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How Does Directional Sound Technology Work?

Posted June 08, 2007 11:21 AM by Steve Melito
Pathfinder Tags: acoustic audio speakers

This week, CR4 interviewed Dr. F. Joseph Pompei, inventor of the Audio Spotlight directional-sound system and founder of Holosonics Research Laboratory. Next week, the Engineer's Place for News and Discussion will meet Elwood "Woody" Norris, Joe Pompei's chief rival. Although these inventors have been profiled by the likes of ABC News, CNBC, Forbes and Newsweek, there's still a story to tell. Based on your feedback, CR4ers want to know more about how directional-sound systems work. Today, we'll turn up the volume and explode what one magazine calls "audio dynamite".

Life Before Directional Sound

Let's start with the basics. Traditional stereo speakers produce sound by moving an electromagnet attached to a flexible cone. Changes in the electromagnet's polar orientation determine the direction of repulsion and attraction. As the voice coil moves back and forth like a piston, the electrical audio signal determines the frequency and amplitude of the sound wave produced by the diaphragm. Typically, a passive crossover breaks the audio signal into different pieces. Drivers such as woofers, tweeters, and midrange devices are used to produce low, high, and mid-spectrum sounds. The speaker's audible sound waves then spread out in all directions like a pebble cast into a pond.

Ultrasound: It's Not Just for Babies

Unlike traditional stereo speakers, directional-sound systems convert an audio signal into an ultrasonic frequency that is focused like a beam of light at a distant target. This narrow beam is inaudible because its high frequency (above 20,000 Hz) is beyond the range of human hearing. Like audible sound waves, however, ultrasound waves get distorted as they travel through the air. But this is not a problem for a good directional-sound system. As Joe Pompei and Woody Norris have learned, there is a way to use this distortion to break ultrasound waves into lower-frequency, audible sound waves. Moreover, because these ultrasound waves can travel along a narrow path, people to the left and right of a target remain in silence.

Got a Minute?

Come on inside Conference Room 4 (CR4). If you point your new directional-sound system at a person standing 100 yards away (hey, it's a big conference room), only that person can hear the song you're playing. Point the emitter at the walls, however, and an unsuspecting listener may think that your violin concerto is being piped in from a hidden speaker near the light switch. Now hang from the ceiling and "shine" the directional-sound system on an unsuspecting listener below. If you get this right, the poor soul may start complaining that he can't get violins out of his head. Tell him not to worry. He doesn't need a psychiatrist. He just needs a directional-sound system like yours in his car and home entertainment center.

Resources:

http://electronics.howstuffworks.com/speaker12.htm

http://www.gotjuice.org/thesoundwar.pdf

http://www.woodynorris.com/Articles/Newsweek3.htm

Steve Melito - The Y Files

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#1

Re: How Does Directional Sound Technology Work?

06/08/2007 11:28 PM

I don't know that this technology will ever capture the music/hi-fi market, but I think it has great potential in the novelty, commercial, military and law enforcement fields. The ability to plant a sound inside the head of a single listener sounds, for example, like a teacher's dream in dealing with difficult students. Sales pitches could change at every display in a store without noise or confusion. Lots of possibilities!

DickL

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#2
In reply to #1

Re: How Does Directional Sound Technology Work?

06/09/2007 4:51 AM

Great-now make it the law that all vehicles have this! NO MORE BOOM BOXES IN THE MIDDLE OF THE NIGHT! (now that "sounds good" to me!)

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#3

Re: How Does Directional Sound Technology Work?

06/09/2007 5:08 PM

Moose, I question the use of this new technology. I have experience the nefarious uses of directional sound and it is frightening. As I said in my replies that disappear, If the advances of technology and science were not continually used to manipulate and control, many more would be interested and less fearful.

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#4
In reply to #3

Re: How Does Directional Sound Technology Work?

06/11/2007 8:40 AM

The current applications are pretty harmless, Roxanne. For example, the Audio Spotlight is used at Walt Disney's Epcot Center and the Boston Museum of Science. I appreciate your concerns about the potential for abuse, but technology is often a double-edged sword. After all, even a sharpened pencil can be used as a weapon.

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#5

Re: How Does Directional Sound Technology Work?

06/11/2007 4:59 PM

Part 1 of the interview with Joe Pompei's competitor, Elwood "Woody" Norris, is now live on The Y Files.

http://cr4.globalspec.com/blogentry/2185/Part-1-Meet-Woody-Norris-Inventor-of-HyperSonic-Sound-HSS

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#6
In reply to #5

Re: How Does Directional Sound Technology Work?

