In the 90s early 00s I got really into car audio, specifically Sound Pressure Level (SPL) competitions. The goal is to make your car into a resonance chamber for a single note and see how high you can get it.
Most competitors just buy a lot of batteries, amps and drivers and call it a day. However being a broke high school student I had to figure out how to win on a budget, so I went deep on the physics. If you go deep enough you start to really get into interesting work on the physics of acoustics and harmonics.
One of the things I learned about was the testing and sound suppression work that went into the Saturn V. A genius acoustical engineer named John Hilliard [1] was a main driving force for designing the systems that would protect the Saturn V from it's own reflected sound waves. Not only that but also creating long range signaling systems for the US Military.
In order to do the testing he needed to do, he had to build a driver that could simulate the SPL of the Saturn V. That meant figuring out a way to go past the 183 dB limit for sine wave in normal atmospheric conditions. You can't actually do that with the standard inductive-coil driver, because the wave becomes "clipped" and effectively turns into a square wave, which will cause the induction coil to burn up very quickly. So they needed to create a new driver that was based on air passage.
Anyway, fascinating engineering work. Unfortunately it wasn't anything I could use in my car but I learned a lot about sound.
> In the 90s early 00s I got really into car audio, specifically Sound Pressure Level (SPL) competitions. The goal is to make your car into a resonance chamber for a single note and see how high you can get it.
[...]
> One of the things I learned about was the testing and sound suppression work that went into the Saturn V
I must admit, I first thought you were talking about “A different kind of company. A different kind of car.” Saturn[0], and not this one[1].
For a time I was very into home/pro speakers that produced tons of bass. I recall reading once about a Kenwood speaker about the size of a fridge that, when driven by a measly 25 watts or so, could rattle the windows of a house across the street. I have no idea if it was real and can't seem to find where I originally read it, but I remember being really taken with the idea.
See the trick to really "loud" bass is finding resonance between the environment and the driver FS (Free Air Resonance). Enclosure size isn't really directly relevant.
The trick is to try and couple all of it, so that there is a resonant point in the environment which matches the resonant point of the Enclosure and the enclosure matches the FS of the driver. If you line up all of these then you can get the whole world to shake on a tiny amount of power.
It's possible that the Kenwood driver just accidentally did that for someone's house and it all lined up. There were tons of old wives tales like this.
Wattage is misleading too. If all your frequencies are dorked up and you have standing waves and cancelling waves all over the place, then you have a sonically chaotic environment no matter what the power you are pumping is.
I was in an elevator recently when this guy with a deep voice started talking. His voice obviously matched the elevators resonance because it just drowned out and dominated everything else.
Quite a peculiar experience!
I can do a deep voice, and I've found I can resonate in a small room like a toilet or bathroom.
Are you familiar with any of the theories that prehistoric megalithic structures were cut and moved with sound waves? There are lots of 20, 50, even 100 ton solid stone blocks around that no one really knows how they were cut or moved about.
I used to design speakers, our best subwoofer was a helmotz resonator which is a bandpass, it has crazy efficiency but on a very narrow band, like everything in life is a trade.
Don't forget: "Disaster Area was a plutonium rock band from the Gagrakacka Mind Zones and was generally regarded as not only the loudest rock band in the Galaxy, but also as being the loudest noise of any kind at all. Regular concert goers judged that the best sound balance was usually to be heard from within large concrete bunkers some thirty-seven miles away from the stage, whilst the musicians themselves played their instruments by remote control from within a heavily insulated spaceship which stayed in orbit around the planet - or more frequently around a completely different planet."[0]
On a more serious note, I did see a band once that I later found out were infamous for their loud gigs. While most in the audience had gone prepared with earplugs, I had none, and for their "finale" (which incidentally didn't feature the band actually on stage presumably because it had become too loud even for them) I had to go outside of the main room and keep my hands over my ears. Even now I sometimes worry that night might have permanently damaged my hearing. The stupid things some people do when they are younger.
As a former guitarist in a loud rock band, I concur. I didn't use hearing protection in my teenage years and 20's, and now (in my 50's) I suffer from tinnitus.
My hearing is actually OK, because at some point, I decided to start using hearing protection (and still do now when I roadie for my son's metal band), but the tinnitus I think could have easily been averted by just not exposing myself to those sorts of volumes at close range when I was young. The damage is permanent and not worth the few seconds of 'coolness' to stand at the front of the stage at a hideously loud live gig.
(NB: My best friend at high school was deaf, and a favourite party trick of his at concerts was to turn his hearing aids off, then stick his head into the cone of any exposed speakers at the front/side of the stage for a minute, then back off and watch other kids come up and try it. In hindsight, that probably permanently damaged the hearing of MANY foolish kids who tried it out of peer pressure or wanting to outdo him, and not something to be proud of upon retrospection.)
