1、BRITISH STANDARD BS ISO 9568:1993 Implementation of ISO 9568:1993 Cinematography Background acoustic noise levels in theatres, review rooms and dubbing rooms UDC 725.824:534.835.46:534.6BSISO9568:1993 This British Standard, having been prepared under the directionof the Consumer Products and Service
2、s Sector Board, was published under theauthority of the Standards Board and comes into effect on 15January1996 BSI 10-1999 The following BSI references relate to the work on this standard: Committee reference CPW/36 Draft for comment 88/42901 DC ISBN 0 580 25108 X Committees responsible for this Bri
3、tish Standard The preparation of this British Standard was entrusted to Technical Committee CPW/36, Cinematography International Coordination, upon which the following bodies were represented: British Kinematograph, Sound and Television Society British Photographic Association ITV Association (ITVA)
4、 The following bodies were also represented in the drafting of the standard, through subcommittees and panels: Association of Independent Cinemas British Broadcasting Corporation British Film and Television Producers Association British Film Institute Broadcasting Entertainment Cinematograph and The
5、atre Union Cinema Exhibitors Association Institute of Amateur Cinematographers Royal Photographic Society Amendments issued since publication Amd. No. Date CommentsBSISO9568:1993 BSI 10-1999 i Contents Page Committees responsible Inside front cover National foreword ii Foreword iii Text of ISO 9568
6、1BSISO9568:1993 ii BSI 10-1999 National foreword This British Standard reproduces verbatim ISO9568:1993 and implements it as the UK national standard. This British Standard is published under the direction of the Consumer Products and Services Sector Board whose Technical Committee CPW/36 has the re
7、sponsibility to: aid enquirers to understand the text; present to the responsible international committee any enquiries on interpretation, or proposals for change, and keep UK interests informed; monitor related international and European developments and promulgate them in the UK. NOTEInternational
8、 and European Standards, as well as overseas standards, are available from Customer Services, BSI, 389 Chiswick High Road, London W4 4AL. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct applicatio
9、n. 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, pages i and ii, theISOtitle page, pagesii toiv, pages1 to3 and a back cover. This standard has been updated (see copyright d
10、ate) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.ISO9568:1993(E) ii BSI 10-1999 Contents Page Foreword iii 1 Scope 1 2 Normative references 1 3 Test conditions 1 4 Measurements 1 5 Sound pressure level classifications 2 Annex A (i
11、nformative) Additional information 3 Figure 1 Noise criteria curves 2ISO9568:1993(E) BSI 10-1999 iii Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally
12、 carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the w
13、ork. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requir
14、es approval by at least 75% of the member bodies casting a vote. International Standard ISO9568 was prepared by Technical Committee ISO/TC 36, Cinematography. Annex A of this International Standard is for information only.iv blankISO9568:1993(E) BSI 10-1999 1 1 Scope This International Standard spec
15、ifies measurement methods and maximum ratings for indoor background sound pressure levels in theatres, review rooms and dubbing rooms. It applies to noise emitted by heating, ventilating and air-conditioning systems, intrusive noise from the projector(s) associated with the theatre and noise emitted
16、 by any other mechanical or electrical equipment in the theatre building. It is intended for application when the background noise is essentially a steady-state sound, without strong time-varying components. It does not apply to intrusive noise from other sources outside the theatre, such as aircraf
17、t, highway traffic, or adjacent theatres, or to noise resulting from the operation of the sound system inthe theatre, or the vibration of the theatre, i.e.movement of the building below20Hz. 2 Normative references The following standards contain provisions which, through reference in this text, cons
18、titute provisions of this International Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of
19、 the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO 266:1975, Acoustics Preferred frequencies for measurements. IEC 651:1979, Sound level meters. 3 Test conditions 3.1 The air-handling system of the theatre shall be brought to the
20、 noisiest state in which it is used during screenings, generally “on”, with cooling compressors operating. Any other mechanical or electrical equipment, such as projector exhaust fans, sump pumps, transformers, or the like, within the theatre building shall be brought to the noisiest state that will
21、 occur during screenings. The projector system shall be running normally, with film. Power to the theatre sound system shall be turned off. 3.2 Measurement equipment shall conform to IEC651, using a class II octave band filter or classIII third-octave band filter in accordance with ISO266. 3.3 The m
22、easurement system shall be set to “slow” reading. 3.4 The measurement system shall be calibrated immediately before use by means of an acoustic calibrator accurate to within 0,5dB for sound pressure level. The calibration shall be checked after use, and if changes greater than 0,5dB are found, the m
23、easurements shall be considered invalid. The acoustic calibrator shall be checked at least once per year against a known source. 3.5 At high frequencies, room background noise levels are often in the same range as ordinary measurement equipment noise. Therefore, care should be taken to ensure that t
