The measurement unit used to express the intensity of sound is the decibel (dB). Decibels provide a logarithmic scale for quantifying sound levels, allowing comparisons between different sounds. A change of 10 dB represents a tenfold increase in intensity, which means sounds perceived louder by the human ear. This measurement is crucial in fields such as acoustics, audio engineering, and public health, as it helps assess noise pollution levels and their potential impact on hearing and overall well-being.