Abstract:
An acoustic sound system usable in electronic entertainment systems that generates highly directional sound. The directed acoustic sound system includes a parametric audio sound system having a modulator for modulating an ultrasonic carrier signal with a processed audio signal, a driver amplifier for amplifying the modulated signal, and a parametric loudspeaker for projecting the modulated and amplified signal through the air for subsequent regeneration of the audio signal along a pre-selected path. The acoustic sound system allows a user to select the parametric loudspeaker, a connectable non-directional loudspeaker, or both loudspeakers for producing audible sound. The acoustic sound system may be employed in the home, in the workplace, or in any other environment where audio leakage is undesirable.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims priority of U.S. Provisional Patent Application No. 60/422,582 filed Oct. 30, 2002 entitled DIRECTED ACOUSTIC SOUND SYSTEM. 
     
    
     
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT N/A  
       BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates generally to sound systems usable in electronic entertainment systems such as televisions, radios, compact disk players, and video games, and more specifically to acoustic sound systems capable of producing highly directional sound.  
           [0003]    In recent years, there has been a dramatic increase in the variety of electronic entertainment systems available in the marketplace. In the not-too-distant past, choices of electronic entertainment were limited primarily to radio, television, the phonograph, and the tape recorder. Today, electronic entertainment choices have expanded beyond traditional radio, television, and tape/disk recording media to include video games, compact disk players, digital video disk players, Internet radio, and MP3 systems. As a result of this dramatic increase in consumer choice, electronic entertainment systems have become ubiquitous both inside and outside the home environment.  
           [0004]    For example, whereas families of the mid-twentieth century may have gathered around the same radio or television in their homes to enjoy favorite radio or television programs, each member of the twenty-first century household may be simultaneously engaged in a different form of electronic entertainment. Not only may such individuals enjoy chosen forms of electronic entertainment in their homes, but they may also enjoy diverse forms of electronic entertainment while walking outdoors, driving in their cars, riding on trains and airplanes, and working at their jobs, due to the reduced size and portability of today&#39;s electronic entertainment systems.  
           [0005]    One drawback of the electronic entertainment systems available today is that the sound they generate is generally non-directional, i.e., the sound radiates essentially in all directions. Because the sound generated by such electronic entertainment systems radiates essentially omnidirectionally, virtually all people in the proximity of the system are forced to listen to the sound, including those who have no need or desire to hear it. This can lead to undue distraction at home and in the car, increased noise pollution in neighborhoods and on public transportation, and decreased efficiency in the workplace.  
           [0006]    It would therefore be desirable to have a sound system for electronic entertainment systems and any other suitable sound-generating systems and devices that avoids the drawbacks of the above-described conventional sound systems.  
         BRIEF SUMMARY OF THE INVENTION  
         [0007]    In accordance with the present invention, an acoustic sound system usable in electronic entertainment systems is provided that generates highly directional sound. Benefits of the presently disclosed directed acoustic sound system are achieved by employing a parametric loudspeaker that generates beams of audible sound with much higher directivity than conventional audio sound sources.  
           [0008]    In one embodiment, the directed acoustic sound system comprises a parametric audio sound system including a modulator for modulating an ultrasonic carrier signal with a processed audio signal, a driver amplifier for amplifying the modulated carrier signal, and a parametric loudspeaker for projecting the modulated and amplified carrier signal through a propagation medium, e.g., the air, for subsequent regeneration of the audio signal along a pre-selected projection path. In a preferred embodiment, the parametric loudspeaker is a parametric array that generates sound beams using at least one membrane-type acoustic transducer. The driver amplifier may include an inductor coupled to the capacitive load of the transducer to form a resonant circuit. The center frequency of the membrane-type transducer, the resonance frequency of the resonant circuit formed by the driver amplifier coupled to the transducer, and the frequency of the ultrasonic carrier signal are equal to the same predetermined value, preferably, at least 45 kHz.  
           [0009]    In the presently disclosed embodiment, the parametric loudspeaker operates by employing the nonlinear interaction between high frequency sound components (preferably in the ultrasonic frequency range) and the propagation medium to generate at least one beam of lower frequency sounds within the propagation medium. The result is a “virtual” sound source that is significantly larger than the wavelengths of the sounds generated by it. The larger the source of the sound, particularly in the axial direction (i.e., in the direction of propagation of the sound beam), the greater its directivity.  
