Water as a sound deadening medium in enclosures???

[doogyscoot]

Please have patience

Has anyone investigated this much, with regard speaker enclosures? Had a search already and though people thought it wouldn't work (due to water allowing waves to travel within it easily) I know it's hardly the most practical of things to work with, especially with lots of electricity flowing round.
Anyway got me thinking about using something like those fillable ice cube bags (obviously not frozen and eventually designed specifically to be more durable) as sound deadening on the internal walls of a cabinet. Basically a cellular material with water (or maybe a gel?)in the cells. Imagine big bubble wrap but filled with water instead. I agree that a layer of water sandwiched between two walls would allow the rapid and efficient transmission of waves between the sandwich materials. However I have a feeling that by housing the water in flexible cells which are not physically fixed to the walls (maybe, say, hung from the top) the waves may be dissipated without being transmitted to the cabinet walls. Kind of like a hydro suspension kinda thing... imagine punching a water bed (bad analogy but the best I can come up with).
I know it will be a lot of messing about, but I'm looking for something to investigate in my final year university design project and this might have some mileage, at least from a testing and analysis/ feasibility perspective.

Thoughts anyone?

It's either this or doing a translam enclosure with hollow walls and filling it with different materials to see what happens...

Any other suggestions for things to investigate in terms of enclosure shapes... or pretty much anything feel free to make em.

[ryoung]

could be worth a shot, keeping the water from getting stinky could get interesting after a while though.....although there are better options that are easier and less messy

[fwater]

Since water does freely transmit waves (altough it would be less compliant in small "cells"), it probably wouldn't be a good dampenning medium. Think of it this way- sound passes through the inner wood wall and looses X amount of energy, then passes through the air and water or cellular configuration almost unimpeaded, the the outside wood wall losing X amount of energy again. Cancel the water between the two panels and fix (laminate) them together; the sound energy lost will not just be 2*X, it will be somewhat higher.

I have yet to experiment with laminating wood and asphalt but I intend to in the near future. Some hobbiests are very pleased with the energy control. Look into replacing the water in your hypothesis with sand- car manufacturers have employed it in luxury cars to keep road noise down.

[doogyscoot]

Thanks guys, my thought was that water responds differently to air waves contacting it directly and via a medium such as the first layer of wood you talk about. (I wouldn't sandwich the cells they would be loosely attached inside a single walled cabinet). Bear with me through another analogy here... If you lay in the bath with your head submerged and someone outside the bath is talking the sound is very very muffled, in fact i suspect that most of the sound will come from the bath itself resonating due to the waves contacting it... thus being the medium through which sound waves are passed to the bathwater. If someone taps on the side of the bath it's really loud because the shock waves are dissipated directly into the water. My thinking is that this is because when hitting the soft surface of open water, the soundwaves are dissipated by displacing, or "wobbling" the surface of the water, albeit on a very small scale, and don't have the solid surface of transmission to transmit directly through the water.

the cells would have to be low pressure so there was slack to allow them to wobble/absorb/damp the waves...

Ummmm.... It's one of those funny ones where you know what you think but can't quite put it into words...

Does anyone think they get what I mean?

Basically I understand that the water itself can transmit sound, it's more how it relates to the surfaces and waves it contacts when not directly sandwiched between what I might as well call "mediums of transmission" for want of a better expression. I think how the mediums contact each other (strongly vs loosely) may make a big difference.

anyway... ho humm.

SAme idea could possibly allow for a more effective method of using bitumen or whatever substance takes your fancy.

[Cal Weldon]

I see what you're thinking and you're certainly not the first to think along those lines. I abandoned my thoughts about when I realized that water transmits too well and the only damping it does seems to be in the uppermost frequencies. Other than that it appears to transmit the other frequencies faster and with lower losses than air, rendering it less than useful for this purpose even with other components added to the scheme. I think the water in between panels such as in constrained layer damping is a worse option than just air in the gap.

Look at how the water is moved in a tsunami versus how a wind blows, that should help.

[KP11520]

Research "Whalesong" and you will be even more convinced!

Regards//Keith

[dnsey]

It sounds as though you're thinking of a form of constrained layer damping.
As has been pointed out, water is not really a suitable medium for this, as it's neither compressible nor particularly massy.

[SY]

Silicone, gentlemen, silicone.

Actually, I think most of the "deadening" properties will come from the impedance mismatch at the planar boundaries. You could just as well have air in there, I thing it might even be better with regard to transmission.

[wakibaki]

There are quite a few knowledgable people visit here. One of the questions I saw asked which got a lot of feedback was about cabinets made of synthetic material such as epoxy-carbon and less exotic substances like concrete.

There is already a body of work documenting the performance of many materials, but nobody could say anything definite about some of the combinations suggested.

If you can't think of an exotic of your own that you favour, you could do the rest of us a service and build a test rig and test a few off-the-shelf or custom materials. Who knows, you might find something really good by accident if you had the convenience of an easy test.

I think something like a hole in the ground with a speaker in it and the test material as a trapdoor with a mic hung over it. You wouldn't get calibrated results, but you'd get good comparative ones.

w

[crazyhub]

Originally posted by doogyscoot

Anyway got me thinking about using something like those fillable ice cube bags (obviously not frozen and eventually designed specifically to be more durable) as sound deadening on the internal walls of a cabinet.

Thoughts anyone?

Don't forget to feed the fish after each listening session