Electroacoustics - Specifications for personal sound exposure meters

Applies to instruments for measurement of A-frequency- weighted sound exposure resulting from steady, intermittent, fluctuating, irregular, or impulsive sound. Specifies acoustical and electrical performance requirements for personal sound exposure meters of one accuracy grade.

Elektroakustik - Anforderungen an Personenschallexposimeter

Electroacoustique - Spécifications des exposimètres acoustiques individuels

S'applique aux instruments de mesure de l'exposition sonore pondérée A en fréquence et résultant de sons stables, intermittents, fluctuants, irréguliers, ou impulsifs. Donne les prescriptions concernant les caractéristiques acoustiques et électriques des exposimètres acoustiques individuels correspondant à une seule classe de précision.

Electroacoustics - Specifications for personal sound exposure meters (IEC 61252:1993)

1.1 Izpostavljenost zvoku je fizikalni kazalnik, ki se uporablja za zvočni tlak in trajanje zvoka na določenem mestu na podlagi sestavnega prekoračenja kvadrata trenutnega frekvenčno-vrednotenega zvočnega tlaka.
1.2 Ta mednarodni standard se uporablja za instrumente za merjenje frekvenčno-vrednotene izpostavljenosti zvoku zaradi neprekinjenih, občasnih, nihajočih, spremenljivih ali impulzivnih zvokov. Instrumenti, skladni s specifikacijami tega mednarodnega standarda, so namenjeni za merjenje izpostavljenosti zvoku pri osebah, ki jih nosijo.
Meritve izpostavljenosti zvoku na delovnem mestu so lahko uporabne za ugotavljanje izpostavljenosti hrupu pri delu v skladu s standardoma ISO 1999 in ISO 9612.
1.3 Ta mednarodni standard določa zahteve glede akustičnih in električnih zmogljivosti za merilnike osebne izpostavljenosti zvoku z enotnim razredom točnosti. Razred točnosti ustreza razredu točnosti za merilnik integracijske zvočne jakosti, ki izpolnjuje zahteve tipa 2 v skladu s standardom IEC 804 za A-vrednoteno raven zvočnega tlaka v obsegu od 80 dB do 130 dB in nazivnem frekvenčnem obsegu od 63 Hz do 8 kHz.
1.4 Tolerance pri odstopanjih v zmogljivosti instrumenta od podanih načrtovanih ciljev predstavljajo učinkovitosti delovanja praktičnih instrumentov. Merilniki osebne izpostavljenosti zvoku morajo delovati znotraj toleranc iz tega mednarodnega standarda v okviru podanih okoljskih pogojev.

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SIST EN 61252:2000
Electroacoustics - Specifications for personal sound exposure meters (IEC
Electroacoustics - Specifications for personal sound exposure meters
Elektroakustik - Anforderungen an Personenschallexposimeter
Electroacoustique - Spécifications des exposimètres acoustiques individuels
Ta slovenski standard je istoveten z: EN 61252:1995
13.140 Vpliv hrupa na ljudi Noise with respect to human
17.140.50 Elektroakustika Electroacoustics
SIST EN 61252:2000 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
ICS 17.1 40.50

Descriptors: Electroacoustic equipment, exposure meters, sound pressure, definitions, indicating instruments, specifications,

characteristics, instrument sensitivity, marking, technical notices
English version
Specifications for personal sound exposure meters
(IEC 1252: 1993)
Electroacoustique Elektroakustik
Specifications des exposim6tres Anforderungen an
acoustiques individuels Personenschallexposimeter
(CEI 1 252: 1 993) (IEC 1252: 1993)

This European Standard was approved by CENELEC on 1995-03-06. CENELEC members are bound to

comply with the CENICENELEC Internal Regulations which stipulate the conditions for giving this

European Standard the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on

application to the Central Secretariat or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). Aversion in any other

language made by translation under the responsibility of a CENELEC member into its own language and

notified to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Denmark, Finland,

