Simple high-pass audio filter, how to read frequencies?

We've been given an assignment to read a wav file and compensate for hearing loss by making a high pass filter. My problem is that I have no idea on how to figure out what frequency the sound is playing at. wavread('sound.wav') only gives me the amplitudes.

I got the impression that you kind of extrapolate the frequency by looking at the differences between consecutive amplitudes somehow, but I'm not sure how. What I'd like to do is get a vector the same length as the sound vector, containing the frequencies of the sound. If that's possible, the rest should be easy I think?

We are certainly not at the level of using the DSP toolbox, Fourier transforms etc. I think we're supposed to manage with wavread and loops. But we have student licenses for Simulink, if that is absolutely necessary.