There are a myriad of free PC Tools out there for circuit simulation, magnetic field, RF/Microwave, etc. are there any free FEA for acoustics?
I have an unusal situation where the structure will model well as 2D, or planar. Usually a 2D structure allows a simplifying assumption, which then means simple software will handle it.
Also, any URLs that technically discuss boundary conditions in AIR? Like differences between AIR that is of different temperature, or air that is carrying huge high frequency [40kHz to 60kHz] audio signal. There are several companies that take advantage of modulatin HF Audio, beaming it out, and letting the air's nonlinearity demodulate the carrier into providing 'beamed' messages. I know the Navy has such for beaming foreign meassages from ship to pirates etc. Info, more importantly experience, in this area would be greatly appreciated.
Try posting to the sci.physics.acoustics or alt.sci.physics.acoustics groups. These groups are more likely to have someone with the expertise you need.
On Sun, 07 Dec 2014 10:27:58 -0700, RobertMacy Gave us:
Search on you tube for a video, because I saw it demonstrated on a TV show once, where they modulated an ultrasonic "carrier" with standard voice signals, and a person 350 feet away, down on the football field could hear it as plain speech, while the person standing right nearby him could not.
The same (nearly) shape dish they use to grab distant sounds with would likely project them as well, with a slight change in the "focus" of the thing.
Thanks for the suggestion, youtube might list some text I can use, they no longer transfer videos to me.
The Company is: LRAD Corporation
16990 Goldentop Rd, STE A San Diego, CA 92127-2415
formatting link
Their product was recently pictured in ?? show where a 3 ft dish was mounted on the side of a ship, on the side of the dish were written some instructions, including lists of English phrases trnslated to ?? It appeared the Operator selected the standardized message and then beamed it. I think they said something about going some 300+ ft. This is a LARGE versionn of the product of advertising in stores, where you walk along an aisle and as you pass in front of an item, you were beamed info, specials, etc. Probably more useful as info in a museum etc, where you walk in front of a display and hear the info. But I remember somethiing about diffiulty getting approvals for these applications because of the huge energy launched in super-audio ranges, sinc it is my understanding that that energy can cause deafness and psychological effecs yet NOT be heard. May be rue, or may be 'disinformation' from competitors.
On Mon, 08 Dec 2014 14:19:35 -0500, Fred McKenzie Gave us:
I would stick to what we have learned and be an artisan, then build, and then test.
So, go with what you know... non-parallel walls. Put some foam shape in the inside corners too, in order to form fillets so that the interior 'pocket' has no reverberatory elements to create a 'sonic spur' with. The mid range cabinet as well, if the driver(s) are not sealed versions.
Then, perhaps slightly pyramidal sub cabinet would give your exterior cosmetic appeal.
THAT would be the main low end driver containment. Acoustic suspension is rare, so the downward firing 'port' is where the finished product tuning would come in Since sealed-cone low end drivers are likely not even made any more. On to of that and slightly a bit back for phase accuracy at the transducer element level, would be your mid cabinet and your tweeter "steeple". There are fully sealed tweeters so no cabinet design is needed there. Plenty of choices, depending on dispersal choice decisions, usually. Mid sections could be further spilt into two drivers as well, technically. One fully sealed and one tuned with the cabinet.
The phase alignment of the exterior faces of the driver elements of the mid and upper drivers are what is important. It is like a slightly tipped back slice of a parabola where the top element faces nearly horizontal.
Before these enclosed sub-woofers came into being, my design of this style had a 12" or 15" forward facing low end driver. Now, I can actually make it look more pyramidal with a down fired design.
I have given you enough to envision the entire thing the way I did. I never made it, but the design idea is solid, since the top end boys still do most certainly phase align their drivers to this day.
I worked for LRAD's main competitor for a year. LRAD never used ultrasound arrays as stated. LRADs products started as tweeter arrays, then branched i nto horn arrays.
My former employer ships products at 159 dB SPL with very narrow beamwidths , using circular disposed phased arrays. This can produce a warning reliabl y at 1500 meters, with a +/- 7.5 Deg beamwidth.
The have one that is much hotter, at but not in mass production.
