In what unit is the intensity or loudness of sound measured?

The intensity or loudness of sound is measured in decibels. This unit quantifies the intensity of sound in a way that reflects the human perception of loudness. The decibel scale is logarithmic, which means that an increase of 10 decibels represents a tenfold increase in intensity. This is particularly important for understanding how we perceive differences in loudness, as human ears do not perceive sound intensity linearly.

Hertz measures frequency, which relates to the pitch of sound rather than its loudness. Joules, a unit of energy, and watts, a unit of power, are related to the energy and work done rather than sound intensity. Hence, when discussing sound levels and loudness, decibels is the appropriate measurement.