1、BRITISH STANDARD BS5877:1980 Guide for Subjective listening tests for sound radio receivers UDC 621.396.62.001.4:159.932.018.2BS5877:1980 This British Standard, having been prepared under the directionof the Electronic Equipment Standards Committee,was published underthe authority of the Executive B
2、oard and comes into effect on 30 April1980 BSI10-1999 The following BSI references relate to the work on this standard: Committee referenceEEL/25 Draft for comment78/25093DC ISBN 0 580 11299 3 Cooperating organizations The Electronic Equipment Standards Committee, under whose direction this British
3、Standard was prepared, consists of representatives from the following Government department and scientific and industrial organizations: British Broadcasting Corporation* British Electrical and Allied Manufacturers Association (BEAMA) British Radio Equipment Manufacturers Association* Cable Televisi
4、on Association of Great Britain* Cable and Wireless Limited Electrical, Electronic, Telecommunications and Plumbing Union Electricity Supply Industry in England and Wales Electronic Components Industry Federation* Electronic Engineering Association* Institution of Electronic and Radio Engineers* Min
5、istry of Defence Post Office* Post Office Engineering Union Scientific Instrument Manufacturers 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: Co
6、nsumer Standards Advisory Committee of BSI Consumers Association Home Office Radio Society of Great Britain Amendments issued since publication Amd. No. Date of issue CommentsBS5877:1980 BSI 10-1999 i Contents Page Cooperating organizations Inside front cover Foreword ii Introduction 1 0 Scope 1 1 C
7、haracteristics of the test room 1 2 Number of panellists 2 3 Qualification of panellists 2 4 Positioning of the test objects 2 5 Reference receiver 3 6 Signal input 3 7 Characteristics of the modulation signals 3 8 Procedure 3 9 Conditions of work and instruction of the panel 4 10 Supply voltage and
8、 stability conditions 4 11 Scoring and scales of subjectivegrading 4 Appendix A Hearing loss frequency characteristics of men and women of different age groups 6 Appendix B Layout of the test room 7 Table 1 Detailed composition of a panel 2 Publications referred to Inside back coverBS5877:1980 ii BS
9、I 10-1999 Foreword This British Standard has been prepared under the direction of the Electronic Equipment Standards Committee. It is technically equivalent to IEC Publication543:1976, published by the International Electrotechnical Commission (IEC), although it has been necessary to make some edito
10、rial changes to improve the clarity of the standard. Some textual errors have also been corrected. Appendix C of IEC Publication543 has been omitted from this British Standard. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are r
11、esponsible for their correct application. 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, pagesi andii, pages1 to8, an inside back cover and a back cover. This standard has be
12、en updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS5877:1980 BSI 10-1999 1 Introduction A need exists for reproducible subjective listening tests for sound radio receivers, because objective measurements
13、 alone have not been found adequate for determining sound quality. As however, subjective tests have an inherent degree of uncertainty, objective tests should still be used wherever possible, particularly for those parameters that are to be included in the terms of acontract. The purpose of this gui
14、de is to define procedures that will permit the comparison of the acoustical performance of various types of household or similar sound radio receivers, in a controlled environment and with an established procedure, to give results that are as reproducible as possible. The listening tests are carrie
15、d out by comparison against a reference receiver. However, this does not exclude certain qualities and impairments from being characterized by absolute judgements. The reference receiver should be selected with great care in all cases because the comparative judgements made are dependent on this ref
16、erence. A description of the reference receiver should also be given with the results. A subjective evaluation, based on this guide, consists of the average judgement of several persons on a given subject. The individual opinions are divided into ranges corresponding to assessment scales, showing fo
17、r each range the number of persons of that opinion. In this way, the subjective evaluation may be presented as an average opinion with a standard deviation. Receivers should be divided into categories of use for comparison so that each is judged within its own category. Such categories might be, for
18、 example: If appropriate, price classifications may be used in connection with such categories. Care should be taken to avoid grouping together receivers providing different ancillary equipment (for example radios and radiograms), unless it is required for particular reasons. 0 Scope This British St
19、andard gives guidance on the procedures for carrying out and evaluating the results of subjective listening tests for the comparison of the acoustic performance of various types of household or similar sound radio receivers in a controlled environment, to give reproducible results. This standard des
20、cribes the requirements for the test room, the composition and qualifications of the judging panel, the setting up and test procedure and the method of scoring. NOTE 1The use of this standard for the assessment of high fidelity equipment should be regarded as provisional (see the footnote to the int
21、roduction). NOTE 2The titles of the publications referred to in this standard are listed on the inside back cover. 1 Characteristics of the test room It is recommended that the characteristics of the test room should be as follows. a) A room of the same type as a living-room with the average charact
22、eristics of domestic surroundings is recommended. The rooms should be approximately rectangular in shape, about30m 2 , with one side slightly longer than the other. The shorter side should be not less than3.5m (see Appendix B) in order to be able to measure stereophonic equipment (stereo base2.5m).
