Abstract:
A sound reproduction apparatus comprising a loudspeaker bar having a plurality of loudspeakers. A loudspeaker bar controller coupled to the loudspeaker bar for processing audio data for the plurality of loudspeakers, the loudspeaker bar controller comprising a spatial enhancement/virtualization system for receiving a surround channel of audio data and processing the surround channel of audio data with a spatial generation/virtualization filter, wherein a left stereo channel of audio data and a right stereo channel of audio data are not processed with the head related transfer function filter. Bass is enhanced for small speakers which are not able to produce bass frequencies.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority under 35 U.S.C. §119 to U.S. Patent Application No. 61/186,795, filed Jun. 12, 2009, entitled “Systems and Methods for Creating Immersion Surround Sound and Virtual Speakers Effects,” which is hereby incorporated by reference for all purposes, and to U.S. application Ser. No. 12/963,443, “System and Method for Reducing Rub and Buzz Distortion,” filed Dec. 8, 2010, which is commonly owned with the pending application and which is hereby incorporated by reference for all purposes. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates generally to stereo audio reproduction and specifically to personal computer speaker bar sound enhancement. 
       BACKGROUND OF THE INVENTION 
       [0003]    Consumers use a surround sound speaker system in a room or other large space to play back multi-channel sound, such as for movies and music. Because of space constraints, other sound systems such as ones for portable electronics use speaker bar instead. Laptop computers also typically have embedded speakers in a speaker bar with tiny speakers. Such a speaker bar has a small form factor and often cannot produce a surround sound effect. Small speakers also cannot produce enough bass energy to make the sound for movies and music satisfying to a listener. The inexpensive speakers used in such portable electronics also have uneven frequency response and distortions. As a result, multi-channel sound played over portable electronics often has poor sound quality. 
       BRIEF SUMMARY OF INVENTION 
       [0004]    In one of many exemplary embodiments of the invention disclosed herein, a sound reproduction apparatus, such as a laptop computer having a set of loudspeakers incorporated within the laptop, is provided. A controller is connected to the set of loudspeakers, and processes audio data for the set of loudspeakers, such as stereo data that is to be converted into surround sound data. The controller includes a spatial enhancement system for receiving a surround channel of audio data and processing the surround channel of audio data with a head related transfer function filter, wherein a left stereo channel of audio data and a right stereo channel of audio data are not processed with the head related transfer function filter. 
         [0005]    For small speakers that are not capable to produce bass frequencies, bass is enhanced by using a harmonics generator. The harmonics levels are equalized with frequency response of each individual speaker. 
         [0006]    Other systems, methods, features, and advantages of the present disclosure will be or become apparent to one with skill in the art upon examination of the following drawings 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 present disclosure, and be protected by the accompanying claims. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0007]    Many aspects of the disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
           [0008]      FIG. 1A  is a diagram of a system for providing a speaker bar controller in accordance with an exemplary embodiment of the present invention; 
           [0009]      FIG. 1B  is a diagram of dimensions that can be used to calculate a desired delay ΔT in accordance with an exemplary embodiment of the present invention; 
           [0010]      FIG. 2  is a diagram of a system for providing a speaker bar controller in accordance with an exemplary embodiment of the present invention; 
           [0011]      FIG. 3  is a diagram of a system for providing a speaker bar controller in accordance with an exemplary embodiment of the present invention; 
           [0012]      FIG. 4  is a diagram of a system for providing a speaker bar controller in accordance with an exemplary embodiment of the present invention; 
           [0013]      FIG. 5  is a diagram of a speaker bar controller in accordance with an exemplary embodiment of the present invention; 
           [0014]      FIG. 6  is a diagram of a head related transfer function virtualization system in accordance with an exemplary embodiment of the present invention; 
           [0015]      FIG. 7  is a diagram of a speaker virtualization system for generating a sound field with greater spatial separation in accordance with an exemplary embodiment of the present invention; 
           [0016]      FIG. 8  is a diagram of immersion effect system in accordance with an exemplary embodiment of the present invention; and 
