Sound intensity is the measure of amplitude at a particular instance of time from a 16 bit .wav file. This is a sample program to demonstrate the calculation of intensity.

Step 1: Read the input wav file
AVIStreamOpenFromFile
(PAVISTREAMobj,lpszWavFilePath,streamtypeAUDIO,0, OF_READ, NULL))

Step 2: Get the raw stream data
AVIStreamInfo
(PAVISTREAMobj,objAVISTREAMINFO,sizeof(objAVISTREAMINFO))

Step 3: Read stream format
AVIStreamReadFormat
(PAVISTREAMobj,AVIStreamStartTime(PAVISTREAMobj), objPCMWAVEFORMAT, sizeof(objPCMWAVEFORMAT))

Step 4: Calculate the size of steam
PCMWAVEFORMAT wf;
long lSize = ((StreamEndTime – StreamBeginTime)* wf.wf.nChannels * wf.wBitsPerSample / 8)
 

Step 5: Audio sampling
 
//pSampleData is an array of lSize
AVIStreamRead(PAVISTREAMobj, StreamBeginTime, StreamEndTime - StreamBeginTime, (void*)pSampleData, lSize, NULL, sizeof(wf));
 
//A loop from begin time to end time and store the max value as tMax
 
enum channel{left, right, mixed}
 
for (i = 0; i< (StreamEndTime - StreamBeginTime); i++)
{
      sample = abs(GetSample(i, left));
      tMax = sample > tMax ? sample : tMax;
}
 
//Sampling of 16 bit audio data which is filled into pSampleData
 
GetSample(long sampleNo, WaveForm::Channel channel)
{
      short *sample16;
      int sample;
      long channels;
 
      if (IsEmpty())
            return 0;
 
      sample16 = (short *)pSampleData;
 
      channels = GetNumChannels() > 1 ? 2 : 1;
      channels = channels * (GetBitsPerSample() == 8 ? 1 : 2);
 
      if (sampleNo >= (long)lSampleDataSize/channels || sampleNo < 0)
            return 0;
 
      if (GetNumChannels() == 2)
{
         if (channel == WaveForm::kLeftChannel || channel == 
                                                 WaveForm::kMixChannels)
                  sampleNo = sampleNo * 2;
         else
                  sampleNo = sampleNo * 2 + 1;
      }
 
      sample = sample16[sampleNo];
     
if (channel == WaveForm::kMixChannels && GetNumChannels() == 2)
      {
                  sample += sample16[sampleNo+1];
                  sample = sample /2;
      }
 
      return sample;
}
 
Step 6: Calculating intensity
 
 
float GetIntensityAtTime(int t)
{
   if(t<0)
      return 0.0f;
     
    double sampleTime;
    long sampleNo;
    int sample = 0;
    float normSample;
    int chnnl;
    int i = 0;
    float divider;
    float minval, maxval;
 
    minval = 0;
    maxval = 100;
 
    sampleTime = (t*160)/4.8; // "Instant" in milliseconds
    sampleNo = (long)(sampleTime * GetSamplesPerSec() / 1000);
    switch (GetNumChannels())
    {
      case 0:
            chnnl = kLeftChannel;
            break;
      case 1:
            chnnl = kRightChannel;
            break;
      default:
            ch = kMixChannels;
            break;
      }
 
      sample = abs(GetSample(sampleNo, chnnl));
           
      if (((float)sample)/tMax < 0)
            sample = 0;
 
      normSample = (float)(sample)/tMax * (maxval - minval) + minval;
 
      return normSample;
}