I'm trying to process audio data. I'm working with Java. I've extracted the audio data to an array. Now I should pass N data samples to a function that calculates the Discrete Fourier Transform (or Fast Fourier Transform, which is more efficient). I've read documentation but I'm getting more and more confused. What I'm trying to calculate is the magnitude spectrum (|X(k)|). Can anyone help me? Thanks
Richard G. Baldwin has a number of very good articles on Fast Fourier Transform algorithms in Java on the Developer.com website. In particular, the following articles should prove to be useful:
Fun with Java, Understanding the Fast Fourier Transform (FFT) Algorithm http://www.developer.com/java/other/article.php/3457251/Fun-with-Java-Understanding-the-Fast-Fourier-Transform-FFT-Algorithm.htm
Spectrum Analysis using Java, Sampling Frequency, Folding Frequency, and the FFT Algorithm http://www.developer.com/java/other/article.php/3380031/Spectrum-Analysis-using-Java-Sampling-Frequency-Folding-Frequency-and-the-FFT-Algorithm.htm
If you only want Magnitude Spectrum of audio, go for jAudio API.
It provides class for calculating MS.
The link from @Sher is broken now. There is an API for the same purpose http://code.google.com/p/musicg/
来源：https://stackoverflow.com/questions/962426/processing-audio-data-using-fourier-transforms-in-java