function freqToFloat(fft) {
  if (fft.freqDomain instanceof Float32Array === false) {
    fft.freqDomain = new Float32Array(fft.analyser.frequencyBinCount);
  }
}
Calculates and Returns the 1/N
 <a href="https://en.wikipedia.org/wiki/Octave_band" target="_blank">Octave Bands</a>
 N defaults to 3 and minimum central frequency to 15.625Hz.
 (1/3 Octave Bands ~= 31 Frequency Bands)
 Setting fCtr0 to a central value of a higher octave will ignore the lower bands
 and produce less frequency groups.

 @method   getOctaveBands
 @for p5.FFT
 @param  {Number}  N             Specifies the 1/N type of generated octave bands
 @param  {Number}  fCtr0         Minimum central frequency for the lowest band
 @return {Array}   octaveBands   Array of octave band objects with their bounds