ISO/PAS 17208-1:2012
(Main)Acoustics — Quantities and procedures for description and measurement of underwater sound from ships — Part 1: General requirements for measurements in deep water
Acoustics — Quantities and procedures for description and measurement of underwater sound from ships — Part 1: General requirements for measurements in deep water
ISO/PAS 17208-1:2012 describes the general measurement systems, procedures and methodologies to be used to measure underwater sound pressure levels from ships at a prescribed operating condition. It presents a methodology for the reporting of one-third-octave band sound pressure levels. The resulting quantities are the sound pressure levels normalized to a distance of 1 m. The underwater sound pressure level measurements are performed in the geometric far field and then adjusted to the 1 m normalized distance for use in comparison with appropriate underwater noise criteria. ISO/PAS 17208-1:2012 does not specify or provide guidance on underwater noise criteria or address the potential effects of noise on marine organisms. It is applicable to any and all underway surface vessels, either manned or unmanned. Its methods have no inherent limitation on minimum or maximum vessel size. It is not applicable to submerged vessels or to aircraft, and is limited to vessels transiting at speeds no greater than 50 knots (25,70 m/s). The measurement methods mitigate the variability caused by Lloyd's mirror surface image coherence effects, but do not exclude a possible influence of propagation effects such as bottom reflections, refraction and absorption. No specific computational adjustments for these effects are given. A specific ocean location is not required for the application of ISO/PAS 17208-1:2012, but requirements for an ocean test site are provided. Among the applications of ISO/PAS 17208-1:2012 are the showing of compliance with contract requirements, the enabling of periodic signature assessments and in research and development. Intended users include government agencies, research vessel operators and commercial vessel owners operating in acoustically sensitive waters.
Acoustique — Grandeurs et modes de description et de mesurage de l'acoustique sous-marine des navires — Partie 1: Exigences générales pour les mesurages en eau profonde
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PUBLICLY ISO/PAS
AVAILABLE 17208-1
SPECIFICATION
First edition
2012-03-01
Acoustics — Quantities and procedures
for description and measurement of
underwater sound from ships —
Part 1:
General requirements for measurements
in deep water
Acoustique — Grandeurs et modes de description et de mesurage de
l'acoustique sous-marine des navires —
Partie 1: Exigences générales pour les mesurages en eau profonde
Reference number
ISO/PAS 17208-1:2012(E)
©
ISO 2012
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ISO/PAS 17208-1:2012(E)
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ii © ISO 2012 – All rights reserved
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ISO/PAS 17208-1:2012(E)
Contents Page
Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Instrumentation . 5
4.1 General . 5
4.2 Hydrophone and signal conditioning . 5
4.3 Data acquisition, recording, processing and display . 6
4.4 Distance measurement . 6
4.5 Acoustic centre . 8
5 Measurement requirements and procedure . 8
5.1 Introduction . 8
5.2 Test site requirements . 8
5.3 Sea surface conditions . 8
5.4 Hydrophone deployment . 9
5.5 Test course and vessel operation . 11
5.6 Test sequence . 11
6 Post-processing . 12
6.1 General . 12
6.2 Background noise adjustments (all grades). 14
6.3 Sensitivity adjustments — All grades . 15
6.4 Distance normalization — All grades . 15
6.5 Grade A-specific post-processing . 16
6.6 Grade B-specific post processing . 17
6.7 Grade C-specific post processing . 17
7 Measurement uncertainty . 18
8 Reporting example . 19
Bibliography . 21
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ISO/PAS 17208-1:2012(E)
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 organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
In other circumstances, particularly when there is an urgent market requirement for such documents, a
technical committee may decide to publish other types of document:
an ISO Publicly Available Specification (ISO/PAS) represents an agreement between technical experts in
an ISO working group and is accepted for publication if it is approved by more than 50 % of the members
of the parent committee casting a vote;
an ISO Technical Specification (ISO/TS) represents an agreement between the members of a technical
committee and is accepted for publication if it is approved by 2/3 of the members of the committee casting
a vote.
An ISO/PAS or ISO/TS is reviewed after three years in order to decide whether it will be confirmed for a
further three years, revised to become an International Standard, or withdrawn. If the ISO/PAS or ISO/TS is
confirmed, it is reviewed again after a further three years, at which time it must either be transformed into an
International Standard or be withdrawn.
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.
ISO/PAS 17208-1 was prepared by Technical Committee ISO/TC 43, Acoustics, Subcommittee SC 1, Noise.
