ISO 532-3:2023
(Main)Acoustics — Methods for calculating loudness — Part 3: Moore-Glasberg-Schlittenlacher method
Acoustics — Methods for calculating loudness — Part 3: Moore-Glasberg-Schlittenlacher method
This document specifies a method for estimating the loudness and loudness level of both stationary and time-varying sounds as perceived by otologically normal adult listeners under specific listening conditions. The sounds may be recorded using a single microphone, using a head and torso simulator, or, for sounds presented via earphones, the electrical signal delivered to the earphones may be used. The method is based on the Moore-Glasberg-Schlittenlacher algorithm. NOTE 1 Users who wish to study the details of the calculation method can review or implement the source code which is entirely informative and provided with the standard for the convenience of the user. This method can be applied to any sounds, including tones, broadband noises, complex sounds with sharp line spectral components, musical sounds, speech, and impact sounds such as gunshots and sonic booms. Calculation of a single value for the overall loudness over the entire period of a time-varying signal lasting more than 5 s is outside the scope of this document. NOTE 2 It has been shown that, for steady tones, this method provides a good match to the contours of equal loudness level as defined in ISO 226:2003[18] and the reference threshold of hearing as defined in ISO 389-7:2019[19].
Acoustique — Méthode de calcul du niveau d'isosonie — Partie 3: Titre manque
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Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 532-3
First edition
2023-07
Acoustics — Methods for calculating
loudness —
Part 3:
Moore-Glasberg-Schlittenlacher
method
Reference number
© ISO 2023
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 General . 4
5 Input signal . 4
5.1 Single microphone . 4
5.2 Two microphones in the ear canals or microphones in a head and torso simulator . 4
5.3 Earphone presentation. 4
6 Instrumentation . 5
7 Description of the method . 5
7.1 General . 5
7.2 Transfer of sound through the outer and middle ear . 6
7.2.1 General . 6
7.2.2 Free-field transfer function . 7
7.2.3 Diffuse-field transfer function . 8
7.2.4 Signal recorded using microphones in the ear canals or using a Head and
Torso Simulator . 8
7.2.5 Earphone presentation . 8
7.3 Calculation of the running short-term spectrum . 8
7.4 Calculation of the running short-term excitation pattern . 9
7.5 Transformation of excitation into specific loudness . 10
7.5.1 General . 10
7.5.2 Reference excitation at the reference threshold of hearing . 10
7.5.3 Gain of the cochlear amplifier for inputs with low sound pressure levels . 11
7.5.4 Calculation of specific loudness from excitation when E /E ≤ E/E . 11
THRQ 0 0
7.5.5 Calculation of specific loudness from excitation when E /E > E/E .12
THRQ 0 0
7.5.6 Calculation of specific loudness from excitation when E/E > 10 .12
7.6 Calculation of short-term specific loudness . 13
7.7 Smoothing of short-term specific loudness and application of binaural inhibition .13
7.8 Calculation of short-term loudness . 15
7.9 Calculation of long-term loudness . 15
7.10 Relationship between loudness level and loudness. 15
7.11 Calculation of the reference threshold of hearing . 16
8 Uncertainty of calculated loudness sounds .17
9 Data reporting .17
Annex A (informative) Software for the calculation of loudness according to the method in
this document .19
Annex B (informative) Test signals used for verification of this document .21
Annex C (informative) Test signals used for verification of equivalence with ISO 532-2 .24
Bibliography .28
iii
Foreword
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iv
Introduction
Loudness and loudness level are two perceptual attributes of sound describing absolute and relative
sensations of sound strength perceived by a listener under specific listening conditions. Due to inherent
individual differences among people, both loudness and loudness level have the nature of statistical
estimators characterized by their respective measures of central tendency and dispersion determined
for a specific sample of the general population.
The object of this document is to specify a calculation procedure based on the physical properties of
sound for estimating loudness and loudness level of sound as perceived by listeners with otologically
normal hearing under specific listening conditions. This procedure seeks numbers that can be used
in many scientific and technical applications to estimate the perceived loudness and loudness level of
sound without conducting separate human observer studies for each application. Because loudness
is a perceived quantity, the perception of which may vary among people, any calculated loudness
value represents only an estimate of the average loudness as perceived by a group of individuals with
otologically normal hearing.
This document describes a method for calculating the loudness of time-varying sounds from the
input signal, which may differ for the two ears. This calculation method is based on Moore-Glasberg-
[1] to [5]
Schlittenlacher loudness calculation algorithms . The method allows calculation of two quantities:
a) The short-term loudness, which is the momentary loudness of a short segment of a sound, such as a
word in a speech sound or a single note in a piece of music.
b) The long-term loudness, which is the loudness of a longer segment of sound, such as a whole
sentence or a musical phrase.
For most everyday sounds, both the short-term loudness and the long-term loudness vary over time.
The loudness of sounds with durations up to 2 s or 3 s is well predicted from the maximum value of the
[4][6] to [8]
long-term loudness reached during presentation of the sound . For long-duration stationary
sounds, the long-term loudness based on the method described in this document is very close to the
[9]
loudness determined using the method described in ISO 532-2 . Deviations can occur for sounds with
strong amplitude fluctuations, such as noises with narrow bandwidth; for such sounds the calculated
loudness is more accurate for this document than for ISO 532-2.
The method of loudness calculation described in this standard can be applied to signals of any duration.
However, it does not directly give an output corresponding to the overall loudness impression of a sound
scene or soundscape over a period of minutes, hours, or days, which is called the “overall loudness” in
this standard. The output of the method of loudness calculation described in this standard can be post-
processed to estimate the overall loudness of a sound scene.
NOTE Post-processing is outside the scope of this document, but some possible methods have been
[10] to [13]
described .
This document describes the calculation procedure leading to estimation of the loudness and loudness
level of time-varying sounds and provides executable computer programs. The software provided with
this document is entirely informative and provided for the convenience of the user. Use of the provided
software is not required for conformity with the document.
NOTE Equipment or machinery noise emissions/immissions can also be judged by other quantities defined
[14] [15] [16] [17]
in various International Standards (see e.g. ISO 1996-1 , ISO 3740 , ISO 9612 , and ISO 11200 ).
v
INTERNATIONAL STANDARD ISO 532-3:2023(E)
Acoustics — Methods for calculating loudness —
Part 3:
Moore-Glasberg-Schlittenlacher method
1 Scope
This document specifies a method for estimating the loudness and loudness level of both stationary
and time-varying sounds as perceived by otologically normal adult listeners under specific listening
conditions. The sounds
...
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