asterisk users - Jan 2008 - Background Noise Elimination

Greetings!

We have a somewhat noisy background in our call center, and I'd like  
to reduce this. Obviously, we could plaster the walls with sound  
absorbing material, but is there anything we can do in software  
either using any algorithms for our open source-based SIP library or  
inside Asterisk itself? Related to this, anyone have a good source  
for good panels?

We are using Plantronics noise canceling headsets, which don't really  
seem to work all that well. Our ancient system handled noise much  
better, but I suspect that was partly due to the Dialogic ADPCM  
algorithm used that just reduced the intelligibility of lower volume  
noises in general. We are using PCMU direct from the agent's mic to  
through Asterisk to PRIs, so we don't "suffer" from compression  
artifacts. The down side, is that you can make out even very quiet  
conversations in the background (like 3 agents to one side.)

How have people handled this? I'm experimenting with a noise gate  
that will lower the volume when the agent isn't talking, but that  
won't help when the agent is talking.

Norman Franke
ASD, Inc.

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Norman Franke wrote:
> Greetings!
> 
> We have a somewhat noisy background in our call center, and I'd like to
> reduce this. Obviously, we could plaster the walls with sound absorbing
> material, but is there anything we can do in software either using any
> algorithms for our open source-based SIP library or inside Asterisk
> itself? Related to this, anyone have a good source for good panels?
> 
> We are using Plantronics noise canceling headsets, which don't really
> seem to work all that well. Our ancient system handled noise much
> better, but I suspect that was partly due to the Dialogic ADPCM
> algorithm used that just reduced the intelligibility of lower volume
> noises in general. We are using PCMU direct from the agent's mic to
> through Asterisk to PRIs, so we don't "suffer" from
compression
> artifacts. The down side, is that you can make out even very quiet
> conversations in the background (like 3 agents to one side.)
> 
> How have people handled this? I'm experimenting with a noise gate that
> will lower the volume when the agent isn't talking, but that won't
help
> when the agent is talking.
Nah, there's nothing really.

The noise gate is your best bet.  I would assume that while an agent is
talking the customer will be listening to the agent, so the background
noise will hardly be noticeable.

The issue is, while two people are talking its pretty hard to remove
just one of them from a wave file.

Try the noise gate and see how you go.

Oh, you might want to try a downwards expander instead (a noise gate but
with ratio as well as threshold).

- --
Kind Regards,

Matt Riddell
Director
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