1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS ISO 28961:2012Acoustics Statisticaldistribution of hearingthresholds of otologicallynormal persons in the agerange from 18 years to 25years under free-field listeningcondition
2、sBS ISO 28961:2012 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 28961:2012.The UK participation in its preparation was entrusted to TechnicalCommittee EH/1/1, Hearing.A list of organizations represented on this committee can beobtained on request to its secr
3、etary.This publication does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2012ISBN 978 0 580 70080 4ICS 13.140Compliance with a British Standard cannot confer immunity fromlegal obligations.This B
4、ritish Standard was published under the authority of theStandards Policy and Strategy Committee on 31 January 2012.Amendments issued since publicationDate Text affectedBS ISO 28961:2012Acoustics Statistical distribution of hearing thresholds of otologically normal persons in the age range from 18 ye
5、ars to 25 years under free-field listening conditionsAcoustique Rpartition statistique des niveaux liminaires daudition de personnes otologiquement normales ges de 18 25 ans dans des conditions dcoute en champ libre ISO 2012Reference numberISO 28961:2012(E)First edition2012-01-15ISO28961INTERNATIONA
6、L STANDARDBS ISO 28961:2012ISO 28961:2012(E)COPYRIGHT PROTECTED DOCUMENT ISO 2012All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission
7、in writing from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright officeCase postale 56 CH-1211 Geneva 20Tel. + 41 22 749 01 11Fax + 41 22 749 09 47E-mail copyrightiso.orgWeb www.iso.orgPublished in Switzerlandii ISO 2012 All rights reservedBS ISO 2896
8、1:2012ISO 28961:2012(E) ISO 2012 All rights reserved iiiContents PageForeword ivIntroduction v1 Scope 12 Normative references .13 Calculation of percentiles of hearing threshold distribution 23.1 General .23.2 Threshold distribution at frequencies lower than 10 000 Hz .23.3 Threshold distribution at
9、 10 000 Hz and higher frequencies 4Annex A (informative) Numerical examples to illustrate the procedure 5Annex B (informative) Selected values of the statistical distribution of hearing thresholds of otologically normal persons in the age range 18 years to 25 years inclusive .6Annex C (informative)
10、Selected values of nullnullnull .9Annex D (informative) Notes on the derivation of the statistical distribution of normal hearing thresholds .10Bibliography .11BS ISO 28961:2012ForewordISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (IS
11、O member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, gove
12、rnmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.International Standards are drafted in accordance with the rules given in the ISO/IEC D
13、irectives, Part 2.The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member b
14、odies casting a vote.Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights.ISO 28961 was prepared by Technical Committee ISO/TC 43, Acoustics.ISO 28961:2012
15、(E)iv ISO 2012 All rights reservedBS ISO 28961:2012IntroductionThe threshold of hearing in a free sound field is specified in ISO 226 and ISO 389-7. Threshold data in these documents were obtained from otologically normal persons in the age range 18 years to 25 years inclusive.As described in ISO 38
16、9-7, the threshold of hearing varies among people; the documents merely present median values of hearing thresholds. However, other values on the threshold distribution of individuals are necessary to evaluate the hearing ability of a person in relation to that of the population. Those values have b
17、een used also in noise evaluation for estimating the ratio of young people with normal hearing in the population who might be able to detect a sound of concern, e.g. an unwanted sound emitted from a machine.This International Standard provides a method for calculating percentiles of the hearing thre
18、shold distribution for one-third-octave-band and other audiometric frequencies from 20 Hz to 16 000 Hz. The mean value of distribution is set to be the threshold of hearing specified in ISO 226 and ISO 389-7. Furthermore, the method has been developed using many of the hearing threshold data on whic
19、h those documents were based.NOTE Percentiles of the hearing threshold distribution can also be determined for bands of noise. However, only percentiles for pure tones are specified in this International Standard because insufficient data for bands of noise are available. Nevertheless, it is possibl
