android聲音檢測儀---分貝儀

文章出處：大黑個人博客--android聲音檢測儀---分貝儀
源碼下載地址：https://github.com/halibobo/SoundMeter

背景

最近小區旁邊工地施工，今一大早就被工地傳來的guang！guang！...吵醒了。很響很響的那種，你們肯定會問具體有多響？具體要多響？怎麼描述呢？頓時就萌生出開發一款記錄聲音響度的app，忙活了一下午於是就出了這個聲音檢測儀

簡介

android端的聲音檢測程式，實時獲取當前周圍環境的聲壓級，也就是平常所說的分貝值

源碼

聲音採集利用系統的MediaRecorder

/**
 * 錄音
 * @return 是否成功開始錄音
 */
public boolean startRecorder(){
    if (myRecAudioFile == null) {
        return false;
    }
    try {
        mMediaRecorder = new MediaRecorder();

        mMediaRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
        mMediaRecorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
        mMediaRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
        mMediaRecorder.setOutputFile(myRecAudioFile.getAbsolutePath());

        mMediaRecorder.prepare();
        mMediaRecorder.start();
        isRecording = true;
        return true;
    } catch(IOException exception) {
        mMediaRecorder.reset();
        mMediaRecorder.release();
        mMediaRecorder = null;
        isRecording = false ;
        exception.printStackTrace();
    }catch(IllegalStateException e){
        stopRecording();
        e.printStackTrace();
        isRecording = false ;
    }
    return false;
}
  /**
  * 獲取聲壓值
  */
 public float getMaxAmplitude() {
     if (mMediaRecorder != null) {
         try {
             return mMediaRecorder.getMaxAmplitude();
         } catch (IllegalArgumentException e) {
             e.printStackTrace();
             return 0;
         }
     } else {
         return 5;
     }
 }

在MainActivity中開啟一個線程定時獲取聲壓值並轉為分貝

private void startListenAudio() {
    thread = new Thread(new Runnable() {
        @Override
        public void run() {
            while (isThreadRun) {
                try {
                    if(bListener) {
                        volume = mRecorder.getMaxAmplitude();  //獲取聲壓值
                        if(volume > 0 && volume < 1000000) {
                            World.setDbCount(20 * (float)(Math.log10(volume)));  //將聲壓值轉為分貝值
                        }
                    }
                    Thread.sleep(100);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                    bListener = false;
                }
            }
        }
    });
    thread.start();
}

自定義顯示分貝值得大圓盤View 取名SoundDiscView

private float scaleWidth, scaleHeight;
private int newWidth, newHeight;
private Matrix mMatrix = new Matrix();
private Bitmap indicatorBitmap;
private Paint paint = new Paint();
static final long  ANIMATION_INTERVAL = 100;


private void init() {
    Bitmap myBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.noise_index);
    int bitmapWidth = myBitmap.getWidth();
    int bitmapHeight = myBitmap.getHeight();
    newWidth = getWidth();
    newHeight = getHeight();
    scaleWidth = ((float) newWidth) /(float) bitmapWidth;  // 獲取縮放比例
    scaleHeight = ((float) newHeight) /(float) bitmapHeight;  //獲取縮放比例
    mMatrix.postScale(scaleWidth, scaleHeight);   //設置mMatrix的縮放比例
    indicatorBitmap = Bitmap.createBitmap(myBitmap, 0, 0, bitmapWidth, bitmapHeight, mMatrix,true);  //獲取同等和背景寬高的指針圖的bitmap

    paint = new Paint();
    paint.setTextSize(55);
    paint.setAntiAlias(true);
    paint.setTextAlign(Paint.Align.CENTER);  //抗鋸齒
    paint.setColor(Color.WHITE);
}


@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    currentAngle = getAngle(World.dbCount); //獲取指針應該顯示的角度
    mMatrix.setRotate(getAngle(World.dbCount), newWidth / 2, newHeight * 215 / 460);   //片相對位置
    canvas.drawBitmap(indicatorBitmap, mMatrix, paint);
    postInvalidateDelayed(ANIMATION_INTERVAL);
    canvas.drawText((int)World.dbCount+" DB", newWidth/2,newHeight*36/46, paint); //圖片相對位置
}

運行發現指針滑動的太突兀，做個緩慢過度

public static float dbCount = 40; 

private static float lastDbCount = dbCount;
public static void setDbCount(float dbValue) {
    dbCount = lastDbCount + (dbValue - lastDbCount) * 0.2f; 
    lastDbCount = dbCount;
}

結果

這裡的分貝值是手機系統錄音時獲取的，手機廠商都對這個值設置了上限而且手機廠商之間都是有差別的，所以獲取聲音的分貝值會有點偏差。但是最終運行起來的效果還是很滿意的。下麵附上源碼
源碼下載地址