So much sound issue on sip truck and voip

Hi everyone,i am using sip trunk-line and from last few day i’m facing the sound issue on outbound and inbound calls.I have already install all suitable code for wave file and mp3 file like G729,g711 ,mpg123 etc Sometime voice clear and some time so much disturbance in playback sound file.How to fix it?

Find what resource is being overloaded and either reduce the load to one it can handle or provide more or bigger resources.