I created an audio spectrum analyzer based on the PiSound board for the Raspberry Pi. The Raspberry Pi uses the Ubuntu Mate 18.04 operation system. The application software is written in Qt with the Qwt library.

The high level block diagram of the project is shown here:

The application was originally written in PyQt, but due to performance reasons it was later converted into a C++ program.

A picture of the application is shown here:

The main display of the program shows on the upper part the sampled signals of both channels of a stereo audio signal. The lower part of the display shows the spectra of both channels. With the mouse markers can be set to measure the attenuation at selectable frequencies of the spectra.

The program allows to measure the THD separately for each channel of a stereo audio signal.

The hardware description and the application software can be downloaded from my Github page here.

The documentation of the whole project is done with LaTeX. The document can be found here.