EN 61094-1:2000

Measurement microphones - Part 1: Specifications for laboratory standard microphones

Specifies mechanical dimensions and certain electroacoustic characteristics for condenser microphones used as laboratory standards for the realization of the unit of sound pressure and for sound pressure measurements of the highest attainable accuracy. The specifications are intended to ensure that primary calibration by the reciprocity method can be readily carried out. Establishes a system for classifying laboratory standard condenser microphones into a number of types according to their dimensions and properties.

Messmikrofone - Teil 1: Anforderungen an Laboratoriums-Normalmikrofone

Microphones de mesure - Partie 1: Spécifications des microphones étalons de laboratoire

Spécifie les dimensions mécaniques et certaines caractéristiques électroacoustiques des microphones à condensateur utilisés comme étalons de laboratoire pour la réalisation de l'unité de pression acoustique et pour les mesures de pression acoustique faites avec la meilleure exactitude possible. Les spécifications sont destinées à assurer que l'étalonnage primaire par la méthode de réciprocité puisse facilement être mis en oeuvre. Etablit un système de classement des microphones à condensateur utilisés comme étalons de laboratoire en un certain nombre de types, selon leurs dimensions et leurs propriétés.

Measurement microphones - Part 1: Specifications for laboratory standard microphnes (IEC 61094-1:2000)

General Information

• Status: Published
• Publication Date: 20-Nov-2000
• Withdrawal Date: 31-Aug-2003
• ICS: 17.140.50 - Electroacoustics
• Technical Committee: CLC/SR 29 - Electroacoustics
• Drafting Committee: IEC/TC 29 - IEC_TC_29
• Parallel Committee: IEC/TC 29 - IEC_TC_29
• Current Stage: 6060 - Document made available - Publishing
• Start Date: 21-Nov-2000
• Completion Date: 21-Nov-2000
• Ref Project: SIST EN 61094-1:2001 - Measurement microphones -- Part 1: Specifications for laboratory standard microphones

Overview

EN 61094-1:2000 (CLC adoption of IEC 61094-1:2000) defines the specifications for laboratory standard condenser measurement microphones used for realizing the unit of sound pressure and for the most accurate sound pressure measurements. The standard sets mechanical dimensions, electroacoustic characteristics and a classification system to ensure reliable reciprocity calibration and interchangeability of laboratory reference microphones.

Key topics and technical requirements

• Scope and purpose: Requirements are intended for condenser microphones used as laboratory standards for primary calibration and high-accuracy sound pressure measurement.
• Reference environmental conditions: 23 °C, 101 325 Pa (static pressure), 50 % relative humidity - used as the baseline for declared characteristics.
• Type designation: A mnemonic system (LS + number + letter) classifies microphones by mechanical configuration and electroacoustic behaviour. Example: LS2P = laboratory standard, mechanical type 2, P for pressure-type sensitivity.
• Sensitivity definitions: Precise definitions and units for open-circuit voltage, pressure sensitivity, free-field sensitivity and diffuse-field sensitivity are provided to ensure consistent calibration and reporting.
• Acoustic and electrical impedance: Acoustic impedance must be specified as a function of frequency; electrical impedance is defined for the ground-shield connection required for measurements.
• Environmental dependencies & stability:
  • Static pressure, temperature and humidity coefficients (dB/Pa, dB/K, dB/% RH) to quantify sensitivity changes.
  • Stability coefficients: long-term (systematic drift, dB/year) and short-term (standard deviation over 10 days, dB).
• Mechanical and identification requirements: Mandatory mechanical dimensions, ground-shield reference configuration (see clause 7.2) and marking for traceability.
• Calibration readiness: Specifications facilitate primary reciprocity calibration (see IEC 61094-2 and IEC 61094-3 for methods).

Applications and users

• Calibration laboratories performing primary reciprocity calibration of microphones.
• National metrology institutes and acoustic labs establishing or maintaining acoustic reference standards.
• Manufacturers of measurement microphones and preamplifiers who need to design devices compatible with laboratory standards and ground-shield configurations.
• Acoustic consultants and research facilities requiring traceable, high-accuracy sound pressure measurements in free-field, diffuse-field or pressure conditions.

