Yes, sound is affected by gravity, but the effect is indirect and not immediately obvious. Gravity influences the propagation of sound waves through its impact on the medium through which the sound travels.
Gravity affects sound waves in two primary ways:
Density Gradient: In a gravitational field, the density of the medium (usually air) can vary with height. As you move higher in the atmosphere, the density decreases. This density gradient can have an impact on the speed of sound. Generally, sound travels faster in denser mediums. So, as sound waves propagate upward in a gravitational field, the decreasing density can cause a decrease in the speed of sound.
Acoustic Waves: Gravity also influences the propagation of acoustic waves by affecting the pressure in the medium. Sound waves are pressure waves, which means they propagate by compressing and decompressing the medium. In a gravitational field, the pressure gradient can be modified, causing changes in the behavior of sound waves. For example, a vertical pressure gradient due to gravity can result in the bending or refraction of sound waves, leading to phenomena like sound focusing or sound shadows.
It's worth noting that these effects are generally small in everyday situations and are more pronounced in extreme conditions or when dealing with large distances, such as in the atmosphere of other planets. In normal circumstances on Earth, the influence of gravity on sound is usually negligible compared to other factors such as temperature, humidity, and the properties of the medium itself.