           [0010]    Accordingly, if a virtual sound source comprising a relatively long beam of ultrasound is generated using multiple frequencies, then the nonlinear interaction between the ultrasound and the propagation medium may be used to generate a narrow beam of audible sound. The directivity of the sound generated by the parametric loudspeaker can be controlled by creating a virtual sound source comprising one or more beams of ultrasound in any suitable geometric configuration, e.g., a disk, a cylinder, or a plane.  
           [0011]    The presently disclosed directed acoustic sound system may be employed in the home, in the workplace, or in any other environment where audio leakage is undesirable. For example, the directed acoustic sound system may be used in conjunction with a television set to allow an individual to watch and to listen to the television while preventing others in the same room from hearing the sound. The directed acoustic sound system may also be used with a radio, a compact disc player, or an MP3 player to allow an individual to listen to audio selections without bothering others nearby. In addition, the directed acoustic sound system may be used with a speakerphone in an office environment to avoid distracting coworkers while enhancing the privacy of the person using the phone.  
           [0012]    By providing electronic entertainment systems and any other suitable sound-generating systems and devices with directed acoustic sound as described above, individuals can listen to such systems without unduly distracting others in the general vicinity of the system.  
           [0013]    Other features, functions, and aspects of the invention will be evident from the Detailed Description of the Invention that follows.  
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0014]    The invention will be more fully understood with reference to the following Detailed Description of the Invention in conjunction with the drawings of which:  
         [0015]    [0015]FIG. 1 depicts an illustrative application of the directed acoustic sound system according to the present invention;  
         [0016]    [0016]FIG. 2 depicts a variation of the illustrative application of the directed acoustic sound system of FIG. 1;  
         [0017]    [0017]FIG. 3 is a block diagram of the directed acoustic sound system of FIG. 1;  
         [0018]    [0018]FIG. 4 is a plan view of a parametric loudspeaker included in the directed acoustic sound system of FIG. 3;  
         [0019]    [0019]FIG. 5 is a schematic diagram of a driver amplifier circuit included in the directed acoustic sound system of FIG. 3;  
         [0020]    [0020]FIGS. 6 a - 6   b  are block diagrams of the directed acoustic sound system of FIG. 3 employed in conjunction with conventional speaker amplifiers; and  
         [0021]    [0021]FIG. 7 is a perspective view of a directional loudspeaker included in the directed acoustic sound system of FIG. 1, the loudspeaker being mounted on a stand. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]    U.S. Provisional Patent Application No. 60/422,582 filed Oct. 30, 2002 entitled DIRECTED ACOUSTIC SOUND SYSTEM is incorporated herein by reference.  
         [0023]    A directed acoustic sound system usable in electronic entertainment systems is disclosed that is capable of generating highly directional sound. The presently disclosed directed acoustic sound system includes a parametric loudspeaker configured to generate audible sound beams with a directivity that is significantly greater than can be achieved using conventional techniques.  
         [0024]    FIGS.  1 - 2  depict illustrative applications  101  and  201  of a directed acoustic sound system  100 , in accordance with the present invention. As shown in FIGS.  1 - 2 , the acoustic sound system  100  is employed in conjunction with a television set  102  for directing at least one audio sound beam  106  provided by the television to a human television viewer  104 . It should be appreciated that the acoustic sound system  100  may alternatively be employed with a conventional broadcast radio, a conventional reel-to-reel or cassette tape recorder, a conventional phonograph, a Compact Disk (CD) player, a Digital Video Disk (DVD) player, a laser disk player, a video game, a desktop computer, a laptop computer, an Internet radio, an MP3 system, a speakerphone, or any other suitable electronic system or device capable of generating audible sound. FIGS.  1 - 2  depict the acoustic sound system  100  in conjunction with the television  102  for purposes of illustration.  
