1、BRITISH STANDARD BS 6840-9: 1987 IEC 268-9: 1977 Sound system equipment Part 9: Methods for specifying and measuring the characteristics of artificial reverberation, time delay and frequency shift equipment IEC title: Sound system equipment Part 9: Artificial reverberation, time delay and frequency
2、shift equipment UDC 621.396+681.84:621.395.61:621.317.6BS6840-9:1987 This British Standard, having been prepared under the directionof the Electronic Equipment Standards Committee,was published underthe authority of the BoardofBSI and comes into effecton 30November1987 BSI 07-1999 The following BSI
3、references relate to the work on this standard: Committee reference EEL/32 Draft for comment 75/26725 DC ISBN 0 580 16222 2 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Electronic Equipment Standards Committee (EEL/-) to Technical Com
4、mittee EEL/32, upon which the following bodies were represented: Association of British Theatre Technicians Association of Sound and Communications Engineers Limited Audio Engineering Society British Educational Equipment Association British Kinematograph, Sound and Television Society British Radio
5、and Electronic Equipment Manufacturers Association British Telecommunications plc Cable Television Association of Great Britain Consumer Standards Advisory Committee of BSI Consumers Association Federation of British Audio Independent Television Companies Association Institution of Electronic and Ra
6、dio Engineers Radio Electrical and Television Retailers Association Royal Institute of British Architects Royal National Institute for the Deaf Society of Cable Television Engineers Training and Educational Systems Testing Bureau Amendments issued since publication Amd. No. Date of issue CommentsBS6
7、840-9:1987 BSI 07-1999 i Contents Page Committees responsible Inside front cover National foreword iii 1 Scope 1 2 Object 1 3 Conditions 1 3.1 Conditions for specifications 1 3.2 Rated conditions and normal working conditions 1 3.3 Other conditions 1 4 General 1 4.1 General 1 4.2 General characteriz
8、ation of the devices 1 4.3 Comparison between characteristics of the devices and those of the amplifier 1 Section 1. Artificial reverberation equipment 5 General 2 5.1 Definition of reverberation 2 5.2 Object 2 5.3 General characteristics 2 5.4 Special characteristics 2 6 Reverberation time 2 6.1 Ch
9、aracteristic to be specified 2 7 Various kinds of reverberation time 2 7.1 Initial reverberation time 2 7.2 Ultimate reverberation time 2 7.3 Method of measurement 3 8 Linearity 3 8.1 Characteristic to be specified 3 9 Frequency response 3 9.1 Characteristic to be specified 3 9.2 Method of measureme
10、nt 3 10 Initial time delay 3 10.1 Characteristic to be specified 3 10.2 Method of measurement 3 11 Additional characteristics 3 11.1 General 3 11.2 Ambient acoustical noise 3 11.3 Safe life expectancy 4 Section 2. Time delay devices 12 General 4 12.1 Types of devices 4 12.2 General characteristics 4
11、 12.3 Special characteristics 4 13 Delay time 4 13.1 Characteristic to be specified 4 13.2 Method of measurement 4 14 Echo 4 14.1 General 4 15 Echo time 4BS6840-9:1987 ii BSI 07-1999 Page 15.1 Characteristic to be specified 4 16 Ambient acoustical noise 4 17 Safe life expectancy 4 Section 3. Frequen
12、cy shift devices 18 General 5 18.1 General characteristics 5 18.2 Special characteristic 5 18.3 Characteristic to be specified 5 18.4 Method of measurement 5 Publications referred to Inside back coverBS6840-9:1987 BSI 07-1999 iii National foreword This British Standard has been prepared under the di
13、rection of the Electronic Equipment Standards Committee and is identical with Publication268-9:1977 “Sound system equipment” Part 9 “Artificial reverberation, time delay and frequency shift equipment” published by the International Electrotechnical Commission (IEC). The text of this Part of BS6840 i
14、s unchanged from the text of BS5428-8 which is now withdrawn. All Parts and Sections of BS5428 will be published as Parts of BS6840 in order to achieve consistency of numbering between the corresponding Parts of the IECPublication and the British Standard. BS6840 consists of the following Parts: Par
15、t 1: Methods for specifying and measuring general characteristics used for equipment performance (Supersedes part of BS5428-1); Part 2: Specification for general terms and calculation methods (Supersedes part of BS5428-1) 1) ; Part 3: Methods for specifying and measuring the characteristics of sound
16、 system amplifiers (Supersedes BS5428-2) 1) ; Part 4: Methods for specifying and measuring the characteristics of microphones (Previously BS5428-3); Part 5: Methods for specifying and measuring the characteristics of loudspeakers (Supersedes BS5428-11 and BS5428-11:Supplement 1) 1) ; Part 6: Methods
17、 for specifying and measuring the characteristics of auxiliary passive elements (Previously BS5428-4); Part 7: Methods for specifying and measuring the characteristics of headphones and headsets (New) 1) ; Part 8: Methods for specifying and measuring the characteristics of automatic gain control dev
