ISO/TS 20065:2022

TECHNICAL ISO/TS
SPECIFICATION 20065
First edition
2022-12
Acoustics — Objective method for
assessing the audibility of tones in
noise — Engineering method
Acoustique — Méthode objective d'évaluation de l'audibilité des
tonalités dans le bruit — Méthode d'expertise
Reference number
© ISO 2022
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ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Measurement procedure . 6
4.1 General . 6
4.2 Measurement instruments . 6
4.3 Merging the basic spectra . 6
5 Evaluation . 6
5.1 General information. 6
5.2 Width, Δf , of the critical band . 7
c
5.3 Determination of prominent tones . 8
5.3.1 General information . 8
5.3.2 Determination of the mean narrow-band level, L , of the masking noise in
S
the critical band . 8
5.3.3 Determination of the tone level L of a tone in a critical band . 9
T
5.3.4 Distinctness of a tone . 10
5.3.5 Determination of the critical band level, L , of the masking noise . 10
G
5.3.6 Masking index . 11
5.3.7 Determination of the audibility, ΔL . 11
5.3.8 Determination of the decisive audibility, ΔL , of a narrow-band spectrum . 11
j
5.3.9 Determination of the mean audibility, ΔL, of a number of spectra .13
6 Calculation of the uncertainty of the audibility, ΔL .13
7 Recommendations on the presentation of results .16
7.1 Measurement . 16
7.2 Acoustic environment . 16
7.3 Instruments for measurement, recording and evaluation . 16
7.4 Acoustic data . 16
Annex A (informative) Window effect and Picket fence effect .17
Annex B (informative) Resolving power of the human ear at frequencies below 1 000 Hz
and geometric position of the critical bands – corner frequencies .20
Annex C (informative) Masking, masking threshold, masking index .22
Annex D (informative) Iterative method for the determination of the audibility, ∆L .23
Annex E (informative) Example for the determination of audibility .27
Bibliography .33
iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
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ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
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www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 43, Acoustics, Subcommittee SC 1, Noise.
This first edition of ISO/TS 20065 cancels and replaces ISO/PAS 20065:2016, which has been technically
revised.
The main changes are as follows:
— guidance on residual sound (5.3.1);
— a file containing a number of other example audio files and a guidance document can be downloaded
from https://standards.iso.org/iso/ts/20065/ed-1/en (from “Prominent tones in wind turbine noise
Round robin test IEC 61400-11, ISO/PAS 20065”);
— editorial changes for clarity, for easier implementation in software, and to meet the latest ISO
standards, including definitions, measures, formulae, aligned and streamlined terminology, and
additional background information.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
TECHNICAL SPECIFICATION ISO/TS 20065:2022(E)
Acoustics — Objective method for assessing the audibility
of tones in noise — Engineering method
1 Scope
This document describes a method for the objective determination of the audibility of tones in
environmental noise.
This document is intended to augment the usual method for evaluation on the basis of aural impression,
in particular, in cases in which there is no agreement on the degree of the audibility of tones. The
method described can be used if the frequency of the tone being evaluated is equal to, or greater than,
50 Hz. In other cases, if the tone frequency is below 50 Hz, or if other types of noise (such as screeching)
are captured, then this method cannot replace subjective evaluation.
NOTE The procedure has not been validated below 50 Hz.
The method presented herein can be used in continuous measurement stations that work automatically.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 1996-1, Acoustics — Description, measurement and assessment of environmental noise — Part 1: Basic
quantities and assessment procedures
IEC 61672-1, Electroacoustics — Sound level meters — Part 1: Specifications
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 1996-1 and the following
apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
NOTE Unless otherwise stated, the reference level for decibel (dB) values in these definitions is 20 µPa.
3.1
tone
sound characterized by a single-frequency component or narrow-band components
3.2
tone frequency
f
T
frequency of the spectral line (3.23) (or mid-band frequency of the narrow-band filter), to the level of
which the tone (3.1) contributes most strongly
Note 1 to entry: Tone frequency is expressed in hertz (Hz).
3.3
tone level
L
T
energy summation of the narrow-band level (3.22) with the tone frequency (3.2), f , and the lateral lines
T
about f , assignable to this tone
T
Note 1 to entry: Tone level is expressed in decibels (dB).
Note 2 to entry: If the critical band (3.5) for the frequency, f , under consideration contains a number of tones,
T
then the tone level, L , is the energy sum of these tones. This level, L , is then assigned to the frequency of the
T T
participating tone that has the maximal value of audibility (3.4), ΔL.
Note 3 to entry: The method for the determination of the tone level, L , of a tone in a critical band is described in
T
5.3.3.
3.4
audibility
ΔL
Audibility of tones is the arithmetic difference between the tone level (3.3), L , and the masking threshold
T
′
(3.15), L
T
Note 1 to entry: Audibility is expressed in decibels (dB).
Note 2 to entry: The method for the determination of the decisive audibility (3.24), ΔL , of a narrow-band spectrum
j
(3.12) is described in 5.3.8.
3.5
critical band
frequency band with a bandwidth (3.17), ∆f within which the auditory system integrates the sound
c
intensity in the formation of loudness and within which it integrates the sound intensity in the
formation of the masking threshold (3.15)
Note 1 to entry: Critical band is expressed in hertz (Hz).
Note 2 to entry: This characteristic of a critical band (see also References [3] and [4]) holds only for a restricted
sound level range. This dependence is neglected here.
3.6
mean narrow-band level of the critical band
L
S
energy mean value of all narrow-band levels (3.22) in a critical band (3.5), except for the spectral line for
the frequency, f , under consideration and all lines that exceed this mean value by more than 6 dB
T
Note 1 to entry: Mean narrow-band level of the critical band is expressed in decibels (dB).
Note 2 to entry: The iterative method for the determination of the mean narrow-band level, L , of the masking
S
noise is described in 5.3.2 and in Annex D.
3.7
critical band level
L
G
level of noise that is assigned to the critical band (3.5) that describes the masking characteristic of the
noise for one or more tones of the noise in this critical band
Note 1 to entry: Critical band level is expressed in decibels (dB).
Note 2 to entry: See narrow-band level (3.22) and Annex C for masking.
Note 3 to entry: For the definition formula for L , see Formula (12).
G
...