java - Obtaining Sound Pressure Level of wav file -

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i trying obtain , represent spl of a wav file recorded internal mic of device. problem values getting seem not logic @ all, i´m getting values on 100 db clapping hands can see here:

image http://s2.subirimagenes.com/imagen/previo/thump_8946906screenshot2014060821.png

this doing:

  • first of all, wav file saved in 16-bit pcm, operate bytes have unique double value normalized between [-1,1] ( don´t operate first 44 bytes wav header).
  • then, following equation spl=10*log(audiosample/iref) obtain each of desired sound levels (being iref=10^-12).
  • at end calculate max , min values set margins of plot.

do guys know im doing wrong? think values should around half of ones obtained

here piece of code:

protected void mithread() {           thread t=new thread()  {             public void run(){             //operaciones ope=new operaciones();             double [] st =new double [arr.length];              int j=0;                 try{                   (int = 44; < s; i+=2) {                     // convert byte pair int                     double audiosample = (double) (array[i+1] << 8 | array[i] & 0xff)/ 32767.0;                      arr[j]=audiosample;  //double                     n[j] = (number)arr[j];  //number                      st[j]=10*math.log10(math.abs((audiosample/math.pow(10, -12)))); //double                     l[j]=(number)(10*math.log10(math.abs((audiosample/math.pow(10, -12)))));  //number                      if(audiosample == 0.0 ){                         if(j!=0){                         l[j]=l[j-1];                         st[j]=st[j-1];                         }else{                             l[j]=0.0;                             st[j]=0.0;                         }                       }                      j=j+1;}                     min=operaciones.minimum(arr);                     max=operaciones.maximum(arr);                     min2=operaciones.minimum(st);                     max2=operaciones.maximum(st);                     }                     catch (nullpointerexception e){                         e.printstacktrace();                         }                  handle.post(proceso);                } }; t.start();                                   }          final runnable proceso=new runnable(){             public void run(){                 //plot.redraw();                 //plot2.redraw();                 toast.maketext(grafica.this,                  "ya se ha cargado todo el array", toast.length_long).show();             }         };

isnt spl standing sound pressure level compared absolute reference?. microphone plugged 16bit precision port think its ok. snr should around 60db have around 44db voice interval. when microphone receives sound signal should go (around 104db if recall 16bit).

spl=20log (pascal/2e-5)


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