           [0017]      FIG. 9  is a diagram of a surround control system that can be used to provide speaker virtualization as well as an immersion effect. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    A detailed description of embodiments of the present invention is presented below. While the disclosure will be described in connection with these drawings, there is no intent to limit it to the embodiment or embodiments disclosed herein. On the contrary, the intent is to cover all alternatives, modifications and equivalents included within the spirit and scope of the disclosure. 
         [0019]      FIG. 1A  is a diagram of a system  100  for providing a speaker bar controller in accordance with an exemplary embodiment of the present invention. System  100  includes speaker bar controller  102 , which can be implemented in hardware or a suitable combination of hardware and software, and which can be one or more software systems operating on a general purpose processor. As used herein and by way of example and not by limitation, “hardware” can include a combination of discrete components, an integrated circuit, an application-specific integrated circuit, a field programmable gate array, a general purpose processing or server platform, or other suitable hardware. As used herein and by way of example and not by limitation, “software” can include one or more objects, agents, threads, lines of code, subroutines, separate software applications, one or more lines of code or other suitable software structures operating in one or more software applications or on one or more processors, or other suitable software structures. In one exemplary embodiment, software can include one or more lines of code or other suitable software structures operating in a general purpose software application, such as an operating system, and one or more lines of code or other suitable software structures operating in a specific purpose software application. 
         [0020]    Speaker bar controller  102  is used to drive left speaker  104 , right speaker  108  and center speaker  106 . In one exemplary embodiment, speaker bar controller  102  is configured based on the dimensions and locations of a sound bar containing left speaker  104 , right speaker  108  and center speaker  106 , and an expected location of a user of a personal computer or laptop computer that incorporates the sound bar, such as by using the dimensions to calculate correction factors for audio processing, as described in greater detail herein. The dimensions of the speaker locations can be stored in speaker bar controller  102  at the factory, and speaker bar controller  102  can detect a location of a user or receive a user input for the location of the user relative to the speaker bar. The speaker parameters can also be measured at the factory, such as to develop a speaker frequency response model for each speaker, each speaker as installed in the sound bar, or other suitable frequency response models. These frequency response models can also or alternatively be stored in speaker bar controller  102  at the factory, and used to provide enhanced speaker sound as described herein. 
         [0021]      FIG. 1B  is a diagram of dimensions that can be used to calculate a desired delay ΔT in accordance with an exemplary embodiment of the present invention. The delay ΔT is determined based on the distance between the ears of a user and each speaker of a sound bar. The diagram of  FIG. 1B  is applicable to the calculation of a delay with respect to left ear  114  relative to locations of a left speaker  110  and a right speaker  112 , but could also or alternatively be applied to right ear  116  and additional speakers, such as a left outer speaker and a right outer speaker. 
         [0022]    The difference in distance between left ear  114  and left speaker  110  is given by D L  and the distance between left ear  114  and right speaker  112  is given by D R . These distances define two triangles, with the third side represented by the distances s L  and s R , respectively. If an assumption is made that the listener is centered between the speakers then S L =(D S −D E )/2 and S R =(D S +D E )/2. Using the Pythagorean theorem, the difference between the distances ΔD=0.5(((D S +D E ) 1/2 +4D 2 ) 1/2 −((D S −D E ) 1/2 +4D 2 ) 1/2 ). The desired delay can be calculated from ΔD by multiplying ΔD by the speed of sound. 
         [0023]    In one exemplary embodiment, the distance between human ears D E  is assumed to be approximately 6 inches. For notebook computers, the distance between speakers D S  typically ranges between 6 inches to 15 inches, depending on the configuration. The distance an average person sits from their notebook computers D S  is assumed to be between 12 to 36 inches in the present embodiment. For other electronic devices, such as a portable DVD player, the distances between the individual speakers and the speakers to the user may be smaller. Exemplary input and output values are shown in Table 1. Given the above assumptions, delays fall between the range of 2 to 11 samples when using 48 kHz sampling rate. For higher sampling rates, such as 96 kHz and 192 kHz, the delay expressed in terms of samples increases proportionally with sampling rate. For example in the last case in Table 1 for 192 kHz, the delay is scaled to 11* 192/48=44 samples. 
         [0000]    
       
