android: Detect sound level

Solution 1:

1. Use mRecorder.getMaxAmplitude();

2. For the analysis of sound without saving all you need is use mRecorder.setOutputFile("/dev/null");

Here´s an example, I hope this helps

public class SoundMeter {

    private MediaRecorder mRecorder = null;

    public void start() {
            if (mRecorder == null) {
                    mRecorder = new MediaRecorder();
                    mRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
                    mRecorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
                    mRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
                    mRecorder.setOutputFile("/dev/null"); 
                    mRecorder.prepare();
                    mRecorder.start();
            }
    }

    public void stop() {
            if (mRecorder != null) {
                    mRecorder.stop();       
                    mRecorder.release();
                    mRecorder = null;
            }
    }

    public double getAmplitude() {
            if (mRecorder != null)
                    return  mRecorder.getMaxAmplitude();
            else
                    return 0;

    }
}

Solution 2:

If you want to analyse a sample of sound taken directly from the microphone without saving the data in a file, you need to make use of the AudioRecord Object as follows:

int sampleRate = 8000;
try {
    bufferSize = AudioRecord.getMinBufferSize(sampleRate, AudioFormat.CHANNEL_IN_MONO,
        AudioFormat.ENCODING_PCM_16BIT);
    audio = new AudioRecord(MediaRecorder.AudioSource.MIC, sampleRate,
            AudioFormat.CHANNEL_IN_MONO,
            AudioFormat.ENCODING_PCM_16BIT, bufferSize);
} catch (Exception e) {
    android.util.Log.e("TrackingFlow", "Exception", e);
}

Then you have to start recording when ready:

audio.startRecording();

Now it's time to start reading samples as follows:

short[] buffer = new short[bufferSize];

    int bufferReadResult = 1;

    if (audio != null) {

        // Sense the voice...
        bufferReadResult = audio.read(buffer, 0, bufferSize);
        double sumLevel = 0;
        for (int i = 0; i < bufferReadResult; i++) {
            sumLevel += buffer[i];
        }
        lastLevel = Math.abs((sumLevel / bufferReadResult));

The last code combines all the different samples amplitudes and assigns the average to the lastLeveL variable, for more details you can go to this post.

Regards!