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AS 60118.9-2007 pdf free download
AS 60118.9-2007 pdf free download.Hearing aids Part 9: Methods of measurement of characteristics of hearing aids with bone vibrator output.
test frequency is more appropriate (so called high-tone hearing aids) 2500 Hz shall be used. If 2500 Hz is used this shall be clearly stated. If the acousto-mechanical sensitivity level available will not permit this, the full on gain control position of the hearing aid shall be used.
Basic force level frequency response curve
The output force level frequency response curve obtained with the gain control in the reference test gain position and with an input SPL of 60 dB
5 Test equipment
5.1 Equipment for the measurement of the output force level
The equipment used for measurement of OFL on the mechanical coupler produced by the
hearing aid, shall comply with the following requirements.
5.1.1 For all measurements a mechanical coupler in accordance with the second edition of IEC 60373 shall be used.
5.1.2 The output force level corresponding to hum, vibration, thermal agitation and other noise sources shall be sufficiently low to ensure that the reading shall drop at least 10 dB when the test signal is switched off
For this purpose a high-pass filter not affecting frequencies of 200 Hz and above may be employed.
5.1.3 The output indicator used shall give the r,m.s. indication within a tolerance of iO.5 dB at a signal crest factor of not more than 3.
NOTE I — Under certain conditions it is necessary to use a selective measuring system in order to ensure that the response of the hearing aid to the signal can be differentiated from inherent noise in the hearing aid. The use of the selective system should be stated in the report on test results
NOTE 2 — it Is well know that the type of output indicator employed may Influence the test results significantly if a non-sinusoidal voltage is being measured. Such non-sinusoidal voltages may be present when making measurements with high input levels.
5.1.4 The overall accuracy of the electronic measuring system following the mechanical coupler shall be within ±0,5 dB at a specified frequency.
5.1.5 The calibration of the mechanical coupler shall be in accordance with the second edition of IEC 60373.
NOTE — The calibration of the mechanical coupler should be repeated sufficiently often, preferably at least once a year, to ensure that it remains within the permitted limits during measurements.AS 60118.9-2007 pdf free download.
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