Create atmospheric pressure with sound - AVS Forum
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Old 03-22-2013, 01:24 AM - Thread Starter
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I would like to know if it is possible to create pressure in an enclosed tank with sound. My first inclination would be to use a frequency that is out of the range of the human hearing range (so that it would not hurt the human) with a large decibel to increase its effect. I do not know what to use to produce sound. The set up for enclosed area currently in consideration is some kind of fish tank-like set-up. This of course is contingent to the resonating frequency of the glass. Any suggestions would be appreciated. The purpose is to create pressure difference without a current ( as opposed to using a pump to increase pressure or a vacuum to decrease pressure).
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Old 03-22-2013, 05:48 AM
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I would like to know if it is possible to create pressure in an enclosed tank with sound. My first inclination would be to use a frequency that is out of the range of the human hearing range (so that it would not hurt the human) with a large decibel to increase its effect. I do not know what to use to produce sound. The set up for enclosed area currently in consideration is some kind of fish tank-like set-up. This of course is contingent to the resonating frequency of the glass. Any suggestions would be appreciated. The purpose is to create pressure difference without a current ( as opposed to using a pump to increase pressure or a vacuum to decrease pressure).

Sound is composed of pressure waves that are sometimes positive and sometimes negative but whose average is zero. Therefore any air pressure created by sound is very temporary - its duration measured in fractions of a second.
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Old 03-22-2013, 08:27 AM
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Sound is composed of pressure waves that are sometimes positive and sometimes negative but whose average is zero. Therefore any air pressure created by sound is very temporary - its duration measured in fractions of a second.

Perhaps a small rotary sub would serve, though? Of course that would take considerable effort as it would be completely custom, but you can drive those things right to DC and just pressurize/depressurize a room, or in this case a tank.

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Old 03-22-2013, 08:38 AM
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Sound is composed of pressure waves that are sometimes positive and sometimes negative but whose average is zero. Therefore any air pressure created by sound is very temporary - its duration measured in fractions of a second.

Perhaps a small rotary sub would serve, though? Of course that would take considerable effort as it would be completely custom, but you can drive those things right to DC and just pressurize/depressurize a room, or in this case a tank.

Why not just use a fan or a pump?

Depending on the range of pressures you desire, tank-type vacuum cleaners that are reversible can be very useful.
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Old 03-22-2013, 08:46 AM
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Why not just use a fan or a pump?

Depending on the range of pressures you desire, tank-type vacuum cleaners that are reversible can be very useful.

Well, in the end that's all a rotary sub really is, a fan with variable angle of attack for the blades. But you're right, if you went with variable and reversible speed for a DC-driven fan motor I'll bet something could be cobbled together pretty quickly. Speed of response wouldn't be much of an issue, and if it technically had massive distortion percentages, who really cares?

So OP, what kind of evil genius science experiment are you trying to run here?

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Old 03-22-2013, 11:18 AM
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Depending on the range of pressures you desire, tank-type vacuum cleaners that are reversible can be very useful.

What you can't see in this picture of one of Clark's legendary Dumax Loudspeaker Testers, is the shop vac hiding behind it. It is at the other end of the hose that comes up beind the left support pylon. In the beginning it was on a variac, if memory serves. Eventually it became computer controlled.



