How to sample microphone on Android without recording to get live amplitude/level?

Question

I was trying to get the amplitude level of a microphone on Android like so:

MediaRecorder recorder = new MediaRecorder(); recorder.setAudioSource(MediaRecorder.AudioSource.MIC);  Timer timer = new Timer(); timer.scheduleAtFixedRate(new RecorderTask(recorder), 0, 1000);  private class RecorderTask extends TimerTask {     private MediaRecorder recorder;      public RecorderTask(MediaRecorder recorder) {         this.recorder = recorder;     }      public void run() {         Log.v("MicInfoService", "amplitude: " + recorder.getMaxAmplitude());     } } 

Unfortunately, this only returns 0 all the time.

It appears that for this to work I have to actually start recording. Is that correct?

If so, do I need to record for 500ms, get amplitude, stop recording and repeat?

Finally, do I have to record to a file? I do not need to save this audio file, can't I just get the current amplitude or highest amplitude since last call of the current live microphone input without recording?

Any help is appreciated, thanks.

Answer 1

The solution from Toumal works, however I wasn't able to get a high enough refresh rate for my needs. So I ended up using the SoundMeter.java class that Toumal linked but modified it to use the code from this answer

Here is the code I used, which provides a much better refresh rate:

import android.media.AudioFormat; import android.media.AudioRecord; import android.media.MediaRecorder;  public class SoundMeter {      private AudioRecord ar = null;     private int minSize;      public void start() {         minSize= AudioRecord.getMinBufferSize(8000, AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_16BIT);         ar = new AudioRecord(MediaRecorder.AudioSource.MIC, 8000,AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_16BIT,minSize);         ar.startRecording();     }      public void stop() {         if (ar != null) {             ar.stop();         }     }      public double getAmplitude() {         short[] buffer = new short[minSize];         ar.read(buffer, 0, minSize);         int max = 0;         for (short s : buffer)         {             if (Math.abs(s) > max)             {                 max = Math.abs(s);             }         }         return max;     }  }