Muting the microphone android

I am trying 开发者_开发问答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);

try {
    Thread.sleep(500, 40);
} catch (InterruptedException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}
 audioService.setMicrophoneMute(false);