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Q: Speaker Design ( Answered,   1 Comment )
Question  
Subject: Speaker Design
Category: Science > Technology
Asked by: chrisl777-ga
List Price: $30.00
Posted: 02 Oct 2004 07:53 PDT
Expires: 01 Nov 2004 06:53 PST
Question ID: 409300
I have seen an arrangement of speakers on the UK television program
Tomorrows World around 7 or 8 years ago that could project a focused
beam of sound with minimal spread or dissapation of the sound. Low
frequency sound surrounded the central sound and interfeared in some
way to cause a beam of sound to be created. Does anyone know of this?
Answer  
Subject: Re: Speaker Design
Answered By: jackburton-ga on 02 Oct 2004 11:13 PDT
 
Hello Chrisl777,
   
I searched through the "Tomorrow's World" cached website, and found
the page relating to this technology.
  
   
From the "Tomorrow's World" website, dated 2nd March 2000 (cached page):
   
"12th January 2000
     
Sound Beam:
Transmits sound in a straight line.
  
The sound beam is a new device which sends sound in a straight line -
like a spotlight. It could be used to talk to just one person in a
crowd, from a distance of up to 200m. Or, to beam music to individuals
on a cinema or plane, instead of headphones.
It's made by Joe Pompei, a researcher at MIT media lab in Boston. Joe
had the idea of using ultrasound, those frequencies that are beyond
our hearing, to act like a 'carrier' for audible sound.
      
Sound Beam Explained 
    
Normal sound is rather like a lightbulb, flooding a room. What Joe has
done is extraordinary: making sound that's more like a spotlight. He
makes use of high frequency ultrasound waves, beyond our hearing,
which travel in straight lines. What Jo does first is combine music
with ultrasound: this recreates the complex wave patterns of the music
at a much higher frequency that can't be heard. He uses a specially
designed speaker to send out this high frequency ultrasound beam.
Physical properties of the air then distort the beam producing a range
of frequencies including audible sound. As Jo knows exactly how much
distortion the air causes, he can predict how to combine the music
with the ultrasound to get the music out again.
The ultrasound transmits audible sound in a long thin beam, just half
a metre wide. The sound quality isn't strong enough yet to cover very
long distances, but once it is, it could be used to pick out just one
person in a crowd: a personal message system in public places like
airports and stations, or even a personal speaker for music."
    
http://web.archive.org/web/20000302223042/www.bbc.co.uk/tw/stories/technology/0001audiospotlight.shtml
    
   
Tomorrow's World - Audio Spotlight Video (69Mb): 
http://www.holosonics.com/media/BBC_TW_AudioSpotlight_1Mbps.mpg
   
   
About the inventor:
    
"Beginning his career in acoustics at 16 as the youngest engineer at
Bose Corporation, Joseph Pompei continued at Bose while earning a
degree in Electrical Engineering with an Electronic Arts minor from
Rensselaer Polytechnic Institute. Recognising the importance and
underutilisation of spatialised sound, he decided to pursue research
in psychoacoustics at Northwestern University, earning a Master's
degree. Acutely aware of the limitations of traditional loudspeakers,
he had the idea of using ultrasound as an acoustic projector, and has
now developed such a device at the MIT Media Lab, continuing his
education to earn a Ph. D."
http://www.holosonics.com/contact.html
    
   
Holosonic Research Labs, Inc. | Technology
http://www.holosonics.com/technology.html
   
    
Similar technologies:
  
HyperSonic Sound - American Technology Corporation
http://www.atcsd.com/tl_hss.html
  
Sound Beam - International Robotics, Inc
http://www.internationalrobotics.com/iri_new_tech-01.html 
   
  
   
Search terms used on Google:
    
single "focused beam of sound"
"HyperSonic Sound"
beam sound "tomorrow's world"
"Joe Pompei" "tomorrow's world"
    
   
    
I hope you find this information useful. If anything is unclear,
please ask for clarification.
    
Best regards,
    
Jackburton
Google Answers Researcher
Comments  
Subject: Re: Speaker Design
From: guzzi-ga on 02 Oct 2004 15:58 PDT
 
Excellent answer by jackburton. I only reinforce the crux (?Physical
properties of the air then distort the beam?) that it is the
non-linear properties of air which generate audible frequencies from
the ultrasonic signal. All materials exhibit a degree of non-linearity
to transmitted waves or energy conveyance if pushed hard enough.

Best

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