FFT and values ​​of the array

[iacoposk8]

In this example:
http://mohayonao.github.com/timbre/documents/fft.html

in the function WaveViewer.animate, there is the following code:

for (i = step, imax = wave.length; i < imax; i += step) {
y = (wave[i] - min) / (max - min);
context.lineTo(i * dx, height - (height * y));
}

wave in the array (I think) there is a list of volumes achieved by the different frequencies at that time from the audio file

1. these volumes in which units are? decibels?
2. for example, in the array, the position 35 corresponds to that frequency?
   thanks :)

[mohayonao]

The function WaveViewer.animate is just sloppy that made for a demo.

It's my understanding that the array contains magnitude spectrum, not decibels.
Decibels and frequencies probably may be calculated as follow.

decibel[i] = 20 * Math.log(array[i]) * Math.LOG10E
frequency[i] = (samplerate / (array.length * 2)) * i

By the way, this repository and document are old anymore.
New project page is here: http://mohayonao.github.com/timbre.js/

thanks.

[iacoposk8]

no way to know the volume of each frequency?
thanks for the answer :)