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;
}

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 ; }
from the result of the fft ( in the frequency domain ) , compute the log amplitude for each positive frequency .
