Why is the Sound Clearer at Night?

The speed of sound in the air is affected by its temperature. The formula for calculating the speed of sound in air is as follows:

V=√γRT

Where the equations show speed of sound is denoted by v, γ is the adiabatic index (approximately 1.4 for air), the gas constant for air (R) with approximately 287 J/(kg·K)) and temperature in Kelvin (T).

When the ground heats up during the day, the air near the surface warms up. According to the equation, the speed of sound (v) increases with increasing temperature (T). Because different layers of air have varied temperatures and, as a result, different sound velocity, this can lead to more variable sound transmission.

When the ground cools at night, a phenomenon known as temperature inversion develops, in which the air near the ground is cooler than the air above it. In terms of temperature layers, this results in a more stable environment. Sound waves traveling through this more homogeneous, cooler air have less variance in speed, resulting in crisper sound transmission.

In conclusion, the temperature-dependent speed of sound influences how sound waves travel through the atmosphere. Sound tends to propagate more reliably at night, when the air near the ground is cooler and forms a more stable temperature profile, resulting in crisper sound transmission compared to the daytime with its fluctuating temperature layers.

Authors: Kalsom Aliah, Auni Nasuha, Chee De Vin & Gs. Dr Ya’akob Mansor

Tarikh Input: 20/12/2023 | Kemaskini: 20/12/2023 | emma