BS ISO 22234-2006 Cinematography - Relative and absolute sound pressure levels for motion-picture multi-channel sound systems - Measurement methods and levels applicable to analog m.pdf

1、 g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58for motion-picture multi-channel sound systems Measurement methods and levels applicable to analog

2、photographic film audio, digital photographic film audio and D-cinema audioICS 37.060.99Cinematography Relative and absolute sound pressure levels BRITISH STANDARDBS ISO 22234:2005BS ISO 22234:2005This British Standard was published under the authority of the Standards Policy and Strategy Committee

3、on 30 June 2006 BSI 2006ISBN 0 580 48828 4The British Standards which implement international publications referred to in this document may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic

4、 Catalogue or of British Standards Online.This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations.Summary of pagesThis docu

5、ment comprises a front cover, an inside front cover, the ISO title page, pages ii and iii, a blank page, pages 1 to 9 and a back cover.The BSI copyright notice displayed in this document indicates when the document was last issued.Amendments issued since publicationAmd. No. Date CommentsA list of or

6、ganizations represented on this committee can be obtained on request to its secretary.Cross-referencesenquiries on the interpretation, or proposals for change, and keep UK interests informed; monitor related international and European developments and promulgate them in the UK.National forewordThis

7、British Standard reproduces verbatim ISO 22234:2005 and implements it as the UK national standard.The UK participation in its preparation was entrusted to Technical Committee CPW/36, Cinematography, which has the responsibility to: aid enquirers to understand the text; present to the responsible int

8、ernational/European committee any Reference numberISO 22234:2005(E)INTERNATIONAL STANDARD ISO22234First edition2005-11-15Cinematography Relative and absolute sound pressure levels for motion-picture multi-channel sound systems Measurement methods and levels applicable to analog photographic film aud

9、io, digital photographic film audio and D-cinema audio Cinmatographie Niveaux de pression sonore relatifs et absolus pour les systmes de films cinmatographiques sonores multicanaux Mthodes de mesure et niveaux applicables aux films sonores photographiques analogiques, aux films sonores photographiqu

10、es numriques et laudio de D-cinma BS ISO 22234:2005ii iiiForeword 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 carried out through ISO technical committee

11、s. 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 work. ISO collaborates closely with the Inter

12、national Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International St

13、andards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the sub

14、ject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 22234 was prepared by Technical Committee ISO/TC 36, Cinematography. BS ISO 22234:2005blank1Cinematography Relative and absolute sound pressure levels for motion-picture multi-channel sound sy

15、stems Measurement methods and levels applicable to analog photographic film audio, digital photographic film audio and D-cinema audio 1 Scope This International Standard specifies the measurement methods and wide-band sound pressure levels for motion-picture control rooms, review rooms, and indoor t

16、heatres. Together with ISO 2969, it is intended to assist in standardization of reproduction of motion-picture sound in such rooms. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies.

17、For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 2969:1987, Cinematography B-chain electro-acoustic response of motion-picture control rooms and indoor theatres Specifications and measurements IEC 60268-17:1990, Sound system equipment Part

18、 17: Standard volume indicators IEC 61672-1:2002, Electroacoustics Sound level meters Part 1: Specifications 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 absolute sound pressure spatially averaged sound pressure level of a single channel o

19、f a theatrical sound system measured with broadband pink noise at the reference electrical level as a stimulus NOTE The 0 dB (reference) level for sound pressure is 20 N/m2. 3.2 average responding meter meter which provides a voltage indication proportional to the average value of the rectified sign

20、al, with ballistics as described in IEC 60268-17 3.3 bass extension technique of taking low-frequency information from a film sound-track, processing it, and sending it to a sub-woofer, as opposed to an LFE channel NOTE See A.3. BS ISO 22234:20052 3.4 B-chain final chain that part of a motion-pictur

21、e sound reproduction system, as shown in Figure 1 for a typical film system, commencing at the input terminals of the main fader and terminating in the listening area defined in Figure 2 in which sound pressure level measurements are taken NOTE See A.7. 3.5 electroacoustic response B-chain spatially

22、 averaged frequency response measured in one-third octave bands as described in ISO 2969 NOTE The electroacoustic response is expressed in decibels. 3.6 LFE channel discrete low-frequency effects channel, normally having an upper bandwidth between 80 Hz and 125 Hz 3.7 pink noise stochastic signal ha

23、ving a continuous spectrum with equal energy per equal logarithmic interval of frequency, and with a Gaussian probability distribution of instantaneous amplitude 3.8 reference electrical level voltage measured by an average responding voltmeter of wide-band pink noise using a measurement band pass f

24、ilter of 22 Hz to 22 kHz bandwidth when the test signal is at reference recorded level, and when the fader is at its normal setting NOTE See A.5 and A.7. 3.9 reference recorded level level of pink noise equivalent to 50 % modulation on an analog photographic sound-track, or the equivalent level on a

25、 digital photographic sound-track or a digital cinema (D-cinema) sound-track (typically in each case 20 dB below 100 % modulation) 3.10 relative sound pressure level sound pressure level of one channel when compared with another during reproduction of the wide-band test signal of 3.1, as opposed to

26、the sound pressure level in one frequency range when compared with another 3.11 wide-band pink noise pink noise having a bandwidth exceeding the normal acoustic frequency range NOTE A suitable test signal should have a frequency response flat to within 0,5 dB when measured in one-third octave bands

27、with centre frequencies from 25 Hz to 20 kHz with an integrating averaging technique. 3.12 wide-band sound level meter meter which conforms to IEC 61672-1 BS ISO 22234:20053Key 1 A-chain 8 insertion point for test signals 2 B-chain 9 B-chain equalizer 3 non-sync 10 power amplifier 4 magnetic 11 cros

