What environmental condition enhances sound absorption?

Humidity enhances sound absorption because moist air tends to absorb sound waves better than dry air. This occurs because water vapor molecules can interact with sound waves, causing them to lose energy as they propagate through the atmosphere. Higher humidity levels generally mean that there are more water molecules in the air, which leads to increased sound energy absorption.

In contrast, cool temperatures may lead to denser air, which can transmit sound waves more effectively rather than absorb them. Dry air contains fewer moisture molecules, and consequently, it leads to less sound absorption. High altitudes, while they may have cooler temperatures and lower air pressure, do not inherently promote sound absorption in the same manner as humidity does. Thus, the presence of humidity is a significant factor in enhancing sound absorption, making it the correct answer.