octave band in which the measurement is made. The values of SM in table4 may be determined by measuring the mean-Square pressure at six Points spaced at least 1/2 apart along the path. For measure

8、ments A. = 3,5 m. with A-weighting, assume 7.6.3 Location of path within test room The path shall contain only microphone positions that meet the requ irements of 7.3. If the path or a Portion of the path tan be included within a plane, this plane shall not lie within IO” of a parallel to any room s

9、urface. 7.6.4 Speed of traverse The path shall be traversed by the microphone at a constant Speed. The repetition rate of the microphone traverse (or the scanning rate for an array of fixed microphones) shall be related to the integrating time or time constant of the instrumentation System. For RC-s

10、moothing, the traverse or scanning period shall be less than twice the time constant. If an integrator is used, a Single period of the microphone traverse (or the period of scanning the entire microphone array) shall be equal to the integrating time. The total period of Observation is specified in 7

11、.2. 7.7 Array of fixed microphones If an array of fixed microphones is used for the measurements, all microphones and cables shall comply with the requirements of 5.2. The number of microphones to be used shall be de- termined as specified in 7.4 and the microphone pos- itions shall be located as sp

12、ecified in 7.3. If the array or a Portion of the array tan be included within a plane, this plane shall not lie within IO” of a parallel to any room surface. During the sampling of the output of the micro- phones, the precautions given in 7.2 shall be ob- served. 7.8 Correction for background Sound

13、pressure levels Correct the measured band pressure levels for the influence of background noise in accordance with table5. If the background Sound pressure level is less than 4 dB below the Sound pressure level with either the reference Sound Source or the equipment operat- ing, the accuracy of the

14、measurements will be re- duced and no data shall be reported unless it is clearly stated that the background noise requirements of this part of ISO 3743 have not been fulfilled. 15 DIN EN ISO 3743-2:2009-11 EN ISO 3743-2:2009 (E) where Table 5 - Csrretiions for background Sound pressure levels Diffe

15、rente between sound pressure level measured with Sound Source measured with noise Source operating and background operating to obtain Sound Sound pressure level alone pressure level due to noise Source alone 8 Calculation of Sound power levels 8.ll Calculation of mean band pressure levels From the m

16、easured band pressure levels for each octave band of interest and from the measured A- weighted Sound pressure levels, calculate the mean octave-band Ievel and the A-weighted Sound pressure level, $, in decibels, from the following expression: q = 10 Ig + (1 O”- + 109Lp2 + . . . + 1 O”.Lpn)l dB L J

17、where L Pl is the octave-band level or A-weighted for the first measurement, in decibels; L Pn is the octave-band level or A-weighted for the nth measurement, in decibels; n is the total number of measurements for a particular octave band or with the A- weighting network inserted, 8.2 Direct method

18、for determining Sound power levels The approximate band power levels or A-weighted Sound power level of the Source, T,=l s; V is the volume of the test room; V. = 1 m3. NOTE 16 The constant 13 d5 instead of 14 d5 (which appears in other International Standards) and the Variation of the reverberation

19、 time with frequency account approxi- mately for the increase in Sound energy density near the surfaces of the special reverberation test room and near the Source. 8.3 Comparison method for determining band power levels Place a reference Source meeting the requirements laid down in annex A on the fl

20、oor of the test room at least 1,5 m from any Wall. The minimum distance between the Source and any microphones shall fulfil the requirements of 7.3. Determine the mean Sound pressure Ievel of the ref- erence Source in each octave band, Lpr, using no fewer than six microphone positions, background no

21、ise corrections (if necessary) and the calculation procedure of 8.1. Then calculate the Sound power level produced by the Source, be, in decibels (reference: 1 pW), in each octave band within the frequency range of interest as follows: a) subtract the band pressure level produced by the reference So

22、und Source, Lpr (after corrections for background noise in accordance with 7.8) from the known Sound power level produced by the reference Sound Source; b) add the differente to the band pressure level of the Source under test, Lpe (after corrections for background noise in accordance with 7.81, i.e