When I was younger we used to go to these warehouse parties in the industrial zones of the city. Nobody was anywhere around after 8 so it was pretty much a free for all.
Anyway they would set up these massive speakers and absolutely blast the music. There was one guy who would occasionally show up, tripping hard on god knows what, and dance with his head pretty much buried in the cone of an 18" driver. I mean like non-stop for 5 or so hours.
As we got to know more of the regulars we learned that he was deaf, and by doing that he could feel the music and all it's intricacies running through his body. Always made me smile after learning that. Never got to meet him though, because he was always, well, way off in space so to speak.
Yeah... some bars don't do their sound well either. Went to a very small bar to watch a show one time and for the size of the room the volume was far too high and I did not have earplugs. Made the poor decision of staying and getting too close to the speakers as well while taking photos.
Have some (very light) permanent hearing loss and tinnitus from that night and I completely regret it. I'm just grateful it didn't do even more damage
I was camping in west Wales (UK) in summer and there were some really odd sounds coming in off the sea. The sounds were not audibly ‘loud’; you could here them but they sounded like they were a long way off. What was strange was that they ‘hurt’ the eardrum and could be felt in the chest.
I speculated that it was big guns or something. But I’ve no idea really.
Does anyone know what this could be? The internet is particularly unhelpful.
Somewhat related, the huge explosion in China (Tianjin) as captured on video. Not sure how loud that explosion was, but it looked apocalyptic. In some of the angles you can see the shock wave.
I'd like to recommend Simon Winchester's "Krakatoa
The Day the World Exploded, August 27, 1883" to anyone interested in learning more about the Krakatoa eruption. It's quite a story.
The author draws a comparison between Krakatoa and the Saturn V, one being a singular energetic event, and the other being a sustained projection of energy.
On the one hand, you have a shockwave of pressure differential travelling out from a central point of release, and on the other you have sustained stimulation due to a high-volume controlled dump of potential energy.
That the consistent oscillations of the Saturn V can melt concrete and set fire to grass at a distance by disturbing the air and conveying thermal energy through kinetic collisions alone doesn't really seem like a useful correlation to an impulse event that reverberates across the entire atmosphere.
If I had my druthers, though, I'd wager that the gravity waves of a supermassive black hole merger, as detected by LIGO, would likely make for a better analogue to the Krakatoa event.
The Saturn V engines are loud, but the nature of the concept is probably better modeled by the fact that you can boil water with a high-end kitchen blender or similar food processing appliance.
There's a volume threshold above which the pressure wave in the air reaches the amplitude where the lows fall below the vacuum, right? But what happens if you give the air particles energy level above that threshold?
> But there’s a limit to how loud a sound can get. At some point, the fluctuations in air pressure are so large that the low pressure regions hit zero pressure—a vacuum—and you can’t get any lower than that. This limit happens to be about 194 decibels for a sound in Earth’s atmosphere. Any louder, and the sound is no longer just passing through the air, it’s actually pushing the air along with it, creating a pressurized burst of moving air known as a shock wave.
That makes me wonder, why didn't this eruption leave a more of a trail in popular culture of the time? Shouldn't it have been the THING everybody would talk about non-stop for a few years afterwards?
Well, for one thing there was no telecommunication, so most people may not have known it was a global event.. people (outside of the range where it was entirely ear-shattering) may have just thought "huh, I guess they're firing the guns down at the battery" and only months later found out it was some faraway volcano
Also note the ground around the point of explosion being turned over by the shock wave as it moves out. That video was a great illustration of how the pressure wave moves out in all directions as an expanding ball - it is too easy to misinterpret the wave as a flat circle moving outwards from a point, rather than a sphere.
Most competitors just buy a lot of batteries, amps and drivers and call it a day. However being a broke high school student I had to figure out how to win on a budget, so I went deep on the physics. If you go deep enough you start to really get into interesting work on the physics of acoustics and harmonics.
One of the things I learned about was the testing and sound suppression work that went into the Saturn V. A genius acoustical engineer named John Hilliard [1] was a main driving force for designing the systems that would protect the Saturn V from it's own reflected sound waves. Not only that but also creating long range signaling systems for the US Military.
In order to do the testing he needed to do, he had to build a driver that could simulate the SPL of the Saturn V. That meant figuring out a way to go past the 183 dB limit for sine wave in normal atmospheric conditions. You can't actually do that with the standard inductive-coil driver, because the wave becomes "clipped" and effectively turns into a square wave, which will cause the induction coil to burn up very quickly. So they needed to create a new driver that was based on air passage.
Anyway, fascinating engineering work. Unfortunately it wasn't anything I could use in my car but I learned a lot about sound.
[1] https://en.wikipedia.org/wiki/John_Kenneth_Hilliard