France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain,

Sweden, Switzerland and United Kingdom.
European Committee for Electrotechnical Standardization
Comitk Europken de Normalisation Electrotechnique
Europaisches Komitee fur Elektrotechnische Normung
Central Secretariat: rue de Stassart 35, B - 1050 Brussels
1995 Copyright reserved to CENELEC members
Ref. No. EN 61252:1995 E
---------------------- Page: 2 ----------------------
Page 2
EN 61 252: 1995
The text of the International Standard IEC 1252:1993, prepared by IEC TC 29,

Electroacoustics, was submitted to the formal vote and was approved by CENELEC as

EN 61 252 on 1995-03-06 without any modification.
The following dates were fixed:
- latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 1995-1 2-1 5
- latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 1995-1 2-1 5
Annexes designated "normative1' are part of the body of the standard.
Annexes designated "informative" are given for information only.
In this standard, annex ZA is normative and annexes A and B are informative.
Annex ZA has been added by CENELEC.
Endorsement notice

The text of the International Standard IEC 1252:1993 was approved by CENELEC as a

European Standard without any modification.
---------------------- Page: 3 ----------------------
ANNEX ZA (normative)

7h1s Europeijn Standard incorporate:; by dated or untlated refer'c?ncu, pr.ovis lons

from other publications. These normative references are cited at the
iippropriate places in the text and the publicat~ons arc listed hereafter.. For
dated references, subsequent amendments t.o or revisions ol' any of these
publications apply to this Europe amendment or revision. For undated references t.he latest edition of the
publ~cdtion referred to applies.
NOTE : When the internnational publlcat.ion has been modified by CtNtLEC
common mod ~f ications, indicated by (mod), the relevdnt ENIHD applies.
Pub'I icatior~ Date '[itle
- . - - - . . - - -. - . . . . ,. . . . , .- . - - -
50(801) 1984 International Electrotechnical
Vocabulary (IEV) . Chapter 801:
Acoustics and electro--acoustics
65 1. 1919 Pound level meters IN bOfj51 1994
801 -2 1984 Electromagnetic compatibility for EN 60801-2 1993
industrial-process measurement dnd
control equipment - Part 2:
Electrostdtic discharge requirements
801- 3 1984 Part 3: Radiated electromagnetic field HLI 481.3 S1. 1987
HI14 1985 Integrating-averaging sound level meters EN 60804% 1994
94 % 1.388 Sound calibrators IiD 556 S1 '1. 13 1 1.
Other pub l i~ations:
- - - - - - - - - . . - .
IS0 26h:1975 - Acoustics - Preferred frequencies for measurements

IS0 '1683: 138:3 -- Ar:oust ics - Preferred r.cfer.en(;e quarlt rt ics for ,j(:our;t:c levc 1.;

IS0 19913:1990 - Acoustits - Determination of occupat.iona1 noise explosure anti
cS,l imat ion of nolie ~nduced hclir inq imp~l iraenl
150 9612:199x - Acoustics - Guidelines for the measurement and assessment of
exposure to noise in the work ~ng environment ( In prepdrdt ]on)
. . . - - - - . . . . . . . - .
* EN 60804 -1nc-ludes A1:1989 to IEC 804
---------------------- Page: 4 ----------------------
First edition
Electroacoustique —
des exposimètres
acoustiques individuels
Electroacoustics —
Specifications for personal sound
exposure meters
de reproduction réservés — Copyright — all rights reserved
© CEI 1993 Droits
No part of this publication may be reproduced or utilized in
Aucune partie de cette publication ne peut être reproduite ni
any form or by any means, electronic or mechanical,
utilisée sous quelque forme que ce soit et par aucun pro-
including photocopying and microfilm, without permission
cédé, électronique ou mécanique, y compris la photocopie et
in writing from the publisher.
les microfilms, sans l'accord écrit de l'éditeur.

