public void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

    // Get the minimum buffer size required for the successful creation of an AudioRecord object. 
    int bufferSizeInBytes = AudioRecord.getMinBufferSize( RECORDER_SAMPLERATE,RECORDER_CHANNELS,RECORDER_AUdio_ENCODING
                                                         ); 
    // Initialize Audio Recorder.
    AudioRecord audioRecorder = new AudioRecord( MediaRecorder.AudioSource.MIC,RECORDER_SAMPLERATE,RECORDER_AUdio_ENCODING,bufferSizeInBytes
                                                );
    // Start Recording.
    audioRecorder.startRecording();

    int numberOfReadBytes   = 0; 
    byte audioBuffer[]      = new  byte[bufferSizeInBytes];
    boolean recording       = false;
    float tempFloatBuffer[] = new float[3];
    int tempIndex           = 0;
    int totalReadBytes      = 0;
    byte totalByteBuffer[]  = new byte[60 * 44100 * 2];


    // While data come from microphone. 
    while( true )
    {
        float totalAbsValue = 0.0f;
        short sample        = 0; 

        numberOfReadBytes = audioRecorder.read( audioBuffer,bufferSizeInBytes );

        // Analyze Sound.
        for( int i=0; i<bufferSizeInBytes; i+=2 ) 
        {
            sample = (short)( (audioBuffer[i]) | audioBuffer[i + 1] << 8 );
            totalAbsValue += Math.abs( sample ) / (numberOfReadBytes/2);
        }

        // Analyze temp buffer.
        tempFloatBuffer[tempIndex%3] = totalAbsValue;
        float temp                   = 0.0f;
        for( int i=0; i<3; ++i )
            temp += tempFloatBuffer[i];

        if( (temp >=0 && temp <= 350) && recording == false )
        {
            Log.i("TAG","1");
            tempIndex++;
            continue;
        }

        if( temp > 350 && recording == false )
        {
            Log.i("TAG","2");
            recording = true;
        }

        if( (temp >= 0 && temp <= 350) && recording == true )
        {
            Log.i("TAG","Save audio to file.");

            // Save audio to file.
            String filepath = Environment.getExternalStorageDirectory().getPath();
            File file = new File(filepath,"AudioRecorder");
            if( !file.exists() )
                file.mkdirs();

            String fn = file.getAbsolutePath() + "/" + System.currentTimeMillis() + ".wav";

            long totalAudioLen  = 0;
            long totalDataLen   = totalAudioLen + 36;
            long longSampleRate = RECORDER_SAMPLERATE;
            int channels        = 1;
            long byteRate       = RECORDER_BPP * RECORDER_SAMPLERATE * channels/8;
            totalAudioLen       = totalReadBytes;
            totalDataLen        = totalAudioLen + 36;
            byte finalBuffer[]  = new byte[totalReadBytes + 44];

            finalBuffer[0] = 'R';  // RIFF/WAVE header
            finalBuffer[1] = 'I';
            finalBuffer[2] = 'F';
            finalBuffer[3] = 'F';
            finalBuffer[4] = (byte) (totalDataLen & 0xff);
            finalBuffer[5] = (byte) ((totalDataLen >> 8) & 0xff);
            finalBuffer[6] = (byte) ((totalDataLen >> 16) & 0xff);
            finalBuffer[7] = (byte) ((totalDataLen >> 24) & 0xff);
            finalBuffer[8] = 'W';
            finalBuffer[9] = 'A';
            finalBuffer[10] = 'V';
            finalBuffer[11] = 'E';
            finalBuffer[12] = 'f';  // 'fmt ' chunk
            finalBuffer[13] = 'm';
            finalBuffer[14] = 't';
            finalBuffer[15] = ' ';
            finalBuffer[16] = 16;  // 4 bytes: size of 'fmt ' chunk
            finalBuffer[17] = 0;
            finalBuffer[18] = 0;
            finalBuffer[19] = 0;
            finalBuffer[20] = 1;  // format = 1
            finalBuffer[21] = 0;
            finalBuffer[22] = (byte) channels;
            finalBuffer[23] = 0;
            finalBuffer[24] = (byte) (longSampleRate & 0xff);
            finalBuffer[25] = (byte) ((longSampleRate >> 8) & 0xff);
            finalBuffer[26] = (byte) ((longSampleRate >> 16) & 0xff);
            finalBuffer[27] = (byte) ((longSampleRate >> 24) & 0xff);
            finalBuffer[28] = (byte) (byteRate & 0xff);
            finalBuffer[29] = (byte) ((byteRate >> 8) & 0xff);
            finalBuffer[30] = (byte) ((byteRate >> 16) & 0xff);
            finalBuffer[31] = (byte) ((byteRate >> 24) & 0xff);
            finalBuffer[32] = (byte) (2 * 16 / 8);  // block align
            finalBuffer[33] = 0;
            finalBuffer[34] = RECORDER_BPP;  // bits per sample
            finalBuffer[35] = 0;
            finalBuffer[36] = 'd';
            finalBuffer[37] = 'a';
            finalBuffer[38] = 't';
            finalBuffer[39] = 'a';
            finalBuffer[40] = (byte) (totalAudioLen & 0xff);
            finalBuffer[41] = (byte) ((totalAudioLen >> 8) & 0xff);
            finalBuffer[42] = (byte) ((totalAudioLen >> 16) & 0xff);
            finalBuffer[43] = (byte) ((totalAudioLen >> 24) & 0xff);

            for( int i=0; i<totalReadBytes; ++i )
                finalBuffer[44+i] = totalByteBuffer[i];

            FileOutputStream out;
            try {
                out = new FileOutputStream(fn);
                 try {
                        out.write(finalBuffer);
                        out.close();
                    } catch (IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }

            } catch (FileNotFoundException e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            }

            //*/
            tempIndex++;
            break;
        }

        // -> Recording sound here.
        Log.i( "TAG","Recording Sound." );
        for( int i=0; i<numberOfReadBytes; i++ )
            totalByteBuffer[totalReadBytes + i] = audioBuffer[i];
        totalReadBytes += numberOfReadBytes;
        //*/

        tempIndex++;

    }
}

检查这个link.