How to isolate a specific frequency using a spectrum analyzer program?

Question

Sound processing

I am writing a diploma on the topic of preventing the effects of sounds of certain frequencies on a person. As far as I understand, spectrum analyzers decompose the spectrum into frequencies. In the future, I would like to select a certain range so that a computer program (for example, in python or c ++) can react to it. Does this already exist in any form or do I need to change the Fourier transform formulas myself?