code: private void stopBluetooth() {
          Log.d(TAG, "stopBluetooth");
  
          if (mIsCountDownOn) {
              mIsCountDownOn = false;
              mCountDown.cancel();
          }
  
          // Need to stop Sco audio connection here when the app
          // change orientation or close with headset still turns on.
          mContext.unregisterReceiver(mBroadcastReceiver);
          mAudioManager.stopBluetoothSco();
          mAudioManager.setMode(AudioManager.MODE_NORMAL);
      }
docs: Unregister broadcast receivers and stop Sco audio connection
  and cancel count down.