However, by the time of its publication, responsibility for this document, as well as for future underwater
acoustics work, had been transferred to Subcommittee SC 3, Underwater acoustics.
ISO/PAS 17208 consists of the following parts, under the general title Acoustics — Quantities and procedures
for description and measurement of underwater sound from ships:
Part 1: General requirements for measurements in deep water [Publicly Available Specification]
Measurements in shallow water is to form the subject of a future part of ISO 17208.
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ISO/PAS 17208-1:2012(E)
Introduction
This part of ISO 17208 was developed to provide a standardized measurement method for the quantification
and qualification of a ship's underwater (radiated) noise, and is aimed at promoting consistency of reported
sound measurements from shipping sources. Reduction of all types of vessel emissions — most notably,
ballast water and engine emissions — became an issue in the decade prior to its publication. More recently,
those concerns came to include underwater noise and its the impact on marine animals.
Excessive underwater noise has the potential to interfere with a marine animal's ability to perform a variety of
critical life functions, including navigation, communication and finding food. Because of this, the environmental
impact statements of underwater projects such as pile-driving, pipe-laying and oil exploration now include
assessments of the impact of underwater noise.
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PUBLICLY AVAILABLE SPECIFICATION ISO/PAS 17208-1:2012(E)
Acoustics — Quantities and procedures for description and
measurement of underwater sound from ships —
Part 1:
General requirements for measurements in deep water
1 Scope
This part of ISO 17208 describes the general measurement systems, procedures and methodologies to be
used to measure underwater sound pressure levels from ships at a prescribed operating condition. It presents
a methodology for the reporting of one-third-octave band sound pressure levels. The resulting quantities are
the sound pressure levels normalized to a distance of 1 m. Since the underwater sound pressure levels are
affected by the presence of the free surface (and sometimes the bottom), such quantities are sometimes
called “affected source levels” (see ANSI/ASA S12.64-2009). This part of ISO 17208 refers to the result of
these measurements as “radiated noise levels”.
The underwater sound pressure level measurements are performed in the geometric far field and then
adjusted to the 1 m normalized distance for use in comparison with appropriate underwater noise criteria.
However, this part of ISO 17208 does not specify or provide guidance on underwater noise criteria or address
the potential effects of noise on marine organisms.
This part of ISO 17208 is applicable to any and all underway surface vessels, either manned or unmanned. Its
methods have no inherent limitation on minimum or maximum vessel size. It is not applicable to submerged
vessels or to aircraft, and is limited to vessels transiting at speeds no greater than 50 knots (25,70 m/s). The
measurement methods mitigate the variability caused by Lloyd's mirror surface image coherence effects, but
do not exclude a possible influence of propagation effects such as bottom reflections, refraction and
absorption. No specific computational adjustments for these effects are given. A specific ocean location is not
required for the application of this part of ISO 17208, but requirements for an ocean test site are provided.
Among the applications of this part of ISO 17208 are the showing of compliance with contract requirements,
the enabling of periodic signature assessments and in research and development. Intended users include
government agencies, research vessel operators and commercial vessel owners operating in acoustically
sensitive waters.
This part of ISO 17208 offers three grades of measurement — A, B and C — each with a stated applicability,
test methodology, uncertainty, system repeatability and complexity. A summary of the attributes of each grade
is given in Table 1. Application of the three grades of measurement to the same ship under the same
conditions does not necessarily result in the same radiated noise level.
2 Normative references
The following referenced documents are indispensable for the application 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.
IEC 60565, Underwater acoustics — Hydrophones — Calibration in the frequency range 0,01 Hz to 1 MHz
IEC 61260, Electroacoustics — Octave-band and fractional-octave-band filters
ANSI S1.1, American National Standard Acoustical Terminology
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ISO/PAS 17208-1:2012(E)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ANSI S1.1 and the following apply:
3.1
acoustic centre
position at which it is assumed that all of the noise sources are co-located as a single point source
NOTE For the purposes of this document, the position is on a ship.
3.2
background noise
noise from all sources (biotic and abiotic) other than the source under test
NOTE 1 For the purposes of this document, the source under test is a ship.
NOTE 2 See 6.2 for background noise adjustments.
[SOURCE: ISO 11202:2010, 3.17, modified]
3.3
beam aspect
direction to either side of the ship under test
NOTE Beam aspect is in reference to the location of the hydrophones. Another approach for hydrophone
measurement (not applied here) is bottom aspect, where the hydrophone(s) are mounted at or near the sea floor.