Related standards

• IEC 61094 series (Parts 2 & 3): reciprocity calibration methods.
• IEC 60050 (801): acoustics and electroacoustics terminology.
• Referenced mechanical standard: ASME B1.1 (for thread forms) as noted in the standard.

Keywords: EN 61094-1:2000, measurement microphones, laboratory standard microphones, condenser microphones, reciprocity calibration, sound pressure, acoustic impedance, microphone sensitivity, LS microphone classification.

Standards Content (Sample)

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Measurement microphones - Part 1: Specifications for laboratory standard microphnes (IEC 61094-1:2000)Messmikrofone -- Teil 1: Anforderungen an Laboratoriums-NormalmikrofoneMicrophones de mesure -- Partie 1: Spécifications des microphones étalons de laboratoireMeasurement microphones -- Part 1: Specifications for laboratory standard microphones33.160.50PriborAccessories17.140.50ElektroakustikaElectroacousticsICS:Ta slovenski standard je istoveten z:EN 61094-1:2000SIST EN 61094-1:2001en01-september-2001SIST EN 61094-1:2001SLOVENSKI
STANDARD
NORMEINTERNATIONALECEIIECINTERNATIONALSTANDARD61094-1Deuxième éditionSecond edition2000-07Microphones de mesure –Partie 1:Spécifications des microphones étalonsde laboratoireMeasurement microphones –Part 1:Specifications for laboratory standardmicrophones Commission Electrotechnique Internationale International Electrotechnical CommissionPour prix, voir catalogue en vigueurFor price, see current catalogueÓ IEC 2000
Droits de reproduction réservés
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Copyright - all rights reservedAucune partie de cette publication ne peut être reproduite niutilisée sous quelque forme que ce soit et par aucun procédé,électronique ou mécanique, y compris la photocopie et lesmicrofilms, sans l'accord écrit de l'éditeur.No part of this publication may be reproduced or utilized inany form or by any means, electronic or mechanical,including photocopying and microfilm, without permission inwriting from the publisher.International Electrotechnical Commission3, rue de Varembé
Geneva, SwitzerlandTelefax: [phone]e-mail: [e-mail] IEC web site
http://www.iec.chCODE PRIXPRICE CODENSIST EN 61094-1:2001

61094-1 Ó IEC:2000– 3 –CONTENTSPageFOREWORD .5Clause1Scope.72Normative references.73Terms and definitions.74Reference environmental conditions.135Classification of laboratory standard microphone.135.1General.135.2Type designation.156Characteristics of laboratory standard microphones.156.1Sensitivity.156.2Acoustic impedance.156.2.1General.156.2.2Equivalent volume of a microphone.156.3Upper limit of the dynamic range of a microphone.176.4Static pressure dependence of microphone sensitivity.176.5Temperature dependence of microphone sensitivity.176.6Humidity dependence of microphone sensitivity.176.7Electrical insulation resistance.196.8Stability of microphone sensitivity.196.9Pressure-equalizing leakage.197Specifications.197.1Mechanical dimensions.197.2Ground shield reference configuration.237.3Electroacoustical specifications.257.4Identification markings.27SIST EN 61094-1:2001

