1、March 2011 Translation by DIN-Sprachendienst.English price group 20No part of this translation 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
2、17.140.20!$n1 and if the source under test is omnidirectional, several locations shall be used for the reference sound source along the sides of the source under test, separated by a distance equal to dm. b) If a/dm1 and if the source under test has clearly definable sound emission areas, one locati
3、on of the reference sound source shall be used for each emission area. c) If a/dmu1 and if the source under test is omnidirectional, but it is impossible to use a location on top of the source under test, four locations for the reference sound source shall be used, one adjacent to each vertical side
4、 of the reference box. 7.4 Microphone positions 7.4.1 General The aim is to position the microphones around the sides of the noise source under test so that each position is situated similarly in relation to the sound-emitting areas of the source, i.e. for a particular microphone position, either th
5、ere is a line of sight to each sound-emitting area or each area is screened. Positions to be avoided are those to which only a few parts of the source are emitting sound. In total, three or four microphone positions are to be used (see 7.4.3), distributed as evenly as possible around the noise sourc
6、e under test. The same positions and microphone orientations are to be used for measurements made on the noise source under test, the reference sound source, and the background noise. The measurement distance, dm, from the respective microphone positions to the nearest point of the reference box is
7、to be selected so that, if possible, the microphone positions are in a part of the test environment where the sound field is reverberant, i.e. a region in which LfW 7 dB (see Table 2). No microphone position shall be closer than 0,5 m to any boundary surface of the test environment. If the environme
8、nt is sufficiently spacious, and if the noise source under test is located away from all boundary surfaces, the microphones shall be positioned round all four vertical sides of the reference box. The microphone positions shall be spaced at least 2 m from each other. If the ceiling is high and sound
9、absorbing, and frequencies greater than 2 000 Hz are important, if possible, at least two of the microphone positions shall be above the source. DIN EN ISO 3747:2011-03 EN ISO 3747:2010 (E) 13 7.4.2 Zoning The test environment shall be divided into zones in which differences can be denoted in the so
10、und-radiating patterns in the horizontal plane around the noise source under test (ST) and the reference sound source (RSS) in its various locations. The zones are used in choosing locations for the reference sound source and the microphone positions. The different zones are identified and given not
11、ations in Table 1. Table 1 Zones of the test environment Direct line of sight to sound-emitting areas Distances from the microphone position of ST of RSS dm aEffect on the sound power estimation Notation of the zone Yes No Strong overestimate + No Yes Strong underestimate Yes Yes dm(ST)dm(RSS)Undere
12、stimate Yes Yes dm(ST) dm(RSS)(within 10 %) Negligible over- or underestimate +/ No No Either strong over- or underestimate +/ a(ST) indicates source under test; (RSS) indicates reference sound source. 7.4.3 Selection of microphone positions If the noise source under test is omnidirectional and the
13、reference sound source is located on top of it, all the zones fall into one or other of the notations + or +/ and one microphone position shall be selected on each free side of the source under test, in compliance with the requirements of 7.4.1. In all other cases, microphone positions shall be soug
14、ht in a +/ zone. If this is not possible, one microphone position shall be selected in a + zone, one in a +/ zone and one or two positions in zones. Unless the test environment is highly reverberant (no acoustic treatment of walls or ceiling, no large absorbing obstacles) no microphone positions sho
15、uld be located in a +/ zone. NOTE It can prove impossible to have all microphone positions in direct line of sight of the reference sound source (see B.2 and B.4). 7.5 Measurement of sound pressure levels for a noise source which emits steady or non-steady noise Time-averaged sound pressure levels f
16、rom the noise source under test, for each octave band within the frequency range of interest, Lpi(ST), shall be obtained, at each microphone position, i (i = 1, 2 n), and from the reference sound source, Lpi(RSS). A suitable averaging time for the reference sound source is 30 s. If the sound output
