improve update alg
set max volume
123
fft computation
ifft transform
ifft transform
add computation of amplitude spectrum
some spectrum transforms
stft
start to implement tests for fft module
test for ifft, found some strange effect in computation of n-th coefficient of 2*n fourier transform;
temporary fix using some hack
test for stft
complete test the fft module
spectral substruction alg
firs working implementation of spectral substraction
psnr computation
improve spectral sub alg-thm
improve spectral sub alg-thm
denoise filter class
refactoring