The nonlinear, ultrasonic, arrays are expensive, not very suited to mind co ntrol (see TeeVee, Enter the Net/Matrix for that!) They are mainly used for museums and small point of sale displays. They have limitations on their e ffective distance, and forget aiming them thru a wall, they immediately bou nce off most wall materials.
I've been on the receiving end of the small ultrasound arrays. Since there is no apparent source, even when bounced off a wall, your mind immedialy sa ys, "Whats This?", because the brains wet signal processor does not hear th e subtle cues it uses for tracing a signal path. You move your head fast an d the effect breaks up. Neat toy, and yes it has the narrow beamwidths adve rtised, but not very practical.
You are probably correct, the only way to do this is empirically.
Interesting description of speaker design, but this is not speaker design. However, there is some speaker design in here to launch the high energy, high freq signal. Sadly, I don't even know the rlationship between diaphragm displacement and compression waves, like stuff.
Thanks for the suggestion, youtube might list some text I can use, they no longer transfer videos to me.
The Company is: LRAD Corporation
16990 Goldentop Rd, STE A San Diego, CA 92127-2415
formatting link
Their product was recently pictured in ?? show where a 3 ft dish was mounted on the side of a ship, on the side of the dish were written some instructions, including lists of English phrases trnslated to ?? It appeared the Operator selected the standardized message and then beamed it. I think they said something about going some 300+ ft. This is a LARGE versionn of the product of advertising in stores, where you walk along an aisle and as you pass in front of an item, you were beamed info, specials, etc. Probably more useful as info in a museum etc, where you walk in front of a display and hear the info. But I remember somethiing about diffiulty getting approvals for these applications because of the huge energy launched in super-audio ranges, sinc it is my understanding that that energy can cause deafness and psychological effecs yet NOT be heard. May be rue, or may be 'disinformation' from competitors.
On Mon, 08 Dec 2014 14:19:35 -0500, Fred McKenzie Gave us:
I would stick to what we have learned and be an artisan, then build, and then test.
So, go with what you know... non-parallel walls. Put some foam shape in the inside corners too, in order to form fillets so that the interior 'pocket' has no reverberatory elements to create a 'sonic spur' with. The mid range cabinet as well, if the driver(s) are not sealed versions.
Then, perhaps slightly pyramidal sub cabinet would give your exterior cosmetic appeal.
THAT would be the main low end driver containment. Acoustic suspension is rare, so the downward firing 'port' is where the finished product tuning would come in Since sealed-cone low end drivers are likely not even made any more. On to of that and slightly a bit back for phase accuracy at the transducer element level, would be your mid cabinet and your tweeter "steeple". There are fully sealed tweeters so no cabinet design is needed there. Plenty of choices, depending on dispersal choice decisions, usually. Mid sections could be further spilt into two drivers as well, technically. One fully sealed and one tuned with the cabinet.
The phase alignment of the exterior faces of the driver elements of the mid and upper drivers are what is important. It is like a slightly tipped back slice of a parabola where the top element faces nearly horizontal.
Before these enclosed sub-woofers came into being, my design of this style had a 12" or 15" forward facing low end driver. Now, I can actually make it look more pyramidal with a down fired design.
I have given you enough to envision the entire thing the way I did. I never made it, but the design idea is solid, since the top end boys still do most certainly phase align their drivers to this day.
I worked for LRAD's main competitor for a year. LRAD never used ultrasound arrays as stated. LRADs products started as tweeter arrays, then branched into horn arrays.
My former employer ships products at 159 dB SPL with very narrow beamwidths, using circular disposed phased arrays. This can produce a warning reliably at
1500 meters, with a +/- 7.5 Deg beamwidth.
The have one that is much hotter, at but not in mass production.
The nonlinear, ultrasonic, arrays are expensive, not very suited to mind control (see TeeVee, Enter the Net/Matrix for that!) They are mainly used for museums and small point of sale displays. They have limitations on their effective distance, and forget aiming them thru a wall, they immediately bounce off most wall materials.
I've been on the receiving end of the small ultrasound arrays. Since there is no apparent source, even when bounced off a wall, your mind immedialy says, "Whats This?", because the brains wet signal processor does not hear the subtle cues it uses for tracing a signal path. You move your head fast and the effect breaks up. Neat toy, and yes it has the narrow beamwidths advertised, but not very practical.
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