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1、BRITISH STANDARD BS 5941:1980 IEC 655:1979 Specification for Values for the difference between free-field and pressure sensitivity levels for one-inch standard condenser microphones UDC 621.395.616.089.6:621.317.39:534.6 Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 12:58:40 GMT+00:00 2006,
2、 Uncontrolled Copy, (c) BSI BS 5941:1980 This British Standard, having been prepared under the direction of the Electronic Equipment Standards Committee, was published under the authority of the Executive Board and comes into effect on 30 September 1980 BSI 12-1999 The following BSI references relat
3、e to the work on this standard: Committee reference EEL/24 Draft for comment 78/24190 DC ISBN 0 580 11497 X Cooperating organizations The Electronic Equipment Standards Committee, under whose direction this British Standard was prepared, consists of representatives from the following Government depa
4、rtment and scientific and industrial organizations: British Broadcasting Corporation* British Electrical and Allied Manufacturers Association (BEAMA) British Radio Equipment Manufacturers Association Cable and Wireless Limited Cable Television Association of Great Britain Electrical, Electronic, Tel
5、ecommunications and Plumbing Union Electricity Supply Industry in England and Wales Electronic Components Industry Federation Electronic Engineering Association Institution of Electronic and Radio Engineers* Ministry of Defence Post Office* Post Office Engineering Union Scientific Instrument Manufac
6、turers Association The organizations marked with an asterisk in the above list, together with the following, were directly represented on the committee entrusted with the preparation of this British Standard: British Association of Otolaryngologists British Medical Association British Society of Aud
7、iology Department of Health and Social Security Department of Industry (National Physical Laboratory) Health and Safety Executive Institute of Physics Hearing Aid Industry Association Institute of Sound and Vibration Research Manchester Area Health Authority Medical Research Council Royal Aeronautic
8、al Society Royal National Institute for the Deaf Society of Hearing Aid Audiologists Limited Amendments issued since publication Amd. No.Date of issueComments Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 12:58:40 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5941:1980 BSI 12-1999i Contents
9、 Page Cooperating organizationsInside front cover National forewordii 1Scope1 2Object1 3Background1 4Classification of microphones1 4.1Classification according to geometrical configuration1 4.2Classification according to acoustical characteristics2 5Tables of data2 Appendix A Classification of some
10、types of microphones according to acoustical characteristics4 Figure 11 Table I Values for the difference between free-field and pressure sensitivity levels in decibels for normal incidence (0)3 Table II Values for the difference between free-field and pressure sensitivity levels in decibels for gra
11、zing incidence (90)3 Publications referred toInside back cover Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 12:58:40 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5941:1980 ii BSI 12-1999 National foreword This British Standard, published under the direction of the Electronic Equipment Sta
12、ndards Committee is identical with IEC Publication 655 “Values for the difference between free-field and pressure sensitivity levels for one-inch standard condenser microphones” published in 1979 by the International Electrotechnical Commission (IEC). Terminology and conventions The text of the Inte
13、rnational Standard has been approved as suitable for publication, without deviation, as a British Standard. Some terminology and certain conventions are not identical with those used in British Standards. A British Standard does not purport to include all the necessary provisions of a contract. User
14、s of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Cross-references International StandardCorresponding British Standard IEC 327:1971BS 5677:1979 Method (precision) for pressure calibrati
15、on of one-inch standard condenser microphones by the reciprocity technique (Identical) IEC 486:1974BS 5679:1979 Method (precision) for free-field calibration of one-inch standard condenser microphones by the reciprocity technique (Identical) Summary of pages This document comprises a front cover, an
16、 inside front cover, pages i and ii, pages 1 to 4, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Licensed Copy: sheffieldun sheffieldun, na,
17、 Mon Dec 04 12:58:40 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5941:1980 BSI 12-19991 1 Scope This standard gives values for the difference between free-field and pressure sensitivity levels for one-inch standard condenser microphones. 2 Object The object of this standard is to give the values t
18、hat are to be added to the pressure sensitivity level of a microphone in order to obtain the free-field sensitivity level when a very high accuracy is not called for or when conditions for carrying out an accurate free-field calibration are not available. Data are given for the commonly used types o
19、f one-inch condenser microphones, categorized according to the acoustical properties and the geometrical configurations of the microphones; they relate to microphones used without the protective grid. NOTECorresponding data for microphones which are used with a protective grid in the free-field case
20、 are not specified in this standard. The values given have been derived from measurements of the pressure and free-field sensitivity levels of a number of microphones carried out in accordance with IEC Publication 327, Precision Method for Pressure Calibration of One-inch Standard Condenser Micropho
21、nes by the Reciprocity Technique, and IEC Publication 486, Precision Method for Free-field Calibration of One-inch Standard Condenser Microphones by the Reciprocity Technique, respectively, to which reference should be made concerning terminology, microphone preamplifier configurations, etc. 3 Backg
22、round According to the definitions of the free-field and pressure sensitivities of microphones, the two sensitivities will differ from each other for the following reasons: a) Owing to the effects of diffraction, the introduction of a microphone into a free progressive sound wave disturbs the sound
23、field. Thus the sound pressure at the microphone diaphragm is not equal to the free-field value. b) Owing to diffraction the sound pressure over the diaphragm of the microphone is not uniform and, for a specific microphone, is affected by the acoustic impedance of that microphone. c) The output volt
24、age of a particular microphone may not be proportional to the mean value of the sound pressure over the diaphragm because the microphone is more sensitive to a sound pressure at the centre of the diaphragm. The effect of Item a) is taken into account by considering various microphone configurations.