3.4
frequency response
frequency range a system is able to measure, for a given uncertainty and repeatability, from the lowest
frequency to the highest stated frequency
3.5
closest point of approach
CPA
point at which the horizontal distance (during a test run) from the acoustic centre of ship under test is the
closest to the hydrophone(s)
NOTE The distance at the closest point of approach is defined by the symbol d as used in Equation (1).
CPA
3.6
commence exercise
COMEX
start test range location
position of the vessel under test when twice (2) the “start data” distance ahead of the CPA
NOTE See Figure 4.
3.7
data window angle
angle subtended at the hydrophone, between the start data location and the end data location
NOTE The data window angle is expressed as a value in degrees, as shown in Figure 4. For all grades of
measurement, the data window angle is 30°.
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ISO/PAS 17208-1:2012(E)
3.8
data window length
DWL
distance between the start data location and end data location
NOTE The DWL is defined by the distance at CPA and the data window angle of 30°, as given in Equation (1) and
shown in Figure 4.
3.9
data window period
DWP
time taken by the vessel under test to travel the data window length at a certain speed
NOTE See Equation (2) and Figure 4.
3.10
end data location
position of the acoustic centre of the vessel under test where data recording is ended
NOTE End data location is one data window length after the start data location. See Figure 4.
3.11
finish exercise
FINEX
end test range location
position of the vessel under test when twice (2) the “start data” distance past the CPA
NOTE See Figure 4.
3.12
field calibration
method of using known inputs, possibly using physical stimuli (such as a known and calibrated/traceable
acoustic or vibration source) or electrical input (charge or voltage signal injection) at the input (or other stage)
of a measurement system in order to ascertain that the system is responding properly (i.e. within its stated
uncertainty) to the known stimulus
3.13
geometric far field
horizontal distance from the ship under test at which the assumption of source co-location causes less than
1 dB of error when adjusting to the reference distance
3.14
hydrophone cable drift angle
angle between the vertical axis and the line created between the fixed support of the hydrophone cable and
the hydrophone
3.15
insert voltage calibration
known, calibrated and traceable input stimulus in the form of an electrical input injected at the input (or other
stage) of a measurement system in order to ascertain that the system is, in fact, responding properly (i.e.
within the system's stated uncertainty and repeatability) to a known stimulus
3.16
Lloyd's mirror surface image coherence effects
alteration of radiated-noise levels caused by the presence of a free (pressure release) surface
NOTE Radiation from the “surface image” constructively and destructively influences the source's direct radiation. For
the purposes of this document, these effects are considered as part of the source's radiation, causing it to exhibit a vertical
directivity, necessitating the acquisition angle(s) be defined for each grade.
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ISO/PAS 17208-1:2012(E)
3.17
measurement uncertainty
maximum difference between the measured resulting signature radiated noise level and the true signature
radiated noise level stated in decibels for a given measurement system, for one-third-octave bands using a
given measurement method (averaging time, bandwidth-time product, etc.)
NOTE This concept is extensively treated in ISO/IEC Guide 98-3:2008 (GUM).
3.18
measurement repeatability
expected difference between signature-radiated noise levels resulting from successive measurements on the
same vessel at the same operating condition, carried out under the same conditions of measurement with the
same equipment at the same location, stated in decibels and in one-third-octave bands
NOTE This concept is extensively treated in ISO 3534-1.
3.19
measurement system
data acquisition system consisting of, but not limited to, one or more transducer(s), conditioning amplifier(s),
analogue-to-digital converter(s), digital signal processing computer and ancillary peripherals
3.20
omni-directional hydrophone
underwater sound pressure transducer that responds equally to sound from all directions
3.21
slant range
distance from the acoustic centre of the vessel under test to each hydrophone
3.22
overall ship length
longitudinal distance between the forward-most and aft-most perpendicular of a ship
3.23
resulting signature-radiated noise level
measure of the underwater noise radiated by a surface vessel, obtained by averaging the far-field sound
pressure level and scaling this quantity according to spherical spreading to a standard reference distance of
1 m from the acoustic centre of the source
NOTE 1 The signature-radiated noise level is defined as the outcome of the procedure in Clause 6. Specifically, it is
the variable, L , on the left hand side of Equation (9).
s
NOTE 2 The signature-radiated noise level is also sometimes referred to as an “affected source level” or “signature.”