         [0025]    As shown in FIG. 1, the directed acoustic sound system  100  includes a parametric array configured as a circular disk. The parametric array includes at least one acoustic transducer. It is noted that the parametric array may alternatively be configured as a cylinder, a plane (e.g., a rectangle), or any other suitable geometric shape. The acoustic sound system  100  is coupled to at least one audio output channel (not shown) of the television  102 . Further, the acoustic sound system  100  is mounted on top of the television  102  so that the audio sound beam  106  generated by the system is directed toward the television viewer  104 . Because the audio sound beam  106  generated by the acoustic sound system  100  is highly directional, the television viewer  104  can watch and listen to the television  102  without unduly distracting others nearby.  
         [0026]    It is noted that the disk comprising the parametric array may alternatively be mounted near the television viewer  104  (e.g., on a stand located either above or to one side of the viewer  104 ), or directly mounted on the ceiling or a wall, so long as the audio sound beams  106  generated by the acoustic sound system  100  are substantially directed toward the viewer  104 . In each case, the sound generated by the acoustic sound system  100  will only be substantially heard by listeners in the direct path of the sound beam.  
         [0027]    For example, the parametric array and/or the reflector surface(s) may be mounted using cable hangers, picture hooks, ball mounts, or any other suitable hanging apparatus. In the preferred embodiment, ball joints are employed to allow the position of the parametric loudspeaker to be easily controlled.  
         [0028]    As shown in FIG. 2, the directed acoustic sound system  100  is mounted on top of the television  102  so that the audio sound beam  106   a  generated by the system is directed upward toward a solid surface  108 . Because solid surfaces generally reflect sound easily, the audio sound beam  106   a  is redirected by the surface  108  to direct a reflected audio sound beam  106   b  toward the television viewer  104 . For example, the solid surface  108  may comprise a clear piece of plastic, and the disk may be permanently mounted within the housing of the television  102 . Such a configuration not only provides a more aesthetically pleasing appearance, but it also allows a more thorough integration of the television electronics to facilitate fabrication of the system.  
         [0029]    It is understood that the solid surface  108  may alternatively comprise any other suitable solid surface in a room containing the television  102 . For example, any suitable wall or ceiling may be used as a sound reflector. The use of walls behind the listener may allow him or her to perceive sounds from the rear, as commonly generated by home theater systems. In this case, the listener typically remains in the direct path of the reflected audio sound beam because the sound directivity after reflection generally does not change. The home theater listening experience may be enhanced by using a number of walls to direct multiple reflected sounds toward the listener.  
         [0030]    In the event some of the audio sound beams reaching the listener come from undesired directions (e.g., when some sound beams inadvertently reflect off of the ceiling or a wall), spatial Digital Signal Processing (DSP) filtering may be employed to eliminate the unwanted sound. Spatial DSP filtering may also be employed to create a psycho-acoustical perception of sound originating from directions other than that actually occurring in reality. This typically involves subtle filtering and delaying of audio signals before directing the sound to the listener. It is understood that two or more audio sound beams generated using any of the above-described configurations may be employed for stereo listening.  
         [0031]    [0031]FIG. 3 depicts an illustrative embodiment  300  of the directed acoustic sound system  100  (see FIG. 1). In the illustrated embodiment, the directed acoustic sound system  300  comprises a parametric audio sound system including a signal generator  301 , an optional matching filter  316 , a driver amplifier  318  coupleable to optional beam steering control circuitry  324 , and a parametric array  322 , which comprises one or more acoustic transducers. A parametric audio system like that included in the directed acoustic sound system  300  is disclosed in co-pending U.S. patent application Ser. No. 09/758,606 filed Jan. 11, 2001 entitled PARAMETRIC AUDIO SYSTEM, which is incorporated herein by reference.  
