Patent Publication Number: US-8121336-B2

Title: Directional loudspeaker to reduce direct sound

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The invention relates to loudspeaker directivity control. In particular, the invention relates to a loudspeaker for generating an indirect sound field greater than a direct sound field. 
     2. Related Art 
     Loudspeaker systems may be included in a variety of environments. One type of environment is a vehicle in which the loudspeaker system is coupled to an audio system. Loudspeaker systems may be placed throughout the vehicle to produce sound in the vehicle. The sound produced may be degraded because of the vehicle&#39;s interaction with the outside environment and the nature of the interior of the vehicle. For example, exterior vehicle noise such as road noise, wind noise, and surrounding vehicle sounds may interfere with the sound environment inside the vehicle. 
     As another example, the interior design and boundary walls of the vehicle may affect the acoustics of a vehicle audio system. Specifically, the placement of seats, passengers, and vehicle structures such a pillars, windows, and headliners may affect sound reflections. For audio systems that seek to reproduce multi-channel sound sources, or create an illusion of spaciousness within the vehicle, the available placement of speakers may not allow optimal, sound reproduction. 
     In home theater environments, the placement of listener positions and surrounding walls may affect the acoustics of the room. Listeners may want to experience a spaciousness of sound sources wherever they may be seated. Therefore, a need exists for a loudspeaker system that can produce a spacious sound experience within various environments. 
     SUMMARY 
     The disclosure provides an enhanced audio experience in an enclosed or partially enclosed environment with a multi-directional loudspeaker. One example of a multi-directional loudspeaker system includes a directional loudspeaker system. The loudspeaker may include loudspeaker elements that produce an indirect sound field greater than a direct sound field at a listener position. The loudspeaker elements may include dipole loudspeakers (such as electrodynamic planar loudspeakers). The loudspeaker elements may be mechanically baffled, or the loudspeaker elements may be configured with an acoustic waveguide and deflector to produce the indirect sound fields. 
     The invention also provides a sound processing system to implement a bidirectional loudspeaker system with electronic enhancement. The sound processing system may include an input unit, a sound processor, memory, and an output unit. The sound processor processes an input sound source to generate an indirect sound field greater than a direct sound field at a listener position. 
     Other systems, methods, features and advantages of the invention will be, or will become, apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the following claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like referenced numerals designate corresponding parts throughout the different views. 
         FIG. 1  illustrates an example directional loudspeaker system with two dipole loudspeaker elements. 
         FIG. 2  illustrates an example directional loudspeaker system with two baffled loudspeaker elements. 
         FIG. 3  illustrates an example directional loudspeaker system with summed loudspeaker sources. 
         FIG. 4  illustrates an example directional loudspeaker system positioned in compartments of a vehicle. 
         FIG. 5  illustrates an example directional loudspeaker system positioned in compartments of a vehicle with summed loudspeaker sources. 
         FIG. 6  illustrates an example directional loudspeaker system with a speaker placed in the rear compartment of a vehicle. 
         FIG. 7  illustrates an example directional loudspeaker system with one speaker output channeled along the headliner of a vehicle. 
         FIG. 8  illustrates an example directional loudspeaker with an acoustic waveguide and a channel. 
         FIG. 9  illustrates the example directional loudspeaker system of  FIG. 1  showing the virtual speaker locations of the indirect sound field. 
         FIG. 10  illustrates an example sound processing system for creating an indirect and direct sound field in the directional loudspeaker system. 
         FIG. 11  illustrates an example process to create an indirect and direct sound field in the directional loudspeaker system. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  illustrates an example directional loudspeaker  100 . The loudspeaker system  100  may be placed in an enclosure, such as a vehicle or a home theater environment. The vehicle or home theater environment may have boundary walls  104  defining the enclosure. The boundary walls may be ceilings  105 , floors, windows  107 , and walls. The loudspeaker  100  is configured to include one or more listener positions  101  and  120  where a listener may experience the output from the loudspeaker  100 . The loudspeaker  100  may include at least one loudspeaker element  103  and  113 . A loudspeaker element  103  or  113  may include a second loudspeaker element  123  or  133  positioned near the loudspeaker element  103  or  113  respectively. The second loudspeaker element  123  and  133  may allow the loudspeaker element  103  and  113  to operate in phase with respect to the sound fields radiated from the loudspeaker. 
