1、STD*BSI BS EN bOb45-2-ENGL 1797 = Lb24bb7 Ob38bb5 79T M BRITISH STANDARD Audiometers Part 2. Equipment for speech audiometry The European Standard EN 606452 : 1997 has the status of a British Standard ICs 17.140.50 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW BS EN 50645-2
2、: 1997 EC 60645-2 : 1993 BS EN 60645-2 : 1997 Amd.No. National foreword Date Text affected This British Standard is the English language version of EN 606452 : 1997. It is identical with IEC 60645-2 : 1993. The UK participation in its preparation was entrusted to Technical Committee EPM9, Electroaco
3、ustics, which has the responsibility to: - aid enquirers to understand the text, - present to the responsible internationalEuropean committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; - monitor related international and European developments an
4、d promulgate them in the UK A iist of organizations represented on this committee can be obtained on request to its secretary. From 1 January 1997, all lEC publications have the number 60000 added to the old number. For instance, IEC 27-1 has been renumbered as LEX 60027-1. For a period of time duri
5、ng the change over from one numbering system to the other, publications may contain identifiers from both systems. Cross-references Attention is drawn to the fact that CEN and CENELEC Standards normally include an annex which lists normative references to international publications with their corres
6、ponding European publications. The British Standards which implement these international or European publications may be found in the BSI Standards Catalogue under the section entitled International Standards Correspondence Index, or using the Find facility of the BSI Standards Electronic Catalogue.
7、 Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, the EN title page, pages 2 to 20, an inside back cover and a back cover. This British Standard, having been prepared under the
8、 direction of the Electrotechnicai Sector Board, was published under the authority of the Standards Board and comes into effect on 15 September 1997 O BSI 1997 ISBN O 580 27794 1 EUROPEAN STANDARD NORME EUROPEENNE EUROPISCHE NORM EN 60645-2 January 1997 ICs 17.140.60 Descriptors: Acoustics, audiomet
9、ry, audiometers, measurements, auditory perception, clwsification, testing con 1997 CONTENTS INTRODUCTION clause 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Scope and object . Normative references Definitions . General requirements . Minimum requirements for specific types of audiometers Reference con
10、ditions for specification . testing and calibration of speech audiometers Signal level indicator . Output levei control for speech signals . Output sound-pressure level and vibratory force level . Frequency response Harmonic distortion . Signal-to-noise ratio Masking sound . Monitor earphone or loud
11、speaker Talkback system Interrupter switches . Marking and instruction manual . 4 5 5 6 8 0 8 10 10 10 11 12 13 13 14 14 14 14 Annex A . Correction figures for free-field equivalent output for certain types of commonly used earphones . 16 Annex ZA (normative) Normative references to international pu
12、blications with their corresponding European publications . 20 O BSI 1997 - STD.BSI BS EN bOb45-2-ENGL 1997 Lb2qbbS Ob38b70 257 = Page 4 EN 60645-2 : 1997 INTRODUCTION Part 1 of IEC 645 details the requirements for pure-tone audiometers in terms of per- formance characteristics of component modules.
