How do I filter out unwanted frequencies from an audio file?

For my school project I am being asked to remove a high frequency sound from an otherwise normal recording of a guitar. I was not told exactly how to do this only the way I should go about it. I am supposed to open the .wav file then plot it as a function of time and also as a function of frequency. And then I am supposed to find the frequency of the sound. Once I find it, I am supposed to delete it by setging the array element with the appropriate index corresponding to its frequency to zero. I then have to, "Delete the 'mirror image' of the array element." Of course then I have to clean it up and play it back without the sound. How am I supposed to go about doing this with no addons to MATLAB? Would a FFT work?

Answer 1

[Star Strider]

It would appear that the ‘mirror image’ refers to the complex double-sided Fourier transform.

In addition to fft, you will likely find fftshift and related functions helpful.

I leave the rest to you!