         
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                   
                   
                   
                 Samples @ 
                 Samples @ 
               
               
                   
                 d s  (in) 
                 d (in) 
                 Δd (in) 
                 Δτ (ms) 
                 44.1 kHz 
                 48 kHz 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 6 
                 36 
                 0.50 
                 0.04 
                 2 
                 2 
               
               
                   
                 9 
                 30 
                 0.89 
                 0.07 
                 3 
                 3 
               
               
                   
                 10 
                 26 
                 1.13 
                 0.08 
                   
                 4 
               
               
                   
                 12 
                 24 
                 1.45 
                 0.11 
                 5 
                 5 
               
               
                   
                 8 
                 15 
                 1.52 
                 0.11 
                 5 
                 5 
               
               
                   
                 14 
                 22 
                 1.81 
                 0.13 
                 6 
                 6 
               
               
                   
                 15 
                 12 
                 3.13 
                 0.23 
                 10 
                 11 
               
               
                   
               
             
          
         
       
     
         [0024]      FIG. 2  is a diagram of a system  200  for providing a speaker bar controller in accordance with an exemplary embodiment of the present invention. System  200  includes speaker bar controller  202 , which can be implemented in hardware or a suitable combination of hardware and software, and which can be one or more software systems operating on a general purpose processor. 
         [0025]    Speaker bar controller  202  is used to drive left speaker  204 , right speaker  208  and center speaker  206 . In one exemplary embodiment, speaker bar controller  202  is configured based on the dimensions and locations of a sound bar containing left speaker  204 , right speaker  208  and center speaker  206  (which are different from the speakers of system  100  in that left speaker  204  and right speaker  208  are offset and asymnetrc, and cencer speaker  206  is also offset, and an expected ocation of a user of a personal computer or laptop computer that incorporates the sound bar, such as by using the dimensions to calculate correction factors for audio processing, as described in greater detail above. The dimensions of the speaker locations can be stored in speaker bar controller  202  at the factory, and speaker bar controller  202  can detect a location of a user or receive a user input for the location of the user relative to the speaker bar. The speaker parameters can also be measured at the factory, such as to develop a speaker frequency response model for each speaker, each speaker as installed in the sound bar, or other suitable frequency response models. These frequency response models can also or alternatively be stored in speaker bar controller  202  at the factory, and used to provide enhanced speaker sound as described herein. 
         [0026]      FIG. 3  is a diagram of a system  300  for providing a speaker bar controller in accordance with an exemplary embodiment of the present invention. System  300  includes speaker bar controller  302 , which can be implemented in hardware or a suitable combination of hardware and software, and which can be one or more software systems operating on a general purpose processor. 
         [0027]    Speaker bar controller  202  is used to drive left outer speaker  304 , left speaker  306 , center speaker  308 , right speaker  310  and right outer speaker  312 . In one exemplary embodiment, speaker bar controller  302  is configured based on the dimensions and locations of a sound bar containing these speakers, and an expected location of a user of a personal computer or laptop computer that incorporates the sound bar, such as by using the dimensions to calculate correction factors for audio processing, as described in greater detail above. The dimensions of the speaker locations can be stored in speaker bar controller  302  at the factory, and speaker bar controller  302  can detect a location of a user or receive a user input for the location of the user relative to the speaker bar. The speaker parameters can also be measured at the factory, such as to develop a speaker frequency response model for each speaker, each speaker as installed in the sound bar, or other suitable frequency response models. These frequency response models can also or alternatively be stored in speaker bar controller  302  at the factory, and used to provide enhanced speaker sound as described herein. 
         [0028]      FIG. 4  is a diagram of a system  400  for providing a speaker bar controller in accordance with an exemplary embodiment of the present invention. System  400  includes speaker bar controller  402 , which can be implemented in hardware or a suitable combination of hardware and software, and which can be one or more software systems operating on a general purpose processor. 
