Electrical audio signal processing systems and devices – Binaural and stereophonic
Reexamination Certificate
2000-10-05
2004-07-06
Mei, Xu (Department: 2644)
Electrical audio signal processing systems and devices
Binaural and stereophonic
C381S099000, C381S303000, C381S300000
Reexamination Certificate
active
06760446
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to a point source speaker system and more particularly the application of the principles of wave interferometry to the reproduction of stereophonic sound via a point source speaker enclosure.
BACKGROUND ART
Traditionally, audiophiles have focused on the use of two or more speaker systems. Usually, arranged with one speaker to the left of center, another to the right, and a non-directional subwoofer for low band sounds. With the increasing popularity of home entertainment systems and surround sound, additional speakers are added to the system in an attempt to surround the listener with sound for a more life-like experience.
These traditional systems suffer from a number of defects. Most obviously, these systems are cumbersome and require a large amount of space. Some systems utilize six or more speakers, which must be placed in a particular arrangement within the listener's room. Additionally, speakers must be placed in appropriate locations in order to avoid undesirable effects on the sound quality. For example, placing speakers too close to a corner in a room produces reflections which undesirably alter to sound propagation pattern of the speaker.
The best arrangement of speakers in a room is to position the listener and the speakers in an arrangement that forms an isosceles right triangle with the angle at the vertice of the listener being 90° and the speakers being at the vertices along the base of the triangle. In practice, the distance between the speakers and the listener may vary as long as the angle at the vertice of the listener is maintained at 90°.
Even in this ideal set-up, significant problems arise that negatively impact the listener's experience. Each speaker emits a separate acoustic wave. According to the principles of wave theory, the separate waves will interact within the space-time domain to form a resultant wave form that is dependant on the phase of the original waves at particular points in the space-time domain. The interaction will be constructive in the areas of phase alignment creating an increased signal or bright spot. At points where the phase between the two original waves is 180° out of phase the interaction is destructive creating null or dead spots.
This wave interference phenomenon is akin to the effects created by a light interferometer which demonstrates the wave properties of light. A light beam is split by transmitting the light from a single source through two or more slits. The light output from the slits forms a series of bright rings where the light from each slit is in phase and dark rings where the light from each slit is out of phase.
As a result of this phenomenon as applied to acoustic waves from traditional stereo speakers, the position of the listener in the acoustic wave interference pattern determines the quality of the sound heard by the listener. Thus, if the listener is positioned at a point where the acoustic waves from the speakers are out of phase, the listener will perceive the area as a dead spot.
Additionally, the phenomenon results in what has been coined by some in the audio industry as a “comb filter effect”. This term is borrowed from the field of electronics to describe a particular type of filter in which the filter throughput diagram is shaped like a comb. If a listener moves their head back and forth while listening to conventional speakers, their ears will pass through alternately pass through bright spots and dead spots (i.e., areas where the acoustic waves are in phase and out of phase, respectively. As a result the sound heard by the listener fades in and out as the listener's head moves.
Additionally, the standard two or three speaker (the third being a subwoofer) speaker arrangement also suffers the additional defect of having a weak center channel. This is partially remedied in surround sound speaker set-ups by adding a center speaker, but this utilizes additional space in the room and increases the cost of the system.
SUMMARY OF THE INVENTION
The present invention eliminates these defects through the use of, a point source speaker enclosure and interferometric processing of the L and R stereo signals.
In accordance with the illustrated preferred embodiment, the present invention provides a novel, cost effective point source speaker system.
It is an object of the invention to provide a point source speaker system for reproducing stereophonic sound.
Another object of the invention is to provide a point source speaker system which utilizes the principles of wave interferometry.
An additional object of the invention is to provide a speaker system which is compact without sacrificing sound quality.
It is also an object of the invention to eliminate the problem of dead spots which is inherent in all multiple speaker systems.
An object of the present invention is to provide a point source speaker having a high degree of spatial separation between the left and right stereo channels and a strong center channel.
Another object of the present invention is to eliminate the comb filter effect which is inherent in conventional speaker systems.
Additionally, it is an object of the present invention to provide a high quality speaker system that makes efficient use of space.
The system of the present invention includes, briefly, a point source speaker system, comprising a processor which produces a left minus right (L−R) audio signal, a right plus left (R+L) and a right minus left (R−L) audio signal; three speakers each for audibly transmitting one of the L−R, R+L and R−L audio signals; and a point source speaker enclosure for housing the three speakers in a single enclosure.
The present invention has other objects ad advantages which are set forth in the description of the Best Mode of Carrying Out the Invention. The features and advantages described in the specification, however, are not all inclusive, and particularly, many additional features and advantages will be apparent to one of ordinary skill in the art in view of the drawings, specification, and claims herein.
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Capstone Law Group LLP
Mei Xu
Rosenfeld Mitchell S.
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