23、b) The acoustic response of the room should be fairly smooth and have a reverberation time corresponding to that of a typical living-room. This time is approximately0.5s at500Hz (limits0.4s and0.6s inclusive). Over the frequency range100Hz to5000Hz, there should not be any unusual room resonances, n
24、or flutter echo. c) The lighting within the room should be of medium intensity, so arranged that the lights do not shine directly into the eyes of any panellist. Temperature:20 C to26 C. The degree of relative humidity should be between45% and75%. NOTEDamping elements consisting of domestic furnitur
25、e, curtains and carpets are to be preferred to sound-absorbing panels to ensure the correct relationship between reverberation time and frequency. Rooms with solid floors, covered with pile carpet, and without large areas of glazing are easier to correct. A: personals (pocket receivers) A1 a.m. pers
26、onals A2 f.m. personals A3 a.m./f.m. personals B: portables B1 a.m. portables B2 a.m./f.m. portables C: table sets C1 table sets for a.m. C2 table sets for a.m./f.m. D: other receivers (e.g.larger radiograms) E: high-fidelity equipment a a Great care should be taken in using this method for the asse
27、ssment of high-fidelity equipment. This method is to be regarded as provisional, pending completion of international work on this subject. BS5877:1980 2 BSI 10-1999 The recommended background sound level is less than35dB(A) determined with a sound level meter (scale A). If this level is exceeded, th
28、e level should be stated with the results. The volume of the reference receiver and that of the receiver under test should be adjusted equally to a level acceptable to the listening panel. For guidance only, sound levels that are considered suitable for listening in a domestic living-room are given
29、below: 2 Number of panellists The number of observers needed to obtain a statistically high level of confidence is20 or more. For most purposes, the number of panellists may be reduced to seven (or even fewer); such panels have been found to give reproducible results if the recommendations of clause
30、s3 and9 are followed. 3 Qualification of panellists The panel should be a representative sample of users for the particular type of equipment under test. Consequently, the matters to be considered are: whether the members of the panel are experts or laymen; their degree of musical appreciation; thei
31、r age; their sex; their hearing ability. In general, an appropriate audio test should be made to verify that the listeners do not have a very reduced hearing ability. In those cases where the panel has to be small, it may be convenient to select panellists in a particular manner; for example, it is
32、possible to use the personal standard deviation derived from previous tests (as a measure of reliability) or by an audiogram that indicates: a) the perception of sound level differences of approximately3dB and change of pitch of1% at1000Hz, b) a sensitivity of hearing, in the frequency range up to7k
33、Hz, not worse than the appropriate value indicated in the diagrams in Appendix A; c) the ability to accurately place the image position of a “pink noise” 1)signal source fed to a pair of loudspeakers, set up in the normal stereo fashion. NOTEFor table radios, portable radios and low- and medium-pric
34、ed gramophones, the panel of listeners need not be musically educated, but they should be musically perceptive. For high-quality radios and gramophones or high-fidelity systems, the procedure is generally similar, except that at least half the panel should be musically educated. An example of the de
35、tailed composition of a panel is given in Table 1. As far as possible, the composition of the panel should be such that the number of men and women is equal in each age group. Table 1 Detailed composition of a panel If a higher number of panellists is used, the ratios given above should be maintaine
36、d. In every case the composition of the panel should be stated with the results. 4 Positioning of the test objects To avoid any irrelevant psychological influence, the receivers under test should not be visible to the panel and they should be placed behind a sound-transparent curtain. It is suggeste