61094-1 Ó IEC:2000– 5 –INTERNATIONAL ELECTROTECHNICAL COMMISSION____________MEASUREMENT MICROPHONES –Part 1: Specifications for laboratory standard microphonesFOREWORD1)The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprisingall national electrotechnical committees (IEC National Committees). The object of the IEC is to promoteinternational co-operation on all questions concerning standardization in the electrical and electronic fields. Tothis end and in addition to other activities, the IEC publishes International Standards. Their preparation isentrusted to technical committees; any IEC National Committee interested in the subject dealt with mayparticipate in this preparatory work. International, governmental and non-governmental organizations liaisingwith the IEC also participate in this preparation. The IEC collaborates closely with the InternationalOrganization for Standardization (ISO) in accordance with conditions determined by agreement between thetwo organizations.2)The formal decisions or agreements of the IEC on technical matters express, as nearly as possible, aninternational consensus of opinion on the relevant subjects since each technical committee has representationfrom all interested National Committees.3)The documents produced have the form of recommendations for international use and are published in the formof standards, technical specifications, technical reports or guides and they are accepted by the NationalCommittees in that sense.4)In order to promote international unification, IEC National Committees undertake to apply IEC InternationalStandards transparently to the maximum extent possible in their national and regional standards. Anydivergence between the IEC Standard and the corresponding national or regional standard shall be clearlyindicated in the latter.5)The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for anyequipment declared to be in conformity with one of its standards.6)
Attention is drawn to the possibility that some of the elements of this International Standard may be the subjectof patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.International Standard IEC 61094-1 has been prepared by IEC technical committee 29:Electroacoustics.This second edition cancels and replaces the first edition and corrigendum published in 1992.This second edition constitutes a technical revision.The text of this standard is based on the first edition, the corrigendum and the followingdocuments:FDISReport on voting29/452/FDIS29/461/RVDFull information on the voting for the approval of this standard can be found in the report onvoting indicated in the above table.This publication has been drafted in accordance with the ISO/IEC Directives, Part 3.The committee has decided that this publication remains valid until 2005. At this date, inaccordance with the committee’s decision, the publication will be:· reconfirmed;· withdrawn;· replaced by a revised edition, or· amended.SIST EN 61094-1:2001

61094-1 Ó IEC:2000– 7 –MEASUREMENT MICROPHONES –Part 1: Specifications for laboratory standard microphones1 ScopeThis part of IEC 61094 specifies mechanical dimensions and certain electroacousticcharacteristics for condenser microphones used as laboratory standards for the realizationof the unit of sound pressure and for sound pressure measurements of the highestattainable accuracy. The specifications are intended to ensure that primary calibration bythe reciprocity method can be readily carried out.This part also establishes a system for classifying laboratory standard condenser micro-phones into a number of types according to their dimensions and properties in order tofacilitate the specification of calibration methods, the conducting of inter-laboratorycomparisons involving the calibration of the same microphones in different laboratories, andthe interchangeability of microphones in a given calibration system.2 Normative referencesThe following normative documents contain provisions which, through reference in this text,constitute provisions of this part of IEC 61094. For dated references, subsequentamendments to, or revisions of, any of these publications do not apply. However parties toagreements based on this part of IEC 61094 are encouraged to investigate the possibility ofapplying the most recent editions of the normative documents indicated below. For undatedreferences, the latest edition of the normative document referred to applies. Members of ISOand IEC maintain registers of currently valid International Standards.IEC 60050(801):1994, International Electrotechnical Vocabulary (IEV) – Chapter 801:Acoustics and electroacousticsASME B1.1:1989, Unified inch screw threads (UN and UNR thread form) 13 Terms and definitionsFor the purposes of this part of IEC 61094, the following definitions apply.Remark – The underlined symbols are complex quantities.3.1condenser microphonesmicrophone that operates by variation of electrical capacitance[IEV 801-26-13].NOTE
Only condenser microphones operating by a virtually constant charge obtained from an external polarizingvoltage applied from a source of suitably high internal resistance are considered.——————— 1(American Society of Mechanical Engineers) Reference is given to ASME B1.1 in the absence of an equivalentinternational standard.SIST EN 61094-1:2001