         [0032]    Specifically, the parametric array  322  includes at least one acoustic transducer configured to be driven by the signal generator  301 , which includes a modulator  312  coupled to an ultrasonic carrier signal generator  314 , and one or more audio channels  302 . 1 - 302 .n. For example, the television  102  (see FIGS.  1 - 2 ) may provide one or more audio signals (e.g., audio Left (L) and audio Right (R); see also FIGS. 6 a - 6   b ) to the audio channels  302 . 1 - 302 .n. Optional signal conditioning circuits  306 . 1 - 306 .n receive respective audio signals provided via the audio channels  302 . 1 - 302 .n, and provide conditioned audio signals to a summer  310 . It is noted that such conditioning of the audio signals may alternatively be performed after the audio signals are summed by the summer  310 . The modulator  112  receives a composite audio signal from the summer  310  and an ultrasonic carrier signal from the carrier generator  314 , and modulates the ultrasonic carrier signal with the composite audio signal. The modulator  312  is preferably adjustable in order to vary the modulation index. Amplitude modulation by multiplication with a carrier is preferred, but because the ultimate goal of such modulation is to convert audio-band signals into ultrasound, any form of modulation providing that result may be used. The modulator  312  provides the modulated carrier signal to the optional matching filter  316 , which is configured to compensate for the generally non-flat frequency response of the driver amplifier  318  and the parametric array  322 . The matching filter  316  provides the modulated carrier signal to the driver amplifier  318 , which in turn provides an amplified version of the modulated carrier signal to the acoustic transducer of the parametric array  322 . The driver amplifier  318  may include a delay circuit  320  configured to apply a relative phase shift and/or amplitude shading across multiple frequencies of the modulated carrier signal to steer, focus, or shape the ultrasonic beam generated at the output of the parametric array  322 . The ultrasonic beam, which comprises the high intensity ultrasonic carrier signal amplitude-modulated with the composite audio signal, is demodulated on passage through the propagation medium, e.g., the air, due to the air&#39;s non-linear propagation characteristics, thereby generating audible sound.  
         [0033]    In the preferred embodiment, the frequency of the carrier signal generated by the ultrasonic carrier signal generator  314  is on the order of 45 kHz or higher. Because the audio signals provided via the audio channels  302 . 1 - 302 .n typically have a maximum frequency of about 20 kHz, the lowest frequency components of substantial intensity according to the strength of the audio signal in the modulated ultrasonic carrier signal have a frequency of about 25-35 kHz or higher. Such frequencies are typically above the range of human hearing.  
         [0034]    [0034]FIG. 4 depicts an illustrative embodiment of the parametric array  322  included in the directed acoustic sound system  300  (see FIG. 3). In the illustrated embodiment, the parametric array  322  includes a plurality of acoustic transducers  0 - 11  arranged in a one-dimensional configuration. It should be understood, however, that the plurality of acoustic transducers may alternatively be arranged in 2-3 dimensional configurations. Each of the acoustic transducers  0 - 11  has a generally rectangular shape to facilitate close packing in the one-dimensional configuration. It should be understood, however, that other suitable geometrical shapes (e.g., a disk or a cylinder) and other suitable configurations of the acoustic transducers may be employed. For example, the acoustic transducers may be shaped for arrangement in an annular or “ring” configuration.  
         [0035]    In the preferred embodiment, each of the acoustic transducers  0 - 11  comprises a capacitor transducer, more particularly a membrane-type transducer such as a membrane-type PVDF transducer, a membrane-type electret transducer, a membrane-type electrostrictive transducer, or a membrane-type electrostatic transducer (e.g., a Sell-type electrostatic transducer). In an alternative embodiment, the acoustic transducers  0 - 11  may comprise piezoelectric transducers. It is noted that the bandwidth of the parametric array  322  is preferably on the order of 5 kHz or higher, and more preferably on the order of 10 kHz or higher as enhanced by the matching filter  316 . Membrane-type transducers suitable for use in the acoustic sound system  300  are described in copending U.S. patent application Ser. No. 09/300,200 filed Apr. 27, 1999 entitled ULTRASONIC TRANSDUCERS, and copending U.S. patent application Ser. No. 10/268,004 filed Oct. 9, 2002 entitled ULTRASONIC TRANSDUCER FOR PARAMETRIC ARRAY, which are incorporated herein by reference.  
         [0036]    [0036]FIG. 5 depicts an illustrative embodiment of the driver amplifier  318  included in the directed acoustic sound system  300  (see FIG. 3). In the illustrated embodiment, the driver amplifier  318  includes the delay circuit  320 , an amplifier  504 , a transformer  506 , resistors  508  and  514 , a capacitor  510 , an inductor  512 , the acoustic transducer  0 , and a DC bias source  502 . It is noted that a respective delay circuit  320  is preferably provided for each of the acoustic transducers  0 - 11  (see FIG. 4). FIG. 5 shows the driver amplifier  318  driving only the acoustic transducer  0  for clarity of discussion.  