13、 Some of these modules are common to speech audiometers for example the output level control, transducers, etc. This part 2 of IEC 645 specifies the requirements for speech audiometers- However, to avoid duplication, it only makes reference to pari I of IEC 645-1 where common elements are concerned
14、. Performance requirements are given for both live voice and recorded speech inputs. Although live voice speech audiometry may not be capable of meeting the object of this standard. it is widely practised, particularly with children, and therefore a specification is included in order to ensure as hi
15、gh a degree of reliability as possible. This standard does not specify the speech material that is used for test purposes or the required acoustic properties of the test room. Speech audiometers use earphones, bone vibrators or loudspeakers to present signals to the test subject. In order to relate
16、earphone or bone vibrator listening to sound field listening, the concept of a free-field equivalent output level of an earphone or a bone vibrator as described in IEC 268-7 is used for specification and measurement purposes. The free-field equivalent output method is fundamental in relating earphon
17、e or bone vibrator output level to sound-field measurements and for the comparison of different types of transducers. For audiometric purposes where only earphone measurements with one specific type are made, a requirement may not exist to maintain the free-fieid ear- phone relationship. Therefore,
18、in this standard, specifications of the performance charac- teristics of speech audiometers and relevant calibration and test methods are given with respect to both a free-field equivalent output level method and an uncorrected coupler out- put level method. * * 10 Page 5 EN 60645-2 : 1997 AU DIOMET
19、ERS Part 2: Equipment for speech audiometry 1 Scope and object This part of IEC 645 specifies requirements for audiometers or parts thereof designed to provide a means of presenting speech sounds to a subject in a standardized manner, for example for the measurement of speech recognition. Audiometer
20、s are classified into four types: type A instruments provide a wide range of facilities, while type i3 provides only basic facilities. For both types, the audiometer may be calibrated in terms of a free-field equivalent output level of the earphones and then be des- ignated as type A-E or B-E. This
21、standard excludes the requirements for speech audiometers provided with frequency response adjustments intended to determine an optimal intelligibility frequency response curve for each subject. The purpose of this standard is to ensure that tests of hearing using speech as the test stimulus, on a g
22、iven human ear performed with different audiometers which comply with this standard, shall give substantially the same resulis for a given caiibration method. Two methods of specification, calibration and testing are given for the output levels generated by the earphones and the bone vibrator: a) a
23、free-field equivalent output level method with audiometers of types A-E and B-E; b) an uncorrected coupler output level method with audiometers of types A and B. NOTE - The results will also depend on factors other than the audiometer for example test materid, test room, speakers, etc. 2 Normative r
24、eferences The following normative documents contain provisions which. through reference in this text, constitute provisions of this part of IEC 645. At the time of publication, the editions indicated were valid. All normative documents are subject to revision, and parties to agreements based on this
25、 pan of IEC 645 are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. Members of IEC and IS0 maintain registers of currently valid International Standards. IEC 225: 1966, Octave, half-octave and third-octave band filters intend
26、ed for the analysis of sounds and vibrations IEC 268-7: 1984, Sound system equipment - Part I: Headphones and headsets STD-BSI BS EN bOb45-2-EMGL 1997 Lb2ibbS Ob38b72 02T Page 6 EN 60645-2 : 1997 IEC 268-1 7: 1990, Sound system equipment. Part 17: Standard volume indicators IEC 303: 1970, EC provisi
27、onal reference coupler for the calibration of earphones used in audiometry IEC 318: 1970, An IEC ear simulator, of the wide band type, for the calibration of ear- phones used in audiometry IEC 373: 1990, Mechanical coupler for measurements of bone vibrators IEC 645-1 : 1992, Audiometers - Part I: Pu
28、re-tone audiometers IEC 651 : 1979, Sound level meters IS0 266: 1975, Acoustics - Preferred frequencies for measurements. 3 Definitions For the purpose of this part of IEC 645 the following definitions apply in addition to those given in IEC 645-1. 3.1 equipment for speech audiometry (speech audiome
29、ter): Equipment for the measurement of hearing using speech test material. 3.2 speech signal: A test signal generated by a natural human or synthetic voice. 3.3 hearing level for speech: For a specified speech signal and a specified manner of signal presentation, the speech level minus the appropria
30、te reference speech recognition threshold level. 3.4 speech levei: The sound-pressure level or the vibratory force level of the speech signal as measured in an appropriate coupler, ear simulator or in a sound field with speci- fied frequency weighting and specified time weighting. NOTES 1 For exampl
31、e, the speech level may be expressed as the equivalent continuous sound-pressure level or vibratory force level determined by integration over the duration of the speech signal with frequency weight- ing C. For speech test lists based on single test items separated by silent intervals, the integrati
32、on should not include these intervals. For test lists based on single test items with carrier phrase, the integration should include the test items only. 2 For lists of single test items the equivalent continuous sound-pressure level may be estimated by subtracting 5 dB from the average of the maxim
33、um measured sound-pressure levels using frequency Weighting C and time weighting I. 3.5 speech recognition threshold level: For a given listener, a specified speech signal and a specified manner of signal presentation, the lowest speech level at which the speech recognition score is equal to 50 Yo.
