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RELATED APPLICATION 
   The present application claims the benefit of U.S. Provisional Application No. 60/610,324 filed Sep. 16, 2004, which is incorporated herein in its entirety by reference. 

   FIELD OF THE INVENTION 
   The present invention relates generally to the field of movable or portable acoustic shells for use by performers. More specifically, the present invention relates to a movable or portable acoustic shell including electronically enhanced acoustics to provide performers with a variety of selectable acoustic shell tunings depending upon the type of performance and acoustic characteristics of the surrounding environment. 
   BACKGROUND OF THE INVENTION 
   Portable acoustic shells provide many advantages to today&#39;s performers. One advantage is that performers can be sure of consistent acoustical characteristics as a show travels from location to location. Another advantage is that portable acoustic shells can be used to provide favorable acoustic traits at sites in which the acoustics are generally regarded as poor. A variety of techniques and designs have been used to create portable acoustic shells, for example U.S. Pat. Nos. 3,630,309; 4,241,777; D304,083; 5,524,691; 5,622,011; 5,651,405; and 5,875,591, all of which are commonly assigned to the assignee of the present invention and are all hereby incorporated by reference in their entirety. 
   While portable acoustic shells provide many advantages, they suffer acoustically in comparison to specially designed acoustical rooms. In an enclosed room, designers can eliminate any acoustical effects of the surrounding environment, resulting in a more consistent and controlled environment. In addition, electronic acoustic systems can be coupled with the enclosed room to emulate any number of acoustical venues to provide more realistic practice and rehearsal conditions. An example of such a system is disclosed in U.S. Pat. No. 5,525,765, commonly assigned to the assignee of the present invention, and hereby incorporated by reference in its entirety. 
   While portable acoustic shells provide many advantages, it would be desirable to have a portable acoustic shell that provided the type of acoustic flexibility that is available with an enclosed room. 
   SUMMARY OF THE INVENTION 
   The portable acoustic shell of the present invention overcomes the acoustical limitations associated with currently available portable acoustic shells. By integrating an electrical acoustic system with a portable acoustic shell, an active sound field can be created that encompasses the performers on stage. The active sound field can be tuned through the placement of speakers throughout the shell structure. By tuning the active sound field, both performers and audience members alike can experience the benefit of a portable acoustic shell that is capable of multiple tuning conditions such that it can be adapted for use by groups with differing numbers of performers, as well as in environments that are not acoustically advantageous. 
   The active acoustics shell utilizes a moveable (or portable) acoustics shell, which integrates acoustics technology into the shell to provide electronically enhanced acoustics to the performers on stage and to some extent the audience. The benefit of an active acoustics shell is the ability to “tune” the acoustics characteristics of the shell electronically thus allowing various “tunings” depending on the type of music performance being given. Since these are easily changed, multiple tunings could occur during the same event depending on the desires of the groups using the shell. This also allows for a fairly consistent acoustic environment for the musicians to play in, especially when faced with performance spaces that are not conducive to good performance acoustics. 
   The basic design premise is to create an active sound field from the shells that encompass the performers on the stage. Typically this is done with speakers that are attached to the shell structure. It may also include the addition of speakers located in the overhead reflectors. There is also the need to capture the sound of the performers for processing which is typically (but not restricted to) mounting microphones in the canopy portion of the shells (or could be located in the reflective ceilings above the stage). The sound is captured via the microphones, is equalized based on the transfer function of the shell/stage acoustics (and to some extent the impact of the auditorium area), processed with the acoustics technology and then fed back to the performers on stage via speakers in the shells (and/or overhead reflectors). 
   In one aspect, the present invention relates to a portable acoustic shell including an electronic acoustical system capable of tuning and projecting an active sound field encompassing performers on stage. Typically, the portable acoustic shell comprises a plurality of vertical panel assemblies placed and attached in proximity with one another to define a performance area. The portable acoustic shell may include an overhead canopy structure to partially enclose the area above the performance area. An electronic acoustic system comprises a microphone assembly, an electronic processing assembly and a speaker assembly. The microphone assembly comprises at least one and preferably, a plurality of microphones positioned above the performance area, often in the canopy, to capture the sound generated by the performers. The electronic processing assembly receives the sounds captured by the microphone assembly and processes the sounds based upon the desired tuning characteristics. The processed sounds are then fed back to the performance area and transmitted through the speaker assembly located within the shell structure resulting in the performers and audience members hearing the tuned version of the performance. 
   In another aspect, the present invention relates to a method for tuning sounds generated by a performance within a portable acoustical shell. Generally, desired tuning characteristics are inputted into an electronic acoustical system based upon the type and size of a performance, as well as the acoustical characteristics of the surrounding environment. Actual performance sounds are captured by a microphone assembly and are subsequently transmitted to the electronic acoustical system. The electronic acoustical system processes the sounds based on the previously established tuning characteristics. The tuned sounds are retransmitted and broadcast back to the performance area through a speaker assembly located within the acoustic shell structure. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a prior art portable acoustic shell; 
       FIG. 2  is a perspective view of a prior art vertical panel assembly; 
       FIG. 3  is a side view of the vertical panel assembly of  FIG. 2 ; 
       FIG. 4  is a perspective view of a portable acoustic shell system of the present invention; 
       FIG. 5  is a front view of a vertical panel assembly of the present invention; 
       FIG. 6  is a perspective, front view of the vertical panel assembly of  FIG. 5 ; 
       FIG. 7  is a side view of the vertical panel assembly of  FIG. 5 ; 
       FIG. 8  is a perspective, rear view of the vertical panel assembly of  FIG. 5 ; 
       FIG. 9  is a front view of an absorber panel of the present invention; 
       FIG. 10  is a side view of the absorber panel of  FIG. 9 ; 
       FIG. 11  is a side view of the absorber panel of  FIG. 9 ; 
       FIG. 12  is a perspective view of an electronic acoustic system of the present invention; and 
       FIG. 13  is a flow chart depicting a method of creating an active sound field encompassing a performance area in a portable acoustic shell of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Depicted in  FIGS. 1-3  is an acoustic shell  80  of the type commonly known and used by those of skill in the art, such as Wenger® Corporation&#39;s Legacy™ Acoustical Shell. Generally, acoustic shell  80  is comprised of a plurality of vertical panel assemblies  82  comprising a plurality of vertical panels; for instance, a kicker panel  84 , a lower panel  86 , an upper panel  88  and a canopy panel  90 , mounted to a vertical frame  92 , which is fixedly attached to base assembly  94 . Base assembly  94  is typically sized to provide stability to the vertical panel assembly  82 . Base assembly  94  typically includes a pair of caster assemblies  96   a ,  96   b  to allow for easy positioning and transport of the vertical panel assembly  82 . Between the panel sections, for example, between upper panel  88  and canopy panel  90 , vertical frame  92  can include a hinge assembly  98  to allow for rotatable positioning of the canopy panel  90  in comparison to upper panel  88 , as well as to allow for fold-up and storage of the vertical panel assembly  82 . The panel sections are typically comprised of a composite material to provide a stiff, acoustically reflective surface, while the vertical frame  92  and base assembly  94  are constructed of steel and aluminum for durability and strength. 
   As shown in  FIG. 4 , a portable acoustic shell system  100  of the present invention comprises a remote electronic acoustical assembly  102  integrally wired to a portable acoustic shell  104 . Through the combination of electronic acoustical assembly  102  and portable acoustic shell  104 , a performance area  106  can be enveloped with an active sound field. Using electronic acoustical assembly  102 , the active sound field can be tuned or adjusted to provide a desired acoustic sound. The size and shape of performance area  106  can be varied by changing the orientation or number of vertical panel assemblies  120  that make up portable acoustic shell  104 . 
   A vertical panel assembly  120  of the present invention is further depicted in  FIGS. 5 ,  6 ,  7  and  8 . Generally, vertical panel assembly  120  comprises a plurality of panel sections; for example, a kicker panel  122 ; a lower panel  124 ; a top panel  126 ; and a canopy panel  128 , mounted to a vertical frame  130 , which is fixedly attached to a base assembly  132 . Hanging from canopy panel  128  is a microphone assembly  134 . As shown in  FIG. 7 , a hinge assembly  136  is mounted between top panel  126  and canopy panel  128  to provide rotational movement of the canopy panel  128  in relation to the top panel  126 . Hinge assembly  136  can include a biasing arm  138  and a spring assist  140  to allow for easier manipulation of canopy panel  128 . 
   Absorber panel  142  is depicted in  FIG. 9 . As shown in  FIGS. 10 and 11 , absorber panel  142  typically includes a pair of speaker assemblies  144   a ,  144   b  oriented to face the reflective surface of the vertical panel assembly  120 . In an alternative embodiment, a separating element may be provided between speaker assemblies  144   a ,  144   b.    
   Canopy panel  128  and vertical panel assembly  120  define an acoustic reflective zone in the performance area  106 . Sounds made by a performer in the acoustic reflective zone are received by microphone assembly  134 . Absorber panel  142  defines an anechoic zone within the performance area  106 . Speaker assemblies  144   a ,  144   b  are oriented toward vertical panel assembly  120  so that the sound they produce will reach a performer in the performance area indirectly. 
   The electronic acoustic system  102  is depicted in  FIG. 12 . Generally, electronic acoustic system  102  comprises a microphone preamplifier  152  having a minimum of two channels, an equalizer  154  having a minimum of two channels, a digital signal processor  156  with a minimum of four channels of processing, and an audio amplifier  158  having a minimum of one channel for each channel of the digital signal processor  156 . The components of electronic acoustic system  102  are generally mounted in a frame assembly  160  to provide convenient wiring and operation of the components. Frame assembly  160  can include a plurality of casters to provide for easy transport and positioning of electronic acoustic system  102 . In an alternative embodiment, electronic acoustic system  102  can be located in an enclosure suitable for attachment directly to a vertical panel assembly  120 . In a preferred embodiment, the digital signal processor  156  includes LARES (Lexicon Acoustic Reinforcement and Enhancement System) Digital Signal Processing Technology as manufactured by Lares Associates, Inc., Columbia, Md. Preferably, the components have specifications as described in Table A. However, it should be noted that different and/or additional components with different and/or additional specifications may be used without departing from the spirit or scope of the invention. 
   
