Effects of heat and humidity on sound

Randy Gartner

Randy Gartner

Junior
Jan 12, 2011
465
18
18
72
Pennsylvania
randygartnersound.com
I have long noticed that when it's a really hot and humid day, the Pa just doesn't have that pizazz like it does on a cooler day. Also,when starting out on a humid evening, as soon as the sun starts going down, the system seems to come to life. Here's a quote from an article on the effects of heat and humidity: as sound propagates through air, the air absorbs energy from the sound wave, attenuating (weakening) it. The effect is significant only at frequencies above 2 kHz, and increases with frequency.

So my question is,what are you going doing to compensate for this effect?
 
Randy,

I moved from New Mexico to Florida to compensate ;^).
My system now does not need nearly as much HF boost to compensate for the HF air attenuation the very low humidity in NM caused. The difference was not subtle, I should re-voice my system for the average outdoor conditions now, the first gig I did had to bring down HF on the EQ to avoid too much "sizzle". The problem here in Florida is the indoor air conditioning can be near desert-dry, while outdoors humidity can be 30% or more higher, so for gigs with over a 50 foot "throw", different HF compensation is needed between indoors and out. That said, unless your system can be deployed with HF "shading", when heat goes up and humidity goes down, you only have two choices: too "crispy" up front, or too "muddy" in the cheap seats.

Art
 
Art, outdoors humidity in Florida seems to never be under 30% and I swear I've been there in 300% humidity... you need SCUBA gear instead of a towel or even a squeegee. 8O~8-O~:shock:
 
Tim McCulloch said:
Art, outdoors humidity in Florida seems to never be under 30% and I swear I've been there in 300% humidity... you need SCUBA gear instead of a towel or even a squeegee. 8O~8-O~:shock:
Click to expand...
Tim,

Right, the outdoor humidity will be 30% or more higher than the air conditioned indoors, in other words, 50% RH inside = 80% outside. I am getting used to the humidity, but the rapid humidity/temperature changes going in and out are hard on my knee joints, which have not been the same since bashing my right knee into a log on a boom run in 1995 (found out I'm not much of a lumberjack, especially after drinking beer all day) and slipping on ice and twisting my left knee a few years ago.
But it's all worth it to hear the sparkle of cymbals and the tweet of the birds and chirping of crickets and frogs ;^).
Funny, I went to shoo a frog out of the shop the other day, turned out it had died standing up, completely dried up looking at the air conditioner...

Art
 
  • Like
Reactions: Max Warasila
Randy Gartner said:
I have long noticed that when it's a really hot and humid day, the Pa just doesn't have that pizazz like it does on a cooler day. Also,when starting out on a humid evening, as soon as the sun starts going down, the system seems to come to life. Here's a quote from an article on the effects of heat and humidity: as sound propagates through air, the air absorbs energy from the sound wave, attenuating (weakening) it. The effect is significant only at frequencies above 2 kHz, and increases with frequency.

So my question is,what are you going doing to compensate for this effect?
Click to expand...

Back in the day of the BSS FDS-388 (the first 'big' OmniDrive), BSS had a meteorology probe available. It plugged into the back of the 388 and measured the temp and humidity. I never had access to this accessory and consequently didn't learn much about it, but the answer is yes, automatic compensation has been done.
 
Tim McCulloch said:
Back in the day of the BSS FDS-388 (the first 'big' OmniDrive), BSS had a meteorology probe available. It plugged into the back of the 388 and measured the temp and humidity. I never had access to this accessory and consequently didn't learn much about it, but the answer is yes, automatic compensation has been done.
Click to expand...
Tim,

The meteorology probe was only used to "plug in" the difference in speed of sound which varies slightly with temperature and humidity, which determines how many ms delay are needed for time of flight, really only of concern for long delay lines- it was not used for HF air absorption automatic compensation.

Changing delay times has no failure mode - boosting HF from 3 to 20+ dB to compensate for differing heat vs humidity can easily result in cooked drivers or overly compressed distorted "sizzle", and an automatic HF compensation device would require separate algorithms for each portion of the system that covers a different distance.

Art


 
Thanks for the clarification, Art. You're absolutely right that any compensation would have to have programmed max boosts built in and in retrospect that's more than the 388 was intended to do.
 
Top Bottom