SC4x0 Technical manual
Page 17 of 34
SeaCom
Rev
2.00
7. Audio path & voice control
Below a schematic of the audio path is shown.
All audio is passed through the codec for signal processing. Volume control of the speakers and pre-
gain control of the microphones are all made via processor control. There are no mechanical
adjustable.
All microphone inputs are balanced inputs for maximum noise suppression.
7.1 Acoustic considerations
To select the right setup for the installation is important to optimum sound quality.
In general, hands free works best in quiet areas, but if an external speaker is added it could be
functional in areas with moderate ambient noise.
If installed in areas with a very high level of ambient noise, headset is the only right solution.
Care should be taken to select headset or handset capable when making installations in high noise
areas.
If the microphone sensitivity is too high, it might suffer from signal saturation or cause the input to
suffer for saturation.
Location Ambient
noise
level
Operation
Bridge, Offices, Mess, etc Low
Hands free, handset.
Voice control: 10dB .. 25dB
ECR, Galley, SCC
Medium
Hands free, handset, possibly assisted by
external speaker.
Voice control: 30dB .. 40dB
ER, SGR, Generator
High
Handset, headset.
Thruster, Hydraulics
Very high
Headset and in some cases handset.
7.2 Voice control considerations
To get optimum performance from the automatic voice control when using hands free, the level of
speech must be approx. 10dB above background noise level. If not, voice control cannot detect voice
from noise and thus control direction of speech.
This is very important when using headset or hands free in every noisy areas, especially when using
headset in extreme noisy areas in one end and hands free at the other end, even more if combined
with VOX for the headset.
To be able to go above the background noise level, may require a high sound pressure that will
saturate the microphone input if the microphone is too sensitive or if the gain is too high.
Line
Handset
Handset
Local
Local
Headset
Headset
Ext. speaker
CODEC
yP control
