Sound levels are a measure of which phenomenon?

• A. The temperature of air
• B. The vibration of molecules in a medium such as air
• C. The rate of chemical reaction in the atmosphere
• D. The speed of light in air

Answer: (B)

Sound levels quantify how strong the pressure fluctuations are as air molecules vibrate and propagate a pressure wave through a medium. When an object vibrates, it compresses and rarefies the surrounding air, creating waves; the larger those pressure variations, the louder the sound, and the decibel scale measures that amplitude. So the phenomenon being measured is the vibration and resulting pressure changes of molecules in a medium such as air.

The other options don’t describe what sound level measures: temperature of air affects how fast sound travels but not the loudness itself; the rate of a chemical reaction is unrelated to sound intensity; and the speed of light concerns electromagnetic waves, not mechanical sound waves.