Power Supply - BRUEL & KJAER 4212 Instructions And Applications

To reduce the effect of disturbing signals, a great amount of which is found
to consist of frequencies b elow 150Hz
(ci s), a high pas
s filter is inserted in
series with the microphone in the artifical ear. A smilar filter is also used
in the regulating microphone circuit to avoid faulty level regulations to take
place. The filters introduce an overall attenuation of o.5 db.
If it is desired to use the artificial ear without filter, a switch on the back of
the Test Box enables the filter in the artificial ear circuit to be switched out.
Power Supply.
The power necessary to drive the Cathode Followers and the Microphone
Cartridges is supplied from the associated Microphone Amplifier via the
multicore cables.
The loudspeaker terminals are connected to the socket on the back of the
Test Box.
Flexible connect ing tube mounted
on adapter. The adopter is in this
case replacing the ear insert.
2 cmJ coupler used for
free f ield measurement
on spectacle-type hearing aid
Adaptor provided with
hole for ear insert
Example of mounting of
earpiece in 2cml
coupler
Fig. 6b. Typical mounting of different ear insert arrangements in the
2
cc
coupler of the Artificial Ear. The special adaptors shown are not produced by
Briiel
&
Kjrer, but should be made by the user to meet his specific demand.
9