         [0037]    As shown in FIG. 5, the delay circuit  320  receives the modulated carrier signal from the matching filter  316  (see FIG. 3), applies a relative phase shift and/or amplitude shading to the modulated carrier signal for steering/focusing/shaping the ultrasonic beam generated by the parametric array  322 , and provides the modulated carrier signal to the amplifier  504 . The primary winding of the transformer  506  receives the output of the amplifier  504 , and the secondary winding of the transformer  506  provides a stepped-up voltage to the series combination of the acoustic transducer  0 , the resistor  508 , and the blocking capacitor  510 . Further, a DC bias is applied to the acoustic transducer  0  from the DC bias source  502  via the isolating inductor  512  and the resistor  514 . The capacitor  510  has relatively low impedance and the inductor  512  has relatively high impedance at the operating frequency of the driver amplifier  318 . Accordingly, these components typically have minimal effect on the circuit operation except to isolate the AC and DC portions of the circuit. In an alternative embodiment, the inductor  512  may be replaced by a very large resistor value. It is noted that the blocking capacitor  510  may be omitted when the DC bias is provided by an electret.  
         [0038]    In a preferred embodiment, the secondary winding of the transformer  506  is configured to resonate with the capacitance of the acoustic transducer  0  at the center frequency of the acoustic transducer  0 , e.g., 45 kHz or higher. This effectively steps-up the voltage across the acoustic transducer and provides a highly efficient coupling of the power from the driver amplifier  318  to the acoustic transducer. Without the resonant circuit formed by the secondary winding of the transformer  506  and the acoustic transducer capacitance, the power required to drive the acoustic sound system  300  would be very high, i.e., on the order of hundreds of watts. With the resonant circuit, the power requirement reduction corresponds to the Q-factor of resonance. It is noted that the electrical resonance frequency of the driver amplifier  318 , the center frequency of the acoustic transducer  0 , and the ultrasonic carrier frequency preferably have the same frequency value.  
         [0039]    As described above, the delay circuit  320  (see FIGS. 3 and 5) applies a relative phase shift and/or amplitude shading across multiple frequencies of the modulated carrier signal to steer, focus, or shape ultrasonic beams generated by the parametric array  322 . The parametric array  322 , more particularly the one-dimensional parametric array  322  of FIG. 4, is therefore well suited for use as a phased array. Such phased arrays may be employed for electronically steering audio beams toward desired locations along selected projection paths, without requiring mechanical motion of the parametric array  322 . Further, such phased arrays may be used to vary audio beam characteristics such as the beam width, the beam focus, and the beam spread.  
         [0040]    Specifically, the parametric array  322  operates as a phased array by manipulating the phase relationships between the acoustic transducers included therein to obtain a desired interference pattern in the ultrasonic field. For example, the one-dimensional parametric array  322  (see FIG. 4) may manipulate the phase relationships between the acoustic transducers  0 - 11  via the delay circuit  320  (see FIGS. 3 and 5) so that constructive interference of ultrasonic beams occurs in one desired direction. As a result, the one-dimensional parametric array  322  steers the modulated ultrasonic beam in that direction electronically. Further, the direction of the modulated ultrasonic beam may be changed in real-time via the beam steering control circuitry  324  (see FIG. 3).  
         [0041]    [0041]FIGS. 6 a - 6   b  depict the directed acoustic sound system  300  employed in conjunction with conventional speaker amplifiers. In the preferred embodiment, the signal handling capability of the acoustic sound system  300  accommodates the use of conventional loudspeakers  604  and/or the directional acoustic transducer loudspeaker  322 , depending on the needs of the listener and the characteristics of the listening environment.  
         [0042]    As shown in FIG. 6 a , the television  102  (see FIGS.  1 - 2 ) provides audio L and audio R signals to a conventional speaker amplifier  602  and to the parametric array processor/amplifier of the directed acoustic sound system  300 . For example, the speaker amplifier  602  may comprise a class AB audio speaker amplifier, a class D audio speaker amplifier, or any other suitable audio speaker amplifier for driving the conventional loudspeakers  604 . In the illustrated embodiment, the speaker amplifier  602  and the acoustic sound system  300  are connected in parallel. It is noted that the acoustic sound system  300  may include a stereo parametric array amplifier, or a mono parametric array amplifier requiring a combination of the audio L and audio R channels. In the configuration of FIG. 6 a , the conventional speaker system including the loudspeakers  604  may be muted or turned-off when it is desired to hear only the acoustic sound system including the directional loudspeaker  322 . Similarly, the acoustic sound system including the directional loudspeaker  322  may be muted or turned-off when it is desired to hear only the conventional speaker system including the loudspeakers  604 .  
