Audience Heat Messes With Concert Sound - Stacked vs Flown PA
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- Опубліковано 21 лип 2024
- A simple demo showing and hearing one key reason that flown PA systems are better that ground stacked systems.
00:00 Intro
01:25 Test setup
02:22 Ground vs flown
03:00 Audience brings heat
04:16 Stacked sound vs flown with and without audience
05:42 Refracted sound due to heat
07:29 Outdoor thermal issues
08:31 Outro
For more on this subject check out
• Why Crowded Shows Soun... for more in depth info on heat sound refraction
Also I have started a UA-cam membership area where I release videos early and post exclusive additional content for the huge price of $4.99 a month. An area where I can better interact with sound humans outside of the general public. Come join us if you are interested!
/ @daverat
This is literally history at its finest. Someone taking a lifetime of wisdom in a specialized field and sharing it in a way many many people can understand it. God bless
Awesome and thank you
@@DaveRat No, seriously, Jacob is right and THANK YOU Dave
Not only is he sharing his knowledge, Dave always does an incredible job for visualizing all the concepts. Often time these experiments are so good and cool they should be adopted in school physics classes
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This is the type of every show phenomenon that people wouldn’t believe if you didn’t demonstrate it to them like this very cool no pun intended
This is like Mythbusters for audiophiles
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Please, never stop making content. I absolutely love these videos.
It's amazing how audible the difference is! Seriously cool (pun intended) 😁
Just a wee correction though, if I may - hot air is less dense than the cooler air above it. Rather than sound bouncing off the hot air layer, it's actually the cool air bending the sound upwards like a banana. This diverts some acoustic energy away from the listener (as you say). HF bends more, so more HF energy is diverted away than low frequency, causing the loss of HF that you demonstrate.
By angling down, the 'banana' effect (not a scientific term!) still occurs but not in a big way because of the ratio you talk about.
If anyone wants to read more, check out stuff on refraction', particularly refraction of sound.
It's amazing we can hear refraction in such a 'try this at home' set-up. Thanks for another great demo! 👍 So glad you're doing these again. Keep 'em coming!
Agreed, the speed of sound is faster in warm air causing refraction away from heat
@@DaveRat Bob Hiel's book has info on a sound system designed to take advantage of this at a large racetrack. I think that may have been the first big sound system that was flown to exploit this diffraction effect. If I could find my copy of the book I would give more details. I do remember that the horns were about 5' long and we're pointed down about 30°. The horn's axis intersected the pavement about half way to the first spectators. Earlier systems had used ground stacks in the infield. In the mornings it just about ripped people's heads off because it was way too loud. But that was not enough when it got hot. The power required then was huge and people miles away could hear the announcements better that those in the stands because essentially the sound just bent over the top of the stands, bypassing the audience.
James Drissel that’s incredibly interesting. I live in indianapolis and have gone to several races at the world famous Indianapolis Motor Speedway. As a live reinforcement sound engineer for several years, even I can tell the sound system for all those in the infield is absolutely garbage. I never thought about the air density though. The temperature of the track can become incredibly high during the day, so it makes so much sense now.
If I may correct this even further. Some brief background on sound propagation:
Density variations of air can be ignored. Sound refraction is related to the velocity gradient of air, following Snell's law in a first order approximation. Ignoring wind and humidity, the speed of sound simply relates to temperature (of dry air), named in literature the adiabatic speed of sound. In that case, sound refraction is related to the temperature gradient. For horizontally propagating sound through a vertical temperature gradient you can state that "sound refracts up for a negative gradient and down for a positive gradient" and steeper the gradient, the stronger the refraction.
To generalize this a bit more you do also need to take the relative orientations between the direction of sound propagation and the temperature gradient into account. So the effect is strongest when the direction of sound propagation is orthogonal to temperature gradient (or velocity) and is zero when sound propagation is tangential to the temperature gradient. In case of the latter, sound propagation will only notice a velocity decrease (or increase) but no directional change occurs.
An awesome book (for experts) on the physics of acoustics is the book by Allen Pierce doi.org/10.1007/978-3-030-11214-1
To go back to the equally awesome demonstration with the candles:
The audience (or candles) near the ground cause a negative temperature gradient and sound propagation from the ground stack to the microphone is orthogonal to this temperature gradient, maximizing the refraction upward. For the flown speaker, the relative angle with respect to the temperature gradient is smaller than 90degrees reducing the refraction. Also equally important for the flown speakers in the nonlinear gradient. It's likely weaker for the path from the flown speaker to the microphone (further away from the candles) than for straight through the heat source for the ground stack.
