Talk:Long range acoustic device

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Description is Inaccurate

The LRAD uses a phased array which via constructive and destructive interference causes the sound to be more directionalized. It is not just a big speaker as the article suggests. Look at a description on How Stuff Works dot com.

Actually, read reference #1. Phased array or not, any loudspeaker with the same diameter will have exactly the same (if not more) directivity as this device. Beranek is a much better reference than howstuffworks.

I have seen a video about one of these devices it is designed to only project in a 90 degree or 180 degree one of these could be taken out by a sniper our somone with a shotgun Dudtz 9/24/05 12:46 PM EST

Made the distances consistent, if they are wrong please change them, but a yard is roughly a metre. There are three feet to both a yard and a metre. (Notice: metre, not meter, tee hee hee). 134.226.1.136 15:38, 6 November 2005 (UTC)

On second thoughts, I'm going to leave the measurements as they are primarily, and just clean up the conversions as per the Manual Of Style Zaf 04:14, 9 November 2005 (UTC)

Hmmm. I'm still no happy with it, with conversions removed it reads: .....33 inches in diameter. At maximum volume, it can emit a warning tone that is 151 decibels at 1 metre..... It just seems wrong to have inches in one sentance and metres in another. And I'm really not sure what a Watt per metre means (decibel conversion). -- Zaf 04:21, 9 November 2005 (UTC)

Added a description of the sound. Some early news reports indicated that it emitted an infra-sonic or low frequency sound that knocked people over. That's not the case. A 105 dbSPL signal at low frequencies just isn't enough to do much of anything, other than maybe make somebody want to dance. But 105 dbSPL in the 2k to 5k range is debilitating. Description adapted from The link to the german website describing the company producing a similar product for Jazz and Classical music concerts no longer works, does anyone know the name of the company or an updated link? -- Zaf 04:31, 9 November 2005 (UTC)

[edit] Threshold of pain

"At maximum volume, it can emit a warning tone that is 151 dBSPL (1000 W/m²) at 1 metre, a level that is very capable of permanently damaging hearing, and 50 times the normal human threshold for pain."

What threshold of pain figure is being used to arrive at this factor of 50? -- 70.81.118.123 06:07, 28 April 2006 (UTC)

Hmm, actually, that should be 150 dBSPL, which I just fixed. Anyway, the threshold of pain is described as being around 120 to 140 dB. Since the threshold of hearing is I₀ = 10^-12 watts/m², and I_DB = 10 log₁₀( I / I₀), the exact figure that would make 150 dB fifty times the threshold of pain would be 133.0 dB. — TheKMan^talk 09:46, 28 April 2006 (UTC)

Works for me (though maybe someone should mention that in the article). Thanks. -- 70.81.118.123 16:04, 29 April 2006 (UTC)

Well, I added a link to the Absolute threshold of hearing article, which shows a range for threshold of pain. I think I'll stick in a number as well. Thanks — TheKMan^talk 14:00, 30 April 2006 (UTC)

[edit] Focus and frequency

Quote: "...can emit sound in a 15 to 30° beam (only at high frequency)..."

Does that mean the LRAD is only capable of a 'beam' that focused when projecting high-frequency sound, or that it is totally incapable of projecting low-frequency sound? -Toptomcat 15:58, 30 October 2006 (UTC)

The wave number is NOT defined as 2πf, but rather 2π/λ. I cannot remember the formula used to express speaker directionality but I would like to verify it, given the aforementioned mistake.

The paragraph which mentions a regular loudspeaker and the wave number is extremely confusing. If this is true, what's the difference between LRAD and a big speaker? What does wave number have to do with it? I'm of the opinion this should be removed or cleaned up to make sense and to fit well with the article.

[edit] Remove?

There is no difference, and that's important to point out. It's been claimed by the manufacturer and press that this is somehow a highly directional speaker. But it isn't - at least any more so than any other speaker of equal size. The wave number discussion illustrates it pretty well I think. JohnDoe4 19:25, 5 June 2007 (UTC)