Abstract:
There is disclosed an omnipresent sound system for use by a listener in an artificial reality system which operates to couple sound with the presented objects such that as the sound moves with respect to the user, the user will have the perception of the changing sound both in pitch and in volume. The sound system is comprised of a series of piezoelectric elements spaced apart around a user&#39;s head. The system is designed to program each element individually so as to create the illusion of omnipresent three-dimensional sound in conjunction with images presented to the listener, which images define an artificial environment.

Description:
TECHNICAL FIELD OF THE INVENTION 
     This invention relates to sound systems and more particularly to such systems that present sound to a listener in a &#34;full wrap-around&#34; manner. 
     CROSS REFERENCE TO RELATED APPLICATIONS 
     The following patent applications are cross-referenced to one another, and all have been assigned to Texas Instruments Incorporated. These applications have been concurrently filed and are hereby incorporated in this patent application by reference. 
     
         ______________________________________U.S. Pat. applicationSer. No.    Filed    Title______________________________________593,196     10/05/90 Method and Apparatus for Provi-                ding a Portable Visual Display593,823     10/05/90 Method and Apparatus for Moni-                toring Physical Positioning of                a User______________________________________ 
    
     BACKGROUND OF THE INVENTION 
     There are many situations in which full wrap-around sound is desirable for presentation to a listener. One such system is in artificial reality systems where an artificial environment has been created for a user. This environment would typically contain scenes that are created surrounding the viewer, and as the viewer moves in any plane relative to the environment, the scene changes as it would if the viewer were moving in a real environment. 
     In some situations sound is presented to the viewer in conjunction with the projected images such that as the viewer (or sound source) moves closer or further away, the sound will increase or decrease in volume and frequency. At times the sound would appear to come from directly behind, over or below the listener. 
     Conventional stereophonic speakers which are placed over each ear can only approximate the direction of the sound from one side or the other. These speakers are expensive and do not satisfy the requirement that the listener actually hear the sound coming from behind, above, below or from one side. 
     Currently, surround sound or holographic sound or what is called 3-D sound, is generated by using powerful digital signal processors which are basically stereo earphones tricking the ear into perceiving that the sound is coming from behind, around, or from different distances. 
     Thus, a need exists in the art for a speaker system which is lightweight, inexpensive and yet which can create the illusion of sound coming from an omnipresent direction. 
     There is a further need in the art for such a system which can be created and controlled by an artificial reality system and is portable and generatable under processor control. 
     SUMMARY OF THE INVENTION 
     An omnipresent sound system has been constructed using a series of discreet piezoelectric elements in a headband around the user&#39;s head. Each element is individually controllable from signals provided to it from the processor. Thus, sound can be programmed to occur at any position around the user&#39;s head. 
     By judiciously selecting the volume and timing of the sounds from each of the individual piezoelectric elements, the listener will have the sensation of omnipresent stereographic sound which is keyed to the scene being viewed by the viewer in the artificial reality system. The scene being viewed is, in turn, controllable by the sensed motion of the user. 
     Thus, for example, a user can be walking (in the artificially created environment) toward a siren (for example, a flashing light on a vehicle), and the scene of the siren source (vehicle) would be getting larger. Concurrently, the sound from the siren would become louder, and the frequency of the siren could also be changing depending upon the approach angle. Of course, the vehicle could be moving relative to the viewer and the sound would change accordingly. 
     The system to create this illusion of changing sound is designed to send signals to different ones of the piezoelectric elements from time to time to create the illusion of the sound moving. These sound attributes of the created environment are stored in a portable processor and provided to the viewer in conjunction with the proper scene. Thus, the system knows how far the viewer is from an object so it, in turn, knows which one of the piezoelectric elements to turn on. The system knows that as the viewer approaches to view objects, the sound should get louder. If the viewer is looking directly at an object, the sound should come from in front. The viewed objects can also have boundary boxes around them so if the viewer moves into the object, a bump can be heard. In addition, the piezoelectric devices can be made to physically vibrate, thereby creating the &#34;feeling&#34; of sound impacting the viewer. 
     Since the system is object oriented, the closer the viewer gets to an object, the more the sound will change. This is important for applications, such as military and flight simulations. 
     Thus, it is a technical advantage of the invention to provide a sound system which is omnipresent with respect to a viewer and which is lightweight and inexpensive to manufacture. 
     It is a further technical advantage of this invention that such a system is designed to respond to signals provided by a portable processor and generated in conjunction with an artificial reality system to provide sound in coordination with the derived physical presentation of the environment around the viewer. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete understanding of the present invention may be acquired by referring to the detailed description and claims when considered in connection with the accompanying drawings in which like reference numbers indicate like features wherein: 
     FIG. 1 is a helmet mounted virtual reality device with the speaker elements exposed; 
     FIG. 2 is also a helmet mounted virtual reality device; 
     FIG. 3 is a schematic representation of a simulated reality system; 
     FIGS. 4a, 4b and 4c depict a CCD position-orientation sensor in various orientations; 
     FIG. 5 shows a three-dimensional position-orientation sensor;, and 