3.24
sound speed profile
measure of the speed of sound in seawater as a function of depth, measured vertically through the water
column
3.25
start data location
position of the acoustic centre of vessel under test where data recording is started
NOTE See Figure 4.
3.26
test site
location at which the underwater noise measurements are performed
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ISO/PAS 17208-1:2012(E)
3.27
underwater sound pressure level
SPL
L
p
ten times the logarithm to the base 10 of the ratio of the time-mean-square pressure of an underwater sound,
in a stated frequency band, to the square of a reference value, p , expressed in decibels
0
2
p
L 10lg dB
p
2
p
0
where the reference value, p , is 1 µPa
0
NOTE 1 The reference value for underwater is different from that for airborne sound, which is 20 µPa.
NOTE 2 In this part of ISO 17208, the averaging time for the sound pressure level is the DWP (3.9).
[SOURCE: ISO/TR 25417:2007, 2.2, modified]
4 Instrumentation
4.1 General
In order to quantify the underwater sound from a marine vessel, three main instrumentation components are
required: hydrophone(s) and signal conditioning; data acquisition, recording, processing and display system;
and distance measurement system. The requirements for each of the three components will depend on which
of the three grades of measurement is desired. Detailed specifications for each of the measurement systems
are given below. A summary of the attributes of each grade is given in Table 1.
4.2 Hydrophone and signal conditioning
The terms “hydrophone”, “underwater electro-acoustic transducer” and “underwater microphone” may be used
synonymously, but for the purposes of this part of ISO 17208, hydrophone is used, and includes any signal
conditioning electronics either within or exterior to the hydrophone. The hydrophone(s) should have the
sensitivity, bandwidth and dynamic range necessary to measure the ship under test and meet the
performance for each intended grade in accordance with Table 1.
For all grades of measurement, the hydrophone(s) should be omni-directional across the required frequency
range for the grade. However, directional hydrophones may be used, as long as the directional characteristics
are accounted for in the final data processing (see 6.3). The number of hydrophones used to perform the
measurement depends on the grade. The hydrophones may or may not have integral cable. However, the
required performance shall be obtained with the full cable length to be used during the test.
When portable hydrophones are used, they shall be laboratory-calibrated every 12 months in accordance with
IEC 60565 for all required one-third-octave bands. When fixed (i.e. permanently installed underwater)
hydrophones are used, they shall be laboratory-calibrated before installation in accordance with IEC 60565 for
all required one-third-octave bands. The fixed hydrophone calibration shall be confirmed by a comparative
measurement utilizing a calibrated underwater sound source every 12 months.
For Grades A and B, the full measurement system shall be field-calibrated prior to, and daily throughout, the
measurement series, using insert voltage methods (3.15) for all required one-third-octave bands. For Grade C,
the full measurement system shall be field-calibrated prior to, and daily throughout, the measurement series,
using either insert voltage methods for all one-third-octave bands or a single-frequency device (such as a
pistonphone).
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ISO/PAS 17208-1:2012(E)
4.3 Data acquisition, recording, processing and display
For all grades of measurement, the data acquisition, recording, processing, and display system shall be
capable of accurately acquiring, recording, processing and displaying data from the hydrophone(s). Such
systems may comprise tape recorders, computer-based data acquisition systems or hardware-specific
devices (such as spectrum analysers) or combinations of these. The data acquisition system should have an
appropriate sampling rate following Nyquist requirements and appropriate dynamic range for either analogue
or digital systems. All frequency domain-averaging shall be linear, with sampling consistent with the data
window period (DWP) (see 6.1).
For Grade A, the time domain signal from each hydrophone shall be acquired and recorded simultaneously
and shall be sample-accurate for all three channels. Tracking and time stamp data (see 4.4) shall be recorded
synchronously with the acoustic data to enable reconstruction of the track and data processing.
For Grade A measurements, the broadband processing shall cover the one-third-octave bands from 10 Hz to
50 000 Hz in accordance with IEC 61260, Class 1. Narrow-band processing shall be in appropriate
bandwidths relative to the frequencies to be determined up to 5 000 Hz, or higher, as needed.
For Grade B measurements, the broadband processing shall cover the one-third-octave bands from 20 Hz to
25 000 Hz in accordance with IEC 61260, Class 1. Narrow-band processing shall be in appropriate
bandwidths, relative to the frequencies to be determined up to 5 000 Hz, or higher, as needed.
