ISO 2969:2015

INTERNATIONAL ISO
STANDARD 2969
Third edition
2015-06-01
Cinematography — B-chain electro-
acoustic reponse of motion-picture
control rooms and indoor theatres —
Specifications and measurements
Réponse électro-acoustique de la chaîne B des salles de contrôle et
d’exploitation cinématographique — Spécifications et mesurages
Reference number
©
ISO 2015
© ISO 2015, Published in Switzerland
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ii © ISO 2015 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Terms and definitions . 1
3 Method of measurement . 3
4 Characteristic amplitude responses with respect to frequency . 5
Annex A (informative) Factors outside the scope of this International Standard .8
Bibliography .17
Foreword
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The committee responsible for this document is ISO/TC 36, Cinematography.
This third edition cancels and replaces the second edition (ISO 2969:1987), which has been
technically revised.
iv © ISO 2015 – All rights reserved

Introduction
This International Standard is to be used in conjunction with the relevant standards which cover that
part of the motion picture sound system from the transducer to the input terminals of the main fader.
In this International Standard, normative text is text that describes elements of the design that are
indispensable or contains the conformance language keywords: “shall”, “should”, or “may”. Informative text
is text that is potentially helpful to the user, but not indispensable, and can be removed, changed, or added
editorially without affecting interoperability. Informative text does not contain any conformance keywords.
All text in this document is, by default, normative, except: the Introduction, any section explicitly labelled
as “Informative” or individual paragraphs that start with “Note”.
The keywords “shall” and “shall not” indicate requirements strictly to be followed in order to conform
to the document and from which no deviation is permitted.
The keywords, “should” and “should not” indicate that, among several possibilities, one is recommended
as particularly suitable, without mentioning or excluding others; or that a certain course of action is
preferred but not necessarily required; or that (in the negative form) a certain possibility or course of
action is deprecated but not prohibited.
The keywords “may” and “need not” indicate courses of action permissible within the limits of the document.
The keyword “reserved” indicates a provision that is not defined at this time, shall not be used, and may
be defined in the future. The keyword “forbidden” indicates “reserved” and in addition indicates that the
provision will never be defined in the future.
A conformant implementation according to this document is one that includes all mandatory provisions
(“shall”) and, if implemented, all recommended provisions (“should”) as described. A conformant
implementation need not implement optional provisions (“may”) and need not implement them as described.
Unless otherwise specified, the order of precedence of the types of normative information in this
document are as follows: Normative prose is the authoritative definition; Tables are next; followed by
formal languages; then figures; and then any other language forms.
INTERNATIONAL STANDARD ISO 2969:2015(E)
Cinematography — B-chain electro-acoustic reponse of
motion-picture control rooms and indoor theatres —
Specifications and measurements
1 Scope
This International Standard specifies the measurement methods and characteristic electroacoustic
frequency response of the B-chain of motion-picture dubbing theatres (mixing rooms), screening
3 3
rooms, and indoor theatres whose room volume exceeds 125 m (4,414 ft ). It is intended to assist in
standardization of monitoring and reproduction of motion-picture sound in such rooms. The goal is to
have constant perceived loudness and frequency response from installation to installation, and from
position-to-position within an installation. This International Standard does not cover that part of the
motion-picture sound system extending from the transducer to the input source audio selector.
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1
complete sound reproduction system
system used in indoor theatres and screening rooms and in motion-picture sound post-production
facilities such as dubbing theatres, mix rooms and ADR control rooms
Note 1 to entry: The complete system in an indoor theatre or review room is generally considered to consist of an
A-chain and a B-chain.
Note 2 to entry: Represented diagrammatically in Figures 1 and 2.
2.2
pre-emphasized audio track
audio record, either magnetic or photographic, containing high-frequency boost equalization, which is
intended for playback over de-emphasized theatre playback systems
Note 1 to entry: Now very rarely used, but found on all films prior to the mid-1970s. Part of the playback de-
emphasis was generated by use of Curve-N in previous versions of this standard (see 2.10 and A.10).
2.3
wide-range audio track
audio record, either magnetic, analogue photographic or digital, which is intended for playback over
theatre playback systems aligned to this International Standard
Note 1 to entry: This characteristic was previously referred as Curve-X (see 2.9). Such tracks are recorded without fixed
pre- and de-emphasis. Analogue wide-range soundtracks invariably use noise reduction companding technology.
2.4
A-chain (transducer system)
part of a motion-picture audio system extending as far as the input source selector, as shown in
Figures 1 and 2
2.5
B-chain (final chain)
part of a motion-picture sound reproduction system, as shown in Figures 1 and 2, commencing at the
input source audio selector and terminating in the listening area
Figure 1 — Complete theatrical audio reproducing chain — Traditional Film Formats
Figure 2 — Complete theatrical audio reproducing chain — Digital Cinema
2 © ISO 2015 – All rights reserved

