The Importance of FFT Size

As mentionned in the Getting Started section, the FFT Size parameter (found in the Display Panel) is quite important for several tools and processes in SpectraLayers Pro.

It could be explained as the equivalent of focus in photography:

When using a lens with a wide aperture, it’s almost impossible to get every subjects in focus at once, specially when you have close objects and a background objects; you have to choose what subject is the most important for that photo and will focus on that one, leaving the other blurry.


The same goes for the FFT Size parameter, it’s a focus control which instead of choosing a certain depth, choose a certain time/frequency balance.

  • The smaller the FFT Size, the more details you’ll get with time-centric events (such as transient sounds) but the blurrier the tones.
  • The larger the FFT Size, the more details you’ll get with frequency-centric events (such as static tones) but the blurrier the transients.

However spectrograms are not just transients and static tones, there’s a wide variety of frequency shapes in a recording.

See the spectrogram of a human voice for instance : it’s a lot of frequencies stacked on top of each others, which are not just straight lines but wobbling ones; which means they are not purely horizontal or purely verticals, but a mix of both, and they vary over time.


So sometime you may need to focus on the more horizontal parts, sometime on more angled parts, or verticals, or find a compromise to see most of what’s important nearly in focus.

Here’s the same example under 3 differents FFT Size:


As you can notice, some parts are more precisely defined depending on FFT Size chosen. It’s up to you to decide what is relevant and needs to be the most precisely defined.


For instance when working with Reverb Reduction or Click Repair you may want to emphasize temporal events. Or when doing Noise Reduction or Hum Reduction you may prefer to emphasize frequency accuracy.