What range does getAvg() return in Minim?

Apothem

I am trying to create a music visualizer using the FFT in Minim. For my calculations, I need getAvg() to return a number between 0 and 1, which I can then convert to dBA. However, it seems to give me numbers between 0 and some other number like 27 when I play a file with full amplitude noise created in Audacity. So what is getAvg() actually returning and how can I get it to be between 0 and 1?

I have this in my setup function:

fft = new FFT(song.bufferSize(), song.sampleRate());
fft.logAverages(22, bandsPerOctave);

and this in my draw function:

fft.forward(song.mix);
for(int i = 0; i < fft.avgSize(); i++)
{
  float amplitude = fft.getAvg(i);
  println(amplitude);
}

GoToLoop

https://Processing.org/reference/norm_.html

Apothem

Okay, I found an article on StackOverflow that answers my question: https://stackoverflow.com/questions/20408388/how-to-filter-fft-data-for-audio-visualisation

jeremydouglass

To break down the bits of answers above as an aid to future forum-goers with similar questions:

1. What range does minim's FFT.getAvg() return? It is broad, and it depends -- on your input data / FFT bands. This is documented on minim's FFT class reference page:
   
   • http://code.compartmental.net/minim/fft_class_fft.html
2. How do you graph FFT data? Fourier Transforms / FFTs are generally visually graphed on a log scale, and in this case we can use the formula for decibels -- see the StackOverflow answer:
   
   • https://stackoverflow.com/questions/20408388/how-to-filter-fft-data-for-audio-visualisation
3. Implement the decibel scale formula in processing using log10(), which is described on the log() reference page:
   
   • https://processing.org/reference/log_.html
4. How would you adjust any range (such as as you decibels log scale, once it has been adjusted, or anything else) to normalize it to the 0-1 range? As @GoToLoop linked, use norm() -- for non-normal range mapping (such as to a particular range of y pixel height on the screen) use map():
   • https://Processing.org/reference/norm_.html
   • https://processing.org/reference/map_.html

kfrajer

getAvg() doesn't seem to be directly described in Minim's documentation. The describe the concept. There is more information looking at getAverageBandwidth() and associated functions that are shown in the example next:

http://code.compartmental.net/minim/fft_method_getaveragebandwidth.html

http://code.compartmental.net/minim/fft_method_linaverages.html

Kf