Page 12
The NEDSP1061 requires a signal of 50mV rms or
greater for optimum performance. Signals lower than this
may be used but the noise cancellation performance will
degrade, as the signal levels drops. If the unit is used
with low level microphones, the signal will need amplifying
before applying it to the NEDSP1061. The output level
can then be used to attenuate the signal back down to
the original signal level.
Figure 6. Signal levels.
Due to the adaptive nature of the noise cancellation a
small delay may be heard when the audio signal
changes. For optimum performance provide the module
with a constant signal, for example if the unit is installed
into a system employing a push to talk button - insert
the NEDSP1061 in to the audio path before the button.
Audio in
Audio out
Input signal level
Original signal level
NEDSP1061
635mV rms Max
Output level
Post processing
Pre processing
Gain = 1.7
>50mV rms
Page 13
4. Functions
4.1
Noise reduction levels.
8 levels of noise reduction are available. The amount of
noise and tone reduction is shown in the table below.
l
e
v
e
L
n
o
i
t
c
u
d
e
R
e
n
o
T
e
s
i
o
N
e
t
i
h
W
n
o
i
t
c
u
d
e
R
1
B
d
4
B
d
9
2
B
d
5
B
d
1
1
3
B
d
6
B
d
3
1
4
B
d
8
B
d
5
1
5
B
d
6
1
B
d
7
1
6
B
d
1
2
B
d
0
2
7
B
d
5
2
B
d
4
2
8
B
d
5
6
B
d
5
3
4.2
Setting different filter levels.
The levels are set by applying a BCD code to three
jumpers on the module. See the table on the following
page for more information. The positions of the jumpers
are shown in section 2.1 module layout.
Table 3. Tone and noise reduction levels.
