ISO 11904-2:2004

Acoustics — Determination of sound immission from sound sources placed close to the ear — Part 2: Technique using a manikin

ISO 11904-2:2004 specifies basic framework measurement methods for sound immission from sound sources placed close to the ear. These measurements are carried out with a manikin, equipped with ear simulators including microphones. The measured values are subsequently converted into corresponding free-field or diffuse-field levels. The results are given as free-field related or diffuse-field related equivalent continuous A-weighted sound pressure levels. The technique is denoted the manikin technique. ISO 11904-2:2004 is applicable to exposure to sound from sources close to the ear, for example during equipment tests or at the workplace to sound from earphones or hearing protectors with audiocommunication facilities. ISO 11904-2:2004 is applicable in the frequency range from 20 Hz to 10 kHz. For frequencies above 10 kHz, ISO 11904-1 can be used.

Acoustique — Détermination de l'exposition sonore due à des sources placées à proximité de l'oreille — Partie 2: Technique utilisant un mannequin

General Information

• Status: Withdrawn
• Publication Date: 26-Oct-2004
• Withdrawal Date: 26-Oct-2004
• ICS: 17.140.01 - Acoustic measurements and noise abatement in general
• Technical Committee: ISO/TC 43 - Acoustics
• Drafting Committee: ISO/TC 43 - Acoustics
• Current Stage: 9599 - Withdrawal of International Standard
• Completion Date: 04-Mar-2021

Relations

• Revised: ISO 11904-2:2021 - Acoustics — Determination of sound immission from sound sources placed close to the ear — Part 2: Technique using a manikin
• Effective Date: 10-Jul-2021
• Consolidates: ISO 4064-2:1978 - Measurement of water flow in closed conduits — Meters for cold potable water — Part 2: Installation requirements
• Effective Date: 06-Jun-2022

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 11904-2
First edition
2004-11-01


Acoustics — Determination of sound
immission from sound sources placed
close to the ear —
Part 2:
Technique using a manikin
Acoustique — Détermination de l'exposition sonore due à des sources
placées à proximité de l'oreille —
Partie 2: Technique utilisant un mannequin





Reference number
ISO 11904-2:2004(E)
©
ISO 2004

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ISO 11904-2:2004(E)
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ISO 11904-2:2004(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope. 1
2 Normative references. 1
3 Terms and definitions. 2
4 Measurement principle. 3
5 Instrumentation. 3
5.1 Manikin (head and torso simulator) . 3
5.2 Check of calibration. 3
5.3 Filters. 4
6 Determination of free-field or diffuse-field related equivalent continuous A-weighted
sound pressure level . 4
6.1 Measurement of manikin sound pressure level.4
6.2 Conversion to free-field or diffuse-field related sound pressure level . 4
6.3 A-weighting and summation. 6
7 Test report. 6
Annex A (informative) Example of sources of measurement uncertainty. 7
Annex B (informative) Example of an uncertainty analysis . 14
Bibliography . 16

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ISO 11904-2:2004(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.
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 11904-2 was prepared by Technical Committee ISO/TC 43, Acoustics.
ISO 11904 consists of the following parts, under the general title Acoustics — Determination of sound
immission from sound sources placed close to the ear:
 Part 1: Technique using a microphone in a real ear (MIRE technique)
 Part 2: Technique using a manikin