Bureau Central de la Commission Electrotechnique Inte rnationale 3, rue de Varembé Genève,

Commission Electrotechnique Internationale CODE PRIX
International Electrotechnical Commission
Metuayaapopnae 3nettrpoTexHu ecttan HOMHCCHN
Pour prix, voir catalogue en •
For price, see current cata
---------------------- Page: 5 ----------------------
1252 ©IEC:1993 - 3 -
1 Scope
2 Normative references
3 Definitions
4 General pe rformance requirements
5 Reference conditions 19
6 Absolute acoustical sensitivity
7 Frequency weighting
8 Linearity of response to steady signals
9 Response to short-duration signals
10 Response to unipolar pulses
11 Latching overload indicator
12 Sensitivity to various environments
13 Instrument marking
29 14 Instruction Manual
Design-goal A-frequency weighting relative to response at 1 kHz
Table 1
rformance of a complete
and the tolerances DA that apply to the pe
21 personal sound exposure meter
Figure 1 Functional elements of a personal sound exposure meter
Sound exposures and corresponding normalized 8-h-average
sound levels
rformance of a personal
B Recommended tests to verify the pe
sound exposure meter
A.1 Sound exposures and corresponding normalized 8-h-average
sound levels
B.1 Minimum set of target conditions for 1 kHz steady-signal
linearity tests
B.2 Conditions for testing response to short-duration signals
---------------------- Page: 6 ----------------------
1252 ©IEC:1993 - 5 -

1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization

comprising all national electrotechnical committees (IEC National Committees). The object of the IEC is to

promote international cooperation on all questions concerning standardization in the electrical and

electronic fields. To this end and in addition to other activities, the IEC publishes International Standards.

Their preparation is entrusted to technical committees; any IEC National Committee interested in

the subject dealt with may participate in this preparatory work. International, governmental and

non -governmental organizations liaising with the IEC also participate in this preparation. The IEC

collaborates closely with the Inte rnational Organization for Standardization (ISO) in accordance with

conditions determined by agreement between the two organizations.

The formal decisions or agreements of the IEC on technical matters, prepared by technical committees on

which all the National Committees having a special interest therein are represented, express, as nearly as

possible, an international consensus of opinion on the subjects dealt with.

They have the form of recommendations for international use published in the form of standards, technical

reports or guides and they are accepted by the National Committees in that sense.

4) In order to promote international unification, IEC National Committees undertake to apply IEC International

Standards transparently to the maximum extent possible in their national and regional standards. Any

divergence between the IEC Standard and the corresponding national or regional standard shall be clearly

indicated in the latter.

5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any

equipment declared to be in conformity with one of its standards.
International Standard IEC 1252 has been prepared by IEC technical committee 29:
The text of this standard is based on the following documents:
Report on Voting
29(CO)162 29(CO)168

Full information on the voting for the approval of this Standard can be found in the Repo rt

on Voting indicated in the above table.

Specifications in this International Standard for personal sound exposure meters are

consistent, insofar as practical, with comparable specifications in IEC 804 for integrating

sound level meters. The four principal technical differences from the specifications in the

1985 issue of IEC 804 are:
sound exposure is measured and displayed rather than equivalent-continuous
frequency-weighted sound pressure level or sound exposure level;

b) accuracy of squaring and integrating short-duration signals is specified by measure-

ment of the sound exposure of a sequence of repeated constant-amplitude, 1 ms
and 10 ms duration, 4 kHz tonebursts rather than by measurement of the response
---------------------- Page: 7 ----------------------
– 7 –
1252 ©IEC:1993

to single 4 kHz tonebursts of varying amplitudes with durations ranging from 1 ms to

1 s, each single toneburst being accompanied by a continuous, in-phase, low-level,

4 kHz background signal;

specifications for a personal sound exposure meter include a limitation on the differ-

ence between the sound exposure indicated in response to positive-going and
negative-going unipolar pulses; and

d) requirements are not specified for the directional response of the microphone of a

personal sound exposure meter intended to be worn on a person.