06/15/2007 1:42 AM

Hi Moose,

Am I correct in assuming that the basis of directional sound is to use very, very high frequencies that can be directed sharply due to their small wavelengths? The actual audio is then carefully inserted as "difference beats" in the high frequency components?

I believe this is the trick to get bass sounds out of very tiny loudspeakers (like a cell phone's) as well.

-J

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#7
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Re: How Does Directional Sound Technology Work?

06/15/2007 2:10 AM

we have to make clear how the speaker works? then we can judge its sound quality.

plate(flate) speaker is not new type speaker, there are lots of type such speakers on market.

but so sharp drection hant heard.

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#8
In reply to #7

Re: How Does Directional Sound Technology Work?

06/15/2007 7:33 AM

cn:

They've made this technique sound more exotic than it really is. The narrow beam directional signal is characteristic of high frequency audio, just as it is for radio frequencies. You don't hear of 10 MHz radars but, at frequencies above 1 GHz, they work well. In fact, at audio frequencies around 10 KHz and above, it's hard to make an omnidirectional transducer (speaker). The sounds WANT to travel in narrow beams. That's why even distribution of high frequency sounds is a problem for designers of concert halls. They want to be sure that everyone in the audience hears the high notes, no matter where they sit, but the sound is trying to travel in narrow beams. That's not a problem at sub-woofer frequencies. They're so non-directional that you can't even find the speaker by trying to follow the sound.

The modulation isn't magic either. The mixing of two discrete frequencies is given as an example, but it's really just old AM (Amplitude Modulation). In one article, Mr. Norris indicates that he prefers SSB (Single Side Band), but I'm not sure how important that is.

Both experts seem to agree that the audible signal is "detected" by the non-linearity of air. My Momma taught me not to disagree with multimillionaires and PhDs, but, in my humble opinion, the detection of the basic beam happens in the non-linearity of the ear. Inside of your head. It may be different in the case of sounds bouncing off from walls.

Basically, though, this is a fascinating technology that anyone with a workbench, and knowledge of a few basics, can play with. A carrier oscillator of 20 KHz, or above, an audio signal source (Music?), a modulator circuit as found in an AM or SSB transmitter and a Piezo or Magnetic "Tweeter" and you have a start.

DickL

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#10
In reply to #8

Re: How Does Directional Sound Technology Work?

06/15/2007 8:27 AM

DickL, Great explanation!

How do you keep the upper sideband from interferring with the lower side band? They are 180 degree's out of phase. In AM you attenuate one of the side bands and pick the intelligence off of one side of the carrier. How would you do that with sound since both sides are "out there"?

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#11
In reply to #10

Re: How Does Directional Sound Technology Work?

06/15/2007 8:49 AM

Hi Yani:

That's where the non-linearity comes in. Remember the old crystal sets that "detected" audio from RF carriers. They were just diodes (non-linear elements) that passed one polarity of voltage swing, but not the other. That left the audio envelope that could be heard and not cancelled out by the opposite polarity (after filtering out the RF).

The ear is also non-linear. It can have enough sensitivity to hear the lowest whisper and still survive the sound of a nearby jet engine. It's not the same as a diode, but, in my view, can still provide the non-linearity needed to separate the audible sound from the ultrasound "Carrier". I don't have an opinion about the SSB question. My guesses.

DickL

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#12
In reply to #11

Re: How Does Directional Sound Technology Work?

06/15/2007 11:12 AM

Hi DickL, I like your answer, but I still have a nagging feeling that there is more to it.

Our ears are non-linear, yes, but will such AM demodulation cause acceptable sound quality?

The idea of somehow processing the audio into beat frequencies of ultra- (or hyper?) sound so that the natural difference components "demodulate" it, still rings a bell in my mind!

-J

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#13
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Re: How Does Directional Sound Technology Work?

06/15/2007 12:00 PM

Hi Jorrie:

I don't disagree. I just don't see a mechanism for that kind of transmission and demodulation, but I'm certainly not an expert. Any audible components of sound will be too low in frequency to travel 100 yards with the beam and the higher frequencies still require demodulation of some sort. As I recall, both inventors mention non-linear detection. Remember, too, that there is no receiving equipment or sophisticated demodulator. Only air and ears. Again, trusting my very fallible memory, it seems that Mr. Norris was more descriptive in the New York Times Magazine article and provided more detail on the operation of his system. That's been quite a while, though, and things may have changed.

