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Audio path analyzer

This project aims to develop audio analyzer for analyzing audio transport path quality using criteria such as:

  • First-order frequency response
  • Harmonic distortion properties (THD)
  • (DC offset)

Measurement results dashboard panel screenshots (from the Android app https://github.com/KlemenDEV/AudioPathAnalyzerApp):

Screenshot 1

Bode diagram display:

Screenshot 1

It is written for Linux ALSA audio subsystem, so ALSA-dev is required for building:

apt install libasound2-dev

Usage

Allowed options:
  -h, --help                     Prints usage
  -f, --calibration arg          File containing calibration data or where to store it in
  -c, --docalibration            Run calibration and store it in -calibration <file>
  -v, --verifycalibration        Only verify if calibration file is valid for the given parameters
  --frequency_low arg (=20)      Sweep start frequency
  --frequency_high arg (=20000)  Sweep end frequency
  -s, --steps arg (=200)         Sweep frequency steps
  -n, --nosmooth                 Disable frequency response smoothing

Concept

Frequency response is determined by:

  1. Sweeping across the range of sound card using logarithmic scale
  2. Sampling recorded input into a buffer
  3. Windowing the samples and removing DC offset
  4. FFT-ing the data
  5. Detecting peaks
  6. Correlating peaks to the harmonics of the measured frequency
  7. Interpolating FFT bins using parabolic interpolation
  8. Obtaining 0-th harmonic frequency and its amplitude
  9. Calculating THD as additional data

Some tests of this concept can be found in the matlab folder.

Cloning

To clone the submodules too, use:

git clone --recursive https://github.com/KlemenDEV/AudioPathAnalyzer.git