Question

In my application I want to implement methods which record the sound if any sound occurs.

Something similar like this app: Talking Tom Cat

So what should I have to do?
Is there any demo that listens for sound and records it if any sound occurs?

Answer 1

Try this code in your application…

private int RECORDER_CHANNELS = AudioFormat.CHANNEL_CONFIGURATION_MONO;
private int RECORDER_AUDIO_ENCODING = AudioFormat.ENCODING_PCM_16BIT;
private int RECORDER_SAMPLERATE = 44100;
private byte RECORDER_BPP = (byte) 16;

private AudioRecord audioRecorder;

public void arm() {
    // 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.
    audioRecorder = new AudioRecord(MediaRecorder.AudioSource.MIC, RECORDER_SAMPLERATE,
            RECORDER_CHANNELS, 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, 0, 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++;
    }
}

For more details you can also look at this demo…

http://musicg.googlecode.com/files/musicg_android_demo.zip