question: public static double [ ] computeLogAmplitudeSpectrum_FD ( final double [ ] fft ) { double [ ] spectrum = computeAmplitudeSpectrum_FD ( fft ) ; for ( int i = 0 ; i < spectrum . length ; i ++ ) { spectrum [ i ] = Math . log ( spectrum [ i ] ) ; } return spectrum ; }
target:  From the result of the FFT (in the frequency domain), compute the log amplitude for each positive frequency.