_recorder.getMaxAmplitude();

_audioManager = (AudioManager) getSystemService(Context.AUDIO_SERVICE);
 _audioManager.startBluetoothSco();
 _recorder = new MediaRecorder();
 _recorder.setAudioSource(MediaRecorder.AudioSource.DEFAULT);
 _recorder.setOutputFormat(MediaRecorder.OutputFormat.MPEG_4);
 _recorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
 _recorder.setOutputFile(file.toString());
 _recorder.prepare();
 _recorder.start();

_recorder.getMaxAmplitude();