Britannica Sources used in this answer

Why can nighttime temperature inversions carry distant highway, airport, or railroad noise into neighborhoods?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Can bubble curtains protect harbor porpoises from noise pollution? — noise pollution Learn about the impact of underwater noise on marine animals, notably harbour porpoises.

Nighttime temperature inversions facilitate the transmission of distant noise into neighborhoods through the process of refraction.

Under normal daytime conditions, air temperature decreases with altitude, causing sound waves to travel faster near the ground and refract upward, where they dissipate. However, during a temperature inversion, the air temperature increases with elevation. Because sound waves propagate faster in warmer air, the waves traveling at higher altitudes move more quickly than those near the cooler surface. This speed differential causes the sound waves to bend or refract back down toward the ground.

This phenomenon effectively traps sound energy near the surface, allowing noise from sources like highways, airports, or railroads to travel much farther than it would during the day. This is why distant sounds often appear significantly clearer at night, an effect frequently mistaken for the result of reduced ambient noise levels.1