Also, I'm not convinced that real "acceptable" quality sound is a part of all this. Rightly or wrongly, I still think of it as a novelty and not a replacement for present sound systems. Still, it may have an important place in commercial, military or police applications.

DickL

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#14
In reply to #13

Re: How Does Directional Sound Technology Work?

06/15/2007 4:27 PM

It's the air that's nonlinear, not the ear. This is pretty clearly described on the Holsonics website, and the paper references. The air is the "detector" (or demodulator). The ear hears regular sound just like always. The Audio Spotlight sound quality is quite good; distortion is comparable to regular speakers.

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#15
In reply to #14

Re: How Does Directional Sound Technology Work?

06/15/2007 5:38 PM

Guest:

I found the reference to the 1975 paper, but don't have access to it. I do still have a couple of questions. If the detection occurs in the air, it must be happening all along the full length of the beam. Otherwise, how would the beam know where to deliver the audible sound? It seems to me, then, that the whole beam would become the source of audio and everyone near it should be able to hear the sound, not just the targeted individual. I'm comparing it to the path of a supersonic bullet fired from a silenced weapon. You can't hear the "bang" from the muzzle, but the shock wave from the bullet is audible to everyone near its path. That's why they use subsonic loads in silenced weapons. Isn't this analogous?

Sorry to be a nuisance, but I'm curious.

Best Regards

DickL

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#17
In reply to #15

Re: How Does Directional Sound Technology Work?

06/16/2007 10:41 AM

The detection does occur in the full length of the beam - it's like having a giant array of invisible speakers, all pointing in the same direction. This is why it forms such a tight beam.

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#18
In reply to #17

Re: How Does Directional Sound Technology Work?

06/16/2007 12:57 PM

Guest:

So the "array of invisible speakers" produces audible sound over a span of, say, 100 yards. Why does that sound, in the normal, audible frequency range not disperse? I'm puzzled as to why sound emanating from an invisible speaker, say, 1 yard from the transducer, would travel in a tight beam for another 99 yards to the target. You can't usually confine wide-band sound to a tight beam simply by pointing a speaker. Usually, everyone in the room could hear it, particularly the lower frequencies. And what keeps the invisible speakers "all pointing in the same direction" anyway? Thank you for the explanation but I guess I'm still confused.

DickL

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#19
In reply to #18

Re: How Does Directional Sound Technology Work?

06/17/2007 12:40 AM

Hi DickL, "And what keeps the invisible speakers "all pointing in the same direction" anyway? Thank you for the explanation but I guess I'm still confused."

I'm with you here! I do not buy the "air demodulation part". That would destroy the directionality, I think.

The directionality may be purely due the sound that is beamed with an ultrasound carrier, making a smallish speaker a good directional "antenna" (diameter many carrier wavelengths). The carrier must then be demodulated by the ears of the listeners. This correlates with what they say: the sound can be beamed at a spot on the wall and listeners would think that the source is that spot and not the speaker.

-J

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#20
In reply to #19

Re: How Does Directional Sound Technology Work?

06/17/2007 8:20 AM

Hi Jorrie:

BINGO! Greetings to Monavoni (?).

DickL

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#22
In reply to #20

Re: How Does Directional Sound Technology Work?

06/20/2007 10:07 AM

Hello,

I figured I should clear up some misconceptions here.

I assure you all that our website is accurate - the nonlinearity is in the air, not the ear. I've of course studied this area extensively, and there is no doubt about it. The demodulation is happening in the air, and the air alone. The properties of the ear have no contribution. I'm not sure how I can make this more clear.

The illusion of projecting sound against a surface is the same as shining a flashlight on a wall. The sound (or light) reflects from the surface, and the ear (or eye) perceives a source at the point of reflection. There is no additional demodulating occurring at the wall; it's simply a redirection of the beam energy.

I hope this clarifies things.

- Dr. F. Joseph Pompei

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#23
In reply to #22

Re: How Does Directional Sound Technology Work?

06/20/2007 2:50 PM

Hello Dr. Pompei:

You have certainly made your position crystal clear but I remain mystified by some of the questions that have appeared in this string. Educating mystified CR4 participants isn't your responsibility, though. Thank you for your response.

