Multiplying Hd(n) with a window of finite size will return a H(n) of finite size (duh)
Example taking this rectangular window:
Multiplying this with the Hd(n) we get
This is known as windowing
Now, frequency response can be obtained by
Basically, this
Example problem
Hanning window
In the h(n) step at the mid right of the last image, you can see that we are multiplying hd(n) with w(n) which is just 1 with all the values (since its rectangular)
Here its a hanning window which essentially means its weirdly shaped and its not 1 everywhere.
You gotta multiply the coefficients with those weird values accordingly
These are the coefficients
HANNING WINDOW:
Get a table for just hanning window values, and then finally multiply it with the original coeffs and youre done bruddah
Just see if first and last, second and second last and third and third last values match! it needs to