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Audio Physics Question
Old 13th August 2005
Gear Nut
bachconnelly's Avatar

Cool Audio Physics Question

Last night I was watching Flogging Molly play a live outdoor show. I originally was watching FOH but then moved back to bleachers that were off stage right and about 100 yards away. The volume levels of the show from there would change DRASTICALLY. The band would lose up to 30db randomly and at first I was completely baffled. It seemed like a problem with the PA, but I began to wonder if it was wind! That's all I can come up with... but i had never heard of wind affecting sound that much. Am I way off here, or could this be it. I would love an engineer of outdoor live sound to help fill me in!! Also, if any physics guru has some sort of input, I would love to hear that too!! Thanks guys!

Old 13th August 2005
Lives for gear
nukmusic's Avatar

yes the wind if strong enough could effect sound waves if you're listening from a distance. Also being to the right(off center) of the main speakers would effect the sound too.

I've also seen where amps that power one or two set of speakers overheat and shut off and on causing a drop in sound.
Old 14th August 2005

Density could be involved too.

Propagating sound waves tend to bend toward denser air. This can be caused by temperature gradients. If the ground is warm and the air is cooling, the sound will bend toward the cool, dense air and bend skyward, missing you on the ground.

100 yards is a little close to see 30dB difference with out pretty heavy winds and drastically different air temperatures.


Old 16th August 2005
Lives for gear
audioez's Avatar

Sound travels 344 meters per second at 20 degrees centigrade. Tempature and wind are indeed factors of the propagation of sound..

Man I sound like such a nerd
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