ISO 7605:2025

Underwater acoustics — Measurement of underwater ambient sound

This document provides requirements and recommendations for measuring and reporting ambient sound in water, as characterized by sound pressure and selected quantities that can be derived from sound pressure. “Ambient sound” implies sound from any source except sources of self-noise. The scope includes equipment performance, calibration and deployment, digital data acquisition and data processing. Data processing is the process of converting raw data into a form and context necessary to be interpreted by people and computers. The scope includes data analysis and reporting of recordings of duration one day or longer. Five data processing stages are considered: raw digital acquisition data3), sound pressure time series, sound pressure level time series, sound pressure spectra and their statistics. The scope excludes measurement of particle motion. 3)The word data is generally used as a collective noun in this document; the plural form is reserved for cases where the constructive relationship to individual observations or measurements is to be emphasized.

Acoustique sous-marine — Mesurage du son ambiant sous-marin

General Information

• Status: Published
• Publication Date: 22-Jul-2025
• ICS: 17.140.01 - Acoustic measurements and noise abatement in general
• Technical Committee: ISO/TC 43/SC 3 - Underwater acoustics
• Drafting Committee: ISO/TC 43/SC 3 - Underwater acoustics
• Current Stage: 6060 - International Standard published
• Start Date: 23-Jul-2025
• Due Date: 09-Apr-2025
• Completion Date: 23-Jul-2025

Standards Content (Sample)

International
Standard
ISO 7605
First edition
Underwater acoustics —
2025-07
Measurement of underwater
ambient sound
Acoustique sous-marine — Mesurage du son ambiant sous-marin
Reference number
© ISO 2025
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 .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
3.1 Concepts and quantities: Hardware .2
3.1.1 Acoustic measuring systems: Concepts and components .2
3.1.2 Hydrophone characteristics .4
3.1.3 Analogue acquisition system characteristics .5
3.1.4 Sampling system characteristics .6
3.1.5 Acquisition system characteristics .10
3.1.6 Levels and other logarithmic quantities . 12
3.2 Concepts and quantities: Data processing . 15
3.2.1 Temporal windows . 15
3.2.2 Discrete Fourier transform terms .16
3.2.3 Soundscape metrics .19
3.2.4 Data processing logarithmic quantities . 20
3.3 Units .21
3.3.1 Units of logarithmic quantities .21
3.3.2 Units of time .21
4 Symbols and abbreviated terms.22
5 General objectives and outputs.26
6 Equipment .28
6.1 Specification of required equipment performance . 28
6.1.1 Recommended minimum performance specification . 28
6.1.2 Key performance characteristics . 28
6.2 Calibration .32
6.2.1 Calibration requirements for instrumentation .32
6.2.2 Calibration requirements .32
6.2.3 Calibrations checks in situ . 33
6.2.4 Calibration regimen . 33
7 Deployment . .34
7.1 Criteria . 34
7.2 Sources and mitigation of parasitic signals . 34
7.2.1 General . 34
7.2.2 Flow noise . 34
7.2.3 Cable strum . 35
7.2.4 Mechanical noise . 35
7.2.5 Electrical noise . . 35
7.2.6 Biofouling . 36
7.2.7 Protection from damage or loss . 36
7.3 Recommended deployment options . 36
7.3.1 General . 36
7.3.2 Bottom-mounted recorders . 36
7.3.3 Systems cabled back to shore .37
7.3.4 Recovery of measurement systems .37
7.3.5 Risk to aquatic life .37
8 Data processing and calculation of sound pressure .37
8.1 Initial data processing steps .37
8.1.1 General .37
8.1.2 Data format assumptions .37
8.1.3 Processing waveform data .37

iii
8.2 Calculation of sound pressure waveform . 38
9 Basic processing .39
9.1 Calculation of sound pressure level (and decidecade bands) . 39
9.1.1 Sound pressure level . 39
9.1.2 Time-bandwidth product and uncertainty . 40
9.1.3 Calculation of mean-square sound pressure spectral density (‘power spectral
density’) .41
9.1.4 Calculation of standardized band levels .42
9.2 Peak system-filtered sound pressure, peak system-filtered sound pressure level . 46
10 Advanced processing . . 47
10.1 Hybrid millidecade processing .47
10.2 Percentile levels .47
11 Reporting .48
11.1 Reporting purpose and scope . 48
11.2 General requirements . 48
11.2.1 Calibration and system frequency range . . 48
11.2.2 Averaging time . 49
11.2.3 Analysis windows . 49
11.2.4 File formats and scaling factors . 49
11.2.5 System-filtered quantities . 49
11.3 General recommendations .
...

