7.3. SOUND RECORDING
Use stereo recording without compression at 16, 32 or 48 kHz sampling rate if possible. Stereo
recording provides speech intelligibility even in noisy conditions.
Mono recording enables you to record longer sound signals.
Use manual gain level adjustment if possible (Section 7).
In order to avoid useful signal loss, use voice activation mode (Section 7) only if signal level is
stable.
Place microphones as close to the useful signal (speech) source as possible and as far from the
acoustic and electromagnetic noise sources as possible. The closer the microphones are placed to
the acoustic signal (speech) source, the smaller is reverberation (echo), and the higher is gain level
and speech intelligibility.
External microphones are more sensitive and at the same time can be easily concealed (under
jacket’s lapel, shirt’s collar, on the cuff). The distance between external microphones should be
more than 15 cm.
Try to place microphones in such a way as to avoid vibration, impact and rubbing against other
surfaces.
Avoid permanent contact of the voice recorder’s box or external microphones with rough or metal
surfaces (such as table plate, car, concrete structures).
If the mono recording mode is active, the left channel signal will be recorded.
Make a test recording if possible, to be sure that the voice recorder and microphones are correctly
set, and that gain and voice activation levels are adjusted correctly.
To conceal the sound recording process and/or avoid record suppression by special devices (HF
generators) try to keep the voice-recorder with its backside to a supposed detector and/or suppressor.
Automatically switching LCD off is also a good choice in this case. Besides, note that using built-in
microphones greatly decreases the probability of recorder detection.
7.3.2
Manually switching sound recording on/off
You may switch the recording on/off both manually and automatically. If external microphones
are used during sound recording, the microphone switch must be set in the
“EXT”
position (Fig. 6.1
p.6). To switch sound recording on manually, set the switch on the recorder body (or on the remote
control unit) to
“REC”
or
”ON”
(Fig. 6.1 p.3). The
”REC”
message will appear on the screen after
recording is switched on. Record time counter will appear instead of the maximum record duration.
To switch sound recording off, you should set the switch on the recorder (or on the remote control
unit) to
“STOP”
or
“OFF”
(Fig. 6.1 p. 3). The voice recorder will return to the parameters menu.
7.3.3
Voice activation mode (
VA
)
To record sound using voice activation (VA) you should enable this mode (see Section 7) and
define the start/stop recording threshold. If you use VA, Gnome-2M
c
will only record signals ex-
ceeding the defined threshold level. This threshold is displayed as a black arrow (
↓
) To set the
threshold in the “VA” menu select “Level”.
key sets the threshold to 0 dB. The keys
and
disable voice activation mode. To
save VA settings use
key. To adjust threshold value use
and
keys.
Note that even after the signal level gets lower than the threshold value, recording still goes on
for the given period of time (by default for ten seconds). To specify this period of time in the “VA”
menu select “Time”.
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