         [0029]    Speaker bar controller  402  is used to drive left outer speaker  404 , left speaker  406 , center speaker  408 , right speaker  410  and right outer speaker  412 . In one exemplary embodiment, speaker bar controller  202  is configured based on the dimensions and locations of a sound bar containing left outer speaker  404 , left speaker  406 , center speaker  408 , right speaker  410  and right outer speaker  412  (which are different from the speakers of system  300  in that left outer speaker  404 , left speaker  406 , right speaker  410  and right outer speaker  412  are offset and asymmetric, and center speaker  408  is also offset), and an expected location of a user of a personal computer or laptop computer that incorporates the sound bar, such as by using the dimensions to calculate correction factors for audio processing, as described in greater detail above. The dimensions of the speaker locations can be stored in speaker bar controller  402  at the factory, and speaker bar controller  402  can detect a location of a user or receive a user input for the location of the user relative to the sneaker bar. The speaker parameters can also be measured at the factory, such as to develop a speaker frequency response model for each speaker, each speaker as installed in the sound bar, or other suitable frequency response models. These frequency response models can also or alternatively be stored in speaker bar controller  402  at the factory, and used to provide enhanced speaker sound as described herein. 
         [0030]      FIG. 5  is a diagram of a speaker bar controller  500  in accordance with an exemplary embodiment of the present invention. Speaker bar controller  500  includes upmix  502 , downmix  504 , surround system  506 , HRTF virtualization system  508 , bass enhance system  510 , center enhance system  512 , user detector  514 , equalizer  516  and dynamic range compression  518 , each of which can be implemented in hardware, software or a suitable combination of hardware and software, and which can be one or more software systems operating on a general purpose processing platform. 
         [0031]    Upmix  502  and downmix  504  are used to convert a received audio signal into an audio signal that matches a system speaker configuration. In one exemplary embodiment, speaker bar controller  500  can be used in conjunction with a laptop or other personal computer, which can receive audio data in a format that does not match the native speaker configuration. Upmix  502  can be used to convert the received audio data into more channels where necessary (such as from received 2.0 or 3.1 audio data to a 3.1 or 5.1 native format, respectively), and downmix  504  can be used to convert the received audio data into less channels where necessary (such as from received 9.1 or 7.1 audio data to a 5.1 or 3.1 native format). 
         [0032]    Surround system  506  can process received audio data to convert it into a virtualized surround format. In one exemplary embodiment, received audio data can be processed to improve the surround sound quality of the audio data when it is played using the native sound bar speaker configuration. In this exemplary embodiment, the audio data can be received in a surround format, such as 5.1, and can be downmixed to be played in the surround format using the native speakers, such as a 3.0 format. Likewise, the audio data can be received in a stereo (2.0) format and upmixed to be played in a surround format using the native speakers, such as a 3.0 format. 
         [0033]    HRTF virtualization system  508  utilizes head-related transfer function filters to add sound field depth. In one exemplary embodiment, left and right head related transfer function filters can be applied and cross-correlated to each sound channel to add sound field depth. 
         [0034]    Bass enhance system  510  applies bass enhancement algorithms as a function of the frequency response of the speaker bass frequency response. For speakers having poor bass response, one solution is to replace the bass frequency by harmonics with frequencies that are integer multiple of the original frequency, but this process creates a number of problems, including an uneven frequency response of the speaker at the harmonics frequencies. This produce inaccurate level of bass harmonics. In one exemplary embodiment, the frequency response of each speaker can be determined, such as by using the process described in U.S. application Ser. No. 12/963,443, “System and Method for Reducing Rub and Buzz Distortion,” filed Dec. 8, 2010, which is commonly owned with the pending application and which is hereby incorporated by reference for all purposes. Harmonics are equalized according to the inverse of the frequency response measurements. For loudspeakers that are not capable of producing some bass frequencies, it is preferable to use a bass reinforcement method which leaves the original bass content. For loudspeakers that are unable to produce bass frequencies at all, it is preferable to use a bass replacement method, which cuts the original bass content off. In one exemplary embodiment, the frequency response for each speaker can be different, such as where a first harmonic is selected for bass enhancement of a bass frequency for a first speaker, and a second harmonic is selected for bass enhancement of that bass frequency for a second speaker. 
         [0035]    Center enhance system  512  allows the center image to be enhanced where the speaker bar speakers are not symmetric. In one exemplary embodiment, the center channel audio data can be simulated in a two or four speaker sound bar system by playing the center channel audio data through each speaker. Where the speakers are not symmetric, the amplitude and phase associated with the center channel audio data may need to be modified to compensate for the speaker offsets. Center enhance system  512  compensates the audio data based on the native speaker configuration. 
         [0036]    To let listeners hear better on dialogues which are often low in volume in movies, a mixer is used to mix a portion of the surround channels and the left and right channel sound to the center speaker. Also another mixer is used to mix a part of the center channel sound to outer speakers or left and right speakers. 
         [0037]    User detector  514  detects the relative distance between a user and the speaker bar. In one exemplary embodiment, a proximity sensor such as a audio or video ranging system can be used to determine how far away a user is to the speaker bar, so as to automatically adjust delay values and other variables that are used to improve the sound field, as discussed further herein. 
