안드로이드 - 기기의 마이크로 들어오는 소리의 데시벨을 구하는 방법

안드로이드 - 기기의 마이크로 들어오는 소리의 데시벨을 구하는 방법
원본 출처:"http://susemi99.tistory.com/1017
주요 소스는 여기를 참고했다.
http://code.google.com/p/moonblink/


 

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HomeActivity.java

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public class HomeActivity extends Activity {     private AudioReader audioReader;     private int sampleRate = 8000;     private int inputBlockSize = 256;     private int sampleDecimate = 1;            @Override     public void onCreate(Bundle savedInstanceState)     {         super.onCreate(savedInstanceState);         setContentView(R.layout.main);                    audioReader = new AudioReader();         setVolumeControlStream(AudioManager.STREAM_MUSIC);     }            public void doStart(View v)     {         audioReader.startReader(sampleRate, inputBlockSize * sampleDecimate, new AudioReader.Listener()         {             @Override             public final void onReadComplete(int dB)             {                 receiveDecibel(dB);             }                            @Override             public void onReadError(int error)             {                                }         });     }            private void receiveDecibel(final int dB)     {         Log.e("###", dB+" dB");     }            public void doStop(View v)     {         audioReader.stopReader();     } }

데시벨을 표시한다.

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AudioReader.java

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public class AudioReader {     public static abstract class Listener     {         public static final int ERR_OK = 0;         public static final int ERR_INIT_FAILED = 1;         public static final int ERR_READ_FAILED = 2;         public abstract void onReadComplete(int decibel);         public abstract void onReadError(int error);     }            public int calculatePowerDb(short[] sdata, int off, int samples)     {         double sum = 0;         double sqsum = 0;         for (int i = 0; i < samples; i++)         {             final long v = sdata[off + i];             sum += v;             sqsum += v * v;         }         double power = (sqsum - sum * sum / samples) / samples;                    power /= MAX_16_BIT * MAX_16_BIT;                    double result = Math.log10(power) * 10f + FUDGE;         return (int)result;     }            public AudioReader()     {     }            public void startReader(int rate, int block, Listener listener)     {         Log.i(TAG, "Reader: Start Thread");         synchronized (this)         {             int audioBuf = AudioRecord.getMinBufferSize(rate, AudioFormat.CHANNEL_CONFIGURATION_MONO,                     AudioFormat.ENCODING_PCM_16BIT) * 2;                            audioInput = new AudioRecord(MediaRecorder.AudioSource.MIC, rate, AudioFormat.CHANNEL_CONFIGURATION_MONO,                     AudioFormat.ENCODING_PCM_16BIT, audioBuf);             inputBlockSize = block;             sleepTime = (long) (1000f / ((float) rate / (float) block));             inputBuffer = new short[2][inputBlockSize];             inputBufferWhich = 0;             inputBufferIndex = 0;             inputListener = listener;             running = true;             readerThread = new Thread(new Runnable()             {                 @Override                 public void run()                 {                     readerRun();                 }             }, "Audio Reader");             readerThread.start();         }     }            public void stopReader()     {         Log.i(TAG, "Reader: Signal Stop");         synchronized (this)         {             running = false;         }         try         {             if (readerThread != null)                 readerThread.join();         } catch (InterruptedException e)         {             ;         }         readerThread = null;                    // Kill the audio input.         synchronized (this)         {             if (audioInput != null)             {                 audioInput.release();                 audioInput = null;             }         }                    Log.i(TAG, "Reader: Thread Stopped");     }            private void readerRun()     {         short[] buffer;         int index, readSize;                    int timeout = 200;         try         {             while (timeout > 0 && audioInput.getState() != AudioRecord.STATE_INITIALIZED)             {                 Thread.sleep(50);                 timeout -= 50;             }         } catch (InterruptedException e)         {         }                    if (audioInput.getState() != AudioRecord.STATE_INITIALIZED)         {             Log.e(TAG, "Audio reader failed to initialize");             readError(Listener.ERR_INIT_FAILED);             running = false;             return;         }                    try         {             Log.i(TAG, "Reader: Start Recording");             audioInput.startRecording();             while (running)             {                 long stime = System.currentTimeMillis();                                    if (!running)                     break;                                    readSize = inputBlockSize;                 int space = inputBlockSize - inputBufferIndex;                 if (readSize > space)                     readSize = space;                 buffer = inputBuffer[inputBufferWhich];                 index = inputBufferIndex;                                    synchronized (buffer)                 {                     int nread = audioInput.read(buffer, index, readSize);                                            boolean done = false;                     if (!running)                         break;                                            if (nread < 0)                     {                         Log.e(TAG, "Audio read failed: error " + nread);                         readError(Listener.ERR_READ_FAILED);                         running = false;                         break;                     }                     int end = inputBufferIndex + nread;                     if (end >= inputBlockSize)                     {                         inputBufferWhich = (inputBufferWhich + 1) % 2;                         inputBufferIndex = 0;                         done = true;                     }                     else                         inputBufferIndex = end;                                            if (done)                     {                         readDone(buffer);                                                    long etime = System.currentTimeMillis();                         long sleep = sleepTime - (etime - stime);                         if (sleep < 5)                             sleep = 5;                         try                         {                             buffer.wait(sleep);                         } catch (InterruptedException e)                         {                         }                     }                 }             }         } finally         {             Log.i(TAG, "Reader: Stop Recording");             if (audioInput.getState() == AudioRecord.RECORDSTATE_RECORDING)                 audioInput.stop();         }     }            private void readDone(short[] buffer)     {         synchronized (this)         {             audioData = buffer;             ++audioSequence;                            short[] buffer2 = null;             if (audioData != null && audioSequence > audioProcessed)             {                 audioProcessed = audioSequence;                 buffer2 = audioData;             }                            if (buffer2 != null)             {                 final int len = buffer2.length;                 inputListener.onReadComplete(calculatePowerDb(buffer2, 0, len));                 buffer2.notify();             }         }     }            private void readError(int code)     {         inputListener.onReadError(code);     }            private static final String TAG = "WindMeter";     private AudioRecord audioInput;     private short[][] inputBuffer = null;     private int inputBufferWhich = 0;     private int inputBufferIndex = 0;     private int inputBlockSize = 0;     private long sleepTime = 0;     private Listener inputListener = null;     private boolean running = false;     private Thread readerThread = null;     private short[] audioData;     private long audioSequence = 0;     private long audioProcessed = 0;     private static final float MAX_16_BIT = 32768;     private static final float FUDGE = 0.6f; }

가져 온 소스에다 몇개 추가를 했다. 주석까지 있는 버전은 아래 파일을 받으시길...
근데 문제는 0dB가 최대치이고, 보통은 -40dB정도 나온다.
중간에 계산식을 바꾸면 될 것 같은데, 아 몰라 뭐야 무서워

AudioReader.java