ISO 17208-2:2019

INTERNATIONAL ISO
STANDARD 17208-2
First edition
2019-07
Underwater acoustics — Quantities
and procedures for description and
measurement of underwater sound
from ships —
Part 2:
Determination of source levels from
deep water measurements
Acoustique sous-marine — Grandeurs et modes de description et de
mesurage de l'acoustique sous-marine des navires —
Partie 2: Détermination des niveaux de source à partir des mesures
par grands fonds
Reference number
©
ISO 2019
© ISO 2019
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ii © ISO 2019 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Conversion of acoustic source level from radiated noise level measured in deep water .3
4.1 Measurement procedure . 3
4.2 Calculation of source level from radiated noise level performed as in ISO 17208-1 . 3
5 Measurement uncertainty . 4
6 Special requirements for reporting of broadside aspect source level .5
6.1 General . 5
6.2 Special parameters . 5
Annex A (informative) Ship radiated noise source level correction formulae considering
the Lloyd's mirror effect . 6
Annex B (informative) Ship noise source level correction formulae for measurements that
deviate from ISO 17208-1 .11
Bibliography .13
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
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ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
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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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This document was prepared by Technical Committee ISO/TC 43, Acoustics, SC 3, Underwater acoustics.
A list of all parts in the ISO 17208 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
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iv © ISO 2019 – All rights reserved

Introduction
This document has been developed in response to the demand, noted by the International Maritime
Organization (IMO) and its Marine Environment Protection Committee (MEPC), for an International
Standard for measurement of underwater sound radiated from ships. In this document, the sound
radiated by the ship under test is described in terms of an equivalent monopole source level.
The scientific research on the impact of underwater sound on the marine ecosystem necessitates the
accumulation of reliable acoustic output data for common sources such as surface vessels. These data
can be obtained through at-sea measurement by relevant organizations, such as research institutes, by
applying the measurement methodology described in ISO 17208-1. The methodology and measurement
configuration are sufficient to give technically sound acoustic data, but are also suitable for end users
to conduct the measurements in situ in the ocean without access to large fixed noise ranges.
The measurement of underwater sound radiated from ships depends upon various conditions related to
the vessel under test and its surrounding environment. Specifically, the speed, draught and operational
conditions of the engine(s) of the ship influence the level of radiated underwater sound. Waves, current,
depth, temperature and salinity of the water also influence the propagation of underwater sound. The
sea surface and bottom can reflect acoustical waves. Ambient noise sources, such as traffic, industry,
biological, geological or meteorological noise can also interfere with the measurement of underwater
sound radiated from the target ship.
In this document, the radiated noise level measured in deep water (3.1) according to ISO 17208-1 is
converted to monopole source level. The conversion formulae are derived based on the assumption that
the surface is a perfect pressure release boundary.
INTERNATIONAL STANDARD ISO 17208-2:2019(E)
Underwater acoustics — Quantities and procedures for
description and measurement of underwater sound from
ships —
Part 2:
Determination of source levels from deep water
measurements
1 Scope
This document specifies methods for calculating an equivalent monopole source level by converting
radiated noise level values obtained in deep water according to ISO 17208-1. Procedures are also given
for direct calculation from measurements made in deep water with specific hydrophone geometry. The
source level calculated by the procedure in this document is that of an equivalent monopole source at a
specified nominal source depth, and for broadside aspect only. The nominal source depth is intended to
be reported with the equivalent monopole broadside source level value.
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 17208-1:2016, Underwater acoustics — Quantities and procedures for description and measurement
of underwater sound from ships — Part 1: Requirements for precision measurements in deep water used for
comparison purposes
ISO 18405, Underwater acoustics — Terminology
IEC 61260-1, Electroacoustics — Octave-band and fractional-octave-band filters — Part 1: Specifications
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 18405 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
3.1
deep water
water the depth of which is more than 150 m, or 1,5 times the overall length of the ship under test,
whichever is greater
3.2
averaged RNL correction
∆L
difference between source level and radiated noise level
3.3
ship reference point
point on the ship from which the distances are defined
Note 1 to entry: For the purposes of this document, the ship reference point is located transversely at the ship
centreline, longitudinally a quarter-length forward of the stern and vertically at the height of the sea surface.
Note 2 to entry: The location for the ship reference point applies for all frequencies.
3.4
closest point of approach
CPA
point where the horizontal distance (during a test run) from the ship reference point (3.3) of the ship
under test to the hydrophone(s) is the smallest
3.5
radiated noise level
RNL
L
RN
level of the product of the distance from a ship reference point (3.3) of a sound source, r, and the far-field
root-mean-square sound pressure, p (r), at that distance for a specified reference value
RMS
Note 1 to entry: L = 20 log (p /p ) dB + 20 log (r/r ) dB.
RN 10 RMS 0 10 0
Note 2 to entry: Radiated noise level is expressed in decibels (dB).
Note 3 to entry: The reference value for pressure (p ) is 1 μPa. The reference value for distance (r ) is 1 m. The
0 0
combined RNL reference value, p r , is 1 μPa·m.
0 0
Note 4 to entry: The resulting level is denoted “L , dB re 1 μPa·m”. This designation replaces the past use of
RN
“L , dB re 1 μPa @ 1 m”.
p
Note 5 to entry: RNL varies in both horizontal and vertical aspects in the far field. This procedure determines
an azimuthal sector averaged about the hydrophone position and vertical-elevation averaged quantity in the
broadside aspect about the ship reference point.
3.6
nominal source depth
source depth
d
s
nominal depth of the monopole point source from which the sound is considered to originate, and equal
to 0,7 times the ship’s draft
Note 1 to entry: This depth is used for conversion of radiated noise level to equivalent monopole source level.
Note 2 to entry: The calculation is given by Formula (1).
dD=07, (1)
s
where D is the draught of the ship.
Note 3 to entry: The draught of the ship is considered to be the average of the stern and bow draughts.
Note 4 to entry: The choice of the nominal source depth is somewhat arbitrary, and the choice of 70 % of the mean
draft represents a compromise. The value of the nominal source depth is to be reported alongside the equivalent
monopole broadside source level value.
2 © ISO 2019 – All rights reserved

3.7
broadside aspect
aspect normal to ship centre line from bow to stern
Note 1 to entry: For the purposes of this document, the broadside aspect is measured over ±30° angles from the
normal in the horizontal plane and 15° to 45° from the sea surface in the vertical plane.
4 Conversion of acoustic source level from radiated noise level measured in
deep water
4.1 Measurement procedure
According to ISO 17208-1, three hydrophones are used to measure the underwater radiated noise level.
The three hydrophones are positioned vertically in the water column at depths that result from nominal
15°, 30° and 45° angles from the sea surface at a distance equal to the nominal distance at the closest
point of approach, d , which is defined as 100 m or one overall ship length, whichever is the greater.
CPA
The hydrophone geometry refers to ISO 17208-1:2016, Figure 1.
For measurements that deviate from ISO 17208-1, ship noise source level correction formulae are given
in Annex B.
4.2 Calculation of source level from radiated noise level performed as in ISO 17208-1
In the calculation described below, the measured radiated noise level in deep water obtained from the
procedure described in ISO 17208-1 is converted to equivalent monopole source level for broadside
aspect, for an assumed nominal source depth below the ship reference position.
The conversion formula is derived based on
...