25、 The effects of Items b) and c) are taken into account by grouping different microphones according to certain characteristics (see Sub-clause 4.2). 4 Classification of microphones 4.1 Classification according to geometrical configuration Two basic microphone configurations are considered, see Figure
26、 1. Configuration 1 has a flush-mounted diaphragm, whilst configuration 2 has a recessed diaphragm. Figure 1 Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 12:58:40 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5941:1980 2 BSI 12-1999 4.2 Classification according to acoustical characteristic
27、s Two basic types of microphones are considered: A table, given in Appendix A, indicates the correspondence between the above classes and various types of one-inch condenser microphones in general use. 5 Tables of data The following tables contain values for the difference between free-field and pre
28、ssure sensitivity levels in decibels for the various combinations of microphone types and configurations. Table I refers to a plane progressive wave incident at an angle of 0 relative to the normal to the microphone diaphragm (“normal incidence”). Table II refers to a plane progressive wave incident
29、 at an angle of 90 relative to the normal to the microphone diaphragm (“grazing incidence”). The values are based on arithmetic means of data relating to typical samples of microphones within each group. The estimated accuracy is approximately 0.2 dB. NOTEThe tabulated numerical values relate to a m
30、icrophone mounted on the end of a long cylinder, whose diameter is equal to the nominal diameter of the microphone (see IEC Publication 486, Sub-clause 6.4). However, to within the accuracy quoted, they can be taken to remain valid for cylinder lengths in excess of five times the diameter. Type A: M
31、icrophones characterized by having a nearly constant free-field sensitivity at normal incidence over a broad frequency range, commonly known as free-field type microphones. The resonance of the diaphragm is heavily damped. Type B: Microphones characterized by having a nearly constant pressure sensit
32、ivity over a broad frequency range, commonly known as pressure-type microphones. Two groups need to be considered, according to diaphragm impedance: B(i) where the tension of the diaphragm is fairly high, resulting in an equivalent volume of the microphone in the range 0.07 cm3 to 0.11 cm3 of air. B
33、(ii) where the mass and tension of the diaphragm are slightly less, resulting in a higher value of the equivalent volume of the microphone, typically in the range 0.11 cm3 to 0.15 cm3 of air. Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 12:58:40 GMT+00:00 2006, Uncontrolled Copy, (c) BSI B
34、S 5941:1980 BSI 12-19993 Table I Values for the difference between free-field and pressure sensitivity levels in decibels for normal incidence (0) Table II Values for the difference between free-field and pressure sensitivity levels in decibels for grazing incidence (90) Frequency in kHz 0.50.630.81
35、1.251.622.53.15456.381012.51620 Microphone Configuration Type Flush diaphragm A B(ii) 0.1 0.1 0.1 0.1 0.2 0.2 0.3 0.3 0.5 0.5 0.7 0.7 0.9 0.9 1.3 1.3 1.9 1.9 2.7 2.7 3.7 3.7 5.0 4.9 6.3 6.0 7.5 7.0 7.7 7.6 7.1 7.1 6.0 5.8 Recessed diaphragm A B(i) B(ii) 0.1 0.1 0.1 0.1 0.1 0.1 0.2 0.2 0.2 0.3 0.3 0.
36、3 0.5 0.5 0.5 0.7 0.7 0.7 1.0 1.0 1.0 1.5 1.5 1.6 2.3 2.4 2.4 3.5 3.6 3.6 4.9 5.0 5.0 6.8 6.9 6.9 8.9 8.7 8.5 9.7 9.5 9.2 8.9 9.2 8.8 7.5 8.1 7.5 6.5 7.0 6.2 Frequency in kHz 0.511.251.622.53.15456.381012.51620 Microphone Configuration Type Flush diaphragm A B(ii) 0 0 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1
37、 0.1 0.1 0.1 0 0 0 0.2 0 0.4 0.1 0.3 0.1 0.4 0.9 2.7 2.6 6.9 7.0 Recessed diaphragm A B(i) B(ii) 0 0 0 0.1 0.1 0.1 0.1 0.1 0.1 0 0 0 0 0.1 0.1 0.1 0.2 0.2 0.3 0.4 0.4 0.7 0.8 0.8 1.1 1.1 1.1 1.6 1.6 1.6 2.0 1.8 1.6 0.5 0.6 0.3 3.2 2.1 2.5 8.5 Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 12
38、:58:40 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5941:1980 4 BSI 12-1999 Appendix A Classification of some types of microphones according to acoustical characteristics The table below lists some types of microphones in general use classified by their acoustical characteristics in accordance with
39、 Sub-clause 4.2. Microphone Flush diaphragm (configuration 1) Recessed diaphragm (configuration 2) Type ABK 4131 BK 4145 BK 4131 BK 4145 fitted with adaptor ring DB 0111 Type B(i)WE 640 AA MR 103 Type B(ii)BK 4132 BK 4144 BK 4146 BK 4132 BK 4144 BK 4146 fitted with adaptor ring DB 0111 Licensed Copy
40、: sheffieldun sheffieldun, na, Mon Dec 04 12:58:40 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5941:1980 BSI 12-1999 Publications referred to See national foreword. Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 12:58:40 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5941:1980 IEC 655:1979
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