ISO 22234:2005

INTERNATIONAL ISO
STANDARD 22234
First edition
2005-11-15
Cinematography — Relative and absolute
sound pressure levels for motion-picture
multi-channel sound systems —
Measurement methods and levels
applicable to analog photographic film
audio, digital photographic film audio and
D-cinema audio
Cinématographie — Niveaux de pression sonore relatifs et absolus pour
les systèmes de films cinématographiques sonores multicanaux —
Méthodes de mesure et niveaux applicables aux films sonores
photographiques analogiques, aux films sonores photographiques
numériques et à l'audio de D-cinéma

Reference number
©
ISO 2005
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Foreword
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(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
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Attention is drawn to the possibility that some of the elements of this document may be the subject 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.

INTERNATIONAL STANDARD ISO 22234:2005(E)

Cinematography — Relative and absolute sound pressure
levels for motion-picture multi-channel sound systems —
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 theatres. 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. 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 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 of 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 µN/m .
3.2
average responding meter
meter which provides a voltage indication proportional to the average value of the rectified signal, 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.
3.4
B-chain
final chain
that part of a motion-picture 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 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 having 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 filter 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 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 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 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
2 © ISO 2005 – All rights reserved

Key
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 crossover 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
4 Test methods
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 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, 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 one 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 Figure 2. The sub-woofer sound pressure level should b
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