@@psmets1 now we just need to add in the humidity created.by humans to the mix, though less of an impact than heat, as well
another amazingly simple explanation/demonstration, thank you dave! we don’t deserve you 🙏🏼
Who disliked this!??! An example that exaggerates issues that come up with a small practical example and basic explanations of complex issues.
Exactly!
Trolls do this!
Quite simply the best pro audio info resource anywhere right now.
Thank you thank you!
Thats a great demo...I have been trying to get this across to bands / engineers for years that a room changes as it fills up and the temp changes......thank you...i will be passing this along
The demonstration was enough to make my jaw drop. 38 years on stage and would never have understood how much difference a temperature differential could make. Thank you Dave!
And thank you for taking the time to comment and positive responses like yours are what keeps me going on this stuff
Wow!! Love your videos and love the examples to you show. So easy to comprehend.
Wow man. I always learn something new from your videos but this was like learning a whole new field of study or something. I never would have thought you would have to factor in sound refraction due to different temperature layers. That's a whole other level.
Awesome!!
Awesome, awesome content ! (As usual) Very well done, straight to the point and easy to understand. Cheers Dave.
You are back!!! YESSS!! nice vid as always!!!!
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Fascinating experiment! I was definitely surprised by the difference it made.
Very interesting,waiting for more.thank you Dave.
Thanks for all these cool videos Dave, really appreciate the wisdom you impart and the super chill way you deliver it
Thank you Nick!
never realised just how significant the difference is with flown PA. ive only done engineering in a small-ish venue before so the stacks tended to not have any trouble unless a fat guy stood directly infront of them. really good demo of the effect :)
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brilliantly demonstrated! Thanks, Dave!
thank you for making this video. the number of young sound engineers and artists i have explained this too that dont believe me is a big number haha. Awesome video
Wow, i did not expect the effect to be that noticeable.
Thanks for showing us this! This is pretty valuable info!
Cool cool thank you!
Oh lord, the amount of knowledge Dave in keen to share with us makes me want to cry! Thank you once again Dave
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Your demonstrations are so real world man! This is the kind of knowledge that can set a person apart from the rest.
Awesome! Thanks again ✌
Thank you Steve!
Absolute genius way to simplify the physics of sound reacting to an environment. Thanks Dave, stay safe.
Awesome and thank you!
Hi Dave thank you so much for all your replies. I’ve read and liked them all. Great that your videos popped up in my general searches on UA-cam and yes what a learning channel this has become. Master class. Much appreciated 👌
Very cool and thank you Brian!
A great demonstration and a great vid to show to some venue management to convince them of the benefits.
Fantastic demo. One of my favorites so far.
Thank you
I was waiting for another part to this story!
Brilliant demo!
Thank you Mike!
Wow, always glad to learn something new! Especially as I'm 52, rare these days but thast fantastic!
Great demonstration!
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What a great test. Simple but effective. Didn't know this
😳😲 Amazing demonstration! Thank you sir 🤘
A great demonstration of the issues with line arrays also
Mind blowing!
Great demonstration.
Greetings from Germany
Great video! Keep em coming 👍🏻
Amazing and efficient demo Dave ! Thanks from Italy
Thank you and I can't wait to get back to Italy
Dave Rat we wait for you here asap. Anytime you are here the sound is always the best. Keep up the excellent work on youtube, SoundTools and Rat Sound. Stay safe
"..and I will uh.. think of something else and do another video soon" 😅 Amazing! Thanks as always Dave!
Great content! Thanks for making these!!,
Thank you for making interesting videos! Great stuff.
This was fascinating. Thank you
Been in bands for years, never dawned on me about thermal issues, cheers for such a simple, but explanatory demonstration. Subscribed!
Awesome and thank you!
@@DaveRat Hey, you're welcome. My band is only small, but I'm always striving for getting the best sound, with what we have. So someone that can explain something which is quite complex, and me get it within seconds, is worth gold. 💯☺️
I actually had that issue happen at a baseball field in Sacramento- they had plastic flooring and it was hot and my smaart measurements were so weird . I could see the heat in the floor of the plastic .. thanks for this info sir ..
These are so educational, thank you Dave Rat.
Dude - this is a really well done experiment. Easy to replicate, and shows the cause and effect of the ‘audience’ heat.