17、from the noise source under test is as stable as that of the reference sound source, then a similar averaging time is satisfactory, but if it is less stable or undergoes periodic cycles, a longer averaging time is required. In addition, either immediately before or immediately after the sound pressu
18、re levels from the noise source under test are measured, the time-averaged sound pressure levels of the background noise for each octave band, Lpi(B), shall be obtained at each microphone position, over the same measurement time interval as that used for the noise source under test. DIN EN ISO 3747:
19、2011-03 EN ISO 3747:2010 (E) 14 7.6 Measurement of sound pressure levels for a noise source which emits impulsive noise Single event sound pressure levels from the noise source under test for each octave band within the frequency range of interest, LEi(ST), shall be obtained, at each microphone posi
20、tion, i (i = 1, 2 n), either for one single sound event at a time (in which case the process shall be repeated N times, where N W 5), or from several successive, N, sound events (where again N W 5). The measurement time interval shall be long enough to contain all that part of the noise of the event
21、(s), including the decay, which make a significant contribution to the single event sound pressure level. The time-averaged sound pressure levels from the reference sound source, Lpi(RSS), shall also be measured, with an averaging time of 30 s. In addition, either immediately before or immediately a
22、fter the sound pressure levels from the noise source under test are measured, the time-averaged octave-band sound pressure levels of the background noise, Lpi(B), shall be obtained once at each microphone position, over a representative time interval. 8 Calculation of sound power levels and sound en
23、ergy levels 8.1 Corrections for background noise The background noise correction, K1i, at the ith microphone position and in each octave band, shall be calculated using Equation (7): 0,1110 lg(1 10 ) dBpiLiK= (7) where (ST) (B)pipi piLL L= in which Lpi(ST)is the measured (uncorrected) octave-band ti
24、me-averaged sound pressure level at the ith microphone position, with the noise source under test (ST) in operation, in decibels, Lpi(B)is the octave-band time-averaged sound pressure level of the background noise (B) measured at the ith microphone position, in decibels. If, at all microphone positi
25、ons, LpiW 6 dB, the measurement is valid according to this International Standard. If, at any microphone position, Lpi 15 dB, K1iis assumed equal to zero at that position. For values of Lpibetween 6 dB and 15 dB, corrections shall be calculated according to Equation (7). If, at any microphone positi
26、on, Lpi7 dB 4,0 aThese values are applicable to noise sources which emit sound with a relatively “flat” spectrum in the frequency range 100 Hz to 10 000 Hz, i.e. when the octave bands with centre frequencies from 250 Hz to 4 000 Hz have most influence on the A-weighted sound power level or sound ene
27、rgy level. However, if sound at frequencies below 500 Hz is predominant, the reproducibility of sound power level or sound energy level determinations is poorer than that indicated. If there is substantial sound emission at frequencies greater than 2 000 Hz, the noise source can be highly directiona
28、l. If, in such cases, there are strongly absorbing surfaces (e.g. an absorbing ceiling) close to the noise source under test, again the reproducibility of results can be poorer. 9.5 Total standard deviation, tot, and expanded uncertainty, U The total standard deviation and the expanded uncertainty s
29、hall be determined using Equation (22) and Equation (23) respectively. For the purpose of this International Standard, a normal distribution is assumed. Thus a coverage factor of k = 2 shall be used corresponding to a coverage probability of 95 %. The coverage factor and coverage probability shall b
30、e reported together with the expanded uncertainty. EXAMPLE Accuracy grade 2; omc= 2,0 dB; coverage factor k = 2; measured LWA= 82 dB. Machine-specific determinations of R0have not been undertaken thus the value is taken from Table 2 (R0= 1,5 dB). Using Equations (23) and (22) it follows 2221,5 2dB5d
31、BU = + = Additional examples of calculated values for totare given in E.3. NOTE The expanded uncertainty as described in this International Standard does not include the standard deviation of production which is used in ISO 48718for the purpose of making a noise declaration for batches of machines.
