BillFitzmaurice.info

In my experiences the high frequencies really seem to carry in the cold. Passenger jets that are at 10,000 feet+ sound much closer, and the rumble of the jet engines sound to have a lot of high frequency detail.

Bruce Weldy wrote:

Bill Fitzmaurice wrote:Probably not in this case, as even 100 feet out from the FOH the levels were much higher than normal. I attributed it to increased speed of sound in the very dense air.

Interesting. Last Thursday, I set up exactly the same as the Thursday before, ran the same song to check out the system - it didn't have the high-end that was there the week before. I dialed up about 3db of 5k and it came to life.

It was probably higher humidity than the time before. Could that affect certain frequencies more than other? It seems to me that denser air might be tougher on higher frequencies.....could that be the culprit?

Here is link to some info on sound travel thru various atmospheric conditions. http://www.sfu.ca/sonic-studio/handbook ... ation.html. Only really low humidity levels 10%-30% have any real effect on high frequency attenuation. Here is a calculator you can play with to see the effects of temp and humidity on frequency absorption http://www.sengpielaudio.com/calculator-air.htm. I suspect refraction as well in your case, only the higher frequencies being bent upwards. A head wind (from performers perspective) can do that as well as warmer humid air near the ground.

That's an interesting article.
The short piece on temperature inversion seems to best fit what I experienced. It's also interesting to note that the sound source seemed to come from far behind the actual position of the aircraft; this also is explained in the article due to the slower speed of sound in colder air.