CASE STUDIES
The following case studies describe just three of the ways in which you can use
the DNS1500. You can apply the DNS1500 equally to recorded signals and to
‘live’ signals at the point of recording or transmission.
1.
SUPPRESSING TRAFFIC NOISE
The DNS1500 can suppress background noises such as road traffic, aircraft, air
conditioning, wind, rain, and many other common soundstage, location, and OB
problems that contaminate audio. If your signal exhibits any of these problems,
you can suppress them as follows.
First, identify the frequency range(s) in which the noise lies.
You should be able to do this by listening to the problem. However, if this proves
difficult, you can use the following method.
It is not important that you find the perfect settings at the first attempt. In
particular, you will be able to refine your Level and Band Gain settings once you
have found the correct range.
Begin as follows:
Select the correct channel(s)
Ensure that the DNS1500 is not in Bypass
Select Full Range
•
Set all six Band Gain controls to -24dB
•
Raise the Level control until the noise disappears
At this point you have determined an approximate setting for the Level. This is
necessary for determining the range but it is likely that you will refine this later in
the procedure.
When the Level is close to the ideal setting, you should see the Activity LEDs
flicker in response to the signal content.
Now continue as follows:
•
Raise the Band Gain controls to 0dB (no processing occurs)
•
Adjust the Band Gain controls to suppress the noise
You should always attempt to suppress the noise with the minimum of damage to
the desired signal.
In all likelihood, you will find that the leftmost Band Gain controls are pulled down
significantly, whereas the central and rightmost are close to 0dB. This tells you
that the problem does not lie in the upper frequencies, so you should use the
Range Selector to select Low+Mid. Then repeat the steps marked “•”.
If you now find that you are using all six faders in similar fashion, it is likely that
the noise is distributed across the entire Low+Mid range. However, if the
suppression is still heavily biased towards the left hand faders, you should now
select the Low range alone and repeat the procedure.
If you select Low alone and cannot suppress the noise, it is probable that there is
considerable noise energy in the Mid band, so you should return to using
Low+Mid ranges.
For many problems such as traffic noise, the noise will lie primarily in the range
50Hz - 1.5kHz. In this case, Low+Mid will be the correct choice.
Second, optimise the Level control.
Listening carefully to the audio, refine the Level setting so that the noise is
correctly identified without introducing audible artefacts. If this proves difficult,
you can return the Band Gain controls to -24dB for this stage.
The DNS1500 takes a short period to “settle” after moving the Level control
(especially in the lower ranges) so you should not adjust it rapidly.
Third, refine the Band Gain controls for optimum suppression.
Set all six Band Gain controls to 0dB. Now increase and decrease the Gain in
each band separately while listening to the effect that each has on the noise. This
will identify the bands that contain the majority of the noise. (Do not be alarmed if
all six bands contain significant noise. This is not unusual.)
Let’s assume that the
greatest improvement occurs
when you reduce the Gain in
bands 3 and 4. This
suggests that the noise is
concentrated in an
approximate range of 200Hz
to 1kHz. You should now find
the optimum positions for all
six faders. The greatest cuts
will lie in bands 3 and 4,
whereas bands 1, 2, 5 and 6
should remain as close to
0dB as possible to ensure
that minimal signal damage
occurs in the bands that do
not contain much noise.
The final configuration may
look like this:
