1. Take the string and tie the fork to the
centre of the string/thread.
2. Take one end of the string/thread and tie it around your
right index finger (pointer), then tie the other end of the string/thread
around your left index (pointer) finger.
3. Place your fingers (index/pointer) to your ears and let the
fork dangle in front of you.
4. Get someone to tap the fork with the spoon. You should hear
loud ringing in your ears.
The ringing sound travels up the string/thread to your ears.
You could tie other metal objects to the string/thread
to see what sounds travel to your ears.