EN 61094-4:1995
(Main)Measurement microphones - Part 4: Specifications for working standard microphones
Measurement microphones - Part 4: Specifications for working standard microphones
Applies to working standard microphones. Specifies mechanical dimensions and certain electroacoustical characteristics for working standard microphones used in measuring systems for the determination of sound pressure to enable these microphones to be used as transfer standards in the calibration of acoustic measurement instruments.
Meßmikrofone - Teil 4: Anforderungen an Gebrauchs-Normalmikrofone
Microphones de mesure - Partie 4: Spécifications des microphones étalons de travail
S'applique aux microphones étalons de travail. Spécifie les dimensions mécaniques et certaines caractéristiques électroacoustiques des microphones étalons de travail utilisés dans les systèmes de mesure pour la détermination de la pression acoustique afin de rendre possible leur utilisation comme étalons de transfert dans l'étalonnage des appareils de mesures acoustiques.
Measurement microphones - Part 4: Specifications for working standard microphones (IEC 61094-4:1995)
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-september-2002
Measurement microphones - Part 4: Specifications for working standard
microphones (IEC 61094-4:1995)
Measurement microphones -- Part 4: Specifications for working standard microphones
Meßmikrofone -- Teil 4: Anforderungen an Gebrauchs-Normalmikrofone
Microphones de mesure -- Partie 4: Spécifications des microphones étalons de travail
Ta slovenski standard je istoveten z: EN 61094-4:1995
ICS:
17.140.50 Elektroakustika Electroacoustics
33.160.50 Pribor Accessories
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
NORME C E I
INTERNATIONALE IEC
1094-4
INTERNATIONAL
Première édition
STANDARD
First edition
1995-11
Microphones de mesure
Partie 4:
Spécifications des microphones étalons de travail
Measurement microphones
Part 4:
Specifications for working standard microphones
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1094-4 ©IEC:1995 - 3 -
CONTENTS
Page
FOREWORD 5
Clause
1 Scope and object 7
2 Normative references 7
3 Definitions 9
3.1 Working standard microphone
3.2 Principal axis of a microphone 9
3.3 Reference plane of a microphone 9
3.4 Effective front volume of a microphone 9
3.5 Correction grid 9
4 Reference environmental conditions 9
5 Classification of working standard microphones 9
5.1 General 9
5.2 Type designation 11
6 Characteristics of working standard microphones
6.1 Sensitivity 11
6.2 Effective front volume 11
6.3 Upper limit of the dynamic range of a microphone
6.4 Linearity range of the microphone sensitivity level
6.5 Static pressure dependence of microphone sensitivity
6.6 Temperature dependence of microphone sensitivity 13
6.7 Humidity dependence of microphone sensitivity 13
6.8 Stability of microphone sensitivity 13
6.9 Pressure equalizing leakage
7 Specifications 15
7.1 Mechanical dimensions 15
7.2 Electroacoustical specifications
7.3 Identification markings
Annex A – Provisional ground-shield reference configuration for type WS3 microphones 23
1094-4 ©IEC:1995 - 5 -
INTERNATIONAL ELECTROTECHNICAL COMMISSION
MEASUREMENT MICROPHONES
Part 4: Specifications for working standard microphones
FOREWORD
The IEC (International Electrotechnical Commision) is a worldwide organization for standardization comprising all na tional
1)
onal Committees). The object of the IEC is to promote inte rnational cooperation on all
electrotechnical committees (IEC Na ti
ons concerning standardization in the electrical and electronic fields. To this end and in addition to other activities, the IEC
questi
publishes International Standards. Their preparation is entrusted to technical committees; any IEC National Committee interested
rnational, governmental and non-governmental organizations
in the subject dealt with may participate in this preparatory work. Inte
ational Organization for
liaising with the IEC also participate in this preparation. The IEC collaborates closely with the Inte rn
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
2)
rnational consensus of opinion
Committees having a special interest therein are represented, express, as nearly as possible, an inte
on the subjects dealt with.
rnational use published in the form of standards, technical reports or guides and
3) They have the form of recommendations for inte
they are accepted by the National Committees in that sense.