DickL

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#24
In reply to #22

Re: How Does Directional Sound Technology Work?

06/20/2007 8:22 PM

Hi,fipompei,

ultrasonic wave attenuate rapidelly passing through air, so the ultrasonic (as a carrier) disappear at the path and only sound (modulation wave) is residual, is this right? the procedure is just like demodulation.

if so, there will be a quiescent zone existing near resource, right?

that mean we only heard the sound at some distance far away from resource.?

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#25
In reply to #24

Re: How Does Directional Sound Technology Work?

06/20/2007 8:56 PM

Hi cn:

"ultrasonic wave attenuate rapidelly passing through air, so the ultrasonic (as a carrier) disappear at the path and only sound (modulation wave) is residual"

In that case, over some fixed distance, wouldn't the modulated carrier disappear and the beam transition to normal sound? Wouldn't the sound then spread and become audible to everyone and be rapidly attenuated over distance? If one walked along beside the beam for 100 yards, it seems as though there would be a span of silence, followed by increasing, then fading, sound. Lots of questions here.

DickL

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#26
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Re: How Does Directional Sound Technology Work?

06/21/2007 9:13 PM

I guess it is.

if the air is nonlinear to be able to demodulate to sound, how long distance it could transport?

if it needs 1M, for example, we can hear sound at 1-2M range, in the 1M range , we cannt hear anythingg.

if it transport like a cylinder, one stands right it path, and behind him, others will hear nothing, becaue he shelt from the wave. right?

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#27
In reply to #24

Re: How Does Directional Sound Technology Work?

06/26/2007 3:32 PM

Hello cnpower,

That is correct, but demodulation and absorption are two distinct phenomena. The demodulation occurs due to the air's nonlinearity, creating audible sound. Both audible sound and ultrasound travel together for some distance, until the ultrasound, having a much higher absorption rate, is absorbed into the air.

There is a small quiet zone very close to the speaker, but even at a distance of only a few inches there is sufficient demodulation to create enough sound to hear clearly. But the sound amplitude does grow with distance, which is an unusual and surprising experience for most listeners.

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#28
In reply to #27

Re: How Does Directional Sound Technology Work?

06/29/2007 10:01 PM

Thank you for your explain fpompei,

next week, if I get some time, I hope to discuss more about it. if you dont mind and have time.

its interesting.

btw, how much is your products cost?

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#9
In reply to #6

Re: How Does Directional Sound Technology Work?

06/15/2007 8:14 AM

Hi Jorrie,

Glad to have you as part of this discussion. I was about to respond to your questions, but then saw DickL's excellent comment below. Does this answer things?

Moose

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#16

Re: How Does Directional Sound Technology Work?

06/16/2007 7:33 AM

Dickl, wonderful your explain at way of direction. but comprehend it sound mechanism is difficulty. The famouse flate speaker manufacture is NXT in Britain.They are made of special aero meterial.and has same phase osicllation. The inventor wanto ssb can be explain in eletronics. as the carrier has useless information and hsa a big energy, so if cancel it from transmit wave, can save output power. but demodulation has to use syn demodulation method. how to implement at this hand? 70's I ring a bell, microwve can be hearing sometimes by ear in one article.?! may something wonderful we havnt studied. Just like F117 can be detected by some wave length radar,

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#21

Re: How Does Directional Sound Technology Work?

06/19/2007 9:37 PM

you can use a horn to concentrate sound to a direction,

If you visited Tiantan Echo wall (whispering gallery) in Beijing, you will find wonderful pass and refraction sound in it.

another important application is using phase interference to get strong direction of sound. Both speaker box cylendar and super direction mic are basiced on this principle.

its not spot resource, but a planar resources.

I try to explain at part1

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#29

Re: How Does Directional Sound Technology Work?

07/02/2007 9:31 PM

Could we explain this mechanism as illustration?
Where we get the result of the ultrasonic sound in the formula,
U = A(1-m/2)cos wt + (mA/2)cos(w+Ω)t + mAcos(Ωt/2) * cos(w-Ω/2)t

= Acos wt + mAcos(Ωt/2+pi/2)*sin(w+Ω/2)t + mAcos(Ωt/2) * cos(w-Ω/2)t

We can conside the last terms as a beat frequency wave of which amplitude absolute value is 2mAcosΩt and frequency will be w-+Ω/2 (our human hearing is less sense to phase);
Its no other than this amplitude absolute value 2mAcosΩt that drive air particle oscillation outline to cause our hearing.
When m=1 (100% modulate) we have

2AcosΩt (Ω sound band from 0--20kHz)

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#30
In reply to #29

Re: How Does Directional Sound Technology Work?