23、. hve = Lpt? + Fw - L,J where L Pe is the mean band pressure level of the Source under test, in decibels (refer- ence: 20 FPa); L, r is the band power level of the reference Sound Source, in decibels (reference: 1 pw; 16 EN ISO 3743-2:2009 (E) DIN EN ISO 3743-2:2009-11 L PF is the mean band pressure

24、 level of the reference Sound Source, in decibels (reference: 20 ppa). 9 Information to be recorded The information specified in 9.1 to 9.4, when applica- ble, shall be compiled and recorded for all measure- ments made in accordance with the requirements of this part of ISO 3743. 9.1 Sound Source un

25、der test a) Description of the Sound Source under test, in- cluding its - type - technical data, - dimensions, - manufacturer, - serial number, and - year of manufacture. b) Operating conditions. c) Mounting conditions. d Location(s) of noise Source in test room. e) If the test Object has multiple n

26、oise sources, de- scription of Source(s) in Operation during measurements. 9.2 Acoustical environment a) Description of test room, including dimensions, treatment of Walls, ceiling and floor. b) Sketch of the test room showing the location of the Source and room contents. c) Acoustical qualification

27、 of the test room (see 4 7) . . d) Air temperature in degrees Celsius, relative hu- midity as a percentage, and barometric pressure in Pascals. 9.3 Instrumentation a) Equipment used for the acoustical measure- ments, including the name, type, serial number and manufacturer. b) Bandwidth of the frequ

28、ency analyser. c) Frequency response of the instrumentation sys- ten?. d Method used to calibrate the microphone(s), and the date and place of calibration. e) Calibration of the reference Sound Source (see 4 7) . . 9.4 Acoustical data a) The Position and orientation of the microphone path or array (

29、a Sketch should be included if necessary). b) The corrections, in decibels, if any, applied in each frequency band for the frequency response of the microphone, frequency response of the filter in the pass band, background noise, etc. c) The Sound power levels, in decibels (reference: 1 pW), calcula

30、ted for all frequency bands used, and the A-weighted Sound power level, in deci- bels (reference: 1 pW). d) The corrected Sound power levels, tabulated or plotted to the nearest one-half decibel. e) The date and time when the measurements were performed. f) Remarks on subjective impression of noise

31、(audi- ble discrete tones, impulsive Character, spectral content, temporal characteristics, etc.). 10 Information to be reported Only those recorded data (see clause 9) are to be re- ported which are required for the purposes of the measurements. The report shall state whether or not the reported So

32、und power levels have been obtained in full conformity with the requirements of this part of ISO 3743. The report shall state that these Sound power levels are given in decibels (reference: 1 pW). 17 DIN EN ISO 3743-2:2009-11 EN ISO 3743-2:2009 (E) Annex A (normative) Characteristics and calibration

33、 of reference Sound Source kl Ctmaracteristics of reference sound Source The reference Sound Source shall have the charac- teristics specified in A.1.1 to A.l.5. A.1.1 The Sound radiated shall be broad-band in Character without discrete-tone components; i.e. the Sound pressure level in any one-tenth

34、-octave band shall be at least 5 dB below the corresponding octave band level. A.1.2 The reference Sound Source shall be suitably mounted to prevent transmission of Vibration to the structure on which it rests. A.1.3 The directivity index of the Source, in any one-third-octave band, shall not exceed

35、 6 d relative to uniform hemispherical radiation over the frequency range from 100 Hz to IO 000 Hz. AJ.4 The reference Sound Source shall be physi- cally small (maximum dimension preferably less than 0,5 m). A.1.5 The power level in each frequency band shall remain constant, within the tolerantes of

36、 tableA.1, during the useful life of the Source. A.2 Calibration of reference Sound Source The Sound power produced by the reference Sound Source shall be determined in octave and one-third- octave bands with an accuracy as specified in tabteA.l. During calibration, the Source shall be oper- ated on

