ISO/PAS 1996-3:2022

Acoustics - Description, measurement and assessment of environmental noise - Part 3: Objective method for the measurement of prominence of impulsive sounds and for adjustment of L Aeq

This method objectively categorises sources by determination of the prominence of impulsive sound, with the aim of correlating to community response. This method for measuring the prominence of impulsive sounds is intended for sources not identified as gunfire or high-energy impulsive sound. It typically produces adjustments in the range 0,0 dB to 9,0 dB. These adjustments are intended to be used to categorise the sources as either regular impulsive or highly impulsive sound sources and apply the penalty indicated in ISO 1996-1. However, the adjustments may be applied directly, as is done in NT ACOU 112[2], and BS 4142[3]. ISO 1996-2 provides additional guidance for performing these measurements. The method is intended for use on sources with impulsive characteristics that are not already categorised in ISO 1996-1. A non-exhaustive list of examples includes compressed air release, scrap handling, goods delivery, fork lifts with rattling forks, skateboard ramps, industrial shearing, gas discharges, percussive tools in demolition, powered riveting, etc. The method is not intended for use on sounds from firearms. Although the measurements of prominence may give relevant results, research has shown the response to these sources is influenced by factors outside of the scope of this document. In addition, the method is not intended to use for high-energy impulsive sound sources as specified in ISO 1996-1. NOTE This method is not intended for occupational hearing loss, which is outside the scope of this document. See Annex A for recommended additional research.

Acoustique — Description, mesurage et évaluation du bruit de l'environnement — Partie 3: Méthode objective pour le mesurage de l’émergence des bruits impulsifs et pour l’ajustement du L Aeq

General Information

• Status: Published
• Publication Date: 05-Jul-2022
• ICS: 13.140 - Noise with respect to human beings
• ICS: 17.140.01 - Acoustic measurements and noise abatement in general
• Technical Committee: ISO/TC 43/SC 1 - Noise
• Drafting Committee: ISO/TC 43/SC 1/WG 45 - Description and measurement of environmental noise (Revision of ISO 1996-series)
• Current Stage: 9093 - International Standard confirmed
• Start Date: 17-Dec-2025
• Completion Date: 27-Dec-2025

Overview

ISO/PAS 1996-3:2022 - "Acoustics - Description, measurement and assessment of environmental noise - Part 3" defines an objective method to measure the prominence of impulsive sounds and to determine an adjustment to L_Aeq (equivalent continuous A-weighted sound level). The method is intended to correlate measured impulsive characteristics with community response for environmental noise assessment. It is not intended for firearms, high‑energy impulsive sources (per ISO 1996‑1) or occupational hearing-loss assessments.

Key topics and technical requirements

• Prominence (P): An index combining the impulse onset rate and level difference to quantify how prominent an impulse is at the receiver. The general form is P = k1·log(onset rate) + k2·log(level difference); constants are derived from listening tests.
• Onset rate and level difference: Onset rate (OR) is calculated from the slope of the A‑weighted, F‑time-weighted level (threshold: gradients ≥ 10 dB/s define an onset). Level difference (LD) is the difference between onset start and end.
• Measurement instrumentation: Uses Class 1 sound level meters (IEC 61672‑1) with logged A‑weighted, F‑time‑weighted samples. Preferred sampling interval is 10–25 ms; 100 ms is allowed for screening with higher uncertainty.
• Assessment time interval: Default is 30 minutes. The impulse with the highest P during each interval provides the adjustment for that interval; reference-time ratings are energy-averages of assessment intervals.
• Adjustment to L_Aeq: The standard defines how to convert prominence into a penalty/adjustment applied to L_Aeq (typical adjustments are in the range 0.0 dB to 9.0 dB). These adjustments are used to categorise sources (regular impulsive vs. highly impulsive) per ISO 1996‑1, or may be applied directly as in some national methods.
• Data handling: Guidance on excluding residual-source impulses, use of audio recording for unattended surveys, and reporting requirements is included.
• Research guidance: Annex A lists recommended research topics where further work is needed.