     The loudspeaker elements  103  and  113  are mountably positioned integral with the boundary wall proximate a listener position. Placement of the loudspeaker elements  103  and  113  may include mounting the loudspeaker elements  103  and  113  in the ceiling or headliner of the vehicle, such that a loudspeaker element  103  or  113  may be mounted over the head of a listener positioned at one of the listener positions. The loudspeaker element  103  may be mounted within the ceiling or headliner of a vehicle such that the loudspeaker element  103  is wholly or nearly wholly contained below the surface of the ceiling or headliner. The loudspeaker element  103  may then be mounted with a fastener, locking ring, within a groove in the ceiling or headliner, or bolted, glued, or hinged to the ceiling or headliner. The loudspeaker element  103  and  113  may or may not be movable within its position within the boundary wall. The loudspeaker element  103  and  113  may be pivotably mounted to the ceiling or headliner. 
     The loudspeaker element  103  and  113  may be positioned approximately less than two to three feet from the listener position, or on the order of a few feet or less, depending on the configuration of the enclosed space. For example, in a large sport utility vehicle, the loudspeaker element  103  and  113  may be positionable approximately two to three feet from the listener position. In a smaller vehicle, such as a mid-size or compact vehicle, the loudspeaker element  103  and  113  may be positionable approximately one or two feet or less from the listener position. 
     Alternatively, the loudspeaker element  103  may extend partially away in a downward direction from the ceiling or headliner. In that case, the loudspeaker element  103  may be mounted with a fastener to the ceiling or headliner, and the loudspeaker element  103  may be positionable about its mounted position along the boundary wall to adjust the directionality of the sound waves emanating from the loudspeaker element  103 . The loudspeaker element  103  may be further pivotable about either an axis extending perpendicular to the boundary wall plane, or pivotable about an axis formed along the intersection of the plane of the boundary wall surface and the fastening structure mounting the loudspeaker element  103  to the boundary wall. 
     The loudspeaker element  103  and  113  produces an indirect sound field  109  and a direct sound field  111  and  121 . The indirect sound field  109  and  119  may reflect by at least one of the surfaces, such as the ceiling  105 , floors (not shown), windows  107 , or other surface of the enclosure  104 . For example, in  FIG. 1 , the indirect sound field  109  is depicted reflecting by the window  107  of the vehicle. The direct sound field  111  and  121  is propagated substantially parallel to a straight line between the listener position  101  and the loudspeaker element  103  and  113 . The direct sound field  111  and  121  may deviate slightly from the straight line between the listener position  101  and the loudspeaker element  103  and  113  because of diffraction around solid objects in the path of the direct sound field  111  and  121 . 
     The indirect sound field  109  and  119  and the indirect sound field  111  and  121  produced by the loudspeaker elements  103  and  113  may arrive to create a sound experience for a listener positioned at the listener position  101  and  120 . A location substantially beneath the loudspeaker element  103  and  113  is a null zone for sound fields, where the sound pressure in the null zone is substantially zero. The loudspeaker element  103  and  113  may provide directivity control for the sound fields radiated from the loudspeaker. 
     The loudspeaker elements  103  and  113  are configured so that the indirect sound field  109  is greater than the direct sound field  111  at the listener position  101  within the enclosure. A path length of the direct sound field  111  propagating from the first loudspeaker element  103  to the listener position  120  may be substantially equal to a path length of the indirect sound field  119  propagating from the second loudspeaker element  113  to the listener position  120 . 
