What factor most significantly affects the speed of sound in the atmosphere?

The speed of sound in the atmosphere is most significantly affected by the ambient temperature. As the temperature increases, the molecules in the air move faster, allowing sound waves to travel more quickly. This is because sound waves are transmitted through the vibration of molecules; with higher temperatures, the energy and consequent motion of these molecules increase, resulting in a higher speed of sound.

In cooler temperatures, molecular motion slows down, which reduces the speed at which sound waves can propagate. Thus, even small changes in temperature can have a noticeable effect on the speed of sound, making it a crucial factor in determining how quickly sound travels through the atmosphere.

Humidity, altitude, and air pressure also impact the speed of sound, but their effects are less pronounced compared to temperature. For instance, while increased humidity can lead to a slight increase in speed due to the lower average molecular weight of humid air compared to dry air, this is a secondary effect. Similarly, at different altitudes, although temperature generally decreases, the combined effects of pressure and density can complicate the relationship, rendering temperature the primary determinant.