28、sover network 5 photographic 12 loudspeakers 6 preamplifiers and equalizers 13 screen 7 main fader 14 auditorium acoustics Figure 1 Complete film-based theatrical sound reproduction system Key 1 screen 2 limits of seating area Figure 2 Plan view, theatre auditorium BS ISO 22234:20054 4 Test methods

29、4.1 Electroacoustic response The electroacoustic response of each channel should be measured and confirmed to comply with ISO 2969 before measurement of relative and absolute sound pressure levels. 4.2 Measuring equipment The sound pressure level of screen and surround channels should be made using

30、a wide-band sound level meter set to C-weighting and slow response. The sound pressure level of the sub-woofer channel should be made using a one-third octave real-time analyser, or a sound level meter with a one-third octave filter set. 4.3 Test signal The test signal should be wide-band pink noise

31、, fed into the sound system one channel at a time. The pink noise should be inserted into the system prior to the main fader, or at an equivalent point. The fader should be set to its normal setting (see A.5 and A.7). 4.4 Sound pressure level The sound pressure level should be measured in at least o

32、ne position for each screen and surround channel and the measurements for each channel then spatially averaged. If a single location only is selected, it should be position S as shown in Figure 2. All measurement locations should be within the normal seating area as shown in the hatched area in Figu

33、re 2. The sub-woofer sound pressure level should be measured in at least four positions and averaged over time intervals of no less than 30 s. 4.5 Screen channels The relative sound pressure level of each screen channel should be within 0,5 dB of the absolute sound pressure level. 4.6 Surround chann

34、el(s) If there is one single surround channel, then the sound pressure level when playing the test signal should equal that of the absolute sound pressure level. If there are two independent surround channels, left and right, then each should display a sound pressure level such that when they are si

35、multaneously fed the same in-phase test signal the sum should equal the absolute sound pressure level. For two surround channel systems, the individual sound pressure level for each channel will usually be 3 dB below the absolute sound pressure level. (See A.8.) This procedure will ensure compatibil

36、ity for theatres with fewer surround playback channels where the surround information is combined. With three or more surround channels, the individual channel reproduction levels should be set up to be equal to one channel of a two surround channel system. 4.7 Sub-woofer LFE channel, playback of di

37、screte digital photographic sound-track or D-cinema sound-track The sub-woofer channel, when compared with a wide-band screen channel, should show 10 dB of “in-band” gain when viewed on a real-time analyser, i.e. a level in its pass band 10 dB higher than the level in the pass band of the screen cha

38、nnel. See Figures 3 and A.1. 4.8 Sub-woofer channel, for playback of matrix-encoded analog photographic sound-track with bass extension playback processing The bass extension sub-woofer channel, when compared with a wide-band screen channel, should show the same level, i.e. should show no “in-band”

39、gain when viewed on a real-time analyser. See Figures 4, A.2 and A.3. If the test signal is applied to both the centre screen channel and the sub-woofer channel simultaneously, the analyser should show 3 dB of “in-band” gain in the frequency area common to both transducers. BS ISO 22234:20055Key 1 R

40、TA display, single screen channel, wide-band pink noise 2 RTA display, sub-woofer, wide-band pink noise Figure 3 Measurement of subwoofer sound-pressure level, digital LFE sound track, using real-time analyser Key 1 RTA display, single screen channel, wide-band pink noise 2 RTA display, sub-woofer,

41、wide-band pink noise Figure 4 Measurement of subwoofer sound-pressure level, analog photographic sound track with bass extension playback processing, using real-time analyser 5 Reference level The reference level defined as in 3.1 and measured as specified in this International Standard should be 85

42、 dB (C-weighted), for normal theatrical operation. BS ISO 22234:20056 Annex A (informative) General information A.1 Subwoofers and sound-level meters While a wide-band sound level meter is suitable for measuring sound pressure levels of screen and surround channels, it is not suitable for measuremen

43、t of sub-woofer levels. The first reason for this is the differing low-pass cut-off of different sub-woofers. For example, if pink noise and a sound level meter were used to set equal levels between one loudspeaker extending to 125 Hz and another extending to 250 Hz, the sound pressure levels in the

44、 pass band of each loudspeaker would be significantly different, as shown in Figure A.1. Key 1 level error 2 RTA display aComparison of different sub-woofers. bSame sound pressure level. Figure A.1 Setting sound pressure levels of sub-woofers with sound level meters can create level ambiguity A seco

45、nd reason to avoid use of wide-band sound level meters for sub-woofer measurement is the loose tolerance at low frequencies associated with the inexpensive meters typically used. A sound level meter incorporating a one-third-octave filter set may provide acceptable results. BS ISO 22234:20057A.2 In-

46、band gain Using a real-time analyser is the only accurate method of measuring band-limited signal levels. In-band gain is the relative level within the band pass of interest, as seen on a real-time analyser display. A.3 Bass extension With analog photographic sound-tracks, unwanted noises can occur

47、at very low frequencies, below approximately 50 Hz. Two main causes of these noises are ground noise reduction timing errors causing “thumping”, and low-frequency “streaking” noise caused by bad print washing. For this reason, some analog processors strip out low-frequency information, and process i

48、t to remove low-level unwanted components. This processed output is then sent to a dedicated sub-woofer. This technique is known as bass extension. A.4 Subwoofer polarity It is frequently very difficult to determine the best polarity of a sub-woofer by conventional methods of checking the speaker co

49、ne polarity. The effective phase may change with frequency, especially with a discrete digital sub-woofer channel where filter slopes may cause changing phase with frequency. For this reason, it is recommended that sub-woofer polarity be evaluated with pink noise sent to centre and sub-woofer channels simultaneously. The best result should be selected of the two polarities by looking at the resultant combination signal measured with a real-time analyser. In some cases, there may be no apparent signal leve