     The path that the indirect sound field  109  and  119  propagates along, including reflections by of surfaces, such as boundary walls  104  in the enclosure, creates an illusion of spaciousness for the listener located at the listener position  101  and  120 . 
     The loudspeaker elements  103  and  113  may be dipole loudspeakers. Dipole loudspeakers have the property where the sound field produced by the opposing radiating surfaces of the loudspeaker create a dipole field, where the sound pressure in a direction substantially along the axis parallel to a radiating surface of the dipole speaker is null. Dipole loudspeakers may be implemented as a system of in-phase loudspeaker configured back-to-back together, such as the configuration shown in  FIG. 1 . A second loudspeaker element  123  or  133  may be combined with the loudspeaker element  103  and  113  to produce a direct sound field that is in-phase relative to a single loudspeaker element. The dipole loudspeaker may also be implemented as a commercially available system such as an electrodynamic planar loudspeaker. 
     The boundary walls  104  of the enclosure may be substantially reflective of sound waves incident on the boundary walls  104 . Examples of suitable boundary walls include vehicle doors, windshields, side and rear windows, floors, seats, partitions, pillars, and seats located within a vehicle. In a home theater environment, examples of suitable boundary walls include side walls, windows, chairs, furniture, and other substantially hard furnishings. 
       FIG. 2  illustrates an example directional loudspeaker system  200  with two loudspeaker elements  203  and  213 . The loudspeaker elements  203  and  213  depicted in  FIG. 2  may be conventional loudspeaker systems with a channeling device acoustically coupled to the loudspeaker element, where the channeling device is operable to produce a greater indirect sound pressure than a direct sound pressure at a listener position. 
     In  FIG. 2 , the channeling device may be implemented as a mechanical baffle  215  and  216  positioned between the loudspeaker elements  203  and  213  and the listener positions  101  and  120 . The baffle  215  and  216  may deflect the indirect sound field  109  and  119  from a direction directly below the loudspeaker element  203  and  213 . The indirect sound field  109  may reflect by at least one of the boundary walls or surfaces, such as the ceiling  105 , floors (not shown) or windows  107  of the enclosure  104 . The direct sound field  111  and  121  may radiate from one loudspeaker element  203  to a listener position  120  not located directly below the loudspeaker element  203 . Conversely, the direct sound field  111  and  121  from a different loudspeaker element  213  may radiate directly to a listener position  101  not located directly below the loudspeaker element  213 . The position of the baffle  215  creates a zone of reduced sound field below the loudspeaker element  203  and  213 . The indirect sound field  109  and  119  produced by the baffled mechanical loudspeaker  203  is greater than the direct sound field  121  at a listener position  101 . 
     The loudspeaker element  203  and  213  may include a radiating surface  221  and  222  indicating the direction that sound may radiate from the loudspeaker element  203  and  213 . The mechanical baffle  215  and  216  may be positioned proximate to the radiating surface  221  and  222 . The mechanical baffle  215  and  216  may abut the radiating surface  221  and  222  of the loudspeaker element  203  and  213 . The loudspeaker elements  103 ,  113 ,  203 , and  213  need not be of the same configuration within the same loudspeaker system  100  and  200 . The mechanical baffle  215  and  216  may have a dimension 50% greater than the lateral dimension of the loudspeaker element  103  and  113 , such that the radius of the baffle  215  and  216  is greater than the radius of the loudspeaker element  103  and  113 , but less than 1.5 times the radius of the loudspeaker element  103  and  113 . Other baffle dimensions may be available corresponding to different vehicle or room environment configurations and/or acoustics. 
     The channeling device may also include an acoustic lens positioned proximate the radiating surface of the loudspeaker element and the baffle. The acoustic lens is further positioned between the radiating surface of the loudspeaker element and the baffle. The acoustic lens may be configurable to channel or focus the direct sound field radiated by the loudspeaker element  103 . The acoustic lens may be configured to be approximately 20% of the width of the loudspeaker element  103  and  113 . Other acoustic lens dimensions may be available corresponding to different vehicle or room environment configurations and/or acoustics. 
