ISO 532-2:2017

INTERNATIONAL ISO
STANDARD 532-2
First edition
2017-06
Acoustics — Methods for calculating
loudness —
Part 2:
Moore-Glasberg method
Acoustique — Méthode de calcul d’isosonie —
Partie 2: Méthode Moore-Glasberg
Reference number
©
ISO 2017
© ISO 2017, Published in Switzerland
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ii © ISO 2017 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 General . 5
5 Specifications of signals . 5
5.1 General . 5
5.2 Complex tone . 5
5.3 Noise consisting of bands of pink or white noise of defined width . 5
5.4 Mixture of discrete sinusoidal components and bands of pink or white noise . 6
5.5 Sound specified in terms of the sound pressure levels in 29 adjacent one-third-
octave bands . 6
6 Instrumentation . 6
7 Description of the method . 7
7.1 Introduction . 7
7.2 Determination of sound spectrum at the tympanic membrane . 7
7.2.1 General. 7
7.2.2 Free field and diffuse field transfer functions for sound picked up by a
single microphone . 8
7.2.3 Earphones . 8
7.2.4 Signal recorded at eardrum . 8
7.2.5 Head and torso simulator . 8
7.2.6 Interpolation and extrapolation . 8
7.3 Determination of sound spectrum at the oval window . 9
7.4 Transformation of sound spectrum into excitation pattern .10
7.5 Transformation of excitation pattern into specific loudness .13
7.5.1 Introduction .13
7.5.2 Reference excitation at the reference threshold of hearing . .14
7.5.3 Gain of the cochlear amplifier for inputs with low sound pressure levels .14
7.5.4 Calculation of specific loudness from excitation when E /E ≤ E/E .
THRQ 0 0 15
7.5.5 Calculation of specific loudness from excitation when E /E > E/E .
THRQ 0 0 15
10 15
7.5.6 Calculation of specific loudness from excitation when E > 10 .
8 Calculation of loudness and loudness level .16
8.1 Calculation of monaural and binaural loudness (diotic and dichotic stimuli) .16
8.2 Relationship between loudness level and loudness .17
8.3 Calculation of the reference threshold of hearing .18
9 Uncertainty of calculated loudness for stationary sounds .18
10 Data reporting .19
Annex A (informative) Comments regarding binaural loudness.20
Annex B (informative) Results for specific test signals .21
Annex C (informative) Software for the calculation of loudness .26
Bibliography .27
Foreword
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This document was prepared by Technical Committee ISO/TC 43, Acoustics.
A list of all parts in the ISO 532- series, published under the general title Acoustics — Methods for
calculating loudness, can be found on the ISO website.
iv © ISO 2017 – All rights reserved

Introduction
Loudness and loudness level are two perceptual attributes of sound describing absolute and relative
sensations of sound strength perceived by a person 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 the ISO 532- series is to specify calculation procedures based on physical properties of
sound for estimating loudness and loudness level of sound as perceived by persons with otologically
normal hearing under specific listening conditions. Each procedure seeks single 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
ISO 532-1 and ISO 532-2 specify two different methods for calculating loudness which may yield
different results for given sounds. Since no general preference for one or the other method can
presently be stated, it is up to the user to select the method which appears most appropriate for the
given situation. Some major features of each of the methods are described below to facilitate the choice.
This document is limited to calculation of loudness and loudness level of stationary sounds and the
calculations are based on the spectral properties of a sound. This calculation method is based on Moore-
[14-17]
Glasberg loudness calculation algorithms . It starts by converting a specified signal spectrum
into a series of sinusoidal components representing that spectrum. This series is then transformed
into a specific loudness pattern by applying four consecutive transformations, each of which is directly
related to physiological and psychological characteristics of the human hearing system. Loudness is
calculated from the specific loudness pattern.
This document describes the calculation procedures leading to estimation of loudness and loudness
level and provides an executable computer program and code. 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 conformance with this document.
The Moore-Glasberg method is limited to stationary sounds and can be applied to tones, broadband
noises and complex sounds with sharp line spectral components. The method in this document
[18]
differs from those in ISO 532:1975. Method A of ISO 532:1975 (Stevens loudness ) was removed as
this method was not often used and its predictions were not accurate for sounds with strong tonal
components. The method described in this document also improves the precision of calculated loudness
in the low frequency range and allows for calculation of loudness under conditions where the sound
differs at the two ears. It has been shown that this method provides a good match to the contours of
equal loudness level as defined in ISO 226:2003 and the reference threshold of hearing as defined in
ISO 389-7:2005.
The Zwicker method in ISO 532-1 can be applied for stationary and arbitrary non-stationary sounds.
The method for stationary sounds in ISO 532-1 differs slightly from the methods included in the
previous ISO 532:1975, method B, by specifying corrections for low frequencies and by restricting the
description of the approach to numerical instructions only, thus allowing a unique software description.
For reasons of continuity, the method given in ISO 532-1 is in accordance with ISO 226:1987 instead of
the later revised version, ISO 226:2003.
NOTE Equipment or machinery noise emissions/immissions can also be judged by other quantities defined
in various International Standards (see e.g. ISO 1996-1, ISO 3740, ISO 9612 and ISO 11200).
INTER
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