1、BRITISH STANDARD BS 6840-13: 1998 IEC 60268-13: 1998 Sound system equipment Part 13: Listening tests on loudspeakers ICS 33.160.50BS6840-13:1998 This British Standard, having been prepared under the directionof the Electrotechnical Sector Board, was published underthe authority of the Standards Boar
2、d and comes intoeffect on 15 June 1998 BSI 04-1999 ISBN 0 580 29895 7 National foreword This British Standard reproduces verbatim IEC 60268-13:1998 and implements it as the UK national standard. It supersedes BS 6840-13:1987 which is withdrawn. The UK participation in its preparation was entrusted b
3、y Technical Committee EPL/100, Audio, video and multimedia systems and equipment, to Subcommittee EPL/100/3, Equipment and systems in the field of audio, video and audiovisual engineering, which has the responsibility to: aid enquirers to understand the text; present to the responsible international
4、/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. A list of organizations represented on this subcommittee can be obtained on request to its secr
5、etary. From 1 January 1997, all IEC publications have the number 60000 added to the old number. For instance, IEC27-1 has been renumbered as IEC60027-1. For a period of time during the change over from one numbering system to the other, publications may contain identifiers from both systems. Cross-r
6、eferences The British Standards which implement international or European publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic C
7、atalogue. A British Standard does not purport to include all the necessary 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. Summary of pages This document
8、comprises a front cover, an inside front cover, pages i and ii, theIEC title page, page ii, pages 1 to 13 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. Amendment
9、s issued since publication Amd. No. Date CommentsBS6840-13:1998 BSI 04-1999 i Contents Page National foreword Inside front cover Text of IEC 60268-13 1ii blankBS6840-13:1998 ii BSI 04-1999 Contents Page 1 General 1 1.1 Scope 1 1.2 Reference documents 1 1.3 Explanation of terms 1 2 Listening conditio
10、ns 2 2.1 Listening room 2 2.1.1 Room dimensions 2 2.1.2 Reverberation time 3 2.1.3 Environmental conditions 4 2.2 Loudspeaker position and orientation 4 2.2.1 Monophonic reproduction 5 2.2.2 Two-channel stereophonic reproduction 5 2.2.3 Multi-channel stereophonic reproduction 5 2.3 Listening positio
11、n 5 2.4 Level setting 6 2.4.1 Listening level 6 2.4.2 Relative level 6 2.5 Electrical requirements 6 2.5.1 Signal source and amplifiers 6 2.5.2 Switching system 7 2.5.3 Connections 7 2.5.4 Overall frequency response 7 3 Listeners 2 4 Programme material 7 5 Experimental procedure and evaluation 8 5.1
12、 Experimental procedure 8 5.1.1 Single stimulus ratings procedure 9 5.1.2 Paired ratings and paired comparisons procedures 9 5.2 Rating scales and perceptual attributes 9 5.2.1 Rating scales 9 5.2.2 Perceptual attributes and their definitions for this report 9 5.3 Test duration 10 5.4 Instructions a
13、nd preliminary trials 10 5.5 Statistical treatment of the data 10 6 Test report 11 Annex A Instructions for listening tests 12 Annex B Statistical treatment of the data from listening tests 13 Figure 1 Tolerance limits for the reverberation time relative to the average value, T m 3 Table 1 Backgroun
14、d noise levels 4BS6840-13:1998 BSI 04-1999 1 1 General 1.1 Scope The recommendations in this report apply to loudspeakers intended for residential systems and environments. Although the procedures are specifically designed for loudspeakers which are separate sound system components for either monoph
15、onic, two-channel stereophonic or multichannel stereophonic reproduction, they may also be applied to other devices such as complete audio and television receivers with integrated sound. This report gives recommendations for establishing, conducting and evaluating listening tests on loudspeakers. Al
16、though various aspects are under continuing discussion, this report is intended to give the general guidelines. Certain aspects may vary in particular, the listening room may reflect regional construction practices. The tests described in this report are to be performed in a room the size and acoust
17、ical properties of which are similar to those of an “average” living room. Specific recommendations about the room size, acoustical properties, arrangements of loudspeakers and listeners, and environmental conditions are given. This Technical Report describes experimental procedures, including recom
18、mendations on the choice of programme material and the processing and presentation of the final data. It may be useful, when applying the methods of this publication, to also consider some of the recommendations in AES 20, especially as concerns the range of perceptual attributes as listed in 5.2.2.