       FIG. 3  illustrates an example loudspeaker system  300  that indicates the position of “phantom speaker” locations. The loudspeaker system  300  includes one or more second loudspeaker elements  305  and  306 . The second loudspeaker elements  305  and  306  may be positioned on the dashboard of a vehicle, in a pillar or other structural support of the vehicle, or in a center or rear console of the vehicle. The second loudspeaker elements  305  and  306  produce a direct sound field  307  and  308  radiated from the second loudspeaker elements  305  and  306  toward a listener position  101  and  120 . 
     The indirect sound fields  109  and  119  produced by the loudspeaker elements  103  and  113 , and which may be reflected by a boundary  104  and  105 , may be perceived by a listener located at a listener position  101  and  120 . The listener may perceive the indirect sound field  109  and  119  to be radiating from a “phantom source” location  310  and  311 . This phantom source location may be perceived to be the location of the source of the indirect sound field, because the listener may only hear the apparent location of the indirect sound field  109  and  119 . The actual location of the source of the indirect sound field  109  is the loudspeaker element  103  and  113 . For certain dimensions and frequencies, the loudspeaker element  103  and  113  may provide a sharp, focused, indirect sound field “phantom speaker”  310  and  311 . 
     When the indirect sound field  109  and  119  combines with the second loudspeaker direct sound field  307  and  308 , the listener may perceive that the two sound fields  109  and  307  or  109  and  308  sum to produce a second “phantom loudspeaker”  316  and  317 , where the listener may perceive the second phantom loudspeaker  316  and  317  to be positioned outside of the boundary  104  and  105 . The second phantom loudspeaker  316  and  317  is perceived by the listener to be a sharply located loudspeaker, and not a diffuse sound source. The loudspeaker system  300  may therefore provide directivity control for spatial sound effects. 
       FIG. 4  illustrates an example directional loudspeaker  400  including a vehicle separated into a front compartment  430  and a rear compartment  431  with two loudspeaker elements  403  and  413 . The front compartment  430  includes a driver area and front passenger area, and the rear compartment  431  includes an area rearward of the front compartment  430 . A partition  402 , such as a seat or vehicle pillar, may separate the front compartment  430  from the rear compartment  431 . At least one of the loudspeaker elements  403  may be located in the rear compartment  431 , producing a direct sound field  411 , and at least one of the loudspeaker elements  413  may be located in the front compartment  430 , producing a direct sound field  422 . The indirect sound field  409  produced by the loudspeaker element  403  may reflect by the rear window  407  of the rear compartment  431 , and the indirect sound field  419  produced by the loudspeaker element  413  may reflect by the front windshield  417  of the front compartment  430 . The loudspeaker  400  may be used when a listener wishes to hear multichannel sound, such as with Logic 7-configured loudspeaker systems. In such multichannel systems, it may be intended for the listener to perceive sound fields propagating from the rear of the vehicle. The loudspeaker  400  may provide rear-emanating sound fields for listeners positioned in the rear compartment  431  of the vehicle without excessive numbers of loudspeaker elements positioned throughout the rear compartment  431  of the vehicle, if even possible. The loudspeaker elements  103 ,  113 ,  203 , and  213  may be in the same configuration or a different configuration within the loudspeaker system  400 . 
       FIG. 5  illustrates an example directional loudspeaker system as in  FIG. 4 , with second loudspeaker elements  505  and  506 . The second loudspeaker elements  505  and  506  may be positioned in a front dashboard, a front console, a rear panel, rear ledge, vehicle pillar, door, or other structural support. The second loudspeaker elements  505  and  506  may produce a direct sound field  507  and  508  radiated from the second loudspeaker elements  505  and  506  toward a listener position  101  and  120 . 
