BRUEL & KJAER 1022 Instructions And Applications page 38

loooooooooooooooooooooooooooooo~
BrDel
&
KJ .. r
+
&ool &
KJGt
" - 50 2.5
Mem.lringObjoct: _ _ _
db db
Sound
transmission
4020
anallsls
USing
2020
Slave F1lter
3.16 Hz
30 15
Bandwidth
20 10
R.c;No:
Dalt:
Sign.:
Roct;
RMS
Z.OIM;
10 5
LU..Fr;
20
Pot:
so
Wr. Sp.:
8
Papo< Sp.:
0.1
Muhtplyfr.q.
Scaleby;_1_
0 0
50
100 200 500 1000
2000
5000
QP1123
100 1000
Fig.5.17. Sound transmission analysis using a Heterodyne
Slave Filter 2020 with 3.15 Hz bandwidth
1
0000
10 000
Experimental results obtained for a receiving room where a high level of
background noise was present are shown in Fig.5.17. and 5.18. The results
obtained using the
2020
(Fig.5.17.) show a considerable improvement in
signal to noise compared to those obtained with no filter (Fig.5.18.).
Note: To ensure that the compressor circuit is controlled from the funda-
mental of the sound source, another 2020 could
be
used with the 2606 in
the compressor loop.
Automatic Recording of Harmonics in Hearing Aids
Another use of the Heterodyne Slave Filter with the 1 022 is shown
below. The
2020
can be used for frequency rejection whereby it will reject
frequencies by over 40 dB over a 3.15 Hz bandwidth.
38