This International Standard includes two informative annexes. Annex A provides a table of

selected sound exposures and corresponding normalized 8-h-average sound levels.

Annex B describes recommendations for tests to verify the performance of a personal

sound exposure meter.

According to this International Standard, a personal sound exposure meter is intended to

measure sound exposure as the time integral of the square of the instantaneous

A-frequency-weighted sound pressure. This operating principle underlies the measure-

ment of sound exposure level according to IEC 804. It is the "equal-energy exchange rate"

whereby a doubling (or halving) of the integration time of a constant sound level yields a

two-fold increase (or decrease) of sound exposure. Similarly, an increase (or decrease) of

3 dB in a constant input sound level for a constant integration time yields a doubling

(or halving) of the sound exposure.

Noise dose meters usually have been designed to indicate noise dose as a percentage of

a legal limit. The limit and its definition vary from country to country and are subject to

change. To facilitate international comparison of sound exposure records with numerical

values of convenient magnitude, this International Standard specifies an instrument that

indicates sound exposure in pascal-squared hours. An indication of sound exposure with

a unit other than pascal-squared hours is permitted provided the manufacturer specifies a

procedure for converting the indication to pascal-squared hours, for example, a display of

"dose" as a fraction or a percentage of a specified sound exposure in pascal-squared


The principal application for a personal sound exposure meter is the measurement of

sound exposure in the vicinity of a person's head; e.g., for assessment of potential hearing

impairment according to Standards such as ISO 1999. The microphone of a personal

sound exposure Meter may be worn on the shoulder, collar, or other location close to one

ear. For many practical situations, such as in a factory where the sound-incidence angle

may vary widely during the course of workday, the sound exposure indicated by an

instrument worn on a person is likely to be different from that which would be measured in

the absence of the person. The influence of the person wearing a personal sound

exposure meter should be considered when estimating the sound exposure that would

have been measured with the person absent.
---------------------- Page: 8 ----------------------
1252 ©IEC:1993
1 Scope

1.1 Sound exposure is a physical measure that accounts for both the sound pressure

and its duration, at a given location, through an integral-over-time of the square of instan-

taneous frequency-weighted sound pressure.
1.2 This International Standard is applicable to instruments for measurement of

A-frequency-weighted sound exposure resulting from steady, intermittent, fluctuating,

irregular, or impulsive sounds. Instruments complying with the specifications of this Inter-

national Standard are intended to be worn on a person to measure sound exposure.

Measurements of sound exposure in the workplace may be useful for determinations of

occupational noise exposure, in accordance with ISO 1999 and ISO 9612.
rformance require-
1.3 This International Standard specifies acoustical and electrical pe

ments for personal sound exposure meters of one accuracy grade. The accuracy grade

corresponds to that for an integrating sound level meter which complies with the Type 2

requirements of IEC 804 for an A-weighted sound pressure level range from 80 dB to

130 dB and a nominal frequency range from 63 Hz to 8 kHz.

1.4 Tolerances on deviations of an instrument's performance from specified design

ormance capabilities of practical instruments. Personal sound
goals represent the pe rf

exposure meters are required to operate within the tolerances of this International

Standard over specified ranges of environmental conditions.
2 Normative references

The following normative documents contain provisions which, through reference in this

text, constitute provisions of this International Standard. At the time of publication, the

editions indicated were valid. All normative documents are subject to revision, and parties

to agreements based on this International Standard are encouraged to investigate the

possibility of applying the most recent editions of the normative documents listed below.

Members of IEC and ISO maintain registers of currently valid normative documents.