2.6
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 (see 3.4)
2.7
wide-band pink noise
pink noise having a bandwidth exceeding the normal acoustic frequency range
Note 1 to entry: A suitable test signal should have a frequency response flat to within ±0,5 dB when measured in
1/3-octave bands with centre frequencies from 25 Hz to 20 kHz with an integrating averaging technique.
2.8
electroacoustic response
spatially and temporally averaged sound pressure level measured in 1/3-octave bands
expressed in decibels with respect to reference level (see A.9) when wide-band pink noise is applied to
the input source selector (see Figures 1 and 2)
Note 1 to entry: The electroacoustic response is computed as a spatial and temporal average over the listening
area using one of the methods given in A.4.
2.9
Curve-X
X-Curve
B-chain characteristic referred to as Curve-X for wide-range sound tracks, also known as X-Curve
Note 1 to entry: This characteristic typically required some high-frequency equalization boost when older
loudspeakers were in use, but is now easily achievable with contemporary loudspeakers. All contemporary
practice is targeted to the X-Curve.
2.10
Curve-N
B-chain characteristic referred to as Curve-N for use with loudspeakers with much poorer high-
frequency response than those typically now in use (see A.10)
3 Method of measurement
3.1 The electroacoustic response shall be measured with the equipment arranged in accordance with
Figures 3 and 4 (see Annex A).
Figure 3 — Method of measurement of B-chain
Figure 4 — Range of microphone placements
3.2 Sound pressure level (SPL) vs. Frequency measurements (see Annex A) shall be made as follows:
a) On dubbing stages (in mixing rooms), at each of the principal listening positions, such as at the
position of each of the mixing personnel, and at the producer’s location. In rooms with a single
primary listening position, care should be taken that this is not an aberrant location;
b) In screening rooms, at a sufficient number of positions to cover the listening area and to reduce the
standard deviation of measured position-to-position response to less than 3 dB. This will typically
be achieved with four positions;
c) In indoor theatres, at a minimum with the position S as shown in Figure 4, and normally at a sufficient
number of additional other positions to reduce the standard deviation of measured position-to-
position response to less than 3 dB. This will typically be achieved with four positions (see A.3.5).
An extra series of measurement positions will have to be added if the theatre has a balcony.
3.3 Measurements shall be made at a normal seated ear height between 1,0 m and 1,2 m (3.3 ft and
4.0 ft), but not closer than 150 mm (6 in) from the top of a seat, and not closer than 1,5 m (4.9 ft) to any
wall and not closer than 5,0 m (16.4 ft) from the screen loudspeaker(s).
3.4 A suitable single loudspeaker auditorium sound pressure level with wide-band pink noise is 85 dB
SPL C-weighted and slow reading (see A.9).
4 © ISO 2015 – All rights reserved

3.5 The measured level in any 1/3-octave band can be used directly if it exceeds the background noise
in the band by at least 10 dB. If the background noise is between 4 dB and 10 dB below the test signal, the
measurement may be corrected using the techniques described in ANSI/ASA S1.13 (see Table 4).
3.6 A system for playing contemporary stereo films will generally employ a minimum of four wide-
range channels: screen left, centre, and right loudspeaker systems, and a surround channel loudspeaker
system employing a number of individual loudspeakers spaced around the left wall, rear wall and right
wall of the room in such a way as to achieve uniform coverage. Most rooms where digital soundtracks are
played have the surround channel separated into two or three separate channels, left rear and right rear,
or left rear, centre rear and right rear. Such systems are frequently built up out of left wall, left rear, right
rear and right wall banks of speakers. Most of these rooms also have a dedicated low-frequency channel
using one or more sub-woofers. Some rooms may be equipped with two intermediate screen channels,
one between left and centre, and one be
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