Ear-splitting 60 cycle hum it is then. Plug a speaker into the wall outlet. Lots of sound. Briefly.

I did that,many years ago--it didn't sound anything like hum--more like a rifle shot!

 

Addressing the OP's original question.

The problem with high power amplifiers is that both expense & complexity rise rapidly when you try to get very high power levels.

25 watts per channel stereo can make quite a bit of noise,in fact,you could probably get away with 10 watts.

You are unlikely to be able to come up with a new & innovative design,as so many have been designed over the years,so you will probably end up reproducing a standard circuit.

I would guess that in your country,you would tend towards the same types of semiconductors common in Britain & Australia,so circuits from those countries,& possibly Europe would be best to look at.

If you can make an unit which works properly,is constructed to good standards,& show an understanding of why things are done in a particular way,you should do well.
A bit of research on Google should help.

 

If you can make an unit which works properly,is constructed to good standards,& show an understanding of why things are done in a particular way,you should do well.

+1
That's my experience with most teachers. Show eagerness and effort along with at least a little competence.

The only other thing I can think of would be to use a creative, unexpected technology. I've seen engineering open-house projects that turn flames into speakers, for instance. And those devices you can use to turn everyday objects into "speakers" are fun. Such things may have nothing to do with what your teacher is looking for, though. Only you can judge.