Real-time Spectrum Analysis

I want to develop a Real-time Audio Spectrum Analyzer, input to which, needs to be given through a microphone. I know that Spectral Analysis can be done in MATLAB, but can this be done for live (real-time) input? How?

Answer 1

[Honglei Chen]

You can use Spectrum Analyzer to do this.

https://www.mathworks.com/help/dsp/ref/dsp.spectrumanalyzer-system-object.html

Look at the examples in the above page. The signal are fed into the analyzer in batch mode. You can just replace those signals with the one you get from the microphone.

HTH

[Parth Tarabadkar]

I am unable to do exactly that (replacing the signal). May I please know the procedure for interfacing a microphone with MATLAB and accepting real-time signals through it? Are there any special functions to do so?

[Honglei Chen]

You can use AudioRecorder, see examples at https://www.mathworks.com/help/dsp/ref/dsp.audiorecorder-system-object.html

HTH

[Parth Tarabadkar]

Thank you so much Mr. Chen, I am able to do Spectrum Analysis on a real-time audio signal. But I am stuck on the next step where the dB value of a particular frequncy in the spectrum needs to be extracted in a variable and then compared with another constant number (in real-time).

[Honglei Chen]

When you say compare, what do you mean?

If you just want to see the display of spectrum with a constant, I think you should be able to pass in an impulse signal with the threshold value and then the analyzer will display both.

If you really want to get the value itself, then you need to use a different function to do this. Depending on the settings you use in spectrum analyzer, there should be a way to replicate the algorithm with pspectrum. The algorithm of spectrum analyzer is documented in the algorithm section.

https://www.mathworks.com/help/dsp/ref/dsp.spectrumanalyzer-system-object.html#d120e337892

The pspectrum reference page is at

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

HTH

[Parth Tarabadkar]

By compare, I mean that if the input audio signal has a frequency component of 500 Hz and the corresponding gain is +2dB, then I want this value (the number 2) in a variable (say x), so that it could be further compared with any other number which we provide explicitly (say 1), i.e calculate the difference between x and 1 in real time.

[Honglei Chen]

In that case, I'd suggest you to use pspectrum instead of spectrum analyzer to retrive the number.

HTH