A very loud B&M or 2 or 3!

Heck, even if something isn't touching, the vibration can still be transferred to other things over short distances, via the air. It's a lot like electricity in many regards.

I'll admit that I'm not an expert in sound wave theory, but I do know that vibrations do not transfer very well from a solid object, across an air space to another solid object. I've toured several concert halls, and the one thing they typically do to isolate exterior noise is to introduce an air space between the walls.

There are literally thousands of factors that influence vibration. The carbon content of the steel, type of fasteners used, footer size, soil density and on and on.

If that were true then a B&M installed in clay soil would sound different than one in sandy soil, or one with larger footings would sound different than one with smaller footings. Or one over water would sound different than one over land. But that has not been my observation. They pretty much all sound the same to me.

You can talk about vibration theory all you want, I'll stick with my personal observations, and invite you to do the same. Visit your nearby B&M. Stand as close as you can to a support. Listen to where the sound is coming from when the train roars by. It's been my observation that most of the sound comes from the train and the tracks, not from the supports.

Jeffrey Seifert said:
It's been my observation that most of the sound comes from the train and the tracks, not from the supports.

Exactly! :)

Doesn't matter. As Brandon eluded to, you can't just view that in a vacuum. Most of the vibration in a car's combustion engine presumably comes from the pistons moving around and valves opening and closing (not to mention those thousands of little explosions every minute), but the sound dampening comes from the engine mounts and interior of the engine compartment.

What generates the sound is less relevant than that which absorbs it. Some things conduct sound and resonate better than other things. No matter what kind of track we're dealing with here, it's connected to supports. If the vibration is transmitted to supports (and it is, obviously), and those are filled with sand or something, the dissipation of that sound energy is occurring there.

Jeffrey Seifert said:

Heck, even if something isn't touching, the vibration can still be transferred to other things over short distances, via the air. It's a lot like electricity in many regards.

I'll admit that I'm not an expert in sound wave theory, but I do know that vibrations do not transfer very well from a solid object, across an air space to another solid object.

And I never suggested they transfer well across low-density mediums such as air. I merely pointed out that they do transfer. I mean, how would you hear otherwise?

I've toured several concert halls, and the one thing they typically do to isolate exterior noise is to introduce an air space between the walls.

That's correct. And typically, they use a combination of low and high density materials to damp the sound. If you had a steel-framed wall (high density), and simply introduced a small air gap (say, 1/16"), the sound would still transfer quite readily from one side of the steel from to the other.

But this has little, if anything, to do with the subject at hand.

If that were true then a B&M installed in clay soil would sound different than one in sandy soil, or one with larger footings would sound different than one with smaller footings. Or one over water would sound different than one over land. But that has not been my observation. They pretty much all sound the same to me.

That they sound "pretty much" the same to you is of no relevance. Mechanical vibrations, especially in the case of a roller coaster, are about as chaotic and complex a system as you can imagine. You'd have to be some sort of audio savant to be able to differentiate such small deviations in sound, if you knew what to listen for. But not only does your body not have the capacity to hear sound waves beyond a narrow spectrum, your brain doesn't even know what to listen for.

If you were to use accurate instrumentation to measure the sound waves being generated by various identical coasters, and changed certain parameters (the soil density, for instance), you'd be able to differentiate between them. Not only that, but you'd need a completely controlled test to know that your results aren't being tainted by the literally hundreds of factors in play. The temperature of the air changes how things sound, ever so slightly. Wind, humidity, temperature of the track/supports/wheels/train/footers/etc.

To get back to my comparison of mechanical vibration to electricity... You can use devices to measure electrical current accurately (and, similarly, get waveforms that define electrical activity), but you'd be hard-pressed to tell someone which toaster just shocked you more when you stuck a fork in each.

You can talk about vibration theory all you want, I'll stick with my personal observations...

Wow. Are you from Texas, by chance? ;)

Issac New-who?

Jeff said:
Doesn't matter. As Brandon eluded to, you can't just view that in a vacuum.

Agreed - but the idea I was considering is that there are two competing factors at play....sources of sound (i.e., vibration, friction, etc.), and dampening of sound. Like you said, it seems like the supports are being used to dampen noise (sounds that are creted by the trains/tracks)...it was being suggested, or maybe I read into a couple posts, that the noise was emanating from the support structure.

Not sure if you got that impression from what I've posted, but I certainly didn't suggest the sound was originating from the supports, just that the sound is transmitted via (again, among countless other things) the supports:

djDaemon said:
Actually, while the "source" of the sound is indeed the wheels, you wouldn't hear it without the supports and track to act as a means for resonance.

link

So yes, the sound is indeed emanating from the support structure (and other stuff) to your ears, just as the vibrational energy (which ultimately results in sound energy ) originally emanated from the wheels.

dj, while you may be correct in how the sound is transferred, I still think that Jeffrey is also right on a few points. The sound seems to almost exclusively come from the track on B&Ms. Next time you are at IOA and ride Hulk, listen as you are in the line next to a support or standing next to one outside the exit. While the support is visibly vibrating, I think you'll notice that any sound made by the ride (well, the "roar" at least) is coming entirely from above you, not from beside you as it would if the supports were really major conductors of the sound(s) as suggested. If the supports were really the major source of resonance (which I believe is what you're hitting at), wouldn't there be at least noticeable sound similar to the "roar" coming directly from the support as you stand next to it?

Or is the steel thick enough (or made in a way) that while it acts as a very good resonance chamber, sound does not "leak" from the support through the vibration of the steel? I'm not claiming to be an expert or have any real knowledge in this area, more just thinking out loud and reason myself through a question or two.

Mike, I didn't meant to suggest (and I don't think I did) that most or all of the sound was coming from the supports. I was simply questioning the assumption that most or all of the sound was coming from the track, and the subsequent suggestion that the supports were largely irrelevant (which I may have misinterpreted).

Perhaps, going of what Jeff said above, clarification is in order. The large hollow spine on B&M track perhaps works as a better solid-to-air transmission device for the vibration. I'd guess the steel walls of the spine are thinner than that of the supports, so when the vibration travels throughout the structure, that energy is transfered to the air (and thus your ears) via the path of least resistance (again, like electricity), which could be the track spine. That would explain why the sound seems to emanate from above, so what you posit certainly seems reasonable.

When you fill the supports with sand, the vibrational energy travels throughout the structure, but is dissipated to a large degree by the sand, thus reducing the remaining energy and resulting noise.

Again, I wasn't claiming that the sound wasn't coming from the track, but rather, as Jeff said, you cannot look at this process in a vacuum.

Who cares!?! Lets go ride a real coaster - an ANTON!!! :)

maXairMike said:
dj, while you may be correct in how the sound is transferred, I still think that Jeffrey is also right on a few points. The sound seems to almost exclusively come from the track on B&Ms.

That's where it comes from on Intamin rides too. Nothing is rolling on the supports, after all. As I said before, and as Brandon also said, it's where the sound is transmitted to that makes a difference. If there is no substance to absorb it, it's gonna be loud. As track is quite rigidly connected to suports, it only makes sense that the sound will be conducted to them, and that they make a good place to absorb the sound.

Incidentally, someone from CP mentioned that the sand also adds some kind of structural bonus as well, but it wasn't out of an engineer's mouth, so I'm not sure what to think about that.