Talk:Sound from ultrasound

Discussion about the page Talk:HyperSonic Sound

 * This first main section was Talk:HyperSonic Sound; it was moved to Talk:Sound from ultrasound at the merge described in because then there was no pre-existing page at Talk:Sound from ultrasound. Anthony Appleyard 05:22, 4 September 2007 (UTC).

Cleanup
Here are some things I think need fixing up:
 * Needs more reference -- the only references seems to be to companies which are trying to sell this technology.
 * Needs a better description of how it works -- from what I remember, sound usually adds linearly, so interference of ultrasonic sources shouldn't give audible frequencies. Why is this not the case?

Also there are a few more minor points. I would fix these if the above was fixed. Keithdunwoody 01:52, 4 March 2006 (UTC)
 * The statement that ultrasound does not diffract is not strictly true -- this could be expanded.
 * Grammar is poor in some sections.

I rewrote the second paragraph, but this is the only place I actually changed facts: original: "so it seems to the [listener] that the sound appears to be emanating from himself/herself." I'm pretty sure that's incorrect. It should only sound like it's coming from oneself if the beam is hitting their body, not if it's hitting another object, in which case it would sound like it's coming from that object.

This is an assumption (sorry). Megatronium 05:46, 23 April 2006 (UTC)

It definitely still needs more general cleanup. More references, and better grammar, fixing things like fragments starting with "like." --Howdybob 13:04, 1 July 2006 (UTC)

Military Uses
I seem to recall an article a few years back mentioning the use of "directable audio" in psychological warfare (for instance, making an enemy believe his peers to be plotting his death, or that they are surrounded by a mass armed force, or as a useful interrogation technique - "I'm going crazy"). I can't cite the specific article, but there is definitely a Military use for this technology, especially nowadays. Ugly article though. :=)

—Preceding unsigned comment added by 60.240.77.211 (talk) 08:21, 22 March 2008 (UTC)

NPOV
I've placed the NPOV tag on this article. As it stands, the article is extremely poor, and is largely an advertisemant for a product. The fact that the article only uses the trademarked name for American Technology Corporation's process, rather than the generic name (I scarcely think that the US government was doing research under this title) makes the article as it stands an advertisement. Given that the cleanup tag has been on this article for two months now, I would also support deletion. AKAF 07:40, 31 May 2006 (UTC)

Fixed
I debolded the blatent bolding / advertising of the name. Should have no more point of view problems! I hope this helps. Stovetopcookies 08:10, 29 June 2006 (UTC)

The first instance of the title should be bold though. I stil have other concerns. See below. --Howdybob 12:35, 1 July 2006 (UTC)

NPOV, merge ideas
This article has some info that might be relevant but it's still looks like an ad, apparently using a trademark of the American Technology Corporation for the article title. Per above, the military didn't call it "Hypersonic sound" when researching did it? It should either be deleted or re-written in more general terms, with a mention of "Hypersonic Sound". There should be a general name for the method & article, something like "Ultrasonic intermodulation".

It should either be rewritten a bit & renamed, or merged, maybe with Loudspeaker or Directional Sound.

I'm putting back a different NPOV tag because there's more to it than the bold text. It needs to be made clear whether HyperSonic Sound is a trademark, whether the "audio spotlight" is the same thing or another company's implementation, and what other research has been done by others. It should be moved to a more general, neutral title. --Howdybob 12:58, 1 July 2006 (UTC)

I've edit this heavily and think it should stand as HyperSonic Sound as this is likely to become the name for it, much as hoover/dyson became both the commercial and descriptive name for a vacuum cleaner. There is much to be found that refers to Hypersonic sound - though i cant find a ref of a patent for that name from ATC. i am unsure how to edit the contents bit as i would like to add a criticism section regarding ethics of using hypersound.

--Sparkymarkx, 21 August 2006

This has since been reedited - once by an anonymous collaborating on my last edit and again by me today to clean sentence structure up a bit and link to ultrasound article. I think NPOV is fixed now. Sparkymark x 10 September 2006.

Merged

 * I merged from HyperSonic Sound and the relevant sections of loudspeaker and of Directional Sound. Anthony Appleyard 20:00, 10 September 2006 (UTC)
 * The word hypersonic already has a meaning: "much faster than sound". Anthony Appleyard 20:37, 10 September 2006 (UTC)

Update - Makes
Sennheiser has a speaker now on the market called Audiobeam. 13:40, 19 April 2007 User:85.235.16.21

Usage of the term "Sound from ultrasound"

 * Google search for "Sound from ultrasound" shows various meanings. Is there an established name for the process described in this article? Anthony Appleyard 05:51, 17 September 2007 (UTC)

I know there were NPOV issues before, but I really like the name "Audio Spotlight". I know it is a brand name now, but was first coined in 1983, which makes it ok to use in my book. And no, I have no links with the current owner of the brand name!

Skinduptruk 13:44, 4 December 2007 (UTC)

Thinking it over, it does need to refer to the fact that the sound generated is formed in an extremely narrow beam (15 deg) compared to any conventional loudspeaker (30+ deg), although this varies with frequency - this is what makes it cool in the first place. So "directional sound from ultrasound" or "sound beams from ultrasound" might be a start.Skinduptruk (talk) 10:30, 6 December 2007 (UTC)

Some new content
First time wiki user here - in fact this article drew me in!

I have quite a lot to add to the article as it stands, with a good number of sources.

Any comments before I jump in? I hope to get started tomorrow.

Skinduptruk 15:01, 1 December 2007 (UTC)
 * Welcome to Wikipedia! If you haven't read the Wikipedia Tutorial and some of the Manual of Style, now would be a good time to do so. Other than that, be bold and start editing! — Insanity Incarnat  e  18:49, 1 December 2007 (UTC)

Background info
This is a cut down version of a few chapters of my graduate engineering thesis, so forgive any 'anti-wiki' slip ups. I'm keen to discuss any issues, as I still find the effect fascinating. I worked on this technology for about 3 years, in which time I built my own system and heard the effect many times. I'm looking forward to any talk that my first wiki edit may bring!

Skinduptruk 13:44, 4 December 2007 (UTC)


 * Thank you for the contribution! Do you have a link or a reference to your thesis?  We need to confirm that it was your text to donate (unfortunately we do have to ensure we're respecting copyright).  Neil   ☎  09:55, 5 December 2007 (UTC)


 * I promise it's mine! I need to think about it a little, uploading to public domain and all.  I'm confused about the original research aspect now if we are allowed to refer to our own research.  It was only a graduate thesis, not published in a journal or really peer reviewed as such.  Or do simply upload only some chapters?  I will await your advice.Skinduptruk (talk) 10:04, 6 December 2007 (UTC)


 * As your contribution did include a number of references, it's not a very pressing issue, don't worry. If it lacked references then we definitely would have needed a link or a reference. Neil   ☎  16:02, 6 December 2007 (UTC)

I've fixed the inline "bracketed number" references to be wikipedia-style footnotes (which has several advantages, including automatically keeping them in the order they appear in the article, and keeping the text of the cite with the statement it is used as a reference for in the source code), but there are still style issues (talking about the source in the article, e.g. stuff like "can be found at [9]", doesn't flow well.) —Random832 22:11, 5 December 2007 (UTC)

Wikipedia uses TeX syntax to format math formulas. Should the equation "p2(t) = K . P^2 . d/dt^2 ( E^2(t) )" appear as $$p2(t) = K \cdot P^2 \cdot \frac{d}{dt^2} \left ( E^2(t) \right )$$ or $$p2(t) = K \cdot P^2  \cdot \frac{d}{dt^2} \left ( E^{2(t)} \right )$$ —Random832 22:19, 5 December 2007 (UTC)

To start off, I don't know anything about the subject, but the first form seems like the right form. The second looks wrong to me. Martijn Hoekstra (talk) 22:50, 5 December 2007 (UTC)


 * Actualy, it seems even more likely that it should be $$ E(t)^2 $$, but someone more knowledgeble on the topic should comment on that. Martijn Hoekstra (talk) 22:53, 5 December 2007 (UTC)


 * Well I'm amazed at all the work done already! Sorry for the incomplete equation.  Note it is a direct copy from the Berktay paper mentioned, so it could be hunted down there.  The copy I have is $$p_2(t) = K \cdot P_c^2  \cdot \frac{\partial}{\partial t^2} E^2(t)$$  Where  $$p_2(t) =\,$$ Audible secondary pressure wave  $$K = \,$$ misc. physical parameters  $$P_c = \,$$ SPL of the ultrasonic carrier wave  $$E(t) = \,$$ Envelope function (such as DSB-AM)  This equation says that the audible demodulated ultrasonic pressure wave (output signal) is proportional to the twice differentiated, squared version of the envelope function (input signal).  Precompensation refers to the trick of anticipating these transforms and applying the inverse transforms on the input, hoping that the output is then closer to the untransformed input.Skinduptruk (talk) 10:04, 6 December 2007 (UTC)