Advance edition of the International Electrotechnical Vocabulary,
IEC 50(801): 1984,
Chapter 801, Acoustics and electroacoustics
IEC 651: 1979, Sound level meters

IEC 801-2: 1984, Electromagnetic compatibility for industrial-process measurement and

control equipment - Part 2: Electrostatic discharge requirements
---------------------- Page: 9 ----------------------
1252©IEC:1993 -11 -

IEC 801-3: 1984, Electromagnetic compatibility for industrial-process measurement and

control equipment - Pa rt 3: Radiated electromagnetic field requirements
IEC 804: 1985, Integrating-averaging sound level meters
IEC 942: 1988, Sound calibrators
ISO 266: 1975, Acoustics - Preferred frequencies for measurements
Acoustics - Preferred reference quantities for acoustic levels
ISO 1683: 1983,
Acoustics - Determination of occupational noise exposure and estimation
ISO 1999: 1990,
of noise-induced hearing impairment
Acoustics - Guidelines for the measurement and assessment of expo-
ISO 9612: 199X,
sure to noise in the working environment. *
3 Definitions

For the purposes of this International Standard, the following definitions apply. Definitions

are consistent with corresponding definitions in IEC 50(801).
Time integral of squared, instantaneous A-frequency-weighted sound exposure:
sound pressure over a specified event, for example, a working day.
unit for sound exposure is the pascal-squared second, for measurements of
1 Although the primary SI

sound exposure in the workplace, the more-convenient derived unit, the pascal-squared hour, is used in this

International Standard.
2 In symbols, (A-weighted) sound exposure is
(t) d t

(t) is the square of instantaneous A-frequency-weighted sound pressure as a function of time t

where pA2
is pascal-squared

an integration time period starting at t1 and ending at t2. The unit of sound exposure E

is in pascals and the running time t in hours.
hours if A-weighted sound pressure pA
-average sound
3.2 equivalent-continuous A-weighted sound pressure level; time

In decibels, ten times the logarithm to the base ten of the ratio of the time-mean-

T, to the
square, A-frequency-weighted sound pressure, during an averaging time period
square of the standard reference sound pressure.
At present, at the stage of draft.
---------------------- Page: 10 ----------------------
1252 ©IEC:1993 - 13 -

1 In symbols, equivalent-continuous A-weighted sound pressure level L or time-average sound level,

Aeq r
is given by:
dt ] / pot } (2)
) (t)
10 1g {[ ( 1/7 PA2
LAeq,T =

where running time t and averaging time T are expressed in the same units, is the instantaneous

0 is the reference sound pressure of twenty micropascals
A-weighted sound pressure in pascals, and p
(20 µPa) per ISO 1683.

Equivalent-continuous A-weighted sound pressure level during the averaging time period T is related to

the total sound exposure occurring within that period by
0 ,
1 x L
E • (p02
7) [10 Aeq T ] (3)
or, alternatively, by
tAeg T =10Ig [
E/ (p02 T )]
where the unit of time is the same for both sound exposure and averaging time.
normalized 8-h-average sound level: In decibels, level of the time-mean-square,
n of 8 h such that the
A-weighted sound pressure during a normalization time period T

sound exposure therefrom is equal to that of a time-varying sound at a place where total

sound exposure occurs within a time period not necessarily 8 h.
L relative to the reference sound
1 In symbols, a normalized 8-h-average sound level (letter symbol
Aeq shn,),
pressure po and the 8 h normalization time period T, , is given by:
10 Ig [El (p02 ] (5)
Tn )
LAeq,8hn =

2 For computations, a simpler form of Eq.(5) for normalized 8-h-average sound level in decibels is

in pascal-squared hours, after substituting the values of 20 micropascals for
obtained, for sound exposure E
p0 and 8 h for Tn, as
10 Ig [ (Ex 109) / 3,2] =

3 When a total sound exposure is described indirectly by an equivalent-continuous A-weighted sound

pressure level LAeq T , for an averaging time T greater or less than the normalization time period of 8 h,

normalized 8-h-average sound level may be determined from
Aeg T + 10 1g (T/Tn ) (7)
Aeq,Bhn = L

