Question

How does the sound of Thunder propagate in warm and cold air?

Answer 1

Thunder is the term that describes the extreme heat generation due to a lightning flash within a fraction of a second. So what happens during lightning is that the air of the surroundings gets heated up to a temperature of about 30,000°C within an instant. This results in the expansion of air molecules due to exposure to heat. The rate of expansion is dependent on the rate of the heating time period. The faster the air heats, the faster is the rate of expansion of air molecules. This phenomenon is known by the term explosive expansion or thunder. This instant expansion of air results in an immediate contraction of the air molecule to its front resulting in the formation of shock waves. These waves bear similar resemblance with the likes of shock-boom produced during a fireworks explosion.

Sound waves are known to travel faster in warm air than they do in cold air. This is because the molecules of air within the warm air move faster with higher vibrational energy. When the temperature of the air keeps on decreasing with height, thunder is audible up to a range of about 10 miles.

Warmer Air: - Faster sound speed Cooler Air: Slower sound speed / Source Listener

But there exists a phenomenon during winter when the air temperature increases with height and the temperature near the ground surface are cold. This results in a phenomenon known as inversion. the sound waves are refracted back towards the surface of the earth in such scenarios since they travel on faster velocity in the warmer air above than the cold air below. This results in the generation of an additional sound which amplifies the sound of thunder. Thus during winters when the thunderstorms generate in warmer air above a cooler air near the earth's surface, louder thunder sounds are perceived by the ear.

Sound path due to refraction Result: the listener hears additional sound Direct sound path Source