Awesome and thank you!!
Very interesting, what a change it makes.
Elegant explanation. Thanks Dave!
One day in Coachella I asked David for a photograph with him and he very humbly approached and took it, great person David
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This is wild thank you!!
Cool cool thank you Kenneth
Every touring engineer has experienced that difference between the empty room of sound check, and the full, moisture filled Dense air of a packed venue. We all expect to have to add high-end back into our system EQ after the room is full. Your points about a flown system are very well taken. Especially about the distance differential. Really fun presentation. Thanks for that.
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thankyou for sharing the knowledge!👍👍👍
Thanks Dave another interesting and informative demo.
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Holy Shit this makes so much sense and that demo is amazing.
Great dissemination of information.
Thank you Tyler
On some large racetracks the speakers are flown and aimed at the track surface. When it is cold the sound reflects off the pavement into the stands. As it get hotter the sound refracts because the hottest, least dense air is closest to the pavement. The sound then curves up into the stands. In musical venues you may have a similar thing happen with the sound going to a balcony.
Interesting! I really like the learned problem solving that prediction software has yet to be able to show
I have finally met someone that I could talk to for hours about sound... Most people get a deer in the headlights look when I talk for 30 seconds about this stuff... Thanks for your contribution Dave!
Awesome and great to meet ya Mike!
Great demo!
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Great explanation and demo
Hi Dave, my description focussed on cool night air with a distinct warm barrier at crowd level. I am a radio wave propagation specialist as part of my profession with sound engineering being a serious hobby of say 6 years with loads to learn on audio. I spend my nights learning from you! Cape Town South Africa. The next level of experiment would be pulling out a high tech frequency spectrum analyser
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That was unexpected!
Great wisdom!
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dude this was awesome, cheers for the knowledge bomb
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Amazing! thanks for this!!!
informative and cool yet again!
I would not have expected the heat to affect tonality that much! Very helpful
Right? It's surprising.
Never thought I could even hear it with my phone speakers. Great video. Subscribed
Perfect
My favorite experience was running sound for the Romantics at Western Washington University in Bellingham Wa.
As the crowd brought the heat in the room to a higher level, someone decided to open the ocean side windows to cool off the room. the inrush of humid air immediately condensed on the cement beams overhead, and it proceeded to rain in the building....including on my trusty 40 channel Gamble console.....ah, fun memories. The show survived and yes, you could hear a different audio characteristic with each change of the weather.
All this is fun!
Great demo.
Just, mind blowing.
Excellent!
I'm thankful to be existing on this planet while he is.
This is simply the best.
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watch the bending sound waves with heat as it is a worthdwhile watch, loike the rest of Dave's videos. it's like he has a magic touch. the delay and the point source vs line array videos were eye opening, not to mention same sound from two sources :)
Wow. I did not know how heat affects sound. Thanks for the video demonstration
Very cool. I did an AES paper with my friend Mario that I will do a video on covering heat and sound dispersion.
Awesome. I can't wait for that video.
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Amazing !! Thanks Dave 🙏🏿👍🏿👍🏿
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Fantastic video.
Thank you!
This is a perfect example and the point of the video is proven. Why would 7 people dislike a simple experiment? Oh let me guess, they prob wanted to see purple candles. Mr rat thank you for always experimenting and keeping it simple...i decided to double stack my CC on a 10 feet truss and shade them until i get real arrays speakers. Great video
Thank you! And yeah, no idea why people rock the dislikes but all good.
I remember seeing Wilco several years ago. They had all their amps aimed everywhere but at the audience, including one speaker pointed skyward. Crazy how all this stuff works
That's interesting!
Fascinating!
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Great explanation
Awesome thank you
cheers for the candle people, wonderful performance!
Yay candle people!
This is really really interesting. Thanks you maestro for this vdo :D
wow, brilliant and well explained. thank you sir!
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WOW! This might explain why I noticed my instruments sounding different on a very hot day. Im gonna use this if I ever get around to recording that song I complain about the heat. Just have to make sure I dont bbq the condensator
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Aweaome explanation oh and BTW...SUBSCRIBED! Keep them coming!
Thank you
Ha! Very clever simulation. I do simulations, videos and listening tests for my Live Sound students, but I am going to make them watch this video for this particular comparison. This topic often comes up and I just explain it to them, but here they can actually hear what is happening. Cheers!