         [0043]    As shown in FIG. 6 b , the television  102  (see FIGS.  1 - 2 ) provides the audio L and audio R signals to the parametric array processor/amplifier of the directed acoustic sound system  300 . In the illustrated embodiment, the speaker amplifier  602  and the acoustic sound system  300  are connected in series, i.e., the directed acoustic sound system is connected in-line with the conventional speaker system. In this configuration, the listener may select the conventional speaker system, the directed acoustic sound system, or both systems, by simply making a selection using known mechanical and/or electronic techniques. In the event the listener selects the directional loudspeaker  322  only, the audio L and audio R signals are combined and subsequently recreated by the directed acoustic sound system  300 , and the corresponding audio L and R signals normally provided to the conventional speaker amplifier  602  are made to be approximately zero. In the event the listener desires a more traditional listening experience, the audio L and R signals are provided to the speaker amplifier  602  while the signal processing circuitry of the acoustic sound system  300  is placed in an inactive state.  
         [0044]    As shown in FIGS. 6 a - 6   b , the audio L and audio R signals are provided by the television  102  (see FIGS.  1 - 2 ). Such televisions typically have at least one line-out connector for audio output signals. It is noted that the listener may be required to mute the internal loudspeaker of the television when using the line-out connection. In alternative embodiments, the audio output signals may be provided by an auxiliary signal source such as a Video Cassette Recorder (VCR), a cable TV box, a DVD player, or any other suitable signal source. The television  102  may also have a headphone jack (not shown), which may be used to capture audio output signals for subsequent reproduction by the directional loudspeaker  322 . Moreover, audio signals may be provided by multiple electronic systems, e.g., a television, a CD player, and a speakerphone. In this case, the listener may first select the desired system, and then select the conventional speaker system or the directional speaker system for reproducing the audio signals provided by that system.  
         [0045]    [0045]FIG. 7 depicts an illustrative embodiment of a stand  700  for use with a directional acoustic transducer loudspeaker  722  configured as a circular disk. In the illustrated embodiment, the stand  700  may be employed in a freestanding configuration on the television  102  (see FIGS.  1 - 2 ) or on the floor beside the television set or the television viewer. In the preferred embodiment, the stand  700  includes a ball joint  702  to facilitate aiming of the circular disk.  
         [0046]    Having described the above illustrative embodiment of the directed acoustic sound system, other alternative embodiments or variations may be made. For example, in some circumstances, it may be beneficial to use a subwoofer with the acoustic sound system to supplement the low frequencies. Conventional subwoofers are essentially non-directional, so they may be heard by others in the general vicinity of the sound system. However, if the output of the subwoofer is limited to very low frequencies, this tends not to be an issue because such low frequencies are normally not bothersome to humans. In alternative embodiments, a localized subwoofer may be employed in the form of, e.g., a seat-mounted vibrator, pillow, or pad fashioned to present low frequency vibration directly to the intended listener.  
         [0047]    In addition, the parametric array processor may be provided with dynamic compression or equalization functionality to enhance the reproduced audio. For example, a suitable equalization routine may specify a high pass filter frequency corresponding to the desired output level. Because high frequencies generally require less energy to reproduce, more output may be obtained if the low signal frequencies are attenuated. The result would effectively be a high pass filter with frequency controlled via the incoming volume level and/or the listener&#39;s volume settings. Further, because many electronic systems have a line-out connection that is not volume controlled, the parametric array processor/amplifier may be provided with an independent volume control. Moreover, the directed acoustic sound system may be provided with a proximity sensor  326  (e.g., ultrasonic, echo, etc.; see FIG. 3) to detect how far the listener is from the system. The parameters of the parametric array processor may then be optimally adjusted based on the detected proximity information.  
