Operation - BRUEL & KJAER 4212 Instructions And Applications

Operation.
In Fig. 7 is shown a complete measuring arrangement for automatic recording
of frequency characteristics of hearing aids. The loudspeaker is fed from
the BFO the output of which is regulated by means of the amplified output
voltage from the regulating microphone. As microphone amplifier is employed
the Microphone Amplifier Type 2603. By varying the gain of this and adjusting
the input potentiometer for the compressor in the BFO, the sound level in
the Test Box may be adjusted to any value between 50 and 90 db SL.
10
210S
f6(8.t,2
Fig. 7. Set-up for ' a utomatic recording of the frequency craracteristic of
hearing aids.