20、e that this International Standard is applicable to one-third-octave bands of noise.ISO 28961:2012(E) ISO 2012 All rights reserved vBS ISO 28961:2012BS ISO 28961:2012INTERNATIONAL STANDARD ISO 28961:2012(E)Acoustics Statistical distribution of hearing thresholds of otologically normal persons in the
21、 age range from 18 years to 25 years under free-field listening conditions1 ScopeThis International Standard provides descriptive statistics, percentiles, of the hearing threshold distribution whose mean is the reference threshold value specified in ISO 226 and ISO 389-7. The mean and percentile thr
22、esholds are specified under the following conditions:a) the sound field in the absence of the listener consists of a free progressive plane wave (free field);b) the sound source is directly in front of the listener (frontal incidence);c) the sound signals are pure (sinusoidal) tones;d) the sound pre
23、ssure level is measured in the absence of the listener at the position where the centre of the listeners head would be;e) listening is binaural;f) the listeners are otologically normal persons within the age range 18 years to 25 years inclusive.NOTE 1 The nullth percentile threshold is the value of
24、threshold below which nullnull% of the individual thresholds of population fall. The threshold distributions in this International Standard have been derived from the results of comprehensive statistical analyses. See Annex D.NOTE 2 The applicability of the percentiles and the values of parameters g
25、iven in this International Standard to diffuse-field listening conditions has not been examined. They are expected to be applicable to the conditions for the frequencies from 20 Hz to 250 Hz where the threshold difference between free-field and diffuse-field listening conditions is zero as specified
26、 in ISO 389-7:2005, Table 1.The percentiles are given in numerical form for the preferred frequencies in the one-third-octave series from 20 Hz to 16 000 Hz inclusive, in accordance with ISO 266, and for some intermediate audiometric frequencies.The percentiles are applicable to the assessment of an
27、 individuals hearing in relation to the distribution of hearing thresholds under the above conditions. The percentiles can also be used to evaluate the audibility of low-level noise around hearing threshold.NOTE 3 An application example of hearing threshold distribution to noise evaluation can be fo
28、und in ISO 7779:2010, Annex D.2 Normative referencesThe following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applie
29、s.ISO 226:2003, Acoustics Normal equal-loudness-level contours ISO 266, Acoustics Preferred frequenciesISO 389-7:2005, Acoustics Reference zero for the calibration of audiometric equipment Part 7: Reference threshold of hearing under free-field and diffuse-field listening conditions ISO 2012 All rig
30、hts reserved 1BS ISO 28961:20123 Calculation of percentiles of hearing threshold distribution3.1 GeneralThe threshold distribution for the frequencies null below 10 000 Hz shall be approximated by a Gaussian distribution, which is determined using a mean value nullnulland a standard deviation nullnu
31、ll. Using nullnullnulland nullnull, any percentile on the distribution is calculable as specified in 3.2.Percentiles at 10 000 Hz and higher frequencies shall be calculated using a similar procedure, as specified in 3.3. However, a numerical transformation shall be performed first so that the thresh
32、old distribution can be approximated using a Gaussian distribution in the transformed domain.For both frequency ranges, the mean value of the distribution shall be set to the reference threshold in free field nullnullin decibels given in ISO 226 and ISO 389-7.Examples of calculation are shown in Ann
33、ex A. Selected values of the statistical threshold distribution which are calculated following those procedures are presented in tabular and graphical forms in Annex B.3.2 Threshold distribution at frequencies lower than 10 000 HzThe nullth percentile Pnull,nullnullof threshold distribution (referen
34、ce value 20 nullPa) in decibels at frequencies lower than 10 000 Hz shall be calculated using Equation (1):Pnullnullnullnullnullnullnullnullnullnull+ nullnullnullnull(1)where nullnullis a null-score of the proportion of Gaussian distribution which corresponds to the nullth percentile.Selected values
35、 of nullnullare presented in Annex C. The values of standard deviation nullnullfor the threshold distribution at frequencies lower than 10 000 Hz are presented in Table 1. The values are the outcome of comprehensive statistical analyses. The accuracy provided is for calculation only.NOTE As null app