07/03/2007 12:42 AM

This isn't quite right; beat mechanisms are a common misconception. The important part is the nonlinearity, which in the simplest terms can be described as a quadratic. Square the sum of two sine waves and you'll get sum and difference in frequency. A similar analysis applies to a broadband signal.

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#31
In reply to #30

Re: How Does Directional Sound Technology Work?

07/24/2008 2:29 PM

Mr Pompei, there is a serious flow in your argument! You will soon discover the real reason for the creation of the sound - watch the internet carefully (you may remember me, I made a offer of invention previously to you....)

Best regards

Me!

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#32
In reply to #31

Re: How Does Directional Sound Technology Work?

07/24/2008 2:32 PM

Please register with CR4 and message me, Guest. If your "real reason for the creation of sound " is a truly real, I'd like to speak with you.

Moose

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#33
In reply to #31

Re: How Does Directional Sound Technology Work?

07/24/2008 2:48 PM

I assume you meant "flaw".

Please present your information openly; the mechanisms I cite have been well studied and experimentally verified over the last 40 years or so. You're going to have to work much harder to rebuke all of this research, especially as an anonymous web-forum commenter.

Dr. F. Joseph Pompei

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#37
In reply to #33

Re: How Does Directional Sound Technology Work?

07/25/2008 4:09 PM

Dr. Pompei: I am Afrikaans speaking and did mean "flaw" – sorry Eng is not my first language.

Moose: I have a working prototype and am busy filing for patent applications- thus the reason for the secrecy. There will soon be a competing system available to The Audiospotlight, ATC and the Sennheiser system offering some new features…..

Dr. Pompei Question:

If a linear signal passes through a nonlinear medium, harmonics are created at multiples of the fundamental carrier frequency (basic signal processing theory). Question: If an un-modulated ultrasonic carrier signal (40kHz or 60kHz etc) pass through air as a nonlinear medium (as you claim) harmonics should still be created due to the nonlinear medium. When why is there not some form of audible tone created due to the harmonic content in this instance? Why does audible sound only form when the ultrasonic carries is modulated? If the nonlinear theory is correct should we not all be able to hear ultrasonic vehicle alarms etc. ???

Regards

Jacques van der Merwe (previously Me)

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#38
In reply to #37

Re: How Does Directional Sound Technology Work?

07/25/2008 9:03 PM

it seems a patent dispute.

but I dont think its a problem.

Pompei is from USA and he can get patent from there and you are not, so you can get the patent in your country.

Pompei's products have been put into the market for nearly two years, but you still in patent application. time seems not to make for you.

Besides, (Im sorry to speak more a little) your question is not too good to trust us.

Through a nonlinear system, a signal can produce many harmonic waves. we all agree to it, but these harmonics are all multified rates, like 2,3,...n... so if a signal has 30khz will produce 60khz, 90khz, etc, when through a nonlinear system. of cause we cannt hear them as well.

but modulation is another situation. its not difficulty to deduce.

another situation, Have you ever make this experiment:

Two ultrasonic frequencies, one is , say, 60.1khz, another is 60khz, you eventually cannt hear them individually, but make them close together, can you hear a 1khz signal?

I hvnt seen his products so far, only from advertisement. Im also interested in your products occur in the market.

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#39
In reply to #38

Re: How Does Directional Sound Technology Work?

07/25/2008 9:19 PM

another question.

as we all know ultrasonic wave cannt transmit too far distance in the air,

Thats why we often aid with water, oil etc media for our ultrasonic probe couple during inspecting

how to explain, why such speaker can transport sound to a far distance, say, 10M 20M etc,?

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#42
In reply to #39

Re: How Does Directional Sound Technology Work?

07/28/2008 9:28 PM

No people reply this issue?

I answer myself.

As matter fo fact, I made a mistake. I used to think that unltrasonic wave is up to 2M, 5M, 10M and 20Mhz or higher frequency for we sold such frequency probes for UT inspection recently. They have to couple by medium for reliable and efficiencable wotk.

I dont know why I forget any frquency above 20khz can be releted to ultrasonic. At its low terminal, like 40khz or 60khz wave length, it can trasport a long distance like 20M, no problem, in fact we use for distance measure by unltronic is mostly based on the 44.1khz.