37、 the floor in the Same manner as during its intended use. Table A.1 - Calibration accuracy for reference Sound Source One-third-octave-band centre frequencies Tolerante Hz d 100 to 160 23 200 to 4 000 + 0,5 5oooto10000 i-1 NOTE - The tolerantes specified tan only be obtained by more elaborate measur

38、ement procedures than those described in this part of ISO 3743 (see ISO 3745 and ISO 6926). 18 EN ISO 3743-2:2009 (E) DIN EN ISO 3743-2:2009-11 Annex B (informative) Guidelines for the design of special reverberation test rooms B. 1 General For the measurements specified in this part of ISO 3743, th

39、e noise Source (machine, device or com- ponent) should be operated in a test room which has the required acoustical properties specified in clause 4. These characteristics may be obtained in different ways, some of which are described in this annex. B.2 Size and shape of test room The minimum volume

40、 of the test room should be 70 m. The test room should provide an adequate reverberant Sound field for all frequency bands within the frequency range of interest. This requires that the frequencies of the normal modes of the room be well distributed within the frequency range of interest. Some recom

41、mended ratios of dimensions for rec- tangular rooms are given in table B.I. Other ratios may be used, but ratios equal to or closely approximating integers or simple fractions should be avoided. Table B.l - Recommended room dimension ratios for rectangular rooms 0,83 0,47 0,83 0,65 0,79 0,63 NOTE -

42、The Symbols Z, l sions. and I, are the room dimen- If the dimension ratios approximate those of table B.l, rooms with volumes larger than 70 m3 will generally give an improved accuracy for measure- ments at low frequencies. 8.3 Absorption of test room In many cases it is necessary to adapt a room wi

43、th hard surfaces (e.g. concrete Walls) as a test room. The reverberation time of such a room is usually high at low and middle frequencies, but approximates the specified value at the upper limit of the frequency range of interest. The reverberation time of the room at low and middle frequencies tan

44、 be reduced to the recommended values by installing sound-absorptive materials on the Walls and ceiling. To correct the middle and high frequencies, perfor- ated Panels with mineral wool interiors will often be suitable. Information concerning the absorptive prop- erties of such materials is general

45、ly available from manufacturers and test laboratories. Suitable absorbers of low-frequency Sound tan be constructed as membrane absorbers, for example, a wooden frame covered with hardboard and filled with mineral wool. For such an absorber, the approximate value of the frequency, f, in hertz, at wh

46、ich maximum absorption is obtained is given by the formula f sz 60 (Zea)-“* where 1 is the distance of the hardboard from the Wall, in metres; PA is the surface density of the hardboard, in kilograms per Square metre. EXAMPLE An absorber consisting of a wooden frame 0,95 m x 0,65 m x 0,05 m covered

47、with a 4 mm thick hardboard, with a nominal surface density equal to 3,5 kg/m*, as shown in figure B.l, has a Sound ab- sorption characteristic as shown in figure B.2. The samples of sound-absorptive material should be randomly distributed over the entire surfaces of the Walls and ceiling of the tes

48、t room. The materials should be applied in patches not larger than 1,5 m* in area and the requirements of 4.4 should be satisfied. In this way, the desired smooth decay curve may be obtained when the reverberation time is measured. 19 DIN EN ISO 3743-2:2009-11 EN ISO 3743-2:2009 (E) Dimensions in me

49、tres g .- .- ; 8 06 !i k .- Q 05 f 0 m 04 0 01 I 0 Hardboard membrane Wall I 0.95 I Figure B.1 - Hardboard membrane absorber 2 5 IO 3 2 Frequency of membrane absorber, Hz 5 IO4 2x104 Figure B.2 - Sound absorption coefficient a for the membrane absorber measured in a 200 rn3 reverberation room 20 EN ISO 3743-2:2009 (E) DIN EN ISO 3743-2:2009-11 The floor of the test room should be reflecting over the entire frequency range of interest. A floor of painted poured concrete will usually meet the re- quirements of 4.4. In practice, Tnorn is determined by centring the measured values