Abstract： IEC 60318-3:1998 pdf free download.Electroacoustics - Simulators of human head and ear -Part 3: Acoustic coupler for the calibration of supra-aural earphones used in audiometry. 4 Construction 4.1 General The coupler, shown in figure 1, sha...

IEC 60318-3:1998 pdf free download.Electroacoustics - Simulators of human head and ear -Part 3: Acoustic coupler for the

calibration of supra-aural earphones used in audiometry.

4 Construction

4.1 General

The coupler, shown in figure 1, shall be made of a hard, stable, non-magnetic material, such as brass. The coupler consists

essentially of a cylindrical cavity whose acoustic reactance is that of a volume defined in 4.2. The base of the cylindrical cavity is usually formed by the diaphragm of a microphone of high mechanical impedance. The walls of the cavity should be sufficiently

rigid so that flexural vibration does not affect the output of the microphone.

4.2 Critical dimensions

4.2.1 The critical dimensions (see figure 1) of the coupler are those which determine the shape and volume of the cavity terminated by a condenser microphone, the capillary leak, the upper edge (lip) and the 450 angle.

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