     The indirect sound fields  409  and  419  produced by the loudspeaker elements  403  and  413 , and which may be reflected by a boundary  404  and  405 , such as the front windshield or rear window, and may be perceived by a listener located at a listener position  101  and  120 . The listener may perceive the indirect sound field  409  and  419  to be radiate from a “phantom source” location  510  and  511 . This phantom source location may be perceived to be the location of the source of the indirect sound field, because the listener may only hear the apparent location of the indirect sound field  409 . The actual location of the source of the indirect sound field  409  and  419  is the loudspeaker element  403  and  413  respectively. For certain dimensions and frequencies, the loudspeaker element  403  and  413  may provide a sharp, focused, indirect sound field “phantom speaker”  510  and  511 . 
     When the indirect sound field  409  or  419  combines with the second loudspeaker direct sound field  507  or  508 , the listener may perceive that the two sound fields  409  or  419  and  507  or  508  sum to produce a second “phantom loudspeaker”  516  or  517 . The listener may perceive the second phantom loudspeaker  516  and  517  is positioned outside of the boundary  404  and  405 . 
       FIG. 6  illustrates an example directional loudspeaker system as in  FIG. 4 , where the loudspeaker system includes a vehicle separated into a front compartment  430  and a rear compartment  431  with one loudspeaker element  403  located in the rear compartment  430 . The loudspeaker element  403  may be a loudspeaker system with a mechanical baffle  415  positioned between the loudspeaker element  403  and the listener position  401  positioned beneath the loudspeaker element  403 . The loudspeaker element  403  may include a radiating surface  421 , where the baffle  415  may be positioned proximate to the radiating surface  421 . The baffle  415  may abut the radiating surface  421  of the loudspeaker element  403 . The indirect sound field  409  produced by the loudspeaker element  403  may reflect by the rear window  407  of the rear compartment  431 . The direct sound field  411  may radiate from the loudspeaker element  403  to the listener position  420  located in the front compartment  430  of the vehicle. 
       FIG. 7  illustrates an example directional loudspeaker system  700  where the loudspeaker element  703  may include a loudspeaker element  703 , and where a channeling device may include an acoustic waveguide  710 , and an acoustic deflector  720 . The acoustic waveguide  710  may be positioned proximate to the loudspeaker element  703 . The acoustic deflector  720  may be positioned proximate to the acoustic waveguide  710 , and may be positioned to radiate an indirect sound field  709  towards a listener position  101 . The acoustic waveguide  710  may be positioned along the ceiling  105  of the vehicle enclosure, such as a vehicle headliner. The acoustic deflector  720  may abut an intersection of the ceiling  105  and a boundary wall  104  of the enclosure. An example includes the corner joint of window and ceiling  105  of a window  107  in the vehicle. The loudspeaker system  700  may operate when the enclosure has an opening to an outside environment. The acoustic deflector  720  and waveguide  710  may function to provide an indirect sound field  709  to a listener positioned in the listener position  101  when a window next to the listener position  101  is open, for example. Without the acoustic deflector  720 , the indirect sound field  709  may radiate out an open window and not reflect back to the listener. The acoustic deflector  720  may ensure that an indirect sound field  709  is provided to the listener in that circumstance to provide a sense of spaciousness to the listener 
     The direct sound field  711  from the loudspeaker element  730  may propagate substantially parallel to a straight line between the listener position  101  and the loudspeaker element  710 . The loudspeaker element  710  may be a dipole loudspeaker such as an electrodynamic planar loudspeaker. 
       FIG. 8  illustrates an example directional loudspeaker system  800  with a loudspeaker  703 , an acoustic waveguide  710 , and an acoustic deflector  720 . The directional loudspeaker system  800  also may include a second loudspeaker  804 , acoustic waveguide  821 , and acoustic deflector  822  positioned opposite in configuration to the first loudspeaker  703 , acoustic waveguide  710 , and acoustic deflector  720 , and operable to produce an indirect sound field  815 . The indirect sound field  815  may propagate to the listener position  120  in a direction substantially parallel to a straight line between the acoustic deflector  822  and the listener position  120 . 