18、ices (Previously BS5428-7); Part 9: Methods for specifying and measuring the characteristics of artificial reverberation, time delay and frequency shift equipment (Previously BS5428-8); Part 10: Specification for programme level meters (Supersedes BS5428-9) 1) ; Part 11: Specification for applicatio
19、n of connectors for the interconnection of sound system components (Supersedes BS5428-5.2) 1) ; Part 12: Specification for application of connectors for broadcast and similar use (Supersedes BS5428-5.3) 1) ; Part 13: Guide for listening tests on loudspeakers (New); Part 14: Guide for circular and el
20、liptical loudspeakers: outer frame diameters and mounting dimensions (Previously BS5428-5.1); Part 15: Specification for matching values for the interconnection of sound system components (Supersedes BS5428-10) 1) ; Part 16: Guide to the RASTI method for the objective rating of speech intelligibilit
21、y in auditoria (New) 1) . 1) In preparation.BS6840-9:1987 iv BSI 07-1999 Terminology and conventions. The text of the international standard has been approved as suitable for publication as a British Standard without deviation. Some terminology and certain conventions are not identical with those us
22、ed in British Standards; attention is drawn especially to the following. IEC94-4, referred to in the text as being in preparation, has now been published as IEC94-4:1986, and BS6288-4 is in preparation as a British Standard identical to it. A British Standard does not purport to include all the nece
23、ssary provisions of a contract. Users 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 standard Corresponding British Standard IEC225:1966 BS2475:1964 Speci
24、fication for octave and one-third octave band-pass filters (Technically equivalent) IEC 268-1:1985 BS6840 Sound system equipment Part 1:1987 Methods for specifying and measuring general characteristics used for equipment performance (Identical) BS5428 Methods for specifying and measuring the charact
25、eristics of sound system equipment IEC268-3:1969 Part 2:1979 Amplifiers a (Technically equivalent) IEC268-5:1972 Part 11:1977 Loudspeakers a (Identical) ISO140-1960 BS2750 Methods of measurement of sound insulation in buildings and of building elements (Separately published Parts are identical) a Th
26、ese Parts of BS5428 will be withdrawn when revisions of IEC268-3 and IEC268-5 are published and implemented as Parts of BS6840. Summary of pages This document comprises a front cover, an inside front cover, pages i to iv, pages1to 6, an inside back cover and a back cover. This standard has been upda
27、ted (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS6840-9:1987 BSI 07-1999 1 1 Scope This standard applies to devices intended to give reverberation, time delay and frequency shift to signals of an acoustical o
28、rigin. It covers the types of devices commonly employed to achieve special effects in sound recording, broadcasting and public-address systems. 2 Object This standard provides details of the special characteristics and corresponding methods of measurement to be used for artificial reverberation, tim
29、e delay and frequency shift equipment. For the purposes of this standard, the equipment is considered to be an amplifier that has been designed for a special purpose. Reference should therefore be made to IEC Publication268-3, Sound System Equipment, Part 3: Sound System Amplifiers. Because of the l
30、arge variety of principles on which this equipment is based, this standard is not complete. Specifications not covered by this standard should be the subject of agreement between the manufacturer and the user. In general, the methods of measurement given are those which are considered to be the most
31、 directly related to the characteristics. However, this does not exclude the use of other methods which will give equivalent results. 3 Conditions 3.1 Conditions for specifications Reference is made to IEC Publication 268, Part1:General, as concerns: units and system of measurement; frequencies of m
32、easurement; quantities to be specified and their accuracy; marking and symbols for marking; ambient conditions; filters, networks and measuring instruments for noise specification and measurement; individual specification and type specification; graphical presentation of data; scales for graphical p
33、resentation of data; personnel safety and prevention of spread of fire. 3.2 Rated conditions and normal working conditions Reference is made to IEC Publication268-3, Sub-clause 3.2: Rated conditions and normal working conditions changing the term “amplifier” to “device”. 3.3 Other conditions Referen
34、ce is made to IEC Publication 268-3, Sub-clause 3.3: Other conditions changing the term “amplifier” to “device”. 4 General 4.1 General Reference is made to IEC Publication 268-3, Section1: General, with the addition of the Sub-clauses 4.2 and 4.3 as follows. 4.2 General characterization of the devic
35、es Generally, the devices are characterized by electric input and output links coupling an intermediate link which introduces the special characteristic for the kind of device, either a particular transient response, a time delay or a frequency shift. The intermediate link may be of various natures.
