Rational Acoustics

Alex Sostarich
January 18th, 2011, 01:05 AM
Not really directly “audio” measurement hardware ….. but I was wondering what/if anyone is using to monitor humidity and temperature on gigs? I was doing a run of shows for NYE in Chicago and the temperature and humidity change from load in through the multiple shows days was pretty drastic. I went straight to fluke.com and came up with the 971 but it got me thinking, how sweet it would be if smart could capture temp and humidity with each trace. I did see Ferrit Rowe and Preston Soper with an off the shelf home meter when they were through Chicago with the new Martin MLA rig.

So anyone doing this and if so what are you using? Thoughts, good, bad, etc.

January 18th, 2011, 03:56 AM
Hey Alex,
Got a couple of widgets,
ACU>RITE from Home Depot in the garden section, more for trends than accuracy.

The Weather Channel, model# WS-962SU-IT indoor/outdoor with remote transmitter more accurate, has a little guy that strips off to his shorts (I checked they don't make a female model :( also updates time via wireless.
and finally Springfield Precise Temp, very small, not very accurate but good for spotting trends.
In the old days of speed plane racing I used to use a "Sling Psychrometer" and relative humidity tables to mix high nitro fuels :)

Arthur Skudra
January 18th, 2011, 09:57 AM
I use a hardware store digital temperature/humidity/clock that I bought for $30, worked fine for the few times I needed it. Been eyeing that Fluke 971 as well, but really wonder if the added cost is justified?

Here's another brand that looks very interesting:

Dr. J
January 19th, 2011, 05:20 PM
Don't want to be a downer here but according to Bob McCarthy's book -- it takes a 10 degree temperature swing to change it by 1%.

Anyone else see this?

I have the second edition. I will look it up again and post it exactly as he states it. I have read the entire book a couple of times and I am certain he said that.

Alex Sostarich
January 19th, 2011, 06:10 PM
Yep, Page 7 second edition, approximated "1% change in the speed of sound occurs with either a 5[degree]C or 10[degree]F change in temperature." Chart on page 8

The gig in questions that made me start thinking about this was significant. Load in day venue around 40F then three show days with a crowd could get upper 60s with a huge swing in humidity (these are estimates but I would go from multiple layers to a tee shirt each day). Each day the FOH engineer would play back tracks from protools the day before and the band would rehearse in a cold empty venue, then the show would hit and the temperature would start to change quickly.

This was a small room with 4 Subwoofer zones, dual ground stacked line array (vocals and band), with a flown stereo balcony fill. Timing was the key to this one and got me thinking that’s all. With a full load in day followed by 3 show days all in the same venue, same band, same setup it gives you time to think.

James Woods
January 19th, 2011, 06:20 PM
Last summer I did a month long outdoor festival. Usually, it was 45 degrees C at FOH at soundcheck time (16:00) with 15% humidity. By the end of the show we would be at 20º C and 50% humidity.

I would adjust the temperature and humidity on the Galileo every so often, and had no noticable delay misalignment between the different system sections.

In the old days, I had to continually readjust the system delays to keep everything in sync.

Dr. J
January 21st, 2011, 12:34 PM
I was asked the other day if all this was necessary for every gig. Meaning -- is it really necessary or noticeable to the public to make these changes.

My response was: When you have this bug -- it is :D

I am not sure I completely do it for the public. Most of the time they don't care or even really know. I mostly do it because it is a challenge that I love to make it sound the best I can. It feels good.

If you know how to do it and WHY you do it -- then WHY not?

I haven't dealt with the temperature and humidity thing too much although I am not opposed to trying it out. Sounds like fun to me. :D

Arthur Skudra
January 21st, 2011, 05:38 PM
It's not so much the temperature change, it's the change in humidity that can be significant in our work with sound systems, especially when RH hovers around 10-40%, where added absorption from 2KHz and beyond can be troublesome.

Some excellent information worth reading here: http://www.rane.com/pdf/ranenotes/Enviromental%20Effects%20on%20the%20Speed%20of%20S ound.pdf

Calvert Dayton
January 24th, 2011, 01:00 PM
In addition to delays -- and you can easily get a 10 or 20 degree temperature difference between high noon and night time outdoors -- relative humidity (which requires both temperature and absolute humidity to calculate) makes a huge difference in the HF air loss function. This can be kind of a big deal for long throw systems. That's why some of the higher end loudspeaker processors now have air loss compensation filters that require accurate humidity readings to set up properly.

Kip Conner
January 24th, 2011, 05:02 PM
Here's an extreme example for you... Georgia in August.

I have a regular one off that seems to always fall in August. August in Georgia where it's not the heat, but it's the humidty. Our humidity can stay a constant 90% for the whole month where the only relief we get is rain. The PA that gets tuned in June sounds like dog spit for the August show. To do that show we load-in at 1pm- about an hour shy of the hottest part of the day (95F). Our performance starts at 7pm and the temp might drop to 90F, but the humidity stays around 90%.

Another fun time was an outdoor show that we did in Las Vegas. It wasn't necessarily hot that day but the humidity sucked up the high frequency so much that it sounded like the HF drivers had a high low pass filter at 6kHz. The show started I immediately put this stuff back in the PA from the FOH position. About the third song it was under control enough to take a quick walk to find out that I was killing the front 40 feet with the most brittle PA you would have ever heard.

Calvert Dayton
January 28th, 2011, 01:50 PM
Check this baby out: