How to improve chanspy audio quality?

Hi all,

I want to use chanspy function for whisper monitor.

I used ver 1.4.44 asterisk,but the audio quality is bad.
Not only listening to agent channel is bad, but also listening client channel is bad too.

I search the forum,there is a post said upgrading asterisk might improve.

I use AsteriskNOW( Asterisk11),the audio quality still bad.

Are there any ways to improve whisper monitor audio quality?