System to Monitor Frequencies

I have been asked to devise a circuit to monitor the sound volume over a relevant frequency range and ensure that recommended volume at any specified frequency is not exceeded (i.e. predetermined threshold)

It should consist of an appropriate transducer, signal conditioning, ADC, microprocessor (or microcontroller).

What would be the best way to approach this type of problem? I don't need to design the actual components, just a block diagram and justify it.

Because it is a class assignment -

so the transducer is a speaker - picks up sound waves
condition the signal - amplify it so you can convert it from an analog signal to a digital signal (square wave)
You don't need to play with the volume as you will use the micro to determine the frequency of interest.
Then use a DAC instead of an ADC so the micro can produced an analog signal of constant volume.

should be simple enough