     The directional loudspeaker system  800  may also include internal acoustic deflectors  812  and  813 . The internal acoustic deflectors may be operable to produce indirect sound fields  811  and  814 . The indirect sound field  811  may propagate from the loudspeaker  703 , deflect from the internal acoustic deflector  812 , and propagate to the listener position  120 . The indirect sound field  814  may propagate from the loudspeaker  804 , deflect from the internal acoustic deflector  813 , and propagate to the listener position  101 . 
       FIG. 9  illustrates an example loudspeaker system  900  viewed from a location above the vehicle and looking down at the vehicle. The loudspeaker system  900  has a similar configuration to that illustrated in  FIG. 3 , in that a second loudspeaker element  910  and  911  may be positioned along a boundary of the vehicle along with the loudspeaker elements  912  and  913  positionable along the ceiling of the vehicle above a listener position. The loudspeaker elements  912  and  913  produce an indirect sound field, which, when reflected by a boundary, may be perceived by the listener as radiating from a “phantom loudspeaker” position  921  and  922 . The configuration of the loudspeaker elements  912  and  913  may be such that for a certain range of frequencies, the phantom loudspeaker position  921  and  922  may be a sharply defined and localized position as perceived by the listener. The phantom loudspeaker position  921  and  922  therefore may not be perceived as a diffuse source. 
     The second loudspeaker element  910  and  911  may combine with the phantom loudspeaker  912  and  922  to produce a summed loudspeaker  925  and  926 , which appears to radiate a sound field to the listener from a location that may be different from the locations of the second loudspeaker element  910  and  911  or the phantom loudspeaker location  912  and  922 . The summed loudspeaker  925  and  926  may be perceived to be located at a position outside of the boundary, such as outside of the vehicle. The summed loudspeaker  925  and  926  may be perceived to be located at a defined position, rather than a diffuse source location. The summed loudspeaker  925  and  926  may therefore provide an illusion of spaciousness to the listener within the boundary. 
       FIG. 10  illustrates an example loudspeaker processor  1000  adapted to operate with an automobile audio system and bidirectional loudspeaker  100 - 800  to adjust a phase, gain, or delay parameter of the sound field for electronic enhancement, such as for multichannel sound systems like Logic 7®. The loudspeaker processor  1000  may include an input sound source  1001 , an input unit  1005 , a sound processor  1010 , a memory  1015 , an output unit  1020 , and one or more output signals  1025 ,  1026 , and  1027 . The loudspeaker processor  1000  may process a sound source input  1001  by receiving the sound source with an input unit  1005 . The input unit  1005  may include a pre-processor or buffer for the sound source input  1001 . A sound processor  1010  may adjust a phase, gain, or delay parameter of the sound field for electronic enhancement. The sound processor may also store a portion, or all of the sound source input  1001  in a memory  1015  for buffering or later retrieval. The memory  1015  may also store parameters for use by the sound processor  1010  in adjusting the sound source input  1001 , such as gain, delay, and phase parameters. The sound processor may read these parameters from the memory  1015 . The memory  1015  may also contain system parameters for creating the indirect sound field  109  and  119  and the direct sound field  111  and  121  output by the loudspeaker elements  103  and  113 . The sound processor  1010  may generate the indirect sound field  109  and  119  and the direct sound field  111  and  121  based on the type of loudspeaker element  103  and  113  present, and may read any parameters necessary to generate the fields from the memory  1015 . The memory  1015  may also integrate with the sound processor  1010  as a single unit. 
     An output unit  1020  following the sound processor  1010  may then be configured to process the indirect sound field  109  and  119  and the direct sound field  111  and  121  for output to the loudspeaker elements  103  and  113 . The output unit  1020  may create one or more channels  1025 ,  1026 , and  1027  (for example) for output to the loudspeaker elements  103  and  113 . The output unit  1020  may, for instance, be configured to process the sound fields for multichannel distribution or to the different loudspeaker elements  103  and  113  present in the loudspeaker system  100 - 800 . 