         [0038]    Equalizer  516  provides frequency band equalization for channels of audio data. In one exemplary embodiment, equalizer  516  can be used to provide equalization based on expected operating environments, to correct for speaker or enclosure dynamic response, or to provide other suitable equalization. 
         [0039]    Dynamic range compression  518  compensates for increased signals peaks that may be added by other components of speaker bar controller  500 . Dynamic range compression  518  helps to reduce clipping distortion that may be caused by increased signal peaks. In addition to potentially degrading audio quality, clipping distortion can lead to loss of signal data and spatial virtualization. 
         [0040]    In operation, speaker bar controller  500  allows audio content to be optimized for a native speaker configuration of a speaker bar, such as by upmixing or downmixing, surround enhancement processing, HRTF virtualization, bass enhancement that is optimized for the frequency response of the native speakers, center enhancement or a user&#39;s relative position. Speaker bar controller  500  can be used to improve the audio data sound field as a function of the speaker bar configuration. 
         [0041]      FIG. 6  is a diagram of a head related transfer function virtualization system  600  in accordance with an exemplary embodiment of the present invention. Head related transfer function virtualization system  600  can be implemented in hardware or a suitable combination of hardware and software, and can be one or more software systems operating on a digital signal processing platform or other suitable processors. 
         [0042]    Head related transfer function virtualization system  600  includes left head related transfer function filters  602  and  606  and right head related transfer function filters  604  and  608 , which receive left surround input and right surround input, respectively. The output from the filters is then provided to cross cancellation and mixing  610 , which performs cross cancellation of the filtered surround inputs and which also mixes the surround inputs with the left and right channel audio inputs to generate left and right audio output. Applying the head related transfer function filters to the surround audio channel data and not to the front audio channel data provides additional definition in the sound field for the surround channel audio data. 
         [0043]    In operation, head related transfer function virtualization system  600  can be used to provide additional sound field definition for surround audio channel data, by applying a head related transfer function filter to the surround channel audio data. 
         [0044]      FIG. 7  is a diagram of a speaker virtualization system  700  for generating a sound field with greater spatial separation in accordance with an exemplary embodiment of the present invention. Speaker virtualization system  700  can be implemented in hardware or a suitable combination of hardware and software, and can be one or more software systems operating on a digital signal processing platform or other suitable processors. 
         [0045]    Speaker virtualization system  700  receives left channel input signal  702 , left surround channel input signal  706 , right channel input signal  704  and right surround channel input signal  708 , and outputs left channel output signal  764 , left surround channel output signal  762 , right channel output signal  766  and right surround channel output signal  768 . Spread value  710  is also received by speaker virtualization system  700 . Spread control  710  controls the intensity of the widening effect. 
         [0046]    A copy of the left channel input signal  702  is scaled by spread value  710  using multiplier  716 , and is then delayed by delay element  724  and filtered by digital filter  732 . Likewise, a copy of the right channel signal  704  is scaled by spread value  710  using multiplier  716 , and is then delayed by delay element  726  and filtered by digital filter  734 . The surround channels  706  and  708  are also processed in the same manner by multipliers  714  and  720 , respectively, and delay elements  722  and  728 , respectively. 
         [0047]    The left channel signal output processed by digital filter  732  is shown as signal  748 , and is subtracted from the right channel by mixer  742 , and is added back to the original left channel signal by mixer  756  to generate left channel output signal  764 . Similarly, the right channel signal output processed by digital filter  734  is shown as signal  750 , and is subtracted from the left channel by mixer  740 , and added back to the original right channel by mixer  758  to generate right channel output signal  766 . The processed surround channels  746  and  752  are also processed in the same manner by mixer  744 , to generate left surround channel output signal  762  and right surround channel output signal  768 , respectively. 
         [0048]    Mathematically, if left channel input signal  702  is represented by L(t) and right channel input signal  704  is represented by R(t), digital filter  734  transforms R(t) into R′(T) and digital filter  732  transforms L(T) into L′(T), then the resultant left channel signal output by digital filter  732  is S*L′(T−ΔT), where s is the spread value  710  and ΔT is the delay imposed by delay element  724 . Similarly, the resultant right channel signal output by digital filter  734  is S*R′(T−ΔT), the resultant left surround channel signal output by digital filter  730  is S*L S ′(T−ΔT), and the resultant right surround channel signal output by digital filter  736  is S*R S ′(T−ΔT). Therefore, left channel output signal  764  is defined by the equation: 
         [0000]        L   OUT ( T )= L ( T )−( S*R ′( T−ΔT )+ S*L   S ′( T−ΔT )+ S*R   S ′( T−ΔT ))+ S*L′ ( T−ΔT )
 
