Android :: Application Freezes While Muting The Phone

I am trying to toggle the microphone of Android mobile. App. freezes if I run the mute and unmute in a loop, With a delay of say 500ms. Is there a specific reason mobile behaves this way? (Motorola Droid is not even able to mute the phone) however all other mobiles are able to do it. This runs in a loop for 20 times

audioService.setMicrophoneMute(true);
if(audioService.isMicrophoneMute())
{
Toast.makeText(getBaseContext(), "MUTED", 1).show();}
try {
Thread.sleep(1000,90);
}
catch (InterruptedException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
audioService.setMicrophoneMute(false);
if(!audioService.isMicrophoneMute()){
Toast.makeText(getBaseContext(), "Un MUTED", 1).show();