Sound Sound Vibration of air molecules . Sound is a vibration of air molecules that can cause the ear drum to vibrate, producing an auditory sensation. To analyze sound, we need to characterize patterns of vibration.
Frequency is perceived as pitch .
Amplitude is determined by how hard you strike it to set it into motion. Amplitude perceived as loudness . These are pure tones . Any pattern of vibration can be analyzed as the sum of SHMs each with its characteristic amplitude and frequency.