So cool and thank you
@@DaveRat Yours is required watching. I have plenty of viewers for my live sound vids and in one of them I suggest they 'listen to other people as well, with different experiences, like Dave Rat', because we can't just listen to 1 person....I guess 'cause there are people who 'poo poo' some of my remarks; thankfully that is the minority (some people just object to the science part of it) Great channel, man! Stay safe.
Thanks Dave!
Amazing videos Rat makes, great, thank you very much...
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Hi,Dave. I from China, I am trying to learn English watch your video,Thank you for sharing your experience. you are my sound hero,Looking forward to seeing you.-------your five year fans.
Awesome! Hello Ray
Great stuff!
Awesome
@@DaveRat I was aware of temperarture influence on sound, just never realised how much it is...hearing is believing.
Also great vid on the accuracy of human hearing in the horizontal plane vs the vertical....keep these vids coming. love it!
Great video. 😀👍♥️
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Hey Dave. Love your knowledge, thank you for sharing so much with us over the years. With regards to indoor venues, how much does temperature change affect the sound vs absorption from people filling up a venue?
It's very dependant on how full, the temp of people vs temp of venue air, distances, angles of pa vs coverage.
Basically temp, and audience and wind, heat, fly angle, dispersion of the sound toward u desirable surfaces, pa type and so on, all have varying amounts of impact
Dave another great video. I'm going to have to fly over to USA and buy you a beer once it's all back to normal.
Woo hoo! I'm in!
Remember too that warm air, especially where I live (South Florida), has more humidity. There is that factor as well. This also goes to the guy who made the warm air is less dense comment. There is still the humidity factor. Which could be even worse I'd think.
P. S. Dave, thanks for another informative and interesting video.
Humidity actually has less of an impact than heat, in that the variations in sound frequency response and diffraction between the coldest and warmest environments we as humans provide sound for, is less than the impact of the most and least humid environments we encounter. There are quite a few graphs and data sets out there that are worth a google
Love the videos! The demonstration was very clear and easily heard. I do have a question about your explanation, since hot air would be less dense than cold air... Although sound would travel through the denser medium better... I guess the analogy of a stone skipping off water confused me. I am easily confused though.
Yeah, I confused myself as well between the analogy and the reality.
Sound travels faster in warmer air, so there is a refraction away from the heat.
Great videos.
man this is great, you should do a masterclass or somthin haha
Awesome explanation, though I'm using this for almost 15 years without knowing that this is the "right way" =))
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Learn something new everyday.
Very interesting, more ammo to get my church PA up higher. Also explains why some days I can hear outdoor sounds from a lot further away. I originally thought wind was the reason, but it seems much more prevalent on still days.
As in hearing jet ski's etc. whilst several Km away from the bay.
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Thank you Dave. All your videos are very well explained through live demonstration. Hope to hear more from you.
Many thanks for taking the time and effort to do such a great video. So we tune the system to an empty room using pink noise and a RTA. I'm curious to know what other engineers do to compensate for the heat factor when the room fills with people. Or if the speakers are flown, is any compensation really necessary?
I will do a video on soundchecks and also one on stabalizing and compensating for venue temps
Love the demonstration. To appreciate the effects of refraction of audio from the flown line array to the ears of the average crowd, the sensor microphone needs to be placed under/within the heat barrier of the candles. PS reflection can only occur inside of/below the heat barrier off the cold barrier. Refraction in this case occurs where travelling waves move from a higher molecular density (colder air) “the flown arrays” to a less molecular density (warmer air) “bent away” at an obtuse angle, the end result being dispersion. PS Tall people have a better concert audio experience with maximised benefit of flown line array systems.
Wouldn't placing the mic under or within the heat barrier just account for the experience of listeners in the tightly packed crowd area?
One of the issues we ran into was the main stage at Coachella stage left hang was overly audible at the mix position of a tent 700 feet away during the day when the ground was hot and not an issue in the evenings.
During the day we refocused the array down to 200 feet from the 300 feet of it's normal and evening focus.
The mix position in the rent was neither under nor within the heated area yet severely impacteted by the heat.
This same scenario applies to any show where the sound shoots at and over a sense crowd up closer generating heat and refracts above and away from listeners located farther away.
Additionally, a common issue is the less crowded area behind the dance floor or arena floor. The heat generated by the more active and tightly packed humans tends to refract the sound away from the humans in the less warm, less tightly packed humans that are farther away.
That said, a mic under or within the heated area would test for the experience that people toward the middle or back of a densely packed club or arena floor would experience.