37、d that the layout of the test room should be in the general form shown in Appendix B. The illustration is equally applicable for stereophonic and monophonic equipment. The microphone (M) of a sound level meter should be suspended over the panellists above head level. When possible, the loudspeakers
38、of stereophonic equipment should be placed at a distance (D) apart and separated from the listeners according to the manufacturers instructions, but in no case should listener(1) be less than2.5m from the curtain (distance H). for small receivers: approximately60dB(A); for medium receivers: approxim
39、ately75dB(A); for large and high-fidelity receivers: approximately80dB(A) to85dB(A). 1) “Pink noise” is a noise whose spectrum is uniform as a function of frequency over a designated frequency range, as measured in a bandwidth proportional to the frequency. Characteristics of panellists Number of pa
40、nellists Minimum Recommended Maximum Sex Men Women 2 2 3 or 4 4 or 3 5 5 Total 4 7 10 Age Between 15 and 40 Between 40 and 60 Over 60 2 1 1 4 2 1 5 3 2 Total 4 7 10BS5877:1980 BSI 10-1999 3 This arrangement is also satisfactory for monophonic equipment, but not for the case of pocket radios. A monop
41、honic radio is placed in the centre and just behind the sound curtain. All loudspeakers other than those intended to stand on the floor should be placed on a solidly constructed wooden table, approximately750mm to800mm in height, such that the front of each loudspeaker is at the same distance from t
42、he edge of the table nearest to the panel. When testing pocket radios, the panellists should hold the receivers in their hands, shrouded if possible. 5 Reference receiver It is essential to make the assessment by comparison with a reference receiver, preferably a sample that is of a quality correspo
43、nding to the characteristic under consideration and near to the centre of the grading scale. In addition a receiver of the highest quality may be used for evidence of achievable sound quality and as a control for calibration purposes. Consistency between different series of evaluations may be achiev
44、ed by using the same test equipment for comparison. 6 Signal input A predetermined programme according to clause7 should be recorded on, and reproduced by means of, a high quality tape deck. The audio frequency output from the tape deck should be used to modulate a signal generator which feeds, as a
45、 radio frequency signal, to the radio receivers under test. The signal is coupled via a radio loop or other suitable means, for example, a magnetic aerial (as described in BS4054-1) or as a voltage via the proper aerial impedance network. The level of the signal should have an appropriate value and
46、be substantially equal for each receiver. For receivers with an audio frequency input, the tape deck output is fed through a matching network to this input in a separate test. The characteristics of the signal, especially the modulation depth in the case of a.m., the frequency deviation and the pre-
47、emphasis characteristics in the case of f.m. should correspond closely to the transmission standard used. The levels of the input signals used should be stated with the results. 7 Characteristics of the modulation signals The programme should include: classical music (a symphonic piece, a chamber mu
48、sic piece and an operatic song); popular music (light rhythmical music of all types including light classical, dance and jazz with and without vocals); speech (in different languages). In the case of vocal transmission of a text, the speaker should have excellent diction. Suggested duration of each
49、type (approximately): Each test piece should not last more than20s and should be played through the reference equipment immediately before being played through the equipment under test. This procedure should be carried out for each test piece and for each receiver tested. A switchboard should be used so that quick changes between the reference receiver and test receivers are possible, with a period of silence of about0.5s. 8 Procedure 8.1 Adjustment of volume controls. The tests should be conducted using the same volume level for the reference receiver
