Hamming window generates a line

Question

I have an audio file and read all data from the sound card buffer. Then, I convert byte[] to float[] to use them for hamming window. The waveform of the audio is:

after using hamming window:

is the waveform of audio with hamming window right? Where is my mistake?

by the way i use naudio library to process audio:

WaveChannel32 wave = new WaveChannel32(new WaveFileReader("sesDosyası.wav"));
byte []buffer = new byte[wave.length];
float []data = new float[wave.length / 4];
int read = wave.Read(buffer, 0, wave.length);
for (int i = 0; i < read / 4; i++)
{   
    data[i] = BitConverter.ToSingle(buffer, i * 4); //converting byte to float
    chart1.Series["wave"].Points.Add(data[i]); //first waveform
}

for (int j = 0; j < read/4; j++)
{
   data[j] = (float)(0.54 - 0.46 * Math.Cos((2 * Math.PI * data[j]) / (read / 4 - 1)));//hamming
   chart2.Series["wave"].Points.Add(data[j]); //second waveform
}

Answer 1

It appears you are applying the window to the whole wave, so read is going to be huge, so the term inside the cos is always going to be very near 0 for a data between [-1,1].

So you are always getting .54 - .46*cos(0) = .54 - .46*1.0 = .08

From wikipedia, only j should be inside the cosine - that gives the window, which you then multiply by data[j]:

window =  0.54 - 0.46 * Math.Cos( (2*Math.PI * j)/(total - 1) ).
hammed_signal = data[j]*window;

Why are you trying to apply a hamming window to the whole wave?

Answer 2

I think your hamming line is wrong:

data[j] = (float)(0.54 - 0.46 * Math.Cos((2 * Math.PI * data[j]) / (read - 1)));

As your loop goes from 0 to read/4, and you are dividing by read, so if you have read 16 samples, your for loop looks only at the first 4, but divides by 15, not 3.

var total = read / 4;

for (int j = 0; j < total; j++)
{
   data[j] = (float)(0.54 - 0.46 * Math.Cos((2 * Math.PI * data[j]) / (total- 1)));//hamming
   chart2.Series["wave"].Points.Add(data[j]); //second waveform
}