 * The more I think of it, the more I get confused by that part of the equation. If E is a function of t alone, why are there partial deratives? Another point, is it actualy $$\frac{\partial}{\partial t^2}$$, or should it be $$\frac{\partial ^2}{\partial t^2}$$? The second would mean the second time derivative of whatever follows it, the first reduces to $$\frac{1}{2t}\frac{\partial}{\partial t}$$. I know the notation $$E^2(t)$$ is sometime used for $$(E(t))^2$$, but in my oppinion it is ambigious, as it could also mean $$E(E(t))$$. That last thing is just a question of preference though. Martijn Hoekstra (talk) 11:31, 6 December 2007 (UTC)


 * Again, thanks for your interest! I think you are right about the missing exponent in the partial, you jogged my memory that it was a typo in my original transcription.  Sorry about that, but like you say, it is quite weird without it, so I'd say you are correct, please use the 2nd term you suggest in the article.  The E term should equate to E * E, not E of E, it's just a normal multiplication - please adjust to that.  It's a real shame I threw out all my photocopies of the articles I researched for two years, didn't see any need for them, didn't count on wiki coming along.  As for the partial with t only, again I may have not provided the correct context from the original article.  Off the top of my head, it might have something to do with the fact in reality, the envelope function (and the secondary pressure function) is a function of both time and space, both at the speaker face and out into the beam in air formed by the travelling pressure waves.  So the equation is saying something about the effects over time, presumably at a fixed point in space.  So they should both really have a (t,x) not just a (t) - this may well be another transcription error.  But I'm digging deep into the memory banks now to remember the context, which can be quite subtle.  The good news is, I only intended the equation to be a transcription from the article, in order to make a point about how the theory can point to a potential precompensation scheme.  So rest assured the article has the correct version, so one day someone can confirm that.  From memory, the Pompei article also quotes this same equation of Berktay.  And don't forget, this equation is under certain assumptions, so the full physical effect is much more complicated to solve in theory.Skinduptruk (talk) 22:25, 6 December 2007 (UTC)


 * To me, it sounds like $$p_2(t) = K \cdot P_c^2 \cdot \frac{\partial^2}{\partial t^2} E^2(x,t)$$ is the right form. I'll put that in, but do revert or change if you think it's wrong. In my personal oppinion $$p_2(t) = 2K \cdot P_c^2  \cdot \left ( \frac{\partial}{\partial t} E(x, t) \right )^2$$ is the best looking of all options, but that would venture into original research, and only a matter of oppinion on esthetics. Martijn Hoekstra (talk) 16:26, 11 December 2007 (UTC)
 * 2 points: 1 Your second proposed equation is a quite different equation. 2 If there is a space variable on the right hand side, E(x,t), it would seem there should be a space variable on the LHS. 24.5.198.239 (talk) 00:56, 8 January 2008 (UTC)

Safety issues
I anticipate the safety issues will become important so here is a section for them Skinduptruk (talk) 14:33, 11 December 2007 (UTC)


 * In the version I encountered, the statements about safety were not consistent with the sources cited. The sources cited gave ceiling values of 110-115dB, but were stated to give limits for continuous exposure of 145dB.  I recommend that editors continue to check any sources for themselves on this issue, because even among environmental issues I can't think of one in which polluters are more eager to mislead and outright lie than in noise issues (even on signed memoranda of understanding negotiated with local governments!) 70.15.116.59 (talk) 04:02, 15 January 2008 (UTC)
 * I cleaned up the safety a little bit; the OSHA standard is very clear that 145dB is maximum. The 115 only applies when things like ultrasonic water baths are used, and the operator can (say) stick their hand right in it.  145dB is correct for the context of the article.  The other guidelines were all from the late 70's-early 80's, predating OSHA's guidelines, which certainly looked at the same sources. Crxow (talk) 21:33, 16 January 2008 (UTC)
 * I've restored the 115 and plagiarized most of the sentence from OSHA verbatim to avoid any misunderstandings. They say that if there is "any possibility" of touching "water or some other medium".  You don't think there's a chance that a little kid hearing this noise out of nowhere isn't going to put his ear to the sidewalk to try to hear where it's coming from?  The article even says that the 115 can't be used if there's a chance of direct coupling with the source - there's some other table for direct contact with the mastoid bone.  Also, saying that all the 110 and 115 figures are old subjective data from the 1970s and the OSHA figure (which you give as 145) is based on new research from ACGIH in 1987 seems very misleading, when you consider that the "old" ACGIH figure of 115 dB is exactly the same as what the OSHA table actually says.  As for "subjective effects" the article mentions them but doesn't say the decibel figures are based on them.  The bottom line is that when a table says 115 and you write 145 you're running afoul of WP:NOR. Wnt (talk) 18:07, 17 January 2008 (UTC) (same as the IP above)
 * I disagree; the ACGIH standards were written with ultrasonic cleaners (water baths) in mind, not airborne transducers directly. So in these devices there is zero chance that the medium can be contacted, since one doesn't even exist.  There's zero possibility that the ultrasound will penetrate and travel through the sidewalk, and there is no possibility of contact with the mastoid bone.  So the 145dB is clear, correct, and precise, and has nothing to do with NOR - it's data straight from OSHA, just removed from the context of water-bath-ultrasonic cleaners.  For the "subjective effects", the original cited articles (Acton, etc.) make this very clear.Crxow (talk) 04:35, 18 January 2008 (UTC)