36、 The principles most commonly used are: a) For artificial reverberation Excitation of waves in a bounded medium and pick-up at different locations, sometimes combined with electric feedback. b) For time delay Transit-time between record and play-back of a magnetic tape, disk or drum. Transit-time of
37、 a free propagating wave in a medium. Transit-time of a signal in an analogue or digital electric network. c) For frequency shift Modulation of the signal on a high-frequency carrier wave and demodulation of one of the sidebands by means of a frequency which is slightly different from the original c
38、arrier frequency. 4.3 Comparison between characteristics of the devices and those of the amplifier Because the devices considered have electric or electronic input and output characteristics similar to those of amplifiers, their methods of measurement will be similar to those for sound system amplif
39、iers. For both time delay and frequency shift devices, the output signal will represent the input signal in the same way as for an amplifier, with the exception of the time delay and the frequency shift respectively. Therefore all the characteristics and the methods of measurement listed for sound s
40、ystem amplifiers also apply to time delay and frequency shift devices.BS6840-9:1987 2 BSI 07-1999 For these devices, the object of this standard is limited to standards for the two special characteristics time delay and frequency shift respectively and their methods of measurement. It should be born
41、e in mind, however, that the intermediate link may introduce a kind of distortion which is not common to an amplifier, e.g.: wow and flutter and modulation noise for magnetic tape delay; non-linear distortion components other than those listed for amplifiers in modulation/demodulation frequency shif
42、t links. For artificial reverberation devices, the particular transient behaviour of the intermediate link not only introduces special characteristics particular to this kind of device but, moreover, influences other characteristics e.g. frequency response to such an extent that the methods of measu
43、rement for these characteristics have to be matched to the particular behaviour. Therefore, for this kind of device this standard covers also the modifications required with respect to the methods of measurement for amplifiers. For the characteristics to be specified and the relevant methods of meas
44、urement, reference is made to IEC Publication 268-3. Section 1. Artificial reverberation equipment 5 General 5.1 Definition of reverberation In room acoustics, this is the phenomenon that sound energy persists in a room after the sound source has been stopped. For artificial reverberation devices, r
45、everberation refers to the analogue electrical phenomenon that the output signal persists after the input signal has been stopped. 5.2 Object The object of this device is to produce a signal in order to generate effects similar to those of reverberation in a room with given acoustical characteristic
46、s. 5.3 General characteristics For steady-state conditions, the most suitable test shall be chosen from the ones specified for sound system amplifiers (IEC Publication268-3), for professional tape recorders (IEC Publication94-4, in preparation) and for loudspeakers (IECPublication268-5, Part 5: Loud
47、speakers) in which the signal used is pink noise. 5.4 Special characteristics 5.4.1 Reverberation time as a function of frequency (ISO140). 5.4.2 Characteristics of decay linearity of the output level as a function of time, following the transient corresponding to a stop at the input. The level shal
48、l be expressed in decibels. 5.4.3 Frequency response. 5.4.4 Sensitivity to ambient noise. 5.4.5 Initial decay time as a function of frequency. 5.4.6 Additional characteristics. 6 Reverberation time 6.1 Characteristic to be specified If the decay of the signal fits an exponential law, the reverberati
49、on time is that time for the sound pressure level or the output signal level to decrease by 60dB after the input signal has been stopped. NOTEThe decay curve of the signal level may be represented by values of the decay rate. The relation between reverberation time and the decay rate is 7 Various kinds of reverberation time 7.1 Initial reverberation time 7.1.1 Characteristic to be specified When the signal decay does not fit an exponential law, the initial reverberation time is evaluated f