         [0000]    And the right channel output signal  766 , left surround channel output signal  762  and right surround channel output signal  768  are each given by: 
         [0000]        R   OUT ( T )= R ( T )−( S*L ′( T−ΔT )+ S*L   S ′( T−ΔT )+ S*R   S ′( T−ΔT ))+ S*R ′( T−ΔT ),
 
         [0000]        L   SOUT ( T )= L   S ( T )−( S*R ′( T−ΔT )+ S*L ′( T−ΔT )+ S*R   S ′( T−ΔT ))+ S*L   S ′( T−ΔT ),
 
         [0000]      and 
         [0000]        R   SOUT ( T )= R   S ( T )−( S*R −( T−ΔT )+ S*L −( T−ΔT )+ S*L   S ′( T−ΔT ))+ S*R   S ′( T−ΔT )
 
         [0049]    While for simplicity, the equations are expressed as analog signals, the processing can be performed digitally as well on L(n), R(n), L S (n) and R S (n) with their digital counterparts. 
         [0050]    The spread value  710  influences the strength of a widening effect by controlling the volume of the virtual sound. If the spread value is zero, there is no virtualization, only the original sound. Generally speaking, the larger the spread value, the louder the virtual sound effect. As described in the present embodiment, the virtual sound and cross-cancellation mixed with the original audio data can be used to produce an audio output that would sound like an extra set of speakers outside of the original set of stereo speakers. 
         [0051]    An additional feature of speaker virtualization system  700  is in the choice of a predetermined delay value for delay elements  722 ,  724 ,  726  and  728 . In an audio driver for a notebook computer, the selection of delay value  712  can be important for achieving certain wide spatial effects, as previously discussed. The delay is calculated based on the distance between human ears (D E ), the distance between speakers (D S ) and the distance between the listener and the speakers (D), although with outside speakers, the delay values may need to be different based on the emphasis desired for the surround channels. For example, the delay between the left surround channel speaker and a listener&#39;s left ear will be different for each of the left channel speaker, the right channel speaker and the right surround channel speaker. In some sound system configurations, the placement of the speakers may allow a single delay to be used, such as where the outside speakers are located close to the associated front channels, whereas in other system configurations, additional delays for each channel relative to each other channel can be provided (which is not shown here for clarity). Delay elements  722 ,  724 ,  726  and  728  or other delays can be implemented with variable delay units, allowing speaker virtualization system  700  to be configurable to different sound system configurations. As a result, in some embodiments of speaker virtualization system  700 , the delay is programmable through the introduction of delay value  712  which can adjust the delay on delay elements  722 ,  724 ,  726  and  728 . 
         [0052]    Another feature of speaker virtualization system  700  is the addition of the processed left channel signal back into the left channel output signal, the addition of the processed right channel signal back into the right channel output signal, the addition of the processed left surround channel signal back into the left surround channel output signal and the addition of the processed right surround channel signal back into the right surround channel output signal. Because simple cross cancellation can result in a loss of center sound and loss of bass, adding the processed channel signals back into the output signal produces a sound without a significant loss of center sound and bass, preserving the sound quality during cross cancellation. 
         [0053]      FIG. 8  is a diagram of immersion effect system  800  in accordance with an exemplary embodiment of the present invention. Immersion effect system  800  can be implemented in hardware or a suitable combination of hardware and software, and can be one or more software systems operating on a digital signal processing platform or other suitable processors. 