Its pity. no physist out there like to point out the miss out.

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Anonymous Poster
#40
In reply to #38

Re: How Does Directional Sound Technology Work?

07/27/2008 6:37 PM

Hi CNPOWER,

The point is that if air acted like a nonlinear transfer function a 20kHz carrier signal would have created it's first harmonic frequency component at 40kHz etc. Ordinary sound should thus have created ultrasonic frequency components that could easily be measured with a 40kHz ultrasonic receiver. Why does this not happen, nor has this effect been documented in any IEEE article on acoustics (except for mention to the nonlinearity in articles dealing with so called "parametric sound")? Could this effect not easily be verified experimentally if it existed?

You are correct in noting that, should such harmonic components be generated (somehow), it would still not explain why the sound would become audible.

The phenomena you are referring to is called "beat frequencies" This only happen when one pure tone is played into one ear of a human and another pure tone into the other ear. This is clearly not the same situation in this case.

Jacques

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#43
In reply to #40

Re: How Does Directional Sound Technology Work?

07/28/2008 9:44 PM

Hi, Jacques,

You seem to know how to explain this speaker's mechanism,

but you still keep it to yourself. why not show us?

another out of topic,

Do you thnk your message convers again pompei (city) with that like another volcano burst out

[Dont take it seriously, just make a kidding]

Are you from Germany ?

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#44
In reply to #43

Re: How Does Directional Sound Technology Work?

07/29/2008 7:59 PM

The technology seems to be based on paranormal science, no wonder people refer to it as "paranormal sound".

I am from South Africa.

Moose: I do not know all the answers but have discovered some of the secrets. As with any new technology there are limitations, but it is very rewarding to see the reaction of people the first time they are exposed to the sound.

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#45
In reply to #44

Re: How Does Directional Sound Technology Work?

07/30/2008 9:48 PM

further more.

whats paramormal science?

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#46
In reply to #45

Re: How Does Directional Sound Technology Work?

07/31/2008 2:51 PM

New inventions or technological discoveries should be verifiable and results should be repeatable, not contradict known scientific principles and most important of all – stand the test of time!

By paranormal science, I meant that the explanations for the creation of the sound seem to be based on black magic or supernatural principles rather then on known mathematical modeling etc. If the explanation for the principle relies on one main argument e.g. that air has nonlinear properties, should it not be scientifically verifiable and some kind of mathematical or experimental proof, that can independently be tested, be offered for the statement?

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#47
In reply to #46

Re: How Does Directional Sound Technology Work?

08/05/2008 9:43 PM

Hi, Jacques,

I dont know what you are doing? but you cannt give a solution of the super directonal sound now.

Dont suspect Dr.Ponpei's idea. he may be right.

Mordern acoustics seems to indicate that two super strong sounds transmitt through air or other substance, can cause some nonlinear distortion and produce many harmonic waves. the base difference frquency of the harmonic waves has a very strong direction.

Thats what Dr. Ponpei is doing.

Now I believe this theory. and believe Ponpei is right at explain hie products.

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#48
In reply to #47

Re: How Does Directional Sound Technology Work?

08/06/2008 6:12 PM

Hi CNPOWER,

If two slightly different ultrasonic frequencies are output on two ultrasonic transducers in close proximity, an audible to tone would be heard. Because of the summation/ difference interference effect between the waves an audible tone will be created. The tone's frequency will vary as the distance between the transducers are varied. You can do this experiment yourself. This result offers no proof that air act as a nonlinear medium (as suggested by Dr. Pompei and others).

So called "parametric sound" can be created on a single ultrasonic transducer – there clearly is another explanation for the resulting audible sound.

If air had nonlinear properties, would it not have been possible to specify the Total Harmonic Distortion index for the medium. The THD is the (energy of all harmonics frequencies)/ (energy of the fundamental frequency component)%. Do you know of such a figure that has been computed or published for air? Do you realize how large the THD would have to be for any appreciable sound to be generated?

Air is a highly linear medium!

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#49
In reply to #48

Re: How Does Directional Sound Technology Work?

08/06/2008 6:31 PM

Jacques:

Re: "The tone's frequency will vary as the distance between the transducers are varied."

I would expect the (beat) frequency to change with relative motion, but not with position.

Good response.

DickL

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#50
In reply to #49

Re: How Does Directional Sound Technology Work?

