How to improove audio quality on beagle board?

Hi,
     We are trying a VOIP application on beagle board. Signalling is
happening properly .We are making call from some third party phone
(Desktop Phone- SJ phone) to VOIP application running in beagle
board.Call is getting established.I can see in ethereal that RTP
packets are also flowing on both side.
      The sound driver we are using is ALSA.We can hear the audio
(spoken at Desktop phone) at the beagle board side with poor quality
and with delay.For this we have increased the Playback as well Capture
buffer . We tried many combination. but it didnt work. So somebody
have a solution for it ??? Then please share with me....

Thanks & Regards,
Vijay swami

Did you try the process documented at http://code.google.com/p/beagleboard/wiki/BeagleboardRevCValidation just to be sure the record and playback with ALSA is giving reasonable quality with the hardware?