34、NOTE - Speech recognition threshold has been called speech reception threshold. x x m STDeBSI BS EN bOb45-2-ENGL 1777 H LbZYbb7 Ob3b73 Tbb Page 7 EN 60645-2 : 1997 3.6 reference speech recognition threshold level: For a specified speech signal and a specified manner of signal presentation, the media
35、n value of the speech recognition threshold levels of a sufficiently large number of otologically normal test persons, of both sexes. aged between 18 and 25 years inclusive and for whom the test material is appropriate. 3.7 Coupler sensjtivity, coupler sensitivity level of an earphone 3.7.1 coupler
36、sensitlvlty: At a given frequency, the quotient of the sound-pressure generated by the earphone in an acoustic coupler or ear simulator and the voltage applied to the terminals of the earphone. 3.7.2 coupler sensitlvity levei: Twenty times the logarithm to the base ten of the ratio of the coupler se
37、nsitivity to the reference sensitivity, 1 PaN. NOTE - Coupler sensitivity and coupler sensitivity level of a bone vibrator are defined in a corresponding way. 3.8 Free-field sensitivity, free-field sensitivity level of an earphone 3.8.1 free-field sensltivity: At a given frequency and for at least 1
38、0 otologically normal subjects, the quotient of the sound-pressure of a frontally incident plane progressive sound wave (Oo sound incident) and of that voltage of equal frequency which is applied to the terminals of the earphone in order that the subjects, on average, judge the sound wave and the so
39、und produced by the earphone as equally loud; both sounds being received in the same ear. NOTE - Test methods are described in IEC 268-7. Though the loudness comparison may be wrfomied binaurally. the resulting sensitivity is that of a single earphone. 3.8.2 free-fleld sensltivity level: Twenty time
40、s the logarithm to the base ten of the ratio of the free-field sensitivity to the reference sensitivity, 1 PaN. NOTE - free-field sensitivity and free-field sensitivity level of a bone vibrator are defined in a correspond- ing way. 3.9 free-field equivalent earphone output level: For a speech audiom
41、eter, the sound- pressure level generated by an earphone in terms of equivalent free-field sound-pressure level. At a given frequency, this level is derived from the sound-pressure level generated by the earphone in an acoustic coupler oc ear simulator by adding a correction figure representing the
42、difference between the free-field sensitivity level and the coupler sensitivity level for the type of earphone used at the given frequency. NOTE - See note to 3.8. 3.10 free-field equlvalent bone vibrator output level: For a speech audiometer, the vibratory force level generated by the bone vibrator
43、 in terms of free-field equivalent sound- pressure level. At a given frequency this levei is derived from the vibratory force level generated by the bone vibrator on a mechanical coupler by adding a correction figure representing the difference between the free-field sensitivity level and the couple
44、r sensitivity level for the type of bone vibrator used at the given frequency. - - - STD-8SI 8s EN bOb45-2-ENGL 1777 E 1624bb7 Ob38b7t TT2 Page 8 EN 60645-2 : 1997 NOTE - Calibration of a speech audiometer in terms of free-field equivalent output level makes the results of listening tests using diff
45、erent kinds of transducers, .e. earphones. bone vibratos and loudspeakers, directly comparable to each other. 3.1 1 effective masking level for speech: The level of a specified masking sound which is numerically equal to that hearing level for speech to which the speech recognition threshold level f
46、or a specified speech signal for a notional normal person would be raised by the presence of that masking sound. The notional normal person is one whose hearing conforms to the standards for threshold and for masking efficiency (IS0 389 and IS0 8798). 4 General requirements The following subclauses
47、of IEC 645-1 are also requirements of this standard: 5.1 Safety requirements 5.3 Warm-up time 5.4 Supply variation and environmental conditions 5.5 Unwanted sound (with exception of 5.5.3) 5.6 Testing of automatic recording and computer-controlled audiometers 7.3 Accuracy of sound-pressure level and
48、 vibratory force level (2nd paragraph only) 7.4 Hearing level control (subclause 7.4.4 only) 7.5.3 Accuracy of masking level (2nd paragraph only) If supra-aural earphones and a bone vibrator are provided, they shall meet the require- ments of 9.1.1 and 9.2 of JEC 645-1 respectively If the audiometer
49、 has the means of replaying recorded speech material as an integral part of it, tests for conformity shall be performed using a recording of the test signals required. If the replaying device is not an integral part of the audiometer the test signals shall be applied to the electrical input of the audiometer. 5 Minimum requirements for specific types of audiometers Four types of audiometer are specified and the requirements for minimum mandatory facilities are given in table 1. Other facilities are not precluded. 6 Reference conditions for specffication, testing and cal
