From:  Cyrus <invalid@i.like.spam>
Date:  23 Nov 2004 14:39:22 Hong Kong Time
Newsgroup:  news.alt119.net/rec.audio.misc
Subject:  

Re: Directed sonic weapons - new info

NNTP-Posting-Host:  4.246.54.89

In article ,
 boo@fractalfreak.com (eric bazan) wrote:

> (...)
> 
> Deafening silence. Well, I knew this would be a hard sell.
> 
> Let me take one more stab at this, then I'll f*ck off.
> 
> Below is a very interesting link I've uploaded to my site.
> Keep in mind this is from 2000. It talks about new breakthroughs
> by an MIT student (F. Joseph Pompei ) regarding creating,
> focusing, and controlling ultrasound:
> 
> http://www.fractalfreak.com/harass/AudioLight.html
> 
> They talk about new transducers, which, while only a foot in
> diameter, can produce a focused ultrsonic beam with a spread
> of about 3 degrees, and range of 100 meters:
> 
> "
>  In order to obtain such narrow directivity from a traditional
>  loudspeaker system, one would need a loudspeaker array fifty
>  meters across!
> "
> 
> And:
> 
> "
>  The directivity, or narrowness, of an acoustic wave generated
>  by a circular transducer is proportional to the ratio of the
>  diameter of the transducer to the wavelength of the sound. So
>  a transducer much larger than the wavelength of the sound
>  creates a very narrow beam.
> "
> 
> "
>  Audible sound contains wavelengths reaching lengths of several
>  feet, so a reasonably sized loudspeaker will always produce a
>  very wide, non-directional source at lower frequencies. The
>  Audio Spotlight, in contrast, outputs short, millimeter sized
>  ultrasonic waves, which form a very narrow beam even in a
>  small transducer, which in turn generates audible sound.  The
>  nature of the nonlinear transformation also essentially
>  eliminates sidelobes in the resulting beam, and maintains
>  relatively uniform directivity across the entire audible
>  frequency range.
> "
> 
> I'll try to be more specific.
> 
> Could these ultrasonic beams of sound be focused through commonly
> used builing materials, perhaps just a floor or a wall, without
> losing much coherence? (especially if a computer tailored the signal?)
> I'm just talking about a brief second or two burst, because I
> assume the power needed would be high.
> 
> What would be the effects, to the body, of being hit by one
> of these ultrasonic waves? How would it feel? Keep in mind
> these beams can be modulated anyway desired.
> 
> Apparently, using interference, or beats, two or more of these
> beams can be focused to an area of space. Infrasound, and audible
> sound, can be created at the point in space where they interfere. This
> apparently can already be done.
> 
> So already it would be possible to create rumbles or vibrations 
> by focusing these ultrasonic beams.
> 
> Assuming they could be targeted through a house, most of the 
> effects I speculated would be possible.
> 
> I'm talking about a short burst type weapon. Just enough to
> deliver a tap, poke or jolt to the body. Enough to wake someone
> up. This needn't take much energy. I see many possibilites using
> this scheme.
> 
> Am I way off base? Opinions?
> 
> -Eric B

Perhaps you yourself would better understand things if you picked up a 
book that deals with the subjects of human ears, sound, air and 
electricity.

I am by no means an expert or an MIT graduate. But reading further into 
the link on your site only points to basically a directed 'full range' 
speaker for public address systems or for background music in a shopping 
mall etc.

Usually, in order to shake things or disturb people/animals you need 
lower frequencies. In the link you provided, the "Audio Spotlight� 
'extends down to a few hundred Hertz' which is about the mid to lower 
midrange frequencies of human hearing. It also states that it can reach 
upwards beyond the range of human hearing.. which is basically sending 
out radio waves. There are more frequencies traveling through the air at 
any given time than you'll ever know.

Humans can feel lower frequencies (1hz-50hz) (broad generalization for 
those in the know.). Humans can hear midrange frequencies to the lower 
khz region (100hz-20khz~) (another broad generalization.). Anything 
above that (megahertz-gigahertz range) is in the operation range of ham 
radio, cell phones, cordless phones etc.

Lower frequencies can travel through objects, walls, buildings but 
usually are very omnidirectional. Higher frequencies that are audible to 
humans don't travel all that well through anything. Play your stereo, 
walk into another room and close the door. You hear more bass than the 
higher frequencies. Some higher frequencies that are audible to humans 
bounce off of objects.. the link you provided mentions that as well. For 
sound to seem like its coming from another source.

Another thing to mention is loudness.. as measured in db. The link you 
provided mentions this device going to about 90db. I could be wrong but 
i remember the OSHA regulations state that 115db is dangerous for 
workers to be around constantly. Which IMO isn't very loud at all.. but 
can be when listened to for long periods of time.

I didn't go entirely through your site about the things keeping you 
awake at night. My first ideas are the building settling strucuturally, 
neighbors playing bassheavy music elsewhere in the building(because 
buildings aren't built with noise transmission taken into account)and 
rattling things around you. Or it could simply be tinnitus.. the ringing 
in your ears when the noise floor around you gets obscenely low. In 
other words, don't listen to music so loud anymore. There is no cure for 
tinnitus and it only gets worse with age.

hth,

-- 
Cyrus

*coughcasaucedoprodigynetcough*