android AudioRecord amplitude reading from MIC

Question

I am trying to record the sound from the MIC and draw a live graph. I am able to record and draw the graph. The problem is the values that are recorded using the code below are not accurate for example ... the image below is what i get when there is no sound at all present. I have seen examples using the fft but I am noot sure if that will be of any help in my case as I am trying to draw a time domain graph and I see no purpose to convert it to frequency domain (for now). Others are using average power, this might be helpful but I am not sure.

Thanks for any help.

bufferSize = AudioRecord.getMinBufferSize(RECORDER_SAMPLERATE,RECORDER_CHANNELS,RECORDER_AUDIO_ENCODING);

    recorder = new AudioRecord(MediaRecorder.AudioSource.MIC,
            RECORDER_SAMPLERATE, RECORDER_CHANNELS,RECORDER_AUDIO_ENCODING, bufferSize);

    short data [] = new short[bufferSize];

    while (!Thread.interrupted()) {

        recorder.startRecording();

        recorder.read(data, 0, bufferSize);

        recorder.stop();

        for (short s : data)
        {
            try {
                Thread.sleep((long) 300.00);
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            postUI (Math.abs(s));
        }
    }

    recorder.release();

Answer 1

For anyone else looking for a way to do this, check out Samsung's fantastic example complete with source code

Answer 2

Try using a higher sampling rate. The maximum is 48000, but 44100 is standard.

Also, it is possible the microphone is just recording background noise.