Android 录音获取分贝值的办法

参考：http://blog.csdn.net/greatpresident/article/details/38402147

public class MediaRecorderDemo {  
    private final String TAG = "MediaRecord";  
    private MediaRecorder mMediaRecorder;  
    public static final int MAX_LENGTH = 1000 * 60 * 10;// 最大录音时长1000*60*10;  
    private String filePath;  
  
    public MediaRecorderDemo(){  
        this.filePath = "/dev/null";  
    }  
  
    public MediaRecorderDemo(File file) {  
        this.filePath = file.getAbsolutePath();  
    }  
  
    private long startTime;  
    private long endTime;  
  
    /** 
     * 开始录音 使用amr格式 
     * 
     *            录音文件 
     * @return 
     */  
    public void startRecord() {  
        // 开始录音  
        /* ①Initial：实例化MediaRecorder对象 */  
        if (mMediaRecorder == null)  
            mMediaRecorder = new MediaRecorder();  
        try {  
            /* ②setAudioSource/setVedioSource */  
            mMediaRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);// 设置麦克风  
            /* ②设置音频文件的编码：AAC/AMR_NB/AMR_MB/Default 声音的（波形）的采样 */  
            mMediaRecorder.setOutputFormat(MediaRecorder.OutputFormat.DEFAULT);  
                        /* 
             * ②设置输出文件的格式：THREE_GPP/MPEG-4/RAW_AMR/Default THREE_GPP(3gp格式 
             * ，H263视频/ARM音频编码)、MPEG-4、RAW_AMR(只支持音频且音频编码要求为AMR_NB) 
             */  
            mMediaRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);  
  
            /* ③准备 */  
            mMediaRecorder.setOutputFile(filePath);  
            mMediaRecorder.setMaxDuration(MAX_LENGTH);  
            mMediaRecorder.prepare();  
            /* ④开始 */  
            mMediaRecorder.start();  
            // AudioRecord audioRecord.  
            /* 获取开始时间* */  
            startTime = System.currentTimeMillis();  
            updateMicStatus();  
            Log.i("ACTION_START", "startTime" + startTime);  
        } catch (IllegalStateException e) {  
            Log.i(TAG,  
                    "call startAmr(File mRecAudioFile) failed!"  
                            + e.getMessage());  
        } catch (IOException e) {  
            Log.i(TAG,  
                    "call startAmr(File mRecAudioFile) failed!"  
                            + e.getMessage());  
        }  
    }  
  
    /** 
     * 停止录音 
     * 
     */  
    public long stopRecord() {  
        if (mMediaRecorder == null)  
            return 0L;  
        endTime = System.currentTimeMillis();  
        Log.i("ACTION_END", "endTime" + endTime);  
        mMediaRecorder.stop();  
        mMediaRecorder.reset();  
        mMediaRecorder.release();  
        mMediaRecorder = null;  
        Log.i("ACTION_LENGTH", "Time" + (endTime - startTime));  
        return endTime - startTime;  
    }  
  
    private final Handler mHandler = new Handler();  
    private Runnable mUpdateMicStatusTimer = new Runnable() {  
        public void run() {  
            updateMicStatus();  
        }  
    };  
  
    /** 
     * 更新话筒状态 
     * 
     */  
    private int BASE = 1;  
    private int SPACE = 100;// 间隔取样时间  
  
    private void updateMicStatus() {  
        if (mMediaRecorder != null) {  
            double ratio = (double)mMediaRecorder.getMaxAmplitude() /BASE;  
            double db = 0;// 分贝  
            if (ratio > 1)  
                db = 20 * Math.log10(ratio);  
            Log.d(TAG,"分贝值："+db);  
            mHandler.postDelayed(mUpdateMicStatusTimer, SPACE);  
        }  
    }  
}