Sound Properties

The sound that you hear depends on the properties of the sound wave. This is because the eardrum moves differently depending on the amplitude and frequency of the incoming wave, changing the way the hair cells inside the ear vibrate which produces different nerve signals.

The greater the amplitude of a sound wave, the louder the sound. Sound waves with greater amplitudes carry more energy and cause greater variations in pressure near the eardrum, forcing it to oscillate more strongly. This leads to a more energetic vibration of the hair cells and the production of stronger nerve signals, interpreted as louder sounds by the brain. If a sound is too loud it may rupture your eardrum and damage your hearing. The loudness of a sound is measured using the decibel scale.

The greater the frequency of a sound wave, the higher the pitch of the sound. When the sound wave reaches the eardrum, the pressure variations cause it to oscillate with the same frequency as the wave. Some hair cells inside the ear are more sensitive to certain frequencies than others, so changing the frequency of a sound changes which hair cells vibrate, producing different nerve signals. The brain interprets this difference as a change in the sound’s pitch. The human ear can detect frequencies of sound between 20 Hz and 20,000 Hz, but some other animals have much larger hearing ranges.

The properties of a sound wave depend on how its source vibrates. The larger the vibration, the greater the amplitude of the wave. For example, when we hit a drum, the skin stretched over its body vibrates, creating a sound wave as it displaces surrounding air particles. If we hit it harder, it will vibrate more and produce a louder sound. The frequency of the sound produced is the same as that of the vibration. This will depend on the properties of the drum, such as the materials it is made from, its size, and how tightly the skin is stretched over its body.