// Playing sound
    // will play button toggle sound on flash on / off
    private void playSound(){
        if(isFlashOn){
            mp = MediaPlayer.create(MainActivity.this, R.raw.light_switch_off);
        }else{
            mp = MediaPlayer.create(MainActivity.this, R.raw.light_switch_on);
        }
        mp.setOnCompletionListener(new OnCompletionListener() {

            @Override
            public void onCompletion(MediaPlayer mp) {
                // TODO Auto-generated method stub
                mp.release();
            }
        });
        mp.start();
    }