     FIG. 6 shows a schematic of a system with a plurality of interconnected virtual reality devices. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 depicts a portable virtual reality system 10 worn by an individual on his or her head. System 10 consists of a color liquid display screen 101, an array of piezoelectric film elements 102, a position-orientation sensor 12 and a processor 13. 
     Processor 13 generates a visual picture according to helmet 10 orientation information from position-orientation sensor 12 and on board software. Processor 13 creates a three dimensional environment and projects a view of it on screen 101. As the user moves his/her head and, hence, helmet 10, processor 13 changes the image on screen 13 to mimic the view the user would perceive if he/she were actually in the three dimensional environment. Similarly, if the user walks or runs to a new location, processor 13 changes the image on screen 101 as if the user walked or ran the same distance and direction in the three dimensional environment. 
     Note that while screen 101 is a color liquid crystal display, it can be any type of display and can, for example, be positioned close to a user&#39;s eyes with a short focal length. 
     Processor 13 also generates a sound field through piezoelectric elements 102 of sound band 11. Individual elements 102 are separately driven by processor 13. The processor selectively powers piezoelectric film elements 102 on an individual basis to create a directional sound field. By doing so, the processor can create the illusion of a moving sound source and of a stationary sound source when the user&#39;s head or body moves. The sound source would be stationary, i.e., the same sound would continue to come from the same elements when the user stops moving. The sound elements can be small chips or elongated bands, each driven by a separate signal from the processor. 
     FIG. 2 shows a system in which the user, using control 21, manually changes the presented image or manually creates a change in direction or speed with respect to the created environment. Band 22 contains elements 102 and can be adjusted via tightening mechanism 20, which can also be a volume control for the elements. 
     FIG. 3 schematically depicts processor 13, screen 101, speaker elements 11, joystick 21, position-orientation sensor 12 and direction control module 306. Processor 13 takes graphic information stored in a data base and generates images that are displayed on screen 101. Processor 13 also generates sound projected from piezoelectric film segments 102. Processor 13 could be a single processor or multiple processors such as a graphics processor from the TMS340 series and a digital signal processor from the TMS320 series, all available from Texas Instruments Incorporated. The &#39;340 generates images shown on screen 101 and the &#39;320 generates sound on element band 11. Connected to processor 13 is a position-orientation sensor 12. Position-orientation sensor 12 senses the direction that the user is looking. A flux gate compass (not shown) may also be linked to processor 13 to provide absolute north-south orientation information. Direction control block 306 provides processor 13 with information indicating the user&#39;s location and view within the three dimensional environment. Direction control block 306 receives user orientation information from position sensor 12 through processor 13 and from the user directly through joystick 21. Direction control block 306 can determine the user&#39;s position within the three dimensional environment by mathematically integrating the instantaneous orientation information from position-orientation sensor 12. 
     FIGS. 4a, b and c depict an element in an embodiment of a position and orientation sensor 12. Container 40 is fluid filled and has light source 43 (or other source of electronic signals such as infrared or microwave) on one side and CCD 44 (&#34;charge coupled device&#34;) or other electronic signal detectors on the other. CCD 44 is able to sense where light 401 impinges on it from source 43 and when light is blocked by fluid 42. FIGS. 4b and 4c depict different orientations of assembly 40 and hence depict different levels of fluid in device 40. 
     In FIG. 4b as assembly 40 is tilted down, a larger area of CCD 44 is blocked by fluid 42, allowing less light 401 to strike CCD 44. The amount of light impacting CCD 44 can be detected, for example, by using an array of individual CCD (or other detectors) devices, and monitoring, perhaps on a digital basis, the light level. When horizontal, no light gets through to CCD 44. In FIG. 4c fluid completely covers CCD 44. 
     In FIG. 5 a number of CCD assemblies 40 can be combined to indicate the tilt in different axes. Three assemblies, 40a, 40b and 40c are aligned along mutually orthogonal axes and encapsulated in direction sensor 12 to detect motion in three dimensions. The orientation information from assemblies 40a, 40b and 40c is transmitted through cable 301 to processor 13. The CCD assemblies can also provide information on the motion and position of sensor 12 by examining the output of CCD device over time. 
     FIG. 6 shows a schematic of a system with a plurality of interconnected virtual reality devices 10A, 10B and 10N. Although this schematic shows only three virtual reality devices 10, a person skilled in the art will realize that there is no limit on how many such devices are interconnected. Each virtual reality device 10 is connected to a viewer and is operable to provide an artificial viewing environment for this viewer. Each of the virtual reality devices 10 include the elements shown in FIGS. 1 through 5, for example processors 13A through 13N, which correspond to processor 13 in FIGS. 1, 2, 3 and 5. Each processor 13A through 13N is operable to accept data from the viewer to which it is connected as well as from other viewers. Each virtual reality device 10 presents on its screen 101 an artificial viewing environment to its local viewer based upon the data accepted from the local viewer as well as the data accepted from other viewers. The virtual reality device 10 is operative to coordinate the provision of impulse signals to its piezoelectric elements 102 to create a sound field based on data both from the local viewer and from the other viewers. The artificial environment and impulse signals presented to each viewer is unique to that viewer and contains predefined structures. 
     It is possible to use only two devices to obtain all three orientations by taking into account the slope of liquid within each device 40. 
     Although this description describes the invention with reference to the above specified embodiments, it is but one example, and the claims, not this description, limit the scope of the invention. Various modifications of the disclosed embodiment, as well as alternative embodiments of the invention, will become apparent to persons skilled in the art upon reference to the above description. Therefore, the appended claims will cover such modifications that fall within the true scope of the invention.