BRUEL & KJAER 4212 Instructions And Applications page 25

By means of the set-up in Fig. 7 (page 10) it is possible to record automatically
the harmonics of the hearing aid output signal, by using the automatic switching
of the %-octave filters in the A.F. Spectrometer. The B.F.O., the Spectrometer,
. .
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QP 0123 10 100 1000 10000
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Fig. 13. Frequency response of a hearing aid at different sound levels.
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Fig. 14. Set-up for visual check ·on frequency characteristics of hearing aid
spectacles using the Frequency Response Tracer Type 4707. To show how the
hearing aid spectacles are placed in the Test Box, a sectional view of the Box
is given.
23