Practical applications

• Quantifying impulsive environmental noise from industrial processes, goods handling, demolition tools, compressed-air releases, skateboard ramps, powered riveting, fork lifts, etc.
• Providing an objective basis for applying impulsivity penalties to L_Aeq in environmental noise assessments, planning decisions, nuisance investigations, and impact assessments.
• Supporting noise mitigation planning, regulatory enforcement and community response studies by linking measurable impulse characteristics to annoyance.

Who should use this standard

• Acoustical consultants and environmental noise specialists
• Local authorities and planning regulators
• Industrial noise control engineers and site operators
• Researchers studying noise annoyance and impulsive sound metrics

Related standards

• ISO 1996‑1 (basic quantities and assessment procedures)
• ISO 1996‑2 (measurement guidance)
• IEC 61672‑1 (sound level meter specifications)
• Related national methods: BS 4142, NT ACOU 112

Keywords: ISO 1996-3:2022, environmental noise, impulsive sounds, prominence, L_Aeq adjustment, onset rate, level difference, sound level meter, Class 1.

Standards Content (Sample)

PUBLICLY ISO/PAS
AVAILABLE 1996-3
SPECIFICATION
First edition
2022-07
Acoustics — Description,
measurement and assessment of
environmental noise —
Part 3:
Objective method for the
measurement of prominence of
impulsive sounds and for adjustment
of L
Aeq
Acoustique — Description, mesurage et évaluation du bruit de
l'environnement —
Partie 3: Méthode objective pour le mesurage de l’émergence des
bruits impulsifs et pour l’ajustement du L
Aeq
Reference number
© ISO 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Measurements .3
5 Prominence, P . . 5
6 Identification of adjustment to L . 6
Aeq
7 Categorisation of impulsive sound .7
8 Accuracy . 7
9 Test report . 7
Annex A (informative) Research topics . 8
Bibliography . 9
iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
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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).
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. Details of
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on the ISO list of patent declarations received (see www.iso.org/patents).
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expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/
iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 43, Acoustics, Subcommittee SC 1, Noise.
A list of all parts in the ISO 1996 series can be found on the ISO website.
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
Introduction
Noise with prominent impulsive sound is more annoying than continuous types of noise (without
impulses or tones) with the same equivalent sound pressure level. Therefore, an adjustment is
commonly added to the measured L , if prominent impulsive sound is present.
Aeq
In ISO 1996, three categories of impulsive sound have been found to correlate best with community
response, and adjustments are given for each. Sources of impulsive sound are listed for each category.
However, the list is not exhaustive.
This method objectively categorises sources by determining the prominence of impulsive sound at
the receiver point, with the aim of correlating to human response. The resulting adjustments can be
used to categorise the sources or be applied directly. It describes specific methodology for this purpose
and provides guidance to cognizant authorities for categorising sources and their adjustments. It is
intended to complement the ISO 1996-2 measurement method for general purpose environmental noise
assessment.
v
PUBLICLY AVAILABLE SPECIFICATION ISO/PAS 1996-3:2022(E)
Acoustics — Description, measurement and assessment of
environmental noise —
Part 3:
Objective method for the measurement of prominence of
impulsive sounds and for adjustment of L
Aeq
1 Scope
This method objectively categorises sources by determination of the prominence of impulsive sound,
with the aim of correlating to community response. This method for measuring the prominence of
impulsive sounds is intended for sources not identified as gunfire or high-energy impulsive sound. It
typically produces adjustments in the range 0,0 dB to 9,0 dB. These adjustments are intended to be
used to categorise the sources as either regular impulsive or highly impulsive sound sources and
apply the penalty indicated in ISO 1996-1. However, the adjustments may be applied directly, as is
[2] [3]
done in NT ACOU 112 , and BS 4142 . ISO 1996-2 provides additional guidance for performing these
measurements.
The method is intended for use on sources with impulsive characteristics that are not already