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ISO 11904-2:2004(E)
Introduction
ISO 11904 is a series of standards which specify methods for the determination of sound immissions from
sources located close to the ear in which situations the sound pressure level measured at the position of the
exposed person (but with the person absent) does not adequately represent the sound exposure.
In order to make it possible to assess the exposure by means of well-established criteria, the exposure of the
ear is measured and subsequently converted into a corresponding free-field or diffuse-field level. The result is
given as a free-field related or diffuse-field related equivalent continuous A-weighted sound pressure level,
L or L when ISO 11904-1 is used, or L or L when ISO 11904-2 is used.
FF,H,Aeq DF,H,Aeq FF,M,Aeq DF,M,Aeq
ISO 11904-1 describes measurements carried out using miniature or probe microphones inserted in the ears
of human subjects (microphones in real ear, MIRE technique). ISO 11904-2 describes measurements carried
out using a manikin equipped with ear simulators including microphones (manikin technique).
ISO 11904 may, for instance, be applied to equipment tests and the determination of noise exposure at the
workplace where, in the case of exposure from sources close to the ears, the sound pressure level measured
at the position of the exposed person (but with the person absent) does not adequately represent the sound
exposure. Examples of applications are head- and earphones used to reproduce music or speech, whether at
the workplace or during leisure, nailguns used close to the head, and combined exposure from a close-to-ear
sound source and an external sound field.
When specific types of equipment are to be tested (e.g. portable cassette players or hearing protectors
provided with radio receivers), test signals suitable for this particular type of equipment have to be used.
Neither such test signals nor the operating conditions of the equipment are included in ISO 11904 but might
be specified in other standards.
When workplace situations are measured, the various noise sources contributing to the immission should be
identified. Operating conditions for machinery and equipment used might be specified in other standards.
Both parts of ISO 11904 strive for the same result: a mean value for a population of the free-field or the
diffuse-field related level. ISO 11904-1 does this by specifying the mean of measurements on a number of
human subjects; ISO 11904-2 does this by using a manikin, which aims at reproducing the acoustical effects
on an average human adult. However, the two methods yield different measurement uncertainties which can
influence the choice of method. Only the method described in ISO 11904-1 gives results which indicate the
variance in a human population. Information on the uncertainties is given in Annexes A and B.
When using the MIRE technique for measurement of sound from earphones of insert and stethoscopic types,
practical problems can occur with the positioning of microphones in the ear canal. When using the manikin
technique, the head- or earphone has to be coupled to the pinna simulator and ear canal extension as far as
possible in the way it is coupled to the human ear. In cases where head- or earphones or other objects touch
the pinna, a possible deviation in stiffness or shape of the artificial pinna from human pinnae has a significant
impact on the result and can even make the results invalid.
An overview of the differences between the two parts of ISO 11904 is given in Table 0.1.
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ISO 11904-2:2004(E)
Table 0.1 — Overview of differences between MIRE and manikin techniques
Parameter ISO 11904-1 ISO 11904-2
Type of method Microphone in real ear technique Manikin technique
Limitation of the With earphones of insert and stethoscopic Proper coupling may not always be obtained
method type, practical problems can occur with if the artificial pinna deviates from human
positioning of microphones in the ear canal. pinnae in stiffness or shape.
In some cases the exposed person cannot be
replaced by a manikin, e.g., if the person has
to operate equipment.
Main issues Number of subjects Similarity of manikin to humans
affecting accuracy
When tabulated values are used for ∆L or Calibration of manikin
FF,H
∆L :
DF,H
 calibration of ear canal microphone
 accuracy in positioning of microphones in
the ear canal
When individual values are used for ∆L or
FF,H
∆L :
DF,H
 quality of reference sound field
 stability of sensitivity and frequency
response as well as position of ear canal
microphone
Frequency range 20 Hz to 16 kHz 20 Hz to 10 kHz


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INTERNATIONAL STANDARD ISO 11904-2:2004(E)

Acoustics — Determination of sound immission from sound
sources placed close to the ear —
Part 2:
Technique using a manikin
1 Scope
This part of ISO 11904 specifies basic framework measurement methods for sound immission from sound
sources placed close to the ear. These measurements are carried out with a manikin, equipped with ear
simulators including microphones. The measured values are subsequently converted into corresponding free-
field or diffuse-field levels. The results are given as free-field related or diffuse-field related equivalent
continuous A-weighted sound pressure levels. The technique is denoted the manikin technique.
This part of ISO 11904 is applicable to exposure to sound from sources close to the ear, for example during
equipment tests or at the workplace to sound from earphones or hearing protectors with audiocommunication
facilities.
This part of ISO 11904 is applicable in the frequency range from 20 Hz to 10 kHz. For frequencies above
10 kHz, ISO 11904-1 can be used.
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 60942:2003, Electroacoustics — Sound calibrators
IEC 61260:1995, Electroacoustics — Octave-band and fractional-octave-band filters
IEC 61672-1, Electroacoustics — Sound level meters — Part 1: Specifications
ITU-T P.58:1996, Head and torso simulator for telephonometry
1)
GUM:1993 , Guide to the expression of uncertainty in measurement. BIPM, IEC, IFCC, ISO, IUPAC, IUPAP,
OIML, 1995