4 Annex A provides a table of normalized 8-h-average sound levels and corresponding sound exposures.

For example, a sound exposure of 1 Pa2h (irrespective of the period of time over which it is measured)

corresponds to a normalized 8-h-average sound level of nearly 85 dB; a sound exposure of 3,2 Pa2h

corresponds exactly to a normalized 8-h-average sound level of 90 dB.
LEP d in

5 Normalized 8-h-average sound level in Eq.(5) is identical to "daily personal noise exposure

decibels" defined in A rticle 2 of the "European Communities Council Directive of 12 May 1986 on the protec-

tion of workers from the risks related to exposure to noise at work" (Directive 86/188/EEC).

6 Normalized 8-h-average sound level in Eq.(5) is also the same as "noise exposure level normalized to a

nominal 8 h working day, defined in ISO 1999.
---------------------- Page: 11 ----------------------
1252 ©IEC:1993 -15 -
In decibels, lower and upper time-average, A-weighted sound
3.4 sound level range:

pressure levels without exponential time weighting, specified by the manufacturer, within

which linearity requirements of this International Standard are met.
3.5 sound exposure range: Range between an upper and a lower sound exposure,

both to be specified by the manufacturer, within which the requirements of this Inter-

national Standard are met and which are displayed on the sound exposure indicator.

reference direction: Direction of sound incidence specified by the manufacturer
for determining the absolute acoustical sensitivity and frequency response.
Frequency of 1 kHz for determining the absolute acoustical
3.7 reference frequency:
Sound pressure level specified by the manu-
3.8 reference sound pressure level:
facturer for determining the absolute acoustical sensitivity.
Integration time specified by the manufacturer for
3.9 reference integration time:
determining the absolute acoustical sensitivity.
reference sound exposure: Calculated sound exposure corresponding to the

reference sound pressure level, at the reference frequency, applied for the reference

integration time.
4 General performance requirements

4.1 A personal sound exposure meter is a combination of a microphone, an amplifier

with the required A-frequency weighting, a device to square the frequency-weighted sound

pressure signal, an integrator over time, an indicator of sound exposure, and a latching

overload indicator. Sound exposures that have been accumulated during a measurement

period are retained in the memory until the instrument is reset and are not deleted by

triggering of the latching overload indicator.
test point
Amplifier and
Squarer Integrator exposure
Figure 1 - Functional elements of a personal sound exposure meter
---------------------- Page: 12 ----------------------
1252 ©IEC:1993 –17 –

4.2 Because only its overall performance is important, an actual instrument need not be

separable into individual functional elements. However, for convenient description of

required characteristics, the instrument is considered as if it were a combination of the

separate elements shown in figure 1.

4.3 The manufacturer shall provide the means to substitute an electrical input signal in

place of the microphone, for the purpose of performing tests on the complete instrument

without the microphone.

NOTE - The manufacturer may provide an accessible input test point or recommend and provide a dummy

microphone or equivalent input adapter (electrical or non-electrical) for performing electrical tests on the

4.4 An optional (but preferred) accessible output test point may be provided.

4.5 The sound exposure indicator may be built into, or be separate from, the wearable

part of an instrument. The quantity indicated is sound exposure, either as a direct indica-

tion or as a fraction or percentage of a manufacturer-specified sound exposure. If sound

h), the manufacturer shall
exposure is not indicated directly in pascal-squared hours (Pa 2

provide suitable means to convert the indication to sound exposure in pascal-squared


4.6 The smallest increment of sound exposure displayed by the indicator shall be not

2h. The sound exposure range shall be at least from 0,1 Pa h to
greater than 0,1 Pa
99,9 Path.
The sound level range shall extend at least from 80 dB to 130 dB.
The manufacturer shall state in the Instruction Manual the sound exposure range
and the sound level range.

4.9 If the manufacturer-specified ranges of sound exposure and sound level exceed the

minimum requirements of this International Standard, all specifications and associated

tolerances shall apply to the ranges stated by the manufacturer.

