This has been bugging me for a few years, so all of you scientists that understand the nature of sound waves, and the impact that atmospheric conditions have on said waves, here's your chance to dazzle me. My home is just North of I-40. The interstate is a predictable source of noise, especially at night. What I mean by that is that it's generally the same volume of traffic late at night, thereby making the decibel level predictable, within a certain range. My fixed point of reference (driveway) is roughly a 1/2 mile from the interstate. Some nights it sounds like the interstate is literally just across the road. I can hear the individual sounds of trucks jake-braking, cars honking, etc. It's very clear. And the sound is coming from the direction of I-40. At other times the sound is still coming from that direction, but the sound is muted, or almost inaudible. What causes this difference? Bear in mind, from my observation, wind doesn't necessarily cause a correlation in volume. Tonight the atmosphere is very foggy, very dense. Strangely, the sound is coming from an almost due East direction. As I stand facing the end of my driveway, the sound almost always is coming from in front of me as my driveway points south. But tonight the sound is coming from my left. The sound is being diverted somehow. How does this happen?
I was gonna say wind before u said: Please Register or Log in to view the hidden image! Check for a correlation with air temperature then.
Yes - maybe when the ground or air near it is warm, the tendacy of warm air to rise baffles the lateral propagation of sound waves. The changes in air pressure associated with different weather systems is fairly slight, compared to the overall pressure of the atmosphere, but there might be some connection there. Or perhaps the traffic just moves at different speeds in some hours, changing the pitch and penetration of the engine sounds - plus the volume of air turbulence induced by the passage of the vehicles.