1) Corrected and reprinted in 1995.
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ISO 11904-2:2004(E)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
manikin sound pressure level
L
M,exp,f
equivalent continuous sound pressure level in one-third-octave frequency bands with nominal midband
frequency f, measured with the microphone of an ear simulator integrated in a manikin when the manikin is
exposed to the sound under test
3.2
free-field frequency response for use with manikins
∆L
FF,M,f
average human free-field frequency response for use with manikins, corrected for the difference between the
sound transmission inside the average human ear canal and the corresponding transmission of the manikin
ear simulator
NOTE 1 For applicability with manikins, the eardrum reference is replaced by the output of the manikin ear simulator in
tabulated values of ∆L .
FF,M,f
NOTE 2 The free-field frequency response for use with manikins is identical to the amplitude of the head-related
transfer function (HRTF) for frontal sound incidence.
NOTE 3 The human free-field frequency response is defined in ISO 11904-1.
3.3
diffuse-field frequency response for use with manikins
∆L
DF,M,f
average human diffuse-field frequency response for use with manikins, corrected for the difference between
the sound transmission inside the average human ear canal and the corresponding transmission of the
manikin ear simulator
NOTE 1 For applicability with manikins, the eardrum reference is replaced by the output of the manikin ear simulator in
tablulated values of ∆L .
DF,M,f
NOTE 2 The human diffuse-field frequency response is defined in ISO 11904-1.
3.4
free-field related sound pressure level determined with a manikin
L
FF,M
free-field sound pressure level determined with the method of this part of ISO 11904
NOTE 1 The definition may be applied to specific frequencies or frequency bands, weighted or unweighted levels,
specific time weightings, etc., for instance “free-field related equivalent continuous A-weighted sound pressure level" (free-
field related L , also denoted L ).
M,Aeq FF,M,Aeq
NOTE 2 The method is aimed at the mean free-field related sound pressure level that would be obtained with a large
human population.
NOTE 3 The free-field related sound pressure level for a human subject is defined in ISO 11904-1.
3.5
diffuse-field related sound pressure level determined with a manikin
L
DF,M
diffuse-field sound pressure level determined with the method of this part of ISO 11904
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ISO 11904-2:2004(E)
NOTE 1 The definition may be applied to specific frequencies or frequency bands, weighted or unweighted levels,
specific time weightings, etc., for instance “diffuse-field related equivalent continuous A-weighted sound pressure level"
(diffuse-field related L , also denoted L ).
M,Aeq DF,M,Aeq
NOTE 2 The method is aimed at the mean diffuse-field related sound pressure level that would be obtained with a
large human population.
NOTE 3 The diffuse-field related sound pressure level for a human subject is defined in ISO 11904-1.
4 Measurement principle
A manikin (head and torso simulator) is exposed to the sound source(s) in question and, for each of the ear
simulators integrated in the manikin, the sound pressure level is measured in one-third-octave frequency
bands, L .
M,exp,f
Each of the one-third-octave-band levels is adjusted with the free-field or diffuse-field frequency response for
the manikin, ∆L or ∆L , in order to obtain the corresponding free-field related or diffuse-field related
FF,M,f DF,M,f
one-third-octave-band sound pressure levels. These one-third-octave-band levels are adjusted using A-
weighting constants, and subsequently combined to obtain the free-field related or diffuse-field related
equivalent continuous A-weighted sound pressure level, L or L .
FF,M,Aeq DF,M,Aeq
The measurements may be carried out for one or both ears, as appropriate. The free-field or diffuse-field
frequency response for use with manikins is taken from Table 1.
5 Instrumentation
5.1 Manikin (head and torso simulator)
The manikin used shall satisfy the requirements of ITU-T P.58:1996, 4.3 (first paragraph), 5.1 and 6.1, for the
ear simulator and the acoustic characteristics of the manikin respectively.
The manikin used should be checked regularly for compliance with the requirements of ITU-T P.58:1996, 4.3
(first paragraph), 5.1 and 6.1.
In cases where sound sources (such as earphones or hearing protectors with communication facilities) touch
the pinna, they shall be coupled to the pinna simulator and ear canal extension in a way as close as possible
to the way it is coupled to the human ear.
NOTE In cases where head- or earphones or other objects touch the pinna, the deviation in stiffness or shape of the
artificial pinna from human pinnae has a significant impact on the result and may even make the results invalid.
5.2 Check of calibration
The calibration of the microphones and the measuring equipment shall be checked as follows.
For checking the calibration of the measurement system together with the occluded ear simulator, an acoustic
calibrator (class 1 according to IEC 60942:2003) shall be coupled to the occluded ear simulator. The sound
pressure level shall, in this case, be measured without any frequency weighting.
NOTE This measurement is generally conducted with the aid of an adapter in the ear canal extension. It should be
noted that the adapter will change the nominal value for the sound pressure levels of the acoustic calibrator.
The frequency response of the measuring system without
...