Which unit of measurement determines the intensity, or loudness, of sound?

The correct choice is dB, which stands for decibels. This unit is used to measure the intensity of sound, specifically its loudness. The decibel scale is logarithmic, meaning that a small increase in decibels represents a significant increase in actual sound intensity. For instance, an increase of just 10 dB represents a tenfold increase in sound intensity, making it a critical measurement in fields related to acoustics, audio engineering, and health, particularly in understanding the impact of noise on hearing.

The other units listed are relevant to different aspects of sound but do not measure loudness directly. Hertz (Hz) measures the frequency of sound waves, indicating how high or low a sound is. Watts (W) are units of power and can indicate energy used or produced, which can refer to sound power but not the perceived loudness. Pascals (Pa) measure sound pressure, which relates to the physical amplitude of sound waves rather than how loud a sound is perceived by human hearing. Each of these units plays a role in understanding sound characteristics, but dB is specifically focused on measuring sound intensity as perceived.