 * I've added other more recent review papers which are critical of the OSHA guidelines, in an attempt to provide some balance. --80.176.155.103 (talk) 00:07, 19 November 2011 (UTC)
 * The first part of this section remains a problem - "For the nonlinear effect to occur relatively high intensity ultrasonics are required. The SPL involved was typically greater than 100dB of ultrasound at a nominal distance of 1m from the face of the ultrasonic transducer.[citation needed] Exposure to more intense ultrasound over 140dB[citation needed] near the audible range (20–40 kHz) can lead to a syndrome involving manifestations of nausea, headache, tinnitus, pain, dizziness and fatigue" What is the second sentence referring to? The third sentence seems to claim that the subjective effects only occur above 140 dB and cite Canadian Safety documents. However I've read the documents and this claim is not supported, the Canadian's clearly explain that such effects occur due to a range of factors, and refer to reports showing such effects have been documented at SPL's as low as 85 dB. The important point seems to be if there is any audio-frequency in the ultrasound, perhaps caused by the creation of sub-harmonics. I've left things as they are, but they really need removing and rewriting. --80.176.155.103 (talk) 18:14, 19 November 2011 (UTC)

Cleanup 2009
Can somebody correct the section on Modulation? It's incredibly incorrect. You might be able to safely delete the entire thing. The figure is particularly wrong. Here's a passage that makes a little more sense, but could use some peer review. I also have the associated example images, but my account isn't priv'd enough to upload them. They'd be easy enough to replicate.

Here is the passage I had in mind:

The nonlinear interaction results in the mixing of ultrasonic tones in air to produce sum and difference frequencies. A DSB-AM modulation scheme with an appropriately large baseband DC offset, in order to produce the demodulating tone superimposed on the modulated audio spectra, is one method of generating the signal that encodes the desired baseband audio spectra. This technique suffers from extremely heavy distortion as not only the demodulating tone interferes but also every frequency carried on it with each other. The modulated spectra is convolved with itself. This distortion is inversely proportional to the magnitude of the DC offset (demodulation tone) superimposed on the signal. A larger tone results in less distortion. The audio spectra is further distorted by the nature of the nonlinear acoustic effect. The result is filtering of the desired signal by the function -<\omega>^2 in frequency. This distortion may be equalized out with the use of preemphasis filtering.

By the time convolution property of the fourier transform, multiplication in the time domain is a convolution in the frequency domain. Convolution between a baseband signal and a unity gain carrier frequency shifts the baseband spectra in frequency and halves its magnitude, as shown in [Fig] (shows both positive and negative sides of the x-axis).

The modulation depth m is a convenient experimental parameter when assessing the total harmonic distortion in the demodulated signal. It is inversely proportional to the magnitude of the DC offset. THD increases proportionally with the square of m[1].

These distorting effects may be better mitigated by using another modulation scheme that takes advantage of the differential squaring device nature of the nonlinear acoustic effect. Modulation of the second integral of the square root of the desired baseband audio signal, without adding a DC offset, results in convolution in frequency of the modulated spectra with itself due to the nonlinear channel effects. This convolution in frequency is a multiplication in time of the signal by itself, or a squaring. The double integration corrects for the -<\omega>^2 filtering characteristic associated with the nonlinear acoustic effect. This recovers the original spectra and is illustrated in [Fig].

If somebody would be kind enough to fix that, I'd be grateful!

Orac281 (talk) 06:52, 13 August 2009 (UTC)
 * Sounds good. To upload your account needs to be "Autoconfirmed", which needs 4 days and 10 article edits (and no vandalism or such). So you should be able to upload those images very soon, which would be very much appreciated! AKAF (talk) 07:29, 13 August 2009 (UTC)

Organized stalking
This section appears to be poorly-written, barely coherent, unreferenced conspiracy-theory nonsense. In my opinion should be deleted. QuipQuotch (talk) 20:03, 22 February 2015 (UTC)

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