4.10 If the specified lower boundary of the sound level range is less than 80 dB, the

lower boundary of the sound exposure range shall be less than 0,1 Pa2h.

4.11 Specifications in subsequent clauses for the acoustical and electrical performance

of a personal sound exposure meter are applicable for the reference conditions of clause.

5. Clause 12 provides requirements for limits on the changes in the sensitivity of a

personal sound exposure meter when used under environmental conditions different from

the reference conditions.
4.12 A power supply of the type recommended by the manufacturer shall be able to

operate a personal sound exposure meter within all specifications of this International

Standard for at least 8 h at any temperature within the range specified by the manu-

facturer of the personal sound exposure meter. If a personal sound exposure meter is

battery operated, the manufacturer shall provide a method to check that the battery

voltage is sufficient to operate the instrument within the specifications at the time the

---------------------- Page: 13 ----------------------
1252 ©IEC:1993 –19 –

check is made. A check of battery.. condition shall not disturb a measurement of sound

5 Reference conditions

Reference conditions for a personal sound exposure meter are: atmospheric pressure of

101,3 kPa; air temperature of 20 °C; relative humidity of 65 % ; and absence of significant

interference caused by ambient sounds, airflow over the microphone, vibrations, magnetic

fields, electromagnetic fields, or electrostatic fields.

NOTE - Significant interference is when the effect on the indicated sound exposure exceeds ten percent of an

applicable tolerance limit.
6 Absolute acoustical sensitivity

6.1 A means shall be available for the user to check and maintain the sensitivity of a

personal sound exposure meter such that the tolerances in 6.2 for reference sound

exposure are met under the reference conditions. If this means is a sound calibrator, it

shall meet the requirements of IEC 942.
A sound calibrator meeting the Class 1 requirements of IEC 942 is preferred.

2 The integration time period for checking the absolute acoustical sensitivity should not exceed 2 min.

3 If another quantity such as sound pressure level can be displayed, it may be used to check the calibra-

tion of the instrument.

6.2 The personal sound exposure meter shall be checked and, if necessary, adjusted in

accordance with the manufacturer's instructions. Under the reference environmental condi-

tions of clause 5 and for plane-progressive sound waves incident on the microphone from

the reference direction, the indicated sound exposure shall be within the range –21 % to

+26 % of the reference sound exposure at the reference frequency of 1 kHz. This require-

ment shall apply with the microphone of the personal sound exposure meter mounted as

specified by the manufacturer, but not mounted on a person and without an observer

disturbing the sound field.

NOTE - Calibration of the absolute acoustical sensitivity of a personal sound exposure meter may be carried

out by means of a closed-coupler pressure-calibration device, in conjunction with manufacturer-specified

corrections for the free-field response, applicable to the type of microphone used on the personal sound

exposure meter.
7 Frequency weighting

7.1 Under the reference environmental conditions of clause 5 and for plane-progressive

sound waves incident on the microphone from the reference direction and with the refer-

ence sound pressure level at the microphone, a complete personal sound exposure meter,

with the microphone mounted as specified by the manufacturer but not mounted on a

person and without an obse rver disturbing the sound field, shall have the relative

A-weighting frequency characteristic, for constant-amplitude sinusoidal signals, as

specified in table 1. The design-goal A-frequency weighting is a smooth and continuous

function of frequency as specified in IEC 651. At each nominal frequency in table 1, the

ratio of a measured sound exposure to the sound exposure at 1 kHz shall fall within the

---------------------- Page: 14 ----------------------
1252 ©IEC:1993 - 21 -
specified sound-exposure tolerances. At intermediate frequencies, the applicable

tolerances are the wider limits determined from the A-weighting tolerances in decibels

given in table 1.
Table 1 - Design-goal A-frequency weighting relative to response at 1kHz
and the tolerances AA that apply to the performance of a complete
personal sound exposure meter
Nominal A Sound exposure ratio
dB dB
Hz min design-goa

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