Fast Fourier Transform

Audio is a complex signal.
It is a mix of different frequencies.
A Fourier Transform can decompose this signal in individual frequencies.
Likewise if you sum these individual frequencies you get the original sound.

The fast Fourier transform (FFT), is a computer algorithm that computes the discrete Fourier transform much faster than other algorithms

 

FFT graphs are used to display the frequency content of a small sample.

It displays the frequency content (Hz) and the intensity in dB.

You can analyze the performance of a DAC using FFT.

Send a 11 kHz test signal to the DAC and analyze the frequency content of the analog out.

 

TFFT (Temporal Frequency Analysis) plots the frequencies over time.

The intensity of the frequency is represented by a color intensity scale.

 

 

References

1. The Fundamentals of FFT-Based Audio Measurements in SmaartLive - Paul D. Henderson
2. Fast Fourier transform - WikipediA
3. WavePad FFT Sound Analyzer - NCH
4. Mastering The Fourier Transform in One Day - Bernsee