For Grade C measurements, the broadband processing shall cover the one-third-octave bands from 50 Hz to
10 000 Hz in accordance with IEC 61260, Class 1. Narrow-band measurements should be performed only as
needed using the appropriate bandwidth and frequency ranges necessary to quantify any discrete frequency
components.
For monitoring purposes, audio output and display of the data are recommended.
4.4 Distance measurement
Distance measurement is required to determine the horizontal separation between the acoustic centre of the
vessel under test and the position on the sea surface above the hydrophone(s) — continuously and
throughout the data acquisition and processing period for Grade A, and only at the closest point of approach
(CPA) for Grades B and C. The distance measurement device may utilize any method (e.g. optical, acoustical,
GPS, radar) as long as the required accuracy is achieved. For Grades A and B, the distance measurement
system shall be accurate to 2 % of the distance at CPA. For Grade C, the distance measurement system shall
be accurate to 5 % of the distance at CPA.
For all grades of measurement with surface-suspended hydrophones, the distance measurement systems
need only determine the horizontal distance from the sea surface position above the hydrophone(s) to the
acoustic centre of the vessel under test. The slant range from the vessel under test to the hydrophone(s) may
be computed during post-processing of the data in accordance with 6.4. It is not necessary to take into
account any drift that the hydrophones could experience after they are deployed, provided the hydrophone
cable drift angle does not exceed 5°. If the drift angle does exceed 5°, then it shall either be reduced or the
drift angle shall be taken into account when determining the slant range.
For all grades of measurement with bottom-supported hydrophones, the distance range-finding
instrumentation shall only determine the horizontal distance from the sea surface position above the
hydrophone(s) to the vessel under test. The slant range from the vessel under test to the hydrophone may be
computed during post-processing of the data in accordance with 6.4. It is not necessary to take into account
any drift which the hydrophones could experience after they are deployed, provided the hydrophone cable drift
angle does not exceed 5°.
The hydrophone cable drift angle may be estimated by the use of depth gages that indicate the difference in
depth between the hydrophones. If the drift angle is believed to exceed 5°, it can be reduced by attaching a
weight to the end of the hydrophone cable or using a larger buoy for bottom-supported configurations. Drift
angles are usually smaller for free-floating suspensions that do not utilize a data transmission cable (e.g. an
acoustic or electromagnetic data link).
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ISO/PAS 17208-1:2012(E)
For Grade A, distance data shall be recorded to determine the vessel track, horizontal range, and speed for
the entire measurement run (start to end) at a sampling rate no less than the acoustic data. For Grades B and
C, only the distance at CPA shall be recorded, which may be accomplished by recording the subject distance
in a test log.
Table 1 — Summary of measurement grades
Grade
Parameter
A B C
Precision method Engineering method Survey method
Achievable measurement
1,5 dB 3,0 dB 4,0 dB
uncertainty
Measurement repeatability ±1,0 dB ±2,0 dB ±3,0 dB
Bandwidth One-third-octave band
Frequency range
10 Hz to 50 000 Hz 20 Hz to 25 000 Hz 50 Hz to 10 000 Hz
(one-third-octave bands)
Narrowband measurements Required Required As needed
Number of hydrophones Three Three One
Hydrophone geometry See Figure 1 See Figure 1 See Figure 2
Nominal hydrophone depth(s) 15°, 30°, 45° angle 15°, 30°, 45° angle 20° 5° angle (see 5.4)
Minimum water depth Greater of 300 m or Greater of 150 m or Greater of 75 m or
3 overall ship length 1,5 overall ship length 1 overall ship length
Minimum distance at closest
Greater of 100 m or 1 overall ship length
point of approach (CPA)
Distance ranging uncertainty
2 % 2 % 5 %
(at CPA)
Acoustic centre location Determined during testing Halfway between the engine room and the propeller
(see 4.5)
Data window angle (±CPA) ±30°
Data window length, m Determined using Equation (1), shown in Figure 4
Data window time, s Determined Using Equation (2), shown in Figure 4
Data window averaging time ≤1 s One overall sample
Minimum number of runs per Six total: Four total: Four total: at least one
vessel condition three port two port starboard and one port
three starboard two starboard
Recommended weather/sea Wind speed ≤20 kn (see 5.3)
conditions
Portable hydrophone Laboratory calibration every 12 months
calibration
Field calibration as below daily during measurements
Fixed hydrophone calibration Laboratory calibration prior to installation
Confirmation using calibrated sound source every 12 months
Field calibration as below daily during measurements
System field calibration
...
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