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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Status
Withdrawn
Publication Date
21-Feb-2012
Withdrawal Date
21-Feb-2012
Current Stage
9599 - Withdrawal of International Standard
Start Date
21-Mar-2016
Completion Date
21-Mar-2016
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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
---------------------- Page: 1 ----------------------
ISO/PAS 17208-1:2012(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2012

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,

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Published in Switzerland
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

© ISO 2012 – All rights reserved iii
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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.

iv © ISO 2012 – All rights reserved
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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.
© ISO 2012 – All rights reserved v
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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
© ISO 2012 – All rights reserved 1
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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°.
2 © ISO 2012 – All rights reserved
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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.
© ISO 2012 – All rights reserved 3
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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).

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

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

L  10lg dB
where the reference value, p , is 1 µPa

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).
6 © ISO 2012 – All rights reserved
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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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