61094-1 Ó IEC:2000– 9 –3.2laboratory standard microphonecondenser microphone capable of being calibrated to a very high accuracy by a primarymethod such as the closed coupler reciprocity method, and meeting certain severerequirements on mechanical dimensions and electroacoustical characteristics, especially withrespect to stability in time and dependence on environmental conditions3.3open-circuit voltagealternating voltage appearing at the electrical output terminals of a microphone as measuredby the insert voltage technique when the microphone is attached to the ground shieldconfiguration specified in 7.2 but is otherwise unloadedUnit: volt, VNOTE
Owing to the capacitive nature of the microphone, the voltage at the electrical terminals depends on the electricalload presented by the mechanical and electrical attachment of the microphone to a preamplifier. For this reason,preamplifiers used for measuring the open-circuit voltage of a microphone should fulfill the requirements of 7.2.3.4pressure sensitivity of a microphonefor a sinusoidal signal of given frequency and for given environmental conditions, the quotientof the open-circuit voltage of the microphone by the sound pressure acting over the exposedsurface of the diaphragm (i.e. at the acoustical terminals of the microphone), the soundpressure being uniformly applied over the surface of the diaphragm. This quotient is acomplex quantity, but when phase information is of no interest the pressure sensitivity maydenote its modulus onlyUnit: volt per pascal, V/Pa3.5pressure sensitivity level of a microphonelogarithm of the ratio of the modulus of the pressure sensitivity |Mp| to a reference sensitivity.The pressure sensitivity level in decibels is 20 lg (|Mp| / Mr), where the reference sensitivity Mris 1 V/PaUnit: decibel, dB3.6free-field sensitivity of a microphonefor a sinusoidal plane progressive sound wave of given frequency, for a specified direction ofincidence, and for given environmental conditions, the quotient of the open-circuit voltage ofthe microphone by the sound pressure that would exist at the position of the acoustic centreof the microphone in the absence of the microphone. This quotient is a complex quantity, butwhen phase information is of no interest, the free-field sensitivity may denote its modulus onlyUnit: volt per pascal, V/PaNOTE 1
At frequencies sufficiently low for the disturbance of the sound field by the microphone to be negligible,the free-field sensitivity approaches the pressure sensitivity (see 6.9 for practical limitations).NOTE 2
The position of the acoustic centre is a function of frequency.3.7free-field sensitivity level of a microphonelogarithm of the ratio of the modulus of the free-field sensitivity |Mf| to a reference sensitivity.The free-field sensitivity level in decibels is 20 lg (|Mf| / Mr), where the reference sensitivity Mris 1 V/PaUnit: decibel, dBSIST EN 61094-1:2001

61094-1 Ó IEC:2000– 11 –3.8diffuse-field sensitivity of a microphonefor a sinusoidal signal of given frequency in a diffuse sound field and for given environmentalconditions, the quotient of the open-circuit voltage of the microphone by the sound pressurethat would exist at the position of the acoustic centre of the microphone in the absence of themicrophoneUnit: volt per pascal, V/PaNOTE 1
At frequencies sufficiently low for the disturbance of the sound field by the microphone to be negligible,the diffuse-field sensitivity approaches the pressure sensitivity (see 6.9 for practical limitations).NOTE 2
The position of the acoustic centre is a function of frequency.3.9diffuse-field sensitivity level of a microphonelogarithm of the ratio of the modulus of the diffuse-field sensitivity |Md| to a referencesensitivity. The diffuse-field sensitivity level in decibels is 20 lg (|Md| / Mr), where thereference sensitivity Mr is 1 V/PaUnit: decibel, dB3.10electrical impedance of a microphonefor a sinusoidal signal of given frequency, the complex quotient of the voltage applied acrossthe electrical terminals of the microphone by the resulting current through those terminals.The microphone shall be connected to the ground-shield configuration specified in 7.2Unit: ohm, WNOTE
This impedance is a function of the acoustical load on the diaphragm.3.11acoustic impedance of a microphonefor a sinusoidal signal of given frequency, the complex quotient of the sound pressure by thevolume velocity at the diaphragm, the sound pressure being uniformly distributed over thesurface of the diaphragm and the electrical terminals being loaded with an infinite impedanceUnit: pascal second per cubic metre, Pa×s/m³3.12static pressure coefficient of microphone pressure sensitivity levelfor a given frequency, the quotient of the incremental change of pressure sensitivity level bythe incremental change in static pressure producing the change in sensitivityUnit: decibel per pascal, dB/PaNOTE
The static pressure coefficient is a function of frequency as well as static pressure.3.13temperatu
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