         [0048]    In addition, the directed acoustic sound system may employ a remote control device for controlling volume, tone, signal switch selections, etc. For example, the remote control device may employ optical, acoustic, infrared (IR), Radio Frequency (RF), or any other suitable means of remote control. It is noted that RF remote control permits reception without requiring a line-of-sight to the system, and therefore this type of remote control is particularly advantageous when the system is hidden from view. Because it would be desirable to allow the listener to use his or her own existing remote control device, the acoustic sound system may be configured to “learn” the proper codes for “volume up”, “volume down”, etc., from the existing remote control device. The acoustic sound system may also be provided with a memory for retaining the volume setting, the tone setting, the signal switch selections, etc., when system power is turned-off.  
         [0049]    For IR remote control devices, there must typically be a line-of-sight access to the remote receiver. In the preferred embodiment, the remote receiver is mounted in or near the parametric array because the transducer is normally in the line-of-sight of the listener. The remote receiver may then provide the remote control signals to the parametric array processor/amplifier. The acoustic transducer disk or its mounting stand may also provide status information such as the volume setting or the source material selection via a display.  
         [0050]    In the preferred embodiment, a movable motorized disk-mounting stand is provided to account for varying listener positions. The motorized stand may have one or more preset positions corresponding to respective listening positions. Alternatively, the mounting stand may track the listener automatically by sensing sounds produced by the listener&#39;s movements using any suitable sound-sensing mechanism. As described above, a phased array may also be employed to steer the audio sound beams.  
         [0051]    In addition, the directed acoustic sound system may include a fan to cool the system. Instead of having the fan turned-on all of the time, the fan may be activated automatically when the temperature exceeds a predetermined level. Hysteresis/delay may also be employed to prevent the occurrence of undue oscillation of the system resulting from multiple fan cycles.  
         [0052]    In addition, sound absorbing materials may be disposed in the paths of the reflected audio sound beams to prevent sound from reflecting into undesirable areas. The audio sound beams generated by the directed acoustic sound system may also be used to mask background noises, thereby making an area such as an office environment appear quieter to the listener. The acoustic sound system may also be employed to direct white or filtered white noise toward the listener.  
         [0053]    In addition, it was described above that the television  102  (see FIGS.  1 - 2 ) provides audio L and audio R signals to the conventional speaker amplifier  602  and to the parametric array processor/amplifier of the directed acoustic sound system  300  (see FIGS. 6 a - 6   b ). In an alternative embodiment, the audio channel, the speaker amplifier  602 , and the directed acoustic sound system  300  may comprise portions of a speakerphone (also known as a “hands-free” telephone system). For example, the hands-free telephone system may include a telephone receiver configured to receive information representative of the audio channel. Conventional hands-free telephone systems are frequently sources of annoyance and distraction in open-office space environments because the sound leaving the telephone console is typically non-directional—virtually everyone in the vicinity of the system may hear the telephone conversation. By applying a directional speaker to the telephone interface, sound from the telephone can be directed toward the intended listener(s) only. As a result, the sound from the phone will not be substantially heard by others nearby.  
         [0054]    In effect, the audio sound beams generated by the directional speaker of the hands-free telephone system “shine” upon the intended listener(s) from convenient locations in a way that is analogous to a private lighting system in a darkened room. Music-playing functionality may also be added to the hands-free telephone system to allow the user to listen to music at his or her desk without distracting coworkers nearby, and without requiring the use of headphones. Such music-playing capability may be added to the system via an audio jack connected to a host personal computer. It is further noted that the directional speaker may be mounted from a fixture attached to a cubicle by a “swing-arm” assembly like those typically used with desk lamps. This allows the audio sound beams to be aimed directly at the intended listener. Moreover, because it requires virtually no user adjustments, the acoustic sound system may be placed in any convenient location. Audio output signals from the hands-free telephone system (and/or the personal computer) may be provided to the conveniently located acoustic sound system to power the directional speaker.  
         [0055]    It will also be appreciated by those of ordinary skill in the art that further modifications to and variations of the above-described directed acoustic sound system may be made without departing from the inventive concepts disclosed herein. Accordingly, the invention should not be viewed as limited except as by the scope and spirit of the appended claims.