12-04-2011, 04:29 PM
PREPARED BY :
NISHANT KR. SRIVASTAVA
[attachment=12129]
INTRODUCTION
WHAT IS AUDIO SPOTLIGHTING?
It creates focused beams of sound similar to light beams coming out of a flashlight.
It uses ultrasonic energy to create extremely narrow beams of sound that behave like beams of light.
HISTORY
First attempts created a single tone (1975)
Audio tone made directive using a transducer array by Ricoh, Japan (1983)
Systems developed for audio frequencies at MIT’s Media Labs and at American Technology Corporation (1998).
At present, sound quality is a little worse than conventional speakers.
Audio Spotlight
Produces audio beam (like a flash light)
Makes use of interference from ultrasonic waves
Potentially great dynamic range (better than speaker cones)
Audio Spotlight Compared to Speaker
Audio Spotlight Beam Dimensions
Audio Spotlight Distortion
Holy Grail of interactive audio?
Avoid cross-talk cancellation
Track user’s ears and aim spotlight at head
AR; aim it at objects
Open Research
Diffusion (some work with radiosity)
Diffraction
HRTFs with audio spotlights
Integration of graphics and audio hardware for wave tracing (Nvidia?)
Basic Idea
Ex: An ultrasonic signal at 200kHz and another one at 201kHz will generate a 1kHz tone and a 401kHz signal which is inaudible to the human ear.
If an AM signal with a non-zero carrier amplitude is passed through Air, it is self-demodulated
Difficulties
Need powerful ultrasonic sources
modulating these without distortion is difficult
Need an array of transducers that have to be precisely controlled.
Conventional ultrasonic transducer elements introduce too much distortion.
Features
Physically small speakers
No need for crossovers,
tweeters, woofers, voice coils
Power efficient
Directionality
Resultant audio retains directionality of ultrasound source
Acoustic Spotlight
By altering the direction of projection, audio can be made to originate from different locations
Question1: Volume range of the ultrasound speaker?
The volume range of the ultrasound speaker is comparable to traditional speakers but the physical size is smaller. The exact amplitude depends upon the amount of power fed in. The speakers can easily take in 50Watts of power. But since their acoustical impedance is better matched to the acoustical impedance of air, they are more efficient and can produce sound several dBs lounder than a traditional speaker with the same power capability.
2. How to use two ultrasounds to create 3D sound from any point?
Currently, the only technology developed is to use the self-demodulation of a single ultrasound signal to create a sound. This wave can be projected onto a surface of the room and then a listener will perceive the wave as originating from that point. The technology as described cannot be used to created 3D sound from any point in space. It can only be used to make sound originate from any surface in a room.
NISHANT KR. SRIVASTAVA
[attachment=12129]
INTRODUCTION
WHAT IS AUDIO SPOTLIGHTING?
It creates focused beams of sound similar to light beams coming out of a flashlight.
It uses ultrasonic energy to create extremely narrow beams of sound that behave like beams of light.
HISTORY
First attempts created a single tone (1975)
Audio tone made directive using a transducer array by Ricoh, Japan (1983)
Systems developed for audio frequencies at MIT’s Media Labs and at American Technology Corporation (1998).
At present, sound quality is a little worse than conventional speakers.
Audio Spotlight
Produces audio beam (like a flash light)
Makes use of interference from ultrasonic waves
Potentially great dynamic range (better than speaker cones)
Audio Spotlight Compared to Speaker
Audio Spotlight Beam Dimensions
Audio Spotlight Distortion
Holy Grail of interactive audio?
Avoid cross-talk cancellation
Track user’s ears and aim spotlight at head
AR; aim it at objects
Open Research
Diffusion (some work with radiosity)
Diffraction
HRTFs with audio spotlights
Integration of graphics and audio hardware for wave tracing (Nvidia?)
Basic Idea
Ex: An ultrasonic signal at 200kHz and another one at 201kHz will generate a 1kHz tone and a 401kHz signal which is inaudible to the human ear.
If an AM signal with a non-zero carrier amplitude is passed through Air, it is self-demodulated
Difficulties
Need powerful ultrasonic sources
modulating these without distortion is difficult
Need an array of transducers that have to be precisely controlled.
Conventional ultrasonic transducer elements introduce too much distortion.
Features
Physically small speakers
No need for crossovers,
tweeters, woofers, voice coils
Power efficient
Directionality
Resultant audio retains directionality of ultrasound source
Acoustic Spotlight
By altering the direction of projection, audio can be made to originate from different locations
Question1: Volume range of the ultrasound speaker?
The volume range of the ultrasound speaker is comparable to traditional speakers but the physical size is smaller. The exact amplitude depends upon the amount of power fed in. The speakers can easily take in 50Watts of power. But since their acoustical impedance is better matched to the acoustical impedance of air, they are more efficient and can produce sound several dBs lounder than a traditional speaker with the same power capability.
2. How to use two ultrasounds to create 3D sound from any point?
Currently, the only technology developed is to use the self-demodulation of a single ultrasound signal to create a sound. This wave can be projected onto a surface of the room and then a listener will perceive the wave as originating from that point. The technology as described cannot be used to created 3D sound from any point in space. It can only be used to make sound originate from any surface in a room.