         [0054]    Immersion effect system  800  can be used to create an immersion effect. Left channel input signal  802 , which can be shown mathematically as L(T), is separated into its high frequency components L T (T) and low frequency components L B (T), by complementary crossover filters  810  and  808 , respectively. Filter  810  allows frequencies above a given crossover frequency to pass whereas filter  808  allows frequencies below the given crossover frequency to pass. Similarly, right channel input signal  804 , shown mathematically as R(T), is separated into its high frequency components R T  (T) and low frequency components R B (T) by complementary crossover filters  812  and  814 , respectively. Each signal L T (T) and R T (T) is also scaled by spread value  806  using multipliers  816  and  818 , respectively, and is added to R(T) and L(T), respectively, by mixers  822  and  820 , respectively. The results are added back into the low frequency components by mixers  826  and  828 . Left channel output signal  830  can be expressed mathematically as L OUT (T)=L B (T)+L T (T)+S*R T (T), where S represents the spread value. Phase inverter  824  is provided to shift R T (T)+L T (T) by essentially 180°, and right channel output signal  832  can be expressed as R oUT (T)=R 3  (T)-R T  (T)-S*L T  (T). 
         [0055]    The immersion effect is produced when the left ear and right ear respectively perceive two signals that are 180 0  out of phase. The resulting effect is a sound perceived to be near the listener&#39;s ears that appears to diffuse and “jump out” right next to the listener&#39;s ears. The use of the spread value in immersion effect system  800  changes the nature of the immersion effect. For example, if the spread value is set to zero, the right channel signal still has the high frequency components phase inverted relative to the input signal, which still yields the immersion effect. 
         [0056]      FIG. 9  is a diagram of a surround control system  900  that can be used to provide speaker virtualization as well as an immersion effect. Surround control system  900  can be implemented in hardware or a suitable combination of hardware and software, and can be one or more software systems operating on a digital signal processing platform or other suitable processors. 
         [0057]    Surround control system  900  comprises speaker virtualization system  700  and immersion effect system  800  which receives spread value  906 ′. Surround control system  900  can receive effects input  922  to allow a user to control whether to employ the speaker virtualization effect, the immersion effect or no effect. Left fader  914  facilitates a smooth transition between the different modes in the left channel and right fader  916  facilitates a smooth transition between the different modes in the right channel. 
         [0058]    Various fader techniques can be employed within left fader  914  and right fader  916 . In one exemplary embodiment, a three-way fader can be employed is a mixer where left audio output signal  918  can be expressed as L OUT (T)=A*L (T)+A IMM *L IMM (T)+A VIRT *L VIRT (T), where L IMM (T) is the left output audio signal of immersion effect system  800  and L VIRT (T) is the left output audio signal of speaker virtualization system  700 . Likewise, right audio output signal  920  can be expressed as R OUT (T)=A*RL(T)+A IMM *R IMM (T)+A VIRT *R VIRT (T), where R IMM (T) is the right output audio signal of immersion effect system  800  and R VIRT (T) is the right output audio signal of speaker virtualization system  700 . For both output signals, A, A IMM  and A VIRT  gain coefficients. 
         [0059]    It should be emphasized that the above-described embodiments are merely examples of possible implementations. Many variations and modifications may be made to the above-described embodiments without departing from the principles of the present disclosure. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the following claims.