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Attenuation is what most earmuffs or ear defenders do. They make all sounds quieter, which, while protecting your ears, also make conversations difficult.
Compression (or dynamic range compression) is what an ideal earmuff should do. Attenuate the loudest sounds, but let the rest through unmodified.
No doubt electronics could produce a dynamic range compressing earmuff, but, what if there were some material available, to fill the earmuffs, that let small sounds pass but thickened when the noise level got too loud?
Custard Earmuffs.
Patent US20130153328
https://www.google....tents/US20130153328
"the sound absorbing material comprises of a thixotropic material" = custard [mitxela, Jun 16 2016]
Sodium Acetate
https://en.wikipedi...acetate#Heating_pad
Useful [8th of 7, Jun 16 2016]
[link]
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This is excellent, apart from the problem that solids
transmit sound about as well as liquids. |
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A better option might (or might not) be earmuffs
filled with a gas that was on the verge of condensing.
Then, high-pressure sound waves would cause local
condensation of the gas, absorbing the sound.
Smaller sounds would pass unhindered. |
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Szilard-Einstein headphones. |
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//A better option might (or might not) be earmuffs filled
with a gas that was on the verge of condensing.// |
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That would work wonderfully unless there were any
variations in local temperature or pressure. Being
entirely vulnerable to the weather never stopped the
good people of the 1970's British motor industry though,
so maybe a viable product. |
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Actually, if you could get the active part IN the ear canal,
that would take care of the temperature and pressure
differences could be accounted for by a little
piezoelectric doodad to shift the volume about very
slightly. |
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// the weather never stopped the good people of the 1970's British motor industry // |
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... although it did very effectively stop their products (Austin Allegro, anyone ?). |
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The Austin Allegro was superb piece of engineering
and years ahead of its time. That some people
foolishly insisted on using it as a car was something
the manufacturers could hardly have foreseen. |
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// Austin Allegro was superb piece of engineering
and
years ahead of its time// |
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Ah yes. At some point I expect NATO documents to
be
declassified detailing the Austin Allegro as a top
level dis-
engineering project designed to fool the Soviet
Union into
thinking that the UK was incapable of producing
functional mechanical products. The Allegro was
even
exported and assembled in Italy by Innocenti, where
Soviet intelligence would conclude that the British
couldn't design a functional car and that the Italians
had
given up on the concept of aesthetics. This
masterstroke of a project sowed considerable
doubt
among all levels of Soviet society. Did the British
posses
the kind of engineering prowess that allowed a
person of
reasonable means to drive an E-Type Jag to the
airport
and hop on Concorde and be in New York in time
for
Lunch? Or did they put rubber suspension on bad
looking
cars, fit them with rain-soluble electrics and then
paint
the whole thing brown? |
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A confusing effect for the Soviets, I'm sure. |
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No less confusing than British Leyland's master-stroke against the Teutons, the Triumph Acclaim, which translates very nicely as "Sieg Heil !" ... |
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("Sieg",n, victory, success, triumph, conquest; "Heil", v, hail, applaud, acclaim, welcome). |
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Very confusing.. at one extreme, the Supermarine Spitfire, the cavity magnetron, and proper drains; at the other, the British Rail "pork" pie, the steam-powered submarine, and the Austin Princess. |
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//at the other, the British Rail "pork" pie, the steam-
powered submarine, and the Austin Princess.// |
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Better than the British Rail submarine, the Pork
Princess and Austin Steampowers. |
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Why do you think this would work? |
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// sp.: "sp. All aggro" // |
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// solids transmit sound about as well as liquids // True, but although I have no evidence to back this up, I was assuming the transition from liquid to solid would absorb a lot of the energy. |
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But it has come to my attention that, just like almost every other idea that's ever been or will be imagined, custard earmuffs have already been patented. <link> |
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//I was assuming the transition from liquid to solid
would absorb a lot of the energy// |
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Ah, right - in that case, it is not such a stupid idea
after all*. I'm not sure how much energy is
absorbed in the transition, though. |
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[*irrelevant aside: I was once discussing some
work I was doing with another guy in the lab. He
suggested something and I thought about and then
said "You know, that's not such a stupid idea."
Another colleague who was present told me later
that that was not necessarily something good to
say to a Nobel laureate.] |
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// how much energy is absorbed in the transition // |
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That's only part of the problem. Like "instant-heat" pouches <link> the energy can be absorbed by a state-change; but then it has to be dissipated (as heat, usually) or the device will saturate. |
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Walking round with two pots of hot custard strapped to your head may get you some funny looks, and quite possibly a compulsory treatment order. |
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Hmm, the patent describes thixotropic solutions. These
are shear thinning. This makes sense. Essentially incident
sound energy is transmitted to the ear via shear forces
through the sheer thinning substance. Increased
amplitude decreases the percentage of force
transmitted. Nice. Strangely the patent describes a
whole lot of shear thickening substances... |
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You could achieve the same effect with a shear
thickening liquid, increased viscosity could be used to
increase the amount of force applied to an embedded
damper. For example you could have an external
membrane, an internal membrane with a custard filled
interior. If you embed a coarse grid between the two
membranes connected to the frame, then as amplitude
increases more of the sound energy will be transmitted
to the grid, cylinder and frame of the ear piece rather
than going to the air on the other side. |
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//the energy can be absorbed by a state-change; but then it has to be dissipated (as heat, usually) or the device will saturate.// |
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I think the idea's about changing state during the compression bit of the waveform, then back again during expansion, so no buildup of energy (that's another idea). |
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//Austin Allegro// looks like different sections were separately designed by different blind people. I can however see some bits which Honda ripped off for their late 70's Civic. |
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That implies the use of force, which is clearly ludicrous. It's possible to detatch major structural components with no more effort than a hard stare. |
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More likely, the bits in question were simply collected from where they were lying in the gutter. |
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At speeds over 23 mph, the cheap adhesive tape holding the vehicle together starts to fail, causing debris (doors, fixed glass, engine) to fall off. |
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Fortunately, Allegros can't attain 23 MPH*, which is fortunate for the drivers; after all, they've suffered enough already... |
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*Except in free-fall, caused for example by being pushed off a sheer cliff. Quite remarkable how often that happened. |
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I think it is better to have a computer recreate the extererior sounds swapping out words to be from preferred vocabulary. so "expletives" become |
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sexual activity!, sexual activitying sexual activity!, what the sexual activity do you think you are doing! sexual activity. Make love, omit war. |
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^Dammit, beanangel trumps me every time.. |
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The verb "to Trump" is becoming less positive as time
goes on. |
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Hmmm .... is "Clinton" a verb, or a noun ? We ask merely for information... |
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// I think the idea's about changing state during the
compression bit of the waveform, then back again during
expansion, so no buildup of energy (that's another idea). // |
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Then where does the energy go? It must still be dissipated
somehow. (Pressure is conserved in the mechanism you
describe, but energy apparently is not.) |
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^ The crest of the wave hits the medium with enough force to change its state. The phase change keeps some of the energy to itself, thus the transmitted waveform is attenuated in its compression stage. |
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Then the trough comes along with enough force (in the other direction) to change the phase back, releasing the energy which fills the trough a bit, thus attenuating the waveform in its rareification stage. |
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It's similar to simply piling on enough material that the sound is dampened, but more fun and, presumably requires less material. |
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Not completely inanalgous to an IBM "buckling spring" keyboard, where you push down against tension which suddenly becomes less (as the spring buckles, storing some energy), said energy storage returned to the finger when you release the key and the spring unbuckles. If there were a pressure sensor under the keyboard frame it would measure a square'ish wave as the crest and trough were chopped off by the spring buckling and unbuckling, storing/releasing energy. |
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Which is probably what [mit] means. |
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I understand that part (I think). Kinetic energy from the
sound wave is during a crest turned into thermal energy via
the phase change. But then, during the trough, the phase
change is reversed and the energy goes back into the sound
wave. This would seem to result in the sound wave having
the same amount of energy as before. |
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(Actually, it occurs to me now that the phase change from
solid to liquid or liquid to gas would be initiated by pressure
drop (trough) and the opposite phase change by pressure
rise (crest). But the reasoning should still hold.) |
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You can (assuming we're not both wrong) fill troughs with
pressure from crests because pressure is a value that can be
positive or negative (relative to ambient). You can't do the
same with kinetic energy; that's only positive. So something
weird is going on. |
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A compression to solid and a relaxation to liquid are different. One is more ordered and the other more random.
Think about plinko, getting the ball bearing up the board, to the top of the hill, is a finer path compared to coming down. |
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I imagine the custard will convert more energy in packing process during the compression. |
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