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SPA525g best Audio Codec Settings - poor sound quality upstream


I have on going poor voice quality.. the other party claims I sound like I'm underwater.  The issue is intermittent with is frustrating.  I have changed/tried everything... new routers, replaced all connections, opened RTP and UDP ports on router, etc.


I saw an article that suggested the configuration on the phone for the Audio codecs could be wrong... i could not find any recent articles.


What codecs should be selected Preferred codec, 2nd and 3rd, when configuring the table below:

I have these choices: G711a, G711u, G726-32, G729a and G722.


Audio Configuration
Preferred Codec: Use Pref Codec Only: 
Second Preferred Codec: Third Preferred Codec: 
G711u Enable: G711a Enable: 
G729a Enable: G722 Enable: 
G726-32 Enable: Release Unused Codec: 




Many thanks in advance for any help.  Desperate :)!



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Does it happen on more than

Does it happen on more than one phone? If not perhaps it is a hardware issue with the phone/handset itself.

If you make all calls through a single provider you could try forcing a specific codec by disabling all codecs except your main one (or setting second preferred codec and third preferred codec to 'unspecified') and 'use preferred codec only' to yes. 

Is your internet connection quality consistently good? RTP traffic is influenced by poor latency and jitter. Also upstream and downstream bandwidth needs to be sufficient (eg approx 80kbps up and down for g711a).

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