FINAL DRAFT
International
Standard
ISO/FDIS 7605
ISO/TC 43/SC 3
Underwater acoustics —
Secretariat: DIN
Measurement of underwater
Voting begins on:
ambient sound
2025-04-29
Acoustique sous-marine — Mesurage du son ambiant sous-marin
Voting terminates on:
2025-06-24
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
ISO/FDIS 7605:2025(en) © ISO 2025

FINAL DRAFT
ISO/FDIS 7605:2025(en)
International
Standard
ISO/FDIS 7605
ISO/TC 43/SC 3
Underwater acoustics —
Secretariat: DIN
Measurement of underwater
Voting begins on:
ambient sound
Acoustique sous-marine — Mesurage du son ambiant sous-marin
Voting terminates on:
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
© ISO 2025
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
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 Reference number
ISO/FDIS 7605:2025(en) © ISO 2025

ii
ISO/FDIS 7605:2025(en)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
3.1 Concepts and quantities: Hardware .2
3.1.1 Acoustic measuring systems: Concepts and components .2
3.1.2 Hydrophone characteristics .4
3.1.3 Analogue acquisition system characteristics .5
3.1.4 Sampling system characteristics .6
3.1.5 Acquisition system characteristics .10
3.1.6 Levels and other logarithmic quantities . 12
3.2 Concepts and quantities: Data processing . 15
3.2.1 Temporal windows . 15
3.2.2 Discrete Fourier transform terms .16
3.2.3 Soundscape metrics . 20
3.2.4 Data processing logarithmic quantities . 20
3.3 Units .21
3.3.1 Units of logarithmic quantities .21
3.3.2 Units of time . 22
4 Symbols and abbreviations .22
5 General objectives and outputs.26
6 Equipment .28
6.1 Specification of required equipment performance . 28
6.1.1 Recommended minimum performance specification . 28
6.1.2 Key performance characteristics . 28
6.2 Calibration .32
6.2.1 Calibration requirements for instrumentation .32
6.2.2 Calibration requirements .32
6.2.3 Calibrations checks in situ . 33
6.2.4 Calibration regimen . 33
7 Deployment . .34
7.1 Criteria . 34
7.2 Sources and mitigation of parasitic signals . 34
7.2.1 Flow noise . 34
7.2.2 Cable strum . 35
7.2.3 Mechanical noise . 35
7.2.4 Biofouling . 36
7.2.5 Protection from damage or loss . 36
7.3 Recommended deployment options . 36
7.3.1 Bottom-mounted recorders . 36
7.3.2 Systems cabled back to shore .37
7.3.3 Recovery of measurement systems .37
7.3.4 Risk to aquatic life .37
8 Data processing and calculation of sound pressure .37
8.1 Initial data processing steps .37
8.1.1 Data format assumptions .37
8.1.2 Processing waveform data .37
8.2 Calculation of sound pressure waveform . 38
9 Basic processing .39
9.1 Calculation of sound pressure level (and decidecade bands) . 39

iii
ISO/FDIS 7605:2025(en)
9.1.1 Sound pressure level . 39
9.1.2 Time-bandwidth product and uncertainty . 40
9.1.3 Calculation of mean-square sound pressure spectral density (‘power spectral
density’) .41
9.1.4 Calculation of standardized band levels .42
9.2 Peak system-filtered sound pressure, peak system-filtered sound pressure level . 46
10 Advanced processing . . 47
10.1 Hybrid millidecade processing .47
10.2 Percentile levels .47
11 Reporting .48
11.1 Reporting purpose and scope . 48
11.2 General requirements . 48
11.2.1 Calibration and system frequency range . . 48
11.2.2 Averaging time . 49
11.2.3 Analysis windows .
...

