Rtcmd

The radio when I turn it on doesn't make sound/music, but only hear gargling/hissing noise. I'm not sure if it's the radio unit or the speaker is the problem. How do you test to find out what is really the cause of the problem? Thanks.
Calling all experts on this issue who could give me some advice before I buy a new radio or speakers. What is the right tools to take out the radio off the dashboard and where can I get it? Thanks.