24、he measured levels are not influenced in any band by noise in the measurement instrument(s) by testing the measurement instrument(s) under all relevant conditions, including switch settings of any attenuators or gain controls. Do not report noise levels at or below the capability of the instrumentat
25、ion in use. 4 Measurements 4.1 Measurements shall be recorded in octave bands over the range from 31,5Hz to 16kHz as sound pressure levels. 4.1.1 The preferred octave band centre frequencies are31,5Hz,63Hz,125Hz, 250Hz, 500Hz, 1kHz, 2kHz, 4kHz, 8kHz and 16kHz. 4.1.2 If third-octave band measurement
26、equipment is available rather than octave band or switchable bandwidth equipment, measurements may be made in third-octave bands and converted to octave bands by logarithmic addition of three bands (one at the octave band centre and the two surrounding it). The octave band sound pressure level, L, i
27、s then: where L 1 is the sound pressure level of the first third-octave; L 2 is the sound pressure level of the second third-octave; L 3 is the sound pressure level of the third third-octave. L 10 log 10(10 L 1 10 10 L 2 10 10 L 3 10 ) + + =ISO9568:1993(E) 2 BSI 10-1999 4.2 The measurements to be re
28、corded shall be made by taking the mean of the readings at a sufficient number of locations to provide means with standard deviations under2dB; usually, six locations chosen at random within the seating area at seated ear height at least 1,2m (4ft) from any wall surface will suffice unless there is
29、an unusual spatial distribution of background noise. If the total range of the measurements in an octave band is less than4dB, the arithmetic mean may be used; if it is more than4dB, the logarithmic mean shall be used. Some review rooms can be so small that strong room modes will influence the low-f
30、requency band measurements. Thus a small standard deviation can be unobtainable. In such cases, the low-frequency bands can be unreliably reported and shall therefore be neglected in any calculations. 4.3 Plot the spectrum resulting from the recorded measurements on octave band noise criteria graph
31、paper such as that shown inFigure 1. The point of the highest excursion of the background noise spectrum compared to the noise criteria (NC) curves is the NC rating. NOTE 1The original NC curves (see5.1) have been extrapolated to the31,5Hz and the16kHz octave bands for the purposes of this Internati
32、onal Standard. 5 Sound pressure level classifications 5.1 Dubbing rooms, review rooms and premier showings (seeA.3 andA.4) shall have a minimum rating ofNC-20 and a maximum rating ofNC-25. 5.2 First-run theatres shall have a maximum rating ofNC-30. 5.3 Subsequent-run theatres shall have a maximum ra
33、ting ofNC-35. 5.4 Levels beyond NC-45 will result in poor audio reproduction. Figure 1 Noise criteria curvesISO9568:1993(E) BSI 10-1999 3 Annex A (informative) Additional information A.1 The noise criteria curves are for use in rating indoor noise levels. The curves, if followed as design criteria,
34、do not result in neutral sounding background noise spectra. Many listeners observe that an NC spectrum sounds too “rumbly” and too “hissy”, having too much very low-frequency and very high-frequency energy. A constant sloped spectrum at 5 dB per octave from low- to high-frequencies has been observed
35、 as producing a more neutral sounding spectrum and is probably more suitable for design purposes. A.2 The NC rating of a space does not represent the spectrum of the background noise; valuable information about the “quality” of the noise in a space is missing from any single number rating. It can be
36、 useful to retain records of the complete spectrum, since there exist methods to further characterize the noise, such as the RC method, which can yield more information. In particular, spectra with narrow band concentrations of energy sound “tonal”; subjectively, they might be increased in rating by
37、 as much as 8 dB relative to the continuous spectrum, depending upon how far above the average spectrum the tonal component lies. A.3 Too little noise in a theatre or review room can be a problem as well as too much. With too much noise, detail is obscured and, ultimately, intelligibility suffers. W
38、ith too little noise, intermittent intrusive noise may become audible and annoying; therefore, it is advisable to use reasonable background noise levels to mask intrusive noise sources. A.4 Dubbing studios are advised that if the background noise levels in studios are much lower than those in theatr
39、es, low-level sounds which are audible in the dubbing studio can be inaudible in theatres because of masking. A.5 As a guide to whether high levels of vibration are present, measurement of the “linear” weighting of a Type 1 sound level meter compared with the octave band sound pressure level can pro
40、vide useful information; if the level of linear measurement exceeds the logarithmically added sum of the band levels from 31,5 Hz to 16 kHz by more than 3 dB, then vibration which is detectable by the audience is present. A.6 As a practical matter, large diameter microphones are useful for measuring
41、 the sometimes very low theatre noise levels due to their low self-noise, but large diameter microphones also show relatively strong diffraction effects at high frequencies. To obtain an adequate spatial average of high frequencies, the microphone should be rotated at least about a line perpendicula
42、r to the floor and a line perpendicular to the side walls to obtain the average reading at each location for the high-frequency bands.BS ISO 9568:1993 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent national body responsible for preparing BritishStandar
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