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ISO/FDIS 7605:2025(en)
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ISO/TC 43/SC 3
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Secretariat: DIN
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ISO TC 43/SC 3/WG 5
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Date: 2025-03-2004-15
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Underwater acoustics — Measurement of underwater ambient
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sound
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Acoustique sous-marine — Mesure — Mesurage du son ambiant sous-marin
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ISO/FDIS 7605:2023(E2025(en) Formatted: Font: 11 pt, Bold
Formatted: Font: 11 pt, Bold
Formatted: HeaderCentered, Space After: 0 pt, Line
spacing: single
Formatted: Default Paragraph Font
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, Formatted: Default Paragraph Font
or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO
Formatted: Adjust space between Latin and Asian text,
at the address below or ISO’s member body in the country of the requester.
Adjust space between Asian text and numbers
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: + 41 22 749 01 11
Formatted: French (France)
EmailE-mail: [e-mail]
Formatted: French (France)
Website: www.iso.orgwww.iso.org
Formatted: French (France)
Published in Switzerland
Formatted: FooterPageRomanNumber
2 © ISO 2023 – All rights reserved
ii
ISO/FDIS 7605:2025(en)
Formatted: Font: 11 pt, Bold
Formatted: Font: Bold
Formatted: HeaderCentered, Left
Contents
Formatted: Adjust space between Latin and Asian text,
Adjust space between Asian text and numbers
Foreword . vii
Introduction . viii
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
3.1 Concepts and quantities: Hardware . 2
3.2 Concepts and quantities: Data processing . 19
3.3 Units . 26
4 Symbols and abbreviations . 28
5 General objectives and outputs . 34
6 Equipment . 35
6.1 Specification of required equipment performance . 35
6.2 Calibration . 39
7 Deployment . 42
7.1 Criteria . 42
7.2 Sources and mitigation of parasitic signals . 42
7.3 Recommended deployment options . 44
8 Data processing and calculation of sound pressure . 45
8.1 Initial data processing steps . 45
8.2 Calculation of sound pressure waveform . 46
9 Basic processing . 48
9.1 Calculation of sound pressure level (and decidecade bands) . 48
9.2 Peak system-filtered sound pressure, peak system-filtered sound pressure level . 56
10 Advanced processing . 57
10.1 Hybrid millidecade processing . 57
10.2 Percentile levels . 58
11 Reporting . 59
11.1 Reporting purpose and scope . 59
11.2 General requirements . 59
11.3 General recommendations . 61
11.4 Study metadata . 61
11.5 Study outcomes . 63
11.6 Dataset stewardship . 67
Annex A (informative) Examples of deployment . 68
Annex B (informative) Discrete Fourier transform and associated terms . 73
Annex C (informative) Guidance on measuring system performance . 78
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Annex D (informative) List of applications and suggested frequency ranges . 83
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Annex E (informative) QA check on data quality . 84
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Bibliography . 86
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Foreword . 6
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Introduction . 7
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© ISO 2025 – All rights reserved
iii
ISO/FDIS 7605:2023(E2025(en) Formatted: Font: 11 pt, Bold
Formatted: Font: 11 pt, Bold
Formatted: HeaderCentered, Space After: 0 pt, Line
1 Scope . 1
spacing: single
2 Normative references . 1
3 Terms and definitions . 1
3.1 Concepts and quantities: Hardware . 2
3.1.1 Acoustic measuring systems: Concepts and components . 2
3.1.2 Hydrophone characteristics . 4
3.1.3 Analogue acquisition system characteristics . 5
3.1.4 Sampling system characteristics . 7
3.1.5 Acquisition system characteristics . 12
3.1.6 Levels and other logarithmic quantities . 14
3.2 Concepts and quantities: Data processing . 18
3.2.1 Temporal windows. 18
3.2.2 Discrete Fourier transform terms . 19
3.2.3 Soundscape metrics . 23
3.2.4 Data processing logarithmic quantities . 24
3.3 Units . 25
3.3.1 Units of logarithmic quantities . 25
3.3.2 Units of time . 26
4 Symbols and abbreviations . 27
5 General objectives and outputs . 32
6 Equipment . 33
6.1 Specification of required equipment performance . 33
6.1.1 Recommended minimum performance specification . 33
6.1.2 Key performance characteristics . 34
6.2 Calibration . 38
6.2.1 Calibration requirements for instrumentation . 38
6.2.2 Calibration requirements . 38
6.2.3 Calibrations checks in situ . 39
6.2.4 Calibration regimen . 40
7 Deployment . 40
7.1 Criteria . 40
7.2 Sources and mitigation of parasitic signals . 41
7.2.1 Flow noise .
...