How does a sound wave create changing pressure and temperature in a gas?

A sound wave propagates through a gas as a longitudinal wave, creating a mechanical disturbance that consists of alternating regions of compression (high pressure) and rarefaction (low pressure). These regions move through the medium as a periodic variation of pressure around the equilibrium pressure.1

In the context of gas dynamics, these pressure fluctuations are intrinsically linked to changes in density and temperature. As the gas is compressed and expanded by the wave, the process is typically treated as adiabatic, meaning the compressions and rarefactions occur without significant heat exchange with the surroundings. Because pressure, density, and temperature are coupled in such adiabatic flows, the oscillating pressure of the sound wave forces the gas to undergo corresponding periodic variations in temperature.23

When the frequency of these variations is high, the gas molecules may not have sufficient time to redistribute energy among their translational, rotational, and vibrational degrees of freedom, leading to the relaxation phenomenon.43