08/06/2008 10:13 PM

this Doppler effect.

the frequency we hearing varied by relative speed.

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#54
In reply to #49

Re: How Does Directional Sound Technology Work?

08/07/2008 7:06 PM

Hi DickL,

I did the experiment and found the result. In my opinion beat frequencies is another division of acoustics but has nothing to do with so called "parametric sound". You may have noticed that I keep on referring to so called "parametric sound" because personally I think the term "parametric sound" was invented because no simple explanation could be found why an ultrasonic sound source could produce audible sound.

I believe that I may have discovered the true solution but will have to keep it a secret for a short time longer since it seem that I will be going into direct competition with other researchers in the area.

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#51
In reply to #48

Re: How Does Directional Sound Technology Work?

08/06/2008 10:55 PM

Hi, Jacques,

Thats beat frequency is differ from here what we are talking about.

it is what your said above " parametric sound".

air nonlinear property exists at certain condition. it s under strong sound signal. as we ll known, only large signal has nonlinear features.

What you talk about THD etc terms is only a normal condition and the sound intensity is under so called stronger.

Thts what I pullzed ago. it relate to another modern acoustic branch. this is out of my depth.

Pompei may not be an acoustics, but what he quote is right.

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#52
In reply to #48

Re: How Does Directional Sound Technology Work?

08/06/2008 11:37 PM

There is rare acoustictists who even ocassionally visit here in the cr4. its pity. I suggest you cna go to other acoustics forum for help.

atmosphere is an odd medium. people still study it and find many wonderful features. there are many branch for it coming into being. as well as in fluid.

Do you konw classic mechanics and theory of relativity. thats answer.

you metioned thd. tht mean in the normal condition. its not a strictly specification. because you hvnt difine what power do you have.

different power has differnet thd for an audio equipment. total harmocic distortion.

we usually take the 3% total power output (rate) as acceptable.

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#53
In reply to #52

Re: How Does Directional Sound Technology Work?

08/07/2008 7:03 PM

CNPOWER,

The Doppler effect only has relevance to moving objects.

A sound wave is nothing more than a rapid compression of air (or a gas). The ideal gas law states: PV=nRT, all the parameters are linear! Any increase in sound volume directly translates into an increased in (P) pressure. The characteristics of air cannot suddenly change under different pressure conditions. If air had nonlinear characteristics it would contradict the ideal gas law for ether the temperature or the volume would need to vary in a quadratic (or similar) manner to any sudden increase in pressure. If this was true it would be possible to create free energy from compressed air….???

I disagree with Dr. Pompei and would like to hear how he explains this?

Jacques.

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#55
In reply to #53

Re: How Does Directional Sound Technology Work?

08/07/2008 10:54 PM

I seem to believe the theory of nonlinear, DeckL at middle position. and near ours side

I shall reply you later after olympic game opening ceremoney

I can only say, the ideal gas formula is right. but the sound transmiting by the air is an adiabatic process. during this procedure, the cooefficients of Cr is a nonlinear.

Hoever, its out of my depth, Im still interested in your new theory.

I wish you make a clear explination. how long need shall we know it?

--

I strange that cannt access to the cr4 a moment ago, whats matter?

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#41
In reply to #37

Re: How Does Directional Sound Technology Work?

07/28/2008 8:34 AM

Thank you for identifying yourself, Mr. van der Merwe. To further establish your credibility, I hope you'll take the time to register with CR4. Both Mr. Pompeii and one of your other competitors, Woody Norris, have already done so.

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#34
In reply to #31

Re: How Does Directional Sound Technology Work?

07/24/2008 3:59 PM

"watch the internet carefully"??

That's a pretty big job. Any other hints?

DickL

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#35
In reply to #31

Re: How Does Directional Sound Technology Work?

07/24/2008 11:50 PM

Whats the real reason of the creation of the super direction sound? I still interest.

However, as Pompei said I deducted really wrong. in fact I admitted soon it was wrong.

your thread made me remember this topic again.

who are you and what will you speak?

however Mr.Pomper put the products into use. what he explained might be right

but I still think it was demodulated by our ear's nonlinear frature. rather than by air.

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#36
In reply to #31

Re: How Does Directional Sound Technology Work?

07/25/2008 12:04 AM

it seems you are that man who have clarmed the right at your page?

I cannt judge who have the real patent for the device. but I m interested in the principle of the device sound.

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