On which frequency i should apply DWT (wavelet transform), sampling frequency or output bandwidth

i have emotiv epoch for EEG signal acquisition. If band width of Emotiv is 2-43 Hz and sampling frequency is 128 Hz then upto which i should apply DWT, On 2-43 Hz or On 128 Hz?????

[Youssef Khmou]

before trying to answer, can you provide a simple code that demonstrates what you have described ? thanks

Answer 1

[Wayne King]

If your sampling frequency is 128 Hz, then the approximate frequency bands in the DWT are already determined by the sampling frequency.

They are: (Scaling filter band on left, wavelet filter band on right)

[0 32] [32 64] Hz

[0 16] [16 32] Hz

[0 8] [8 16] Hz

[0 4] [4 8] Hz

and so on.

You notice that the band 2-43 Hz is best localized (but certainly not perfectly) in the 1st level approximation coefficients.

What not just use a good filter if you are just using the DWT to perform a frequency-filtering of your signal?