The 4 stages of the Test Procedure
Using the telephone as a typical example, the basic stages in the test procedure are:
1) Setting up the Ear Simulator, e.g. as shown in Fig. 3
2) Calibration check using the G.R.A.S. 42AA Pistonphone with a special adapter for the 43AE
3) Placing the Ear Simulator over the earpiece of the telephone (see example in Fig. 4)
4) Applying a signal to the telephone and analysing the output from the microphone.
Depending on requirements, the signal applied to the telephone could be:
a swept tone, e.g. under laboratory conditions
pink noise, e.g. during mass production of telephones
Pink noise testing is usually quicker, and more economical, than using swept tones.
The following sections deal in more detail with each stage of the test procedure.
1: Setting up the Ear Simulator
Note: the terms generator and analyser refer to a set up which simultaneously sends the test
signal to the earphone and analyses the signal picked up by the Ear Simulator.
With the Ear Simulator assembled and everything switched on, proceed as follows:
1) 12AK Power Module
Connect the free end of the preamplifier cable to the Lemo
Input
socket.
Connect, via a suitable cable, the BNC
Output
to the input of the analyser.
Select
Lin
.
Select a
Gain
that is within the input range of the analyser.
2) Telephone
Connect the earphone of the telephone to the signal output of the generator.
3) Adjust the signal output level from the generator to lie within the normal working range of
the earphone.
Fig. 4.
Place the Ear Simulator centrally over the earpiece of the telephone
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LI0070 – 28 June 2017
