通过麦克风获取噪音

Question

在我的Android应用程序中，我需要自动打开麦克风，记录噪音并计算Db级别。我怎么能这样做？

到目前为止，我尝试了以下代码：

import android.media.MediaRecorder;

public class SoundMeter {

    static final private double EMA_FILTER = 0.6;

    private MediaRecorder mRecorder = null;
    private double mEMA = 0.0;

    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();
            mEMA = 0.0;
        }
    }

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

    public double getAmplitude() {
        if (mRecorder != null)
            return  (mRecorder.getMaxAmplitude()/2700.0);
        else
            return 0;
    }

    public double getAmplitudeEMA() {
        double amp = getAmplitude();
        mEMA = EMA_FILTER * amp + (1.0 - EMA_FILTER) * mEMA;
        return mEMA;
    }

}

但我不能做我需要做的事情。我是Android开发的新手，所以如果您有任何想法，请告诉我。