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Low sound quality on Calls out to PSTN

I have been recieving reports from a remote site that has been newly added to our CUCM cluster that the sound quality on the phones is not too good. It sounds as if the user on the far side is very distant and low, muffled etc.

We are using MGCP and SCCP on the phones. The round trip delay is around 300ms to the site. There is a local ISDN line connected to the ISR on site.

Would packet loss be a factor for calls that break out locally to the PSTN? I can understand how call quality would be affected over site-to-site calls across the WAN but I would think local pstn calls should not be affected as long as the signalling is making it through...

Hall of Fame Super Gold

Re: Low sound quality on Calls out to PSTN

Intercontinental setupo sure doesn't help, but have you tried reloading the router ?

Note is not always guranteed that media will take the short path. Some configurations force media to CM and back.


Low sound quality on Calls out to PSTN


To resolve this issue, perform these steps:

Under the voice port, issue these commands:

    voice-port 0/0

     input gain 1

     output attenuation 2

The shut and no shut commands are required to accept the voice port changes.

Change values, place test calls and adjust as needed. Decrease the output attenuation level by 1 dB after each test call until optimal volume is reached.


Ronak Patel

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Regards Ronak Patel Rate all helpful post by clicking stars below the answer.
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