Android中实时获取音量分贝值详解

package com.example.myapp;

import java.io.File;
import java.io.IOException;

import android.media.MediaRecorder;
import android.os.Handler;
import android.util.Log;

/**
 * amr音频处理
 *
 * @author hongfa.yy
 * @version 创建时间2012-11-21 下午4:33:28
 */
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);
    }
  }
}

package com.example.myapp;

import android.media.AudioFormat;
import android.media.AudioRecord;
import android.media.MediaRecorder;
import android.util.Log;

/**
 * Created by greatpresident on 2014/8/5.
 */
public class AudioRecordDemo {

  private static final String TAG = "AudioRecord";
  static final int SAMPLE_RATE_IN_HZ = 8000;
  static final int BUFFER_SIZE = AudioRecord.getMinBufferSize(SAMPLE_RATE_IN_HZ,
          AudioFormat.CHANNEL_IN_DEFAULT, AudioFormat.ENCODING_PCM_16BIT);
  AudioRecord mAudioRecord;
  boolean isGetVoiceRun;
  Object mLock;

  public AudioRecordDemo() {
    mLock = new Object();
  }

  public void getNoiseLevel() {
    if (isGetVoiceRun) {
      Log.e(TAG, "还在录着呢");
      return;
    }
    mAudioRecord = new AudioRecord(MediaRecorder.AudioSource.MIC,
        SAMPLE_RATE_IN_HZ, AudioFormat.CHANNEL_IN_DEFAULT,
        AudioFormat.ENCODING_PCM_16BIT, BUFFER_SIZE);
    if (mAudioRecord == null) {
      Log.e("sound", "mAudioRecord初始化失败");
    }
    isGetVoiceRun = true;

    new Thread(new Runnable() {
      @Override
      public void run() {
        mAudioRecord.startRecording();
        short[] buffer = new short[BUFFER_SIZE];
        while (isGetVoiceRun) {
          //r是实际读取的数据长度，一般而言r会小于buffersize
          int r = mAudioRecord.read(buffer, 0, BUFFER_SIZE);
          long v = 0;
          // 将 buffer 内容取出，进行平方和运算
          for (int i = 0; i < buffer.length; i++) {
            v += buffer[i] * buffer[i];
          }
          // 平方和除以数据总长度，得到音量大小。
          double mean = v / (double) r;
          double volume = 10 * Math.log10(mean);
          Log.d(TAG, "分贝值:" + volume);
          // 大概一秒十次
          synchronized (mLock) {
            try {
              mLock.wait(100);
            } catch (InterruptedException e) {
              e.printStackTrace();
            }
          }
        }
        mAudioRecord.stop();
        mAudioRecord.release();
        mAudioRecord = null;
      }
    }).start();
  }
}