36、roaches 0 or 100, Pnull,nullbecomes liable to a larger uncertainty of threshold estimation because of uncertainty in the experimental data on which this International Standard is based.ISO 28961:2012(E)2 ISO 2012 All rights reservedBS ISO 28961:2012Table 1 Standard deviation of threshold distributio
37、n, nullnull, at frequencies null lower than 10 000 Hznullin Hznullnullin dB202531,5405063801001251602002503154005006307508001 0001 2501 5001 6002 0002 5003 0003 1504 0005 0006 0006 3008 0009 0006,146,386,486,376,045,404,584,033,793,783,843,843,753,613,543,633,813,914,294,694,945,005,095,024,914,894,
38、865,035,305,385,755,95ISO 28961:2012(E) ISO 2012 All rights reserved 3BS ISO 28961:20123.3 Threshold distribution at 10 000 Hz and higher frequenciesThe threshold distribution at 10 000 Hz and higher frequencies shall be approximated using a Gaussian distribution after individual thresholds are oper
39、ated mathematically using the following power-transformation equation:uuff=()(2)wherenull is an individual threshold in the distribution in decibels (reference value 20 nullPa);nullnullis the parameter that determines the origin of power transformation;nullnullis the exponent of power transformation
40、.Parameters nullnulland nullnullare shown in Table 2. The values are the outcome of comprehensive statistical analyses. The accuracy provided is for calculation only.Hereinafter, a dotted variable denotes a value in the power-transformed domain.Table 2 Parameters for calculating the percentile thres
41、hold at frequencies null of 10 000 Hz and highernullHznullnullnullnullnullnullTf10 00011 20012 00012 50014 00016 000null26,72null11,03null4,537null2,219null1,0336,2710,766 40,567 50,451 10,384 90,216 50,062 831,8610,932 30,715 50,621 50,253 40,038 8917,106,0753,6402,8001,9011,248The nullth percentil
42、e Pxf,of threshold distribution shall be given by Equation (3):PTzxf fxf,=+ (3)whereTfis the mean value of threshold distribution given in ISO 226 and ISO 389-7;nullnullis the standard deviation of threshold distribution at frequencies of 10 000 Hz and higher.Both variables are also shown in Table 2
43、.To derive a percentile threshold (reference value 20 nullPa) in decibels, Pxf,shall be transformed using Equation (4), which is the inverse function of Equation (2), with null and null replaced by Pnull,nulland Pxf,:PPxfxfff,expln=+ (4)NOTE As null approaches 0 or 100, Pnull,nullbecomes liable to a
44、 larger uncertainty of threshold estimation because of uncertainty in the experimental data on which this International Standard is based.ISO 28961:2012(E)4 ISO 2012 All rights reservedBS ISO 28961:2012Annex A (informative) Numerical examples to illustrate the procedureA.1 Example 1The 10th percenti
45、le of hearing threshold of otologically normal persons at the audiometric frequency 1 000 Hz is calculated as follows.Step 1:Table 1, null =1000 Hz, gives 1000429= , dB.Step 2:Table C.1, null=10, gives zx=1282, .Step 3:ISO 226:2003, Table 1 and ISO 389-7:2005, Table 1, null =1000 Hz, gives null10002
46、4= , dB.Step 4:Equation (1), null100024= , dB, zx=1282, , 1000429= , dB, gives P10 100031,= dB.Step 5: The result should be rounded to the nearest integer, i.e. null3 dB.A.2 Example 2The 75th percentile of hearing threshold of otologically normal persons at the audiometric frequency 12 500 Hz is cal
47、culated as follows.Step 1:Table 2, null =12 500Hz, gives 12 5002 219=, , 12 5000 384 9= , , 12 5000 6215= , , and null12 5002 800= , .Step 2:Table C.1, null= 75, gives zx= 0 674 5, .Step 3: Equation (3), null12 5002 800= , , zx= 0 674 5, , 12 5000 6215= , , gives P75 12 5003 219,=Step 4: Equation (4
48、), dotnospP75 12 5003 219,= , 12 5002 219=, , 12 5000 384 9= , , gives P75 12 50018 6,= dB.Step 5: The result should be rounded to the nearest integer, i.e. 19 dB.ISO 28961:2012(E) ISO 2012 All rights reserved 5BS ISO 28961:2012Annex B (informative) Selected values of the statistical distribution of
49、 hearing thresholds of otologically normal persons in the age range 18 years to 25 years inclusiveTable B.1 Pnull,null: the nullth percentiles of threshold distribution at frequency nullnullin HzPnull,nullin dBnull = 5 null = 10 null = 25 null = 50 null = 75 null = 90 null = 9520 68 71 74 79 83 86 8925 58 61 64 69 73 77 7931,5 49 51 55 60 64 68 7040 41 43 47 51 55 59 6250 34 36 40 44 48 52 5463 29 31 34 38 41 44 4680 24 26 28 32 35 37 39100 20 21 24 27 29 32 33125 16 17 20
