Audio Noise with XBee


Any body to help me with a simple problem of integration of an XBeepro module on a PCB where there is also an audio amp line with a speaker.
When the XBee Pro is not powered the audio line is perfect no frequency noise in the speaker. As soon as the XBee Pro is powered i have a frequency noise in the speaker.
I tried to put the audio amp line very far away from the XBeePro, no way ! still have the trouble.
For more information : The XBee Pro is driven with a PIC24H @ 64 mhz @ 115200 baud on UART1, the audio amp is also driven with UART 2 of the same PIC24H
It seems to me this frequency noise comes from some line … power line ? ground line ? or what else ???
Any idea, to get it work with no noise at all in the speaker ?


Yeah, it sounds like something isn’t grounded in the audio amp circuit.

I checked, whatever should be grounded is grounded on the audio amp part.
Since somes pins of XBee are not used, Could it be a problem.
Is this noise propagating by power line ? How to check with a scope ?
How to stop it if it comes by power line ?