19、 It should be understood that the topics of experimental design, experimental execution, and statistical analysis are complex, and that only the most general guidelines can be given. It is recommended that professionals with expertise in experimental design and statistics should be consulted or brou
20、ght in early in the planning of the listening test. The use of multi-channel formats, principally for domestic presentation of cinema, is becoming more widespread. The procedures described in this report are applicable to any number of channels of reproduction. Because of the rapidity with which the
21、 practices in this area are evolving, only the most general guidelines are given. 1.2 Reference documents IEC 60651:1979, Sound level meters. ISO 1996 (all parts), Acoustics Description and measurement of environmental noise. ISO 3382:1997, Acoustics Measurement of the reverberation time of rooms wi
22、th reference to other acoustical parameters. AES 20:1996, AES recommended practice for professional audio Subjective evaluation of loudspeakers. 1.3 Explanation of terms In this report, a number of special terms are used with the following meanings. NOTEFor the convenience of the reader, some specia
23、l terms are defined in 5.2, where they are used. 1.3.1 programme excerpt short piece of music, speech or other type of sound event of approximately 60 seconds duration suitable for assessing the individual characteristics of the sound quality of a loudspeaker under test 1.3.2 stimulus reproduction o
24、f a certain programme excerpt over a certain loudspeaker for monophonic reproduction or a set of loudspeakers for two channel stereophonic or multi-channel stereophonic reproduction 1.3.3 attribute perceived characteristic of a hearing event according to a given verbal or written definitionBS6840-13
25、:1998 2 BSI 04-1999 1.3.4 listening panel whole group of listeners that produce the data from a listening test 1.3.5 session group of trials which are to be evaluated by a listener or listening panel in a continous time period 1.3.6 trial subset of a session which begins with the presentation of a s
26、et of stimuli and ends with their gradings 1.3.7 replication repeated application of the same stimulus in order to reduce the standard deviation of the mean value 1.3.8 reliability 1.3.8.1 intra-individual reliability agreement between a certain listeners repeated ratings of the same stimulus 1.3.8.
27、2 inter-individual reliability agreement between different listeners ratings of the same stimulus 1.3.9 interaction interaction between two variables means that the effects of one variable are different for different values of the other variable. Applied to the ratings in a listening test, an intera
28、ction between loudspeakers and programme excerpts may mean that the differences between the ratings of two (or more) loudspeakers are different for different programme excerpts 2 Listening conditions 2.1 Listening room Ideally the listening room should approximate a residential listening environment
29、 in the geographical region where the test results are intended to apply. Known principles of good listening-room design are presented below. The intention is to assist the user in avoiding major defects which might adversely affect the test results. 2.1.1 Room dimensions 2.1.1.1 General constraints
30、 In rooms of any size the low-frequency response will be affected by the frequency distribution of the room eigentones. In order to ensure a reasonably uniform distribution of low-frequency eigentones the room should preferably have the following dimension ratios: (W/H) # (L/H) # (4,5 (W/H) 4) where
31、 Additionally, the condition L/H 3 and W/H 3 should apply. Initially, when designing a listening room the height should be specified. By following the design criteria, the range of acceptable values for the length/height ratio, the width/height ratio and the length/width ratio can be calculated. Fro
32、m there, it is a simple matter to find the possible room dimensions. L is the length; H is the height; W is the width.BS6840-13:1998 BSI 04-1999 3 For monophonic or two-channel stereophonic reproduction the floor area should preferably be within the range25m 2to40m 2 , and for multichannel stereopho
33、nic reproduction30m 2to45m 2 . 2.1.1.2 Reference room If the room size can be freely chosen, the following dimensions shall be considered to constitute a reference or standard listening room: The use of such a standard listening room allows test results from different locations to be directly compar
34、ed. 2.1.1.3 Small room In small rooms, some adjustments to the recommendations in 2.1.2, 2.2 and 2.3 may be required. These adjustments should be reported in accordance with the requirements of clause 6. 2.1.2 Reverberation time Reflected and reverberant sounds in the listening room have a major inf
