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[asterisk-users] Background Noise Elimination


 
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matt at venturevoip.com
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PostPosted: Mon Jan 07, 2008 7:19 pm    Post subject: [asterisk-users] Background Noise Elimination Reply with quote

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Norman Franke wrote:
Quote:
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
_______________________________________________

http://www.venturevoip.com (Great new VoIP end to end solution)
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jjones at danrj.com
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PostPosted: Tue Jan 08, 2008 8:30 am    Post subject: [asterisk-users] Background Noise Elimination Reply with quote

On Jan 7, 2008, at 6:19 PM, Matt Riddell wrote:

Quote:
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Norman Franke wrote:
Quote:
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).


We have an IP600 located in our colo, a very noisy environment. For a
spooky experience make a phone call and pass the call through a
Ditech audio processor in the path of the PRIs. You will hear no
background noise. You can even use the speakerphone. Even Polycom to
Polycom is not too bad. But an all IP path to anything else and you
cant hardly hear the other person.
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