swap high frequencies with lows and vice versa

invertspectrum.jl

using WAV

name = ARGS[1]

y, rate = wavread(name)

spectrum = fft(y)
quarter = int(length(spectrum) / 4)

newspectrum = zeros(Complex{Float64}, length(spectrum))

for (i, v) in enumerate(spectrum[1:quarter])
    newspectrum[quarter - i + 1] = v
end

ifft!(newspectrum)
out = wavwrite(real(newspectrum), "out_$name", Fs=rate)