IEC 60318-1:1998 pdf download – Electroacoustics – simulators of human head and ear -Part 1: Ear simulator for the calibration of supra-aural earphones

IEC 60318-1:1998 pdf download – Electroacoustics – simulators of human head and ear -Part 1: Ear simulator for the calibration of supra-aural earphones.
IEC 60318-1 relates to the specification of an ear simulator which covers the frequency band 20 Hz to 10 000 Hz and is intended for calibrating supra-aural earphones used in audiometry and telephonometry applied to the ear without acoustical leakage.
NOTE — This device Is not intended for the calibration of circumaural earphones. However, IEC 60318-2 specIfies an adaptor for use wfth this ear simulator to provide an interim acoustic coupler for the calibration of a circumaural audiornetric earphone.
2 Normative reference
The following normative document contains provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the edition indicated was 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 indicated below. Members of IEC and ISO maintain registers of currently valid International Standards.
IEC 61094-4:1995, Measurement microphones — Part 4: Specifications for working stand4 microphones
3 Definitions
For the purpose of this International Standard, the following definitions apply.
ear simulator
device for the calibration of earphones which incorporates a calibrated microphone for the measurement of sound pressure and an acoustic coupler. The overall acoustic impedance of the simulator approximates that of the average human ear in a given frequency band
3.2
supra-aural earphone
earphone applied externally to the outer ear
3.3
circumaural earphone
earphone having a cavity large enough to cover the region of the head including the ear
4.3 Static pressure equalizer
A leak provided to equalize the pressure shall have an acoustic resistance R1 greater than
500 x 106 Pasm —3 and less than 10 9 Pasm —3. This leakage can be coupled to any one of the
three volumes. The sound pressure level difference, developed by a given voltage at the
earphone terminals with the hole plugged or left open, should not be greater than 0,2 dB at any
frequency between 100 Hz and 10 000 Hz.
4.4 Microphone
A microphone forms the base of cavity V1. The acoustic impedance of the microphone shall be high, the equivalent volume being less than 20 mm 3 over the specified range of frequencies. The overall pressure sensitivity of the microphone and associated measuring system over the specified frequency range shall be known with an uncertainty of less than ±0,2 dB for a coverage factor of k =2. The microphone shall be coupled to the volume V1 with a protective grid and with an adequate seal. The microphone shall conform with the requirements of lEG 61094-4 for a type WS2P microphone. The make and model of the microphone shall be specified.
4.5 Material
The ear simulator shall be constructed of a hard, stable, non-magnetic material such as brass.
4.6 Measurement plane
The plane of the microphone diaphragm shall be understood to represent the entrance of the mean human ear canal.
4.7 Example of design
A specific example of the ear simulator is shown in annex B.
5 Coupling of earphone to ear simulator
The earphone to be calibrated shall be applied to the ear simulator without acoustic leakage with a force 4,5 N ± 0,5 N, not induding the weight of the earphone itself. If, for a specific earphone, a different coupling force is specified this shall be stated.
The earphone shall not rest on the sloping side of the ear simulator, but only on the upper edge (or rim).
In the case of earphones with a hard earcap, a thin film of sealing material or thin soft rubber ring should be used on the lip In order to produce an effective seal between the earphone and the upper edge of the coupler.