     The loudspeaker processing system  1000  may be implemented on a microprocessor or microcontroller multi-chip or integrated chip system. The loudspeaker processor  1000  may be implemented with digital signal processing (DSP) systems, as well as DSP algorithms encoded in firmware or instructions stored in the memory  1015 . 
       FIG. 11  illustrates example acts that generate an indirect and direct sound field for a loudspeaker. The input sound source may be pre-processed, at act  1110 , prior to reception by the loudspeaker by incorporating spatial and/or temporal effects to the input sound source. Such effects may include the “spaciousness” effects that the application replicates with the directional loudspeaker through the use of indirect and direct sound fields. Other effects may include multichannel sound effects, delays, equalization, or other electronic enhancements. A system designer may also relate specific vehicle architecture and acoustical characteristics with the input sound source, to modify the steering of the output sound source to correctly align the output sound source with the physical and non-physical (desired phantom speaker) aspects of the loudspeaker system. The loudspeaker system receives, at act  1120 , the input sound source. The loudspeaker may analyze, at act  1130 , the sound source for spatial and/or temporal effects included within the sound source. The analysis may be done by a sound processor  1000  or other processing units included with the loudspeaker. The loudspeaker may store the sound source, at act  1140 , in a memory  1015  or the loudspeaker may retrieve one or more sound source processing parameters. Examples of the sound source processing parameters include parameters for generating the indirect and direct sound fields, acoustic environment specifications, and parameters for electronic enhancement. Other example sound source processing parameters include Logic-7® sound parameters associated with the input sound encoding. In addition, the memory  1015  may buffer all or part of the sound source for processing. The loudspeaker may then incorporate, at act  1150 , electronic enhancement effects into the sound source, such as gain, delay, or phase parameters. The loudspeaker may produce, at act  1160 , one or more channels of sound output including indirect and direct sound field streams. The loudspeaker may then produce an indirect sound field, at act  1170 , by the loudspeaker elements in the loudspeaker. Finally the loudspeaker may produce, at step  1180 , a direct sound field by the loudspeaker elements in the loudspeaker system. 
     The sequence diagram in  FIG. 11  may be encoded in a signal bearing medium, a computer readable medium such as a memory, programmed within a device such as one or more integrated circuits, or processed by a controller or a computer. If the methods are performed by software, the software may reside in a memory resident to or interfaced to the sound processor  1000 , a communication interface, or any other type of non-volatile or volatile memory interfaced or resident to the sound processor  1010 , such as memory  1015 . The memory may include an ordered listing of executable instructions for implementing logical functions. A logical function may be implemented through digital circuitry, through source code, through analog circuitry, or through an analog source such as through an analog electrical, audio, or video signal. The software may be embodied in any computer-readable or signal-bearing medium, for use by, or in connection with an instruction executable system, apparatus, or device. Such a system may include a computer-based system, a processor-containing system, or another system that may selectively fetch instructions from an instruction executable system, apparatus, or device that may also execute instructions. 
     A “computer-readable medium,” “machine-readable medium,” “propagated-signal” medium, and/or “signal-bearing medium” may comprise any means that contains, stores, communicates, propagates, or transports software for use by or in connection with an instruction executable system, apparatus, or device. The machine-readable medium may selectively be, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, device, or propagation medium. A non-exhaustive list of examples of a machine-readable medium would include: an electrical connection “electronic” having one or more wires, a portable magnetic or optical disk, a volatile memory such as a Random Access Memory “RAM” (electronic), a Read-Only Memory “ROM” (electronic), an Erasable Programmable Read-Only Memory (EPROM or Flash memory) (electronic), or an optical fiber (optical). A machine-readable medium may also include a tangible medium upon which software is printed, as the software may be electronically stored as an image or in another format (e.g., through an optical scan), then compiled, and/or interpreted or otherwise processed. The processed medium may then be stored in a computer and/or machine memory. 
     While various embodiments of the invention have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible within the scope of the invention. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents.