For this purpose, initially the time segment from
all of the microphone signals are passed through a band-pass
filter to remove the unwanted low and high frequency noises
that are outside the chirp’s frequency range (see Figure 8.b).
Furthermore, Fractional Fourier transform (FRFT) [37] is
used to remove noise within the frequency range of the chirp.
Unlike Fast Fourier transform (FFT), the FRFT provides a
compact representation of chirp signals, which makes it possible
to remove the noise inside the same frequency region as
the chirp, that cannot be removed with traditional frequency
domain filters.