IEC 61094-1 pdf download Measurement microphones – Part 1: Specifications for laboratory standard microphones
This part of lEC 61094 specifies mechanical dimensions and certain electroacoustic characteristics for condenser microphones used as laboratory standards for the realizationof the unit of sound pressure and for sound pressure measurements of the highest attainable 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-laboratory
comparisons involving the calibration of the same microphones in different laboratories,andthe interchangeability of microphones in a given calibration system.
The following normative documents contain provisions which, through reference in this text,constitute provisions of this part of lEC 61094.For dated references, subsequent
amendments to, or revisions of, any of these publications do not apply. However parties toagreements based on this part of lEC 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 lSoand lEC maintain registers of currently valid lnternational Standards.
lEC 60050(801):1994, International Electrotechnical Vocabulary (IEV) -Chapter 801:Acoustics and electroacoustics
ASME B1.1:1989,Unified inch screw threads (UN and UNR thread form) 1
3Terms and definitions
For the purposes of this part of lEC 61094, the following definitions apply.
Remark -The underlined symbols are complex quantities.
microphone 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.
laboratory standard microphone
condenser microphone capable of being calibrated to a very high accuracy by a primarymethod such as the closed coupler reciprocity method, and meeting certain severe
requirements on mechanical dimensions and electroacoustical characteristics, especially withrespect to stability in time and dependence on environmental conditions
alternating voltage appearing at the electrical output terminals of a microphone as measuredby the insert voltage technique when the microphone is attached to the ground shield
configuration specified in 7.2 but is otherwise unloaded Unit : volt, V
NOTE 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 fufil the requirements of 7.2.
pressure sensitivity of a microphone
for 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 sound pressure 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 only
Unit: volt per pascal, V/Pa
pressure sensitivity level of a microphone
logarithm of the ratio of the modulus of the pressure sensitivity |Mpl to a reference sensitivity.The pressure sensitivity level in decibels is 20 Ig(Mp/ / M.), where the reference sensitivity Mis 1 V/Pa