higher order intermodulation distortion

how can I calculate IMD ( intermodulation distortion ) for audio ? I know the matlab function toi.m , but this gives me only third order . For audio I need the sum of all intermodulation products levels. I would need a IMD function , to write a script to get IMD vs frequency with a sweep or stepped sine .

Answer 1

[UDAYA PEDDIRAJU]

Hi Stephan,

To calculate IMD for audio, you would typically need to perform a spectral analysis of the audio signal and measure the levels of the intermodulation products. One approach could be to use the Fast Fourier Transform (FFT) to obtain the frequency spectrum of the audio signal. Then, you can identify the intermodulation products by looking for peaks in the spectrum at frequencies that are the sum and difference of the original audio frequencies at different orders.

You could follow the below steps:

1. Read the audio signal into MATLAB using the "audioread" function.
2. Apply a windowing function to the audio signal to reduce spectral leakage.
3. Compute the FFT of the windowed audio signal using the "fft" function.
4. Convert the FFT result to a power spectrum by taking the magnitude squared of the FFT result.
5. Identify the peaks in the power spectrum that correspond to the intermodulation products and measure the levels of the intermodulation products.

you can also look at https://www.mathworks.com/help/dsp/ref/distortionmeasurementsconfiguration.html

Answer 2

[jibrahim]

There are multiple features that are relvant to this:

1. spectrum analyzer supports intermodulation distortion measurements
2. There are also function you can use to get the measurements:

https://www.mathworks.com/help/signal/ref/thd.html

https://www.mathworks.com/help/signal/ref/sinad.html

https://www.mathworks.com/help/signal/ref/sfdr.html?s_tid=doc_ta

https://www.mathworks.com/help/signal/ref/snr.html?s_tid=doc_ta