Just another example of why I rarely have to think a creative thought - my friends already beat me to all the good ones!
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Old 03-22-2013, 11:54 AM
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I can't stop getting positively surprised on this forum. HiFI/Sound is a whole world of knowledge that most humans don't know and yet we interact with it since the first day of our lives.
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Old 03-22-2013, 11:42 PM - Thread Starter
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Yeah faire, this is interesting. I realize what you mean arny by not having to have a creative thought because someone has probably done it...which is why i brought this here to ask for help. My plan was going to try and create clouds inside an enclosed area, which is why i mention fish tank because it serves as some kind of visual (and I want there to be transparency, whether 1 side, or all sides.) I've seen people make a little fog in a pressurized soda bottle (which wasn't that impressive). Then I saw this artist Berndnaut Smilde use a fog machine and a spray bottle to collect the fog in one spot to make a cloud (for a very short time though) http://www.washingtonpost.com/blogs/arts-post/post/artist-berndnaut-smilde-creates-indoor-clouds/2012/03/13/gIQA7yAT9R_blog.html That was inspiring but I want it to rain smile.gif Considering how clouds form and precipitate rain it should be possible to do it within a closed area. Fans, compressors, pumps and vacuums all are viable ways to manipulate the atmospheric pressure within the tank (what would you call a tank/room/area that is pressure controlled?) but that brings wind current, and considering the size of the tank it might disrupt any collective gathering of a cloud. But, the wind currents don't keep clouds from being defined and shapely. So, I thought of sound and, if I recal right, when listening to frequencies that are not everyday sounds I think the pressure inside my ears change and seem to be on the way to pop. I was talking to someone doing a research paper on if sound could put out fire due to its effect on the air around it (not just air blowing it out like a sub woofer would do) One other question I have that someone might be able to help me on concerns frequencies the human ear can not pick up. I realize I would need a special device to detect them (what would that be) and probably one to produce them (Audacity can generate tones but only up to 22,000 htz - what could produce these frequencies?) What would be the effects of tones', that are without the hearing range of humans, decibels? What would a higher decibel of a frequency humans cant detect do compared to a lower decibel of the same frequency, considering what I've mentioned before of sounds effects on the atmosphere - lower and higher than human hearing capacity (I heard there are low tones that make you crap - Brown's Tone or something) Any articles that deal with this would be appreciated it - especially sound's effect on the atmosphere around it (the sound's frequency)...Thanks...and it's not evil.
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Old 03-23-2013, 03:54 AM
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What you are looking for is an airtight vessel with one of three things connected to it to manipulate pressure:

1. A large piston or movable septum that can be manipulated to alter the internal volume of the vessel sufficiently. Since it is a contained airtight space, reducing the volume drives pressure up, increasing volume lowers pressure. While a speaker driver(s) could theoretically be used as a piston driven with variable direct current to control the diaphragm/cone position, it wouldn't be my first choice as making it airtight could potentially be a pain and DC to the voicecoil isn't efficient or recommended for long periods. Something like the old servosub or contrabass or whatever it was called with driver disconnected from servo motor and manipulated manually perhaps.

2. Both pressurized air tank and vacuum canister connected to your airtight vessel. By opening a valve one one or the other, you can increase or decrease pressure in the vessel as you add or remove air from it. Pressure tank is easy... think scuba gear. Vacuum canisters exist but are limited in pressure differential to just one atmosphere or so, and thus will be the limiting factor on how far you can manipulate pressure. Note that this is a one time use... if you deplete the vacuum canister or pressurized air tank you will have to disconnect and replace it with another.

3. Extending number 2 above, what you really want is an airtight vessel with a small air compressor attached to it to act as both the pressure tank and vacuum canister as above. If you use say a compressor capable of holding 10 atm of pressure, you want to fill it to 5 atm before connecting it to your vessel and creating the closed airtight environment shared between your vessel and the compressor tank. Note that both inlet and exhaust sides of the compressor should be connected to your vessel. By running the compressor pump you remove air from the vessel (and add it to the tank), lowering pressure in the vessel. Releasing air from the compressor adds it to the vessel and raises pressure (like adding air to a tire). Since you connected the compressor when it was half full, you can swing pressure in your vessel both ways at will and repeatedly. How far you can swing it depends on how large your compressor tank is and its pressure rating. It won't take much at all to swing the pressure over normal weather ranges, and you don't want to go far as a little pressure change on a large surface area creates a lot of force. Please be careful. You could easily implode or explode a fish tank.

I'd go with 3 above as it is the cheapest, most practical way of doing this. So long as air is moved from vessel to compressor tank slowly there shouldn't be undue turbulence. Running the compressor pump is generally a slow process. Just release it from the compressor slowly as well. If you are really concerned, you could place a baffle or diffuser inside the vessel so that you don't get a jet of air streaming into the vessel.

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