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7937 Audio Quality

I have multiple Cisco 7937G conference station along with Mic-Kits for larger rooms installed in offices. When we make a call from the 7937 conference phone the person on the other end describes the caller sounds like thinny, hollow sound and very slightly muffled

The version of code of the conference phones is 1.4(5.7). I have previously upgraded the code to this from 1.4.(4) but there was no difference that I can see.

Conference Room

Worth noting at this point is that we are aware that the conference room acoustics are not ideal. It contains a lot of glass and thin walls and sounds quite hollow just by standing and speaking in the room.

What I am trying to identify is if there is a scientific measurement or values that we can take to see how affected the phone quality is by the room structure?

Also, is there anything I can do to make it sound better, like using specific codecs only. Calls out to the PSTN use g.711mu which is affected by the hollow thinny sound. Some of our ON-Net calls are negotiating to g.729 or even g.711 and also sound similar as above to the PSTN call.

The only call which is not affected is the local LAN calls (or intra-region calls) which will negotiate g.722 codec and this sounds very clear at both ends and does not seem to be affected by the hollow thinny sound...

Is there a way to force inter-site calls across a WAN to negotiate G.722 at all times? All phones in this case would be either a 7937, 7962 or 7942?

Thanks

1 REPLY
Cisco Employee

7937 Audio Quality

Hi,

You are correct, the room acoustics are not ideal as per the following

http://tools.cisco.com/Support/BugToolKit/search/getBugDetails.do?method=fetchBugDetails&bugId=CSCud78163

Enhance echo cancellation capabilities on 7937

Symptom:

Enhancement Request to improve the echo cancellation behavior on 7937 when installed at conference rooms with high acoustics.

Conditions:

Conference rooms with large glass walls would cause high acoustics.

Workaround:

Covering the glass walls with blinds and usage of dampeners would reduce the acoustics

You can try the workaround above by placing dampeners on the glass walls and also by placing some static objects like flower pots, white boards, etc in the room.

Regarding the g722 codec, if the region setting is g711 and both the endpoints involved in the call are g722 capable then g722 is chosen by default. The only consideration here is that for a conference call the software conference bridge will only support g711 codec. As you mentioned that lan calls are negotiating g722, it will be by the above logic, whereas for external calls the codecs defined on dial-peers and region settings with gateway / trunk will determine which codec is negotiated.

HTH

Manish

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