32、10 Information to be recorded 10.1 General The information listed in 10.2 to 10.5, when applicable, shall be compiled and recorded for all measurements made in accordance with this International Standard. DIN EN ISO 3747:2011-03 EN ISO 3747:2010 (E) 22 10.2 Noise source under test The following info
33、rmation shall be recorded: a) a description of the noise source under test (including the manufacturer, type, technical data, dimensions, serial number, and year of manufacture); b) a description of any treatment of auxiliary equipment for the purpose of the test; c) the mode(s) of operation used fo
34、r the test(s), the relevant measurement time interval(s), and description of relevant secondary operating parameters (see 6.3); d) the mounting conditions; e) the location(s) of the noise source in the test environment. 10.3 Test environment The following information shall be recorded: a) a descript
35、ion of the test environment, showing the nature of the building, the construction and any treatment of the walls, floor and ceiling, and a sketch showing the location of the noise source under test and any other contents of the environment; b) a description of the suitability of the environment for
36、the purpose of the test in accordance with 4.1 (giving value(s) for Lf), as appropriate; c) the air temperature, in degrees Celsius, and the static pressure, in pascals, near the noise source at the time of test. 10.4 Instrumentation The following information shall be recorded: a) the equipment used
37、 for the measurements, including the name, type, serial number, and manufacturer; b) the date, place, and methods used to calibrate the sound calibrator and the reference sound source, and to verify the performance of the instrumentation system, in accordance with 5.2; c) the sound power levels of t
38、he calibrated reference sound source in the various positions used. 10.5 Acoustic data The following information shall be recorded: a) the dimensions of the reference box and the measurement distance; b) the microphone positions used for the measurements (with a sketch if necessary); c) the location
39、s used for the reference sound source. For each mode of operation under which the noise source was tested: d) remarks on the subjective impression of the noise emitted by the source under test from aural examinations (directivity, discrete tones or components in narrow bands of frequency, temporal c
40、haracteristics, etc.); DIN EN ISO 3747:2011-03 EN ISO 3747:2010 (E) 23 e) the time-averaged or single event sound pressure levels measured at each microphone position, in octave bands; f) the sound pressure levels of the background noise; g) the sound power levels or sound energy levels, in decibels
41、, in octave bands and A-weighted (if appropriate) rounded to the nearest 0,1 dB a graphical representation may optionally be recorded in addition; NOTE ISO 9296 requires that the declared A-weighted sound power levels, LWAd, of computers and business equipment are expressed in bels, using the identi
42、ty 1 B = 10 dB. h) the expanded uncertainty of the results, in decibels, together with the associated coverage factor and coverage probability; i) the date and time when the measurements were performed. 11 Test report Only those recorded data (see Clause 10) which are required for the purpose of the
43、 measurements shall be reported. The report shall also contain any statements required to be reported by certain clauses in the main body of this International Standard. As this International Standard includes two grades of accuracy, test results shall always state explicitly the uncertainty determi
44、ned by the grade of accuracy achieved accuracy grade 2 (engineering) or accuracy grade 3 (survey). Additionally information may be given on the basis of Annex E. If the reported sound power levels or sound energy levels have been obtained in full conformity with the requirements of this Internationa
45、l Standard, the report shall state this fact. If the levels have not been obtained in full conformity, the report shall not state or imply that they have been. If one or a small number of identifiable discrepancies exist between the reported levels and the requirements of this International Standard
46、, then the report may state that the measurements have been conducted “in conformity with the requirements of this International Standard, except for” and the discrepancies clearly identified. In this case, the term “full conformity” shall not be stated or implied. DIN EN ISO 3747:2011-03 EN ISO 374
47、7:2010 (E) 24 Annex A (normative) Evaluation of the excess of sound pressure level at a given distance For a suitable location of the reference sound source (see 7.3.2 and 7.3.3), the sound pressure level due to the reference sound source, Lp(RSS),r, shall be measured along a straight path with a di
48、rect line of sight, at varying distances, r. The excess of sound pressure level at any given distance shall be determined from Equation (A.1): ()(RSS), (RSS)011dB 20 lg dBfprWrLr L Lr= + (A.1) where LW(RSS)is the sound power level of the reference sound source calibrated in a position similar to tha
49、t used for the measurement, in decibels; Lp(RSS),ris the sound pressure level measured at a distance r, in metres, from the reference sound source, in decibels; r is the distance from the microphone to the reference sound source, in metres; r0is the reference distance, 1 m. If initial measurements show the frequency spectrum of sound emitted by the noise source under test is broad band, and is similar to that from the reference sound source, A-weighted sound pressure levels can be measured directly and the subscript “A” should