35、luence on both timbre and spaciousness. The effectiveness and placement of absorbing materials affect the reverberation time, the degree of diffusion and the interaction between the loudspeaker and the room. Regional practices and preferences will affect what is “typical” in this regard. Technically
36、, both the reverberation time T, and its variation with frequency are important. T should be measured according to ISO 3382 at % octave intervals with furnishing but with no listeners present. Specific attention should be paid at low frequencies in order to obtain valid data. The average value of th
37、e reverberation time, T m , measured from 200 Hz to4000Hz should be within the range from0,3s to0,6s. Where the results of the listening tests are of more than just regional or other specific interest, it is recommended that the limits shown in Figure 1 be adhered to. Figure 1 also applies to the re
38、ference room described in 2.1.1.2, with the additional recommendation that T mshould be0,4s. L = 7,0 m; W = 5,3m; H = 2,7m. Figure 1 Tolerance limits for the reverberation time relative to the average value, T mBS6840-13:1998 4 BSI 04-1999 The tolerances to be applied to T mover the frequency range6
39、3Hz to8000 Hz are given in Figure 1. The listening room should have a ceiling that is mostly reflective and a floor that is mostly absorbent. Ordinary room furnishings are recommended in order to obtain sound diffusing and absorbing properties that are similar to living rooms. If further sound absor
40、ption is needed additional sound absorbing material should be uniformly distributed on the walls in order to obtain the specified reverberation time and to suppress flutter echoes. Chairs should be comfortable with the chair-backs below the shoulders of the seated listeners. An acoustically transpar
41、ent curtain should be used in order to prevent visual observation of the loudspeakers. The acoustical transparency of the curtain should be measured as the difference between room responses measured at the listening position with and without the curtain. In any % octave band up to10kHz the differenc
42、e should be less than0,3dB. 2.1.3 Environmental conditions Extreme climatic conditions should be avoided. Conditions as close as possible to those existing in a normal domestic environment are recommended. Measured conditions should be stated in the test report. The following conditions should be me
43、t: The continuous octave-band background noise level (produced by an air-conditioning system, test equipment hardware or other sources) measured at the listening position with no listeners present should in no circumstances exceed NR 15. See Table 1. This is approximately the same as 20dB to25dB A-w
44、eighted SPL. The background noise should not be perceptibly impulsive, cyclical or tonal in nature. Table 1 Background noise levels 2.2 Loudspeaker position and orientation In general, loudspeakers should be placed and oriented according to the recommendations of the manufacturer as set forth in the
45、 instruction manual. If this information is missing, or is too vague, the manufacturer should be consulted if this is practical. If no useful information can be obtained the following guidelines apply. Loudspeakers intended for floor placement should be placed accordingly. All other loudspeaker syst
46、ems should be positioned so that the treble or treble/mid-range unit is at ear level. ambient temperature 18 C to27 C; relative humidity 25% to75%; barometric pressure 86kPa to106kPa. Octave band centre frequency NR10 SPL relative to204 4Pa NR15 SPL relative to204 4Pa Hz dB dB 31,5 62 65 63 44 47 12
47、5 31 35 250 21 26 500 15 20 1 000 10 15 2 000 7 12 4 000 4 9 8 000 2 7 NOTE 1The NR (noise rating) values in the table originate from the former ISO NR curves, ISO R1996. NOTE 2The background noise measured in octave frequency bands should not exceed the values given in this table.BS6840-13:1998 BSI
48、 04-1999 5 Loudspeakers intended for placement on a bookshelf should be so placed and surrounded by books which substantially fill the shelf. Also it should be noted that bookshelf sized loudspeakers are frequently intended to be placed on stands and away from other surfaces. This distinction must b
49、e observed due to the significant influence the two placements might have on the perceived performance. The loudspeakers should be pointed toward the centre of the listening area unless the design of the loudspeaker explicitly precludes this. Monopole loudspeakers could be placed relatively close to a wall whereas dipole or bipole loudspeakers may require placement further from the room boundaries (probably further than1m). Placement of the loudspeakers can have a greater effect than the intrinsic performance of the loudspeakers. It is t
