Focusing Audio

Alien54 writes: "The fine folks at the MIT Sound Media Lab have come up with a cheap and practical way to focus sound: "A beam of light can be controlled in many ways - it can be aimed at one person in a crowd, spread to fill a room, or projected to create rich, distant imagery. We can now do these very same things with sound. The Audio Spotlight can be used in two major ways: As directed audio, sound is directed at a specific listener or area, to provide a private or area specific listening space. As projected audio, sound is projected against a distant object, creating an audio image. This audio image is literally a projected loudspeaker - sound appears to come directly from the projection, just like light." While still under development, they are testing applications of the device in collaboration with several of their media lab sponsors in preparation for eventual commercial release."

Poor frequency response?

All very interesting, but the information seems to suggest a bottom-end frequency response of a few hunred Hz. The figures, at least, seem to stop at 400Hz.

Now... 400Hz is quite high really. For the musically inclined, concert A is 440Hz. Off the top of my head that's significantly higher than the fundamental frequencies involved in, say, male speech. Until they can get that extended down to somewhere closer to 150Hz (remember - this is logarithmic so one octave is a doubling / halving of frequency) I would think there will be difficulties in using it.

Nick.

PS - Did anyone count the number of `TM's around the place!!

Sonic guns

I'd like to have one mounted on my car. Then, when one of those "boom-box cars" rolls up next to me, I'll point my sound cannon at the driver and burst his eardrums.

Re:safety?

It's quite possible that the device's direct beam could induce extremely severe headaches, either slowly or even right away. Supersonic frequencies are picked up by humans through bone conduction and not really sensed as sound per se, but they do play a role- when I want my stereo to convincingly reproduce the tonalities of incredibly loud sounds, I develop the high-frequency capabilities until it's able to produce very strong ultrasonic output, across the whole signal chain. This is known to be fatiguing to the listener- you have to rein it in quite a bit to allow continuous listening, because some sounds (for instance, abrasive raw electric guitars through peavey amps) are intensely fatiguing to the ear themselves.

Do these MIT speakers kill bugs? Do they cause dogs to howl and cats to hide under the couch? The parallel to a spotlight is apt- it's not safe to look directly into a spotlight.

Subliminal Advertising for the New Millennium

Marketing will have a field day with this. In grocery stores, each aisle will have secret messages aimed at areas to suggest you buy certain products (maybe even aimed lower, for the kiddies).

How long will it be before satellites can beam down messages to whole geographic areas?

Re:drugs vs. technology

were drugs introduced into our society in order to prepare us for the emergence of technologies that would simulate heir same effect?

Yes exactly. As a matter of fact, I am the intelligence behind such an operation. I personally manipulated the DNA of the first hemp plants to ensure that they would produce THC. The actual process of fermentation, that was me too. It really just involved fucking with some yeast. Of course, then I introduced it to man, in the forms of mead and wine, long before recorded history. I also did LSD (at least, I did the real work behind it. In fact, you name it, I put it here, so your feeble little minds wouldn't explode when you saw a laser light show.

Believe me, before I altered space-time, the Disney light parade was an absolute killer.

(Yes, of course this post is sarcastic. My user number is far too high to have been able to do that stuff...)
--

Noise-cancelling use?

Can this technology be used to cancel noises as well as generate sound?

I am thinking that current noise-cancelling technology seems to rely on headphones, since noise is generally omnidirectional. But if this technology were used to determine the direction of the noise source, and shift phase of sounds so the sounds appeared to be coming from the same direction, then one might not have to use headphones.

For example, in a cubicle there are noises all around, from telephones to people talking, and it would be extremely useful to be able to selectively tune out the noises and work without headphones. Currently, I believe "noise cancelling" area systems just generate white noise, which doesn't fix the problem, only create more.

The lower bass tones could be handled in an area system, I think, because they wouldn't be so directional.

I mean, doesn't the world suffer from increasing amounts of "noise pollution" as machines proliferate in our increasingly urban environments? Many people including myself would love to be able to take action to control this environment for ourselves and filter out the annoying noises. A much better use than increasily annoying sales pitches beamed directionally at us without any choice.

Hmmmm some interesting fallout from that...

... it'd be a boon for the hearing impaired in public spaces. Amplified sound targeted to where they are sitting/standing.

I wonder if it could also be used as a weapon. Stun people with an amplified blast long enough to subdue them.

Groupies

Hey you over there. Yeah you with the red dress. Come on up front. The bass player wants to meet you.

safety?

It's nice engineering. But as the page itself points out, there has been lots of prior work in this area.

One very important question is the safety of this kind of approach. The nonlinear effects can't be very efficient, and there must be a lot more energy in the ultrasound than in the audible sound. How safe is it to have large amounts of ultrasound energy beamed at you for extended periods of time? I think I'll stick with headphones.

As an aside, the trademarking is taking on ridiculous proportions: "Audio Image (TM)"? "Directed Audio (TM)"?

Re:Random Street Corner

Forget about ad potential, can you imagine standing at a street corner and hearing, "THIS IS THE VOICE OF GOD!

Actually the article [mit.edu] states that " frequency response, depending on size, extends down to a few hundred Hertz."
I think people will be more surprised than alarmed to discover that the 'voice of god' is a soprano .
- Derwen

drugs vs. technology

consider some of the most common side-effects of popular illegal (in U.S.A. and most) drugs - they alter our perceptions, causing us to see things that aren't there, or hear things that aren't there - "the tree man, it's talking to me"

now a lot of these effects are being duplicated with technology, only they aren't altering the way our brain senses, they are actually creating pseudo-realities for us to exist in (was that ad on the soccer field really there, or was it digitally placed? did the guy sitting next to me see/hear the same ad?)

were drugs introduced into our society in order to prepare us for the emergence of technologies that would simulate heir same effect? imagine what the world would be like if we were suddenly introduced to a whole bunch of mind-bending technologies. Drugs (and the knowledge of the causes of such drugs, for those who don't partake) gives us the background to understand these technologies.

just a thought

-f

Re:Hmmmm some interesting fallout from that...

I wonder if it could also be used as a weapon. Stun people with an amplified blast long enough to subdue them.

IIRC audio weapons have been made with very low freq. audio meant to hit a resonances in people's abdominal cavities. The trouble with the low-freq audio was that it tended to be omni-directional, so it was difficult to aim the cramp-inducing sound field at, say, a crowd of WTO protesters without harming the good people manning the device. One could imagine, however, using multiple, highly columnated, directional beams of slightly differing frequencies (with a low-frequency beat wave) to zap individuals. The resonance is moderately narrow (again, IIRC--someone more in the know please correct me if I'm wrong on this), so the carrier may not need to be of exceptionally high volume in order to drive the resonance to useful amplitudes.

It's been a long time since I read about these, but if I recall correctly the concept was inspired in part by a chicken farm located near a factory in Australia (perhaps New Zealand). The factory put out steady, low-frequency oscillations at a particular frequency that caused the chickens, when they grew to where their heads were a certain size, to die from having their brains scrambled.