In order to promote internati fication, IEC National Committees undertake to apply IEC Intemation Standards transparently
4) onal uni
tional or regional standards. Any divergence between the IEC Standard and the
to the maximum extent possible in their na
er.
corresponding national or regional standard shall be clearly indicated in the latt
International Standard IEC 1094-4 has been prepared by IEC technical committee 29: Electroacoustics.
The text of this standard is based on the following documents:
DIS Report on voting
29/312/RVD
29/295/DIS
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.
rts, under the general title Measurement microphones:
IEC 1094 consists of the following pa
– Pa 1: 1992, Specifications for laboratory standard microphones
rt
Part 2: 1992, Primary method for pressure calibration of laboratory standard microphones by the
–
reciprocity technique
3: 1995, Primary method for free-field calibration of laboratory standard microphones by the
– Part
reciprocity technique
4: 1995, Specifications for working standard microphones
– Part
Annex A is for information only.
1094-4 ©IEC:1995 - 7 -
MEASUREMENT MICROPHONES
Part 4: Specifications for working standard microphones
1 Scope and object
of IEC 1094 is applicable to working standard microphones.
This part
ain electroacoustical characteristics for working standard
rt
It specifies mechanical dimensions and ce
microphones used in measuring systems for the determination of sound pressure to enable these
microphones to be used as transfer standards in the calibration of acoustic measurement instruments.
It establishes a system for classifying working standard microphones into a number of types according to
their dimensions and properties in order to facilitate the specification of measurement systems, the
calibration of measuring systems and microphones by sound calibrators, and the interchangeability of
microphones in given measuring and calibration systems.
principle by which working standard microphones operate.
It does not specify the transduction
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute
of IEC 1094. At the time of publication, the editions indicated were valid. All normative
provisions of this pa rt
ies to agreements based on this part of IEC 1094 are
documents are subject to revision, and pa rt
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 International Standards.
IEC 942: 1988, Sound calibrators
1: Specifications for laboratory standard microphones
Measurement microphones - Part
IEC 1094-1: 1992,
rt 2: Primary method for pressure calibration of
IEC 1094-2: 1992, Measurement microphones - Pa
laboratory standard microphones by the reciprocity technique
3: Primary method for free-field calibration of
IEC/DIS 1094-3: 199x, Measurement microphones - Pa rt
revision of IEC 486)*
laboratory standard microphones by the reciprocity technique (
ANSI B1.1: 1982, Unified inch screw threads**
Guide to the expression of uncertainty in measurement
ISO: 1993,
* At present at the stage of draft international standard (29/294/DIS).
** Reference is given to ANSI B1.1 in the absence of an equivalent International Standard.
1094-4 ©IEC:1995 - 9 -
3 Definitions
of IEC 1094, the following definitions apply in addition to the definitions given
For the purpose of this part
in IEC 1094-1.
working standard microphone: Microphone capable of being calibrated by at least one of the
3.1
following:
a) a method specified in IEC 1094-2 or IEC 1094-3;
b) by comparison with a calibrated laboratory standard microphone;
c) by a sound calibrator as specified in IEC 942.
A working standard microphone meets ce rtain requirements on mechanical dimensions and electro-
acoustical characteristics, especially with respect to stability in time and dependence on environmental
conditions.
Line through the centre of and perpendicular to the diaphragm of
3.2 principal axis of a microphone:
the microphone.
Plane perpendicular to the principal axis immediately in front of
3.3 reference plane of a microphone:
the protection grid of the microphone.
effective front volume of a microphone: At reference conditions, the volume of air that has the
3.4
same acoustic compliance as the cavity bounded by the reference plane, the diaphragm and the outer
ace of the microphone at the reference plane, including the equivalent volume of the
cylindrical su rf
microphone configuration. The effective front volume is generally a function of frequency.
