IEC TS 60318-7:2011 pdf – Electroacoustics – Simulators of human head and ear – Part 7: Head and torso simulator for the measurement of hearing aids.
NOTE Occluded ear simulators differing in detail from that specified in IEC 60318.4, are in current use in aoviie countries, If such devices axe used as pail of the ear Simulator. their characteristics should be staled when giving results 01 measurements of hearing aids or other devices under test made with the head and tOrso simulator.
4.2.5 MaterIals
The manikin shall have a non-porous surtace. with an acoustic impedance which is large compared to that of air, and be of a material which ensures dimensional stability.
The pinna simulator shall be made from a high-quality elastomer. It is recommended that its shore-QO hardness, measured at the surface 15 mm forward to the ear opening, is 35° ± 6°. providing that it conforms with the acoustical specifications (see 4.3). Since the mechanical properties of elastomer materials are likely to change over time, a time period shall be specified for individual pinna simulators (e.g. by means of an expiration date), over which the mechanical characteristics of the material are expected to remain in compliance with this specification.
NOTE Type 0, pinna simulator used for the measurement of a device should be stated together with the test rult
4.2.6 MarkIngs To facilitate azimuth alignment, the torso shall, at the waist, be equipped with markings indicating the direction of 0° azimuth. If the head is removable from the torso, both shall be provided with markings to ensure correct alignment. To assist reproducible placement of hearing aids or other devices under test in and around the pinna, the head surfaces in the immediate vicinity of the pinnae may be equipped with coordinate axis markings. The coordinate axes should be parallel to the axis of rotation (y-axis) and the manikin reference plane (x-axis) respectively, and have the ear canal entrance point (EEP) as their origin. Values on the x-axis shall be positive towards the front of the manikin, on the y-axis positive towards the vertex.
4.2.7 Tolerances
The tolerance on a point of a cross-section relative to contours in the figures shall be ± 4 mm for the torso (Figures 4a) to 4e)), ± 2.5 mm for the head (Figures 5a) to Se)) and ± 1,5 mm for the pinna (Figures 7a) to 7c)). These tolerances also apply for the distance between cross- sections and the reference plane of the manikin.
4.3 AcoustIcal characteristics of the manikin
4.3.1 Free field frequency response
Table 3 gives the manikin free field frequency response for pure tones at third octave intervals, in decibels relative to the free field sound pressure level. Values are stated for an elevation angle of 0°. and the azimuth angles 0°, 90°, 180° and 270° for the right ear. Corresponding symmetrical azimuth angles apply for the left ear.
NOTE I Difficulties nay be experienced when measuring the manikin frequency response at azimuth angle 270° for frequencIes 01 4 kHz and above. This Is due to a combination of reflections from me boundarieS of the test
enclosure, and the head shadow &lect, Hence these values have been omitted in Table 3
NOTE 2 The data in Table 3 are based on the studies by Uaswell and Burfvhard (101 and by Uijnster.Swendsen (l2j. Tb results of Iwo subsequent studies on the manikin are dscribed in (131 and (17),
4.3.2 Tolerances
Tolerances on the manikin free field frequency response are stated in Table 3. The values stated Include the tolerances in the calibration of the occluded ear simulator, but not in the calibration of the free held microphone.
5.2 CalibratIon method
5.2.1 General
Measurement of acoustical characteristics of the manikin shall be performed with equipment conlorming to the following specifications.
5.2.2 Test space and measurement equipment
The test space and Sound source shall provide an approximation to plane progressive waves in free field conditions in the frequency range 100 Hz to 10 000 Hz.
These conditions are deemed to exist if the sound pressure levels measured at distances of 250 mm from the test point do not deviate from the sound pressure level at the test point by more than ± 2 dB. The measurement points for testing compliances shall include two points on the test axis, respectively towards and away from the sound source. Four further measurement points in the test plane shall be Included: two in the reference plane, to the left and right as viewed from the Sound source: the other two on the axis of rotation, above and below the test point.