Begin by making some loud noises, like hitting a drum and clapping your hands. Can you feel the vibration? Can you see the vibration of the drum?
What if you hit harder, smaller things? Tap a drinking glass with a metal spoon. Do you feel vibrations? Can you see them? How is the sound different? Why?
To experiment with changing pitch, set up your own musical instrument: take a shoebox and cut a circle out of the top like in the picture. Roll up the cardboard circle to make a bridge for the guitar and tape it on to the shoebox lid. Now stretch rubber bands around the box, over the hole. Use different sizes and thicknesses of rubber bands. You can either just put the rubberbands around the whole box, or fasten them using thumbtacks or pins or staples, as in the picture. Tape won't be strong enough.
A man playing a tuna-can guitar
When you pluck the rubber bands, do they all make the same sound? Why or why not? Can you predict which rubber bands will make higher or lower pitched sounds? What happens if you make the rubber bands tighter by adding more material to your bridge? What happens if you cover up the circular hole in your box? Why?
Try replacing some of your rubber bands with other materials - a copper wire, a piece of clothesline, a piece of yarn, an electric cord.