categorised in ISO 1996-1. A non-exhaustive list of examples includes compressed air release, scrap
handling, goods delivery, fork lifts with rattling forks, skateboard ramps, industrial shearing, gas
discharges, percussive tools in demolition, powered riveting, etc.
The method is not intended for use on sounds from firearms. Although the measurements of prominence
may give relevant results, research has shown the response to these sources is influenced by factors
outside of the scope of this document. In addition, the method is not intended to use for high-energy
impulsive sound sources as specified in ISO 1996-1.
NOTE This method is not intended for occupational hearing loss, which is outside the scope of this document.
See Annex A for recommended additional research.
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 following terms and definitions 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/
3.1
sound pressure level
L
pAF
A frequency-weighted and F time-weighted sound pressure level
Note 1 to entry: The sound pressure level is as defined in ISO 1996-1.
3.2
impulsive sound
sound with a sudden onset
Note 1 to entry: The definition includes only the onset of a sound, not the sound as a whole. ”Sudden” is based on
an auditive judgement, which is expressed in terms of physical measurements in this method.
Note 2 to entry: The perceived characteristics and prominence of an impulsive sound at the immission point
depends on the character of the emitted sound, the distance and propagation path from the sound source and
the residual sound. Therefore, the onset parameters characterize the impulse independent of the category of the
sound source.
3.3
onset
contiguous part of the positive slope of the time history of L where the gradient exceeds 10 dB/s
pAF
Note 1 to entry: The starting point of an onset is the point where the gradient first exceeds 10 dB/s. The end
point of an onset is the first point after the starting point where the gradient decreases to less than 10 dB/s.
Irregularities (on the onset) shorter than 50 ms are excluded.
3.4
level difference
LD
difference in decibels of L between the level of the end point L and the level of the starting point L
pAF e s
of the onset (3.3)
3.5
onset rate
OR
slope in decibels per second of the straight line that gives the best approximation to the onset (3.3)
between the starting point and the end point
Note 1 to entry: For pass-bys of, e.g. road vehicles, trains or aircraft the onset rates shall be found from the level
range L − (L − L )/2 to L , i.e. over the upper half of the slope, see Figure 1 illustrating the onset rate (OR)
e e s e
and the level difference (LD) based on the time history of the A frequency-weighted and F time-weighted sound
pressure levels.
Key
LD level difference, in decibels
L level at the starting point, in decibels
s
L level at the end point, in decibels
e
OR onset rate, in decibels per second
t starting point, in seconds
s
t end point, in seconds
e
NOTE Gradients of 10 dB/s or more are indicated with short line segments.
Figure 1 — Analysis of the time history of the A frequency-weighted and F time-weighted sound
pressure levels
3.6
assessment time interval
time interval in which any adjustment is applied
Note 1 to entry: This is typically different than the reference time interval, the measurement time interval and
the observation time interval.
4 Measurements
Measurements shall be made with instruments conforming with Class 1 as specified in IEC 61672-1
with the additional logging of L , the A frequency-weighted and F time-weighted sound pressure level,
pAF
at the intervals identified below.
The A frequency-weighted and F time-weighted sound pressure level shall be sampled with time
intervals in the range 10-25 ms (incl.). Alternatively, measurements made on the basis of short-term
L values (e.g. 10 ms) may be used and, if so, shall (e.g. by computation) be approximated to time
Aeq
weighting F before the readings are taken.
NOTE 1 Direct measurements of L are preferred to those based on short-term L values.
pAF Aeq
NOTE 2 Measurements based on a series of short-term L values can be converted to a series of L values
Aeq pAF
by the following Formula (1):
LL
 pnAF,-1eA q,n  
τ τ
   
 
 
10 10
L =⋅10 lg 1-0⋅+110 // dB (1)
   
pnAF,
  
Δt Δt
   
 
 
  
where
L n’th short-term L value, in decibels;
Aeq,n Aeq
L A frequency-weighted and F time-weighted sound pressure level at the time of the n’th L
pAF,n Aeq
value, L ; L = L , in decibels;
Aeq,n pAF,0 Aeq,0
τ time constant for the time weighting, in ms. For F: τ = 125 ms;
Δt time between the L values (and the integration time), in ms.
Aeq
Measurements based on samples with time intervals of 100 ms may be used for surveys and screening,
as many modern sound level meters ca
...