The sounds around us
Sound is what the ear hears. It comes from very fast vibrations. A sound source is an object vibrating very fast: a guitar string, vocal cords, a mosquito beating its wings. The vibration makes the air vibrate and sound waves travel through the air to the ear. The eardrum vibrates and we hear. A strong vibration makes a loud sound and a weak one a quiet sound. If an object vibrates very fast the sound is high; if slowly, low. Many sounds heard together in disorder are noise; loud noise can harm our ears.
Experiments: 1) Put a hand on your throat and say “aaa”: you feel the vibration. 2) Press one end of a ruler to the table edge and flick the free end. If you shorten the free end, does the sound get higher? 3) Stretch a rubber band over a box and pluck it: a tighter band gives a higher sound. Safety: do not make loud noises close to ears and do not turn volume up high.