Specially shaped grid, substituted for the normal protection grid of a microphone,
3.5 correction grid:
for the purpose of changing the directivity response of the microphone, thereby changing the acoustical
classification of the microphone.
4 Reference environmental conditions
The reference environmental conditions are:
– temperature 23,0 °C
101,325 kPa
– static pressure
– relative humidity 50 %
NOTE - The reference temperature is chosen to be 23,0 °C because practical considerations require that most calibrations be
carried out at, or near, this temperature.
5 Classification of working standard microphones
5.1 General
The sound pressure in a given sound field will generally depend on position and should ideally be measured
at a point with a transducer of infinitesimally small dimensions and infinitely high acoustic impedance.
However, the finite dimensions and acoustic impedance of a real microphone, and the mounting of this
microphone cause practical measurements of sound pressure to depart from this ideal.
The effect of diffraction is accounted for by defining different sensitivities of a microphone each referring
to idealized sound fields, for example pressure, free-field, and diffuse-field sensitivities. A microphone is
usually so constructed that one of the above sensitivities is essentially independent of frequency in the
widest possible frequency range.
1094-4 ©IEC:1995 - 11 -
5.2 Type designation
Working standard microphones are described by a mnemonic system consisting of the letters WS (for
Working Standard) followed by a number representing the mechanical configuration and a third letter
representing the electroacoustical characteristic. The third letter may be P, F or D representing,
respectively, microphones having a pressure, free-field or diffuse field sensitivity, which is approximately
independent of frequency in the widest possible frequency range. The designation WS2P thus refers to a
working standard microphone of mechanical configuration 2 having a nearly constant pressure sensitivity
as a function of frequency.
The type designation does not always prevent the use of these microphones under other conditions, such
as pressure, free-field or diffuse field conditions after proper calibration.
6 Characteristics of working standard microphones
6.1 Sensitivity
The sensitivity of the microphone is the open-circuit sensitivity as defined in IEC 1094-1. If the insert voltage
technique is used to determine this sensitivity for type WS1 and WS2 microphones, the appropriate ground-
shield reference configuration given in IEC 1094-1 shall apply. For type WS3 the provisional ground-shield
reference configuration given in annex A is recommended.
NOTE - If the microphone is equipped with a protection grid, this will influence the free-field and diffuse field sensitivities. The
manufacturer should state whether the sensitivity has been specified with or without grid. By definition, the pressure sensitivity
of a microphone does not depend on the presence or absence of a protection grid. However, the sound pressure that is
measured in a small cavity with a microphone is influenced by the microphone grid.
6.2 Effective front volume
rtant quantity when the microphone is calibrated
The effective front volume of the microphone is an impo
with a sound calibrator (see 4.2 item d) of IEC 942) and when used in small couplers such as ear
simulators.
effective front volume shall be specified as a function of frequency in the frequency range from 160 Hz
The
to 1 000 Hz inclusive.
ective front volume are given in clause E.2 of annex E of IEC 1094-2
NOTE - Methods for determining the e ff
6.3 Upper limit of the dynamic range of a microphone
upper limit of the dynamic range shall be stated in terms of the sound pressure level which, throughout
The
the frequency range from 160 Hz to 1 000 Hz, results in a total harmonic distortion of 3 %.
NOTE - At present no generally accepted measuring method exist for determining this upper limit at frequencies above 1 000 Hz.
Linearity range of the microphone sensitivity level
6.4
The sensitivity level of the microphone at reference conditions shall not vary by more than 0,2 dB at any
frequency in the range from 160 Hz to 1 000 Hz when the sound pressure level varies within the range
specified in table 2, item 6.
NOTE - To determine the sensitivity level at the lowest sound pressure levels of the linearity range, narrow band filtering is
usually necessary. The bandwidth of the filter should be small enough to ensure that inherent noise in the measurement set-up
does not influence the result.
1094-4 ©IEC:1995 - 13 -
Static pressure dependence of microphone sensitivity
6.5
The sensitivity of the microphone depends on the static pressure which influences the impedance of the
air enclosed in the cavity behind the diaph
...
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