What unit of measure indicates the intensity or loudness of sound?

The correct choice is decibels, which is the standard unit used to measure sound intensity or loudness. Decibels (dB) provide a logarithmic scale that reflects how humans perceive sound. This means that a small increase in decibels corresponds to a significant increase in perceived loudness.

For instance, sound levels as measured in decibels can help differentiate between various environments: a whisper may measure around 30 dB, normal conversation about 60 dB, and a rock concert can reach levels of 120 dB or more. This data is crucial in fields such as acoustics, audio engineering, and environmental noise control, where understanding sound levels is essential for both safety and quality of life.

The other units mentioned serve different purposes; watts measure electrical power, hertz quantify frequency or cycles per second in sound waves, and volts indicate electrical potential. None of these units directly assess sound intensity, highlighting the unique role that decibels play in measuring sound loudness.