     
       
             
           
             
             
             
           
         
             
               TABLE A 
             
           
           
             
                 
             
             
               Component Specifications 
             
           
        
         
             
               Component 
               Component 
                 
             
             
               Number 
               Name 
               Specifications 
             
             
                 
             
             
               134 
               Microphone 
               Transducer Type: self-polarized 
             
             
                 
               Assembly 
               condenser microphone 
             
             
                 
                 
               Frequency Response: 60 to 20,000 Hz 
             
             
                 
                 
               Signal-to-Noise Ratio re 1 Pa 
             
             
                 
                 
               (A-Weighted): 67 dB 
             
             
                 
                 
               Maximum sound pressure level for 
             
             
                 
                 
               1.0% THD: 115 dB SPL 
             
             
               144a, 
               Speaker 
               Frequency Response: 
             
             
               144b 
               Assembly 
               On Axis (0°) +/− 2 dB from 
             
             
                 
                 
               70-20 kHz 
             
             
                 
                 
               Off Axis (30°) +/− 2 dB 
             
             
                 
                 
               from 70-15 kHz 
             
             
                 
                 
               Sensitivity-room/Anechoic; 89 dB/ 
             
             
                 
                 
               86 dB 
             
             
                 
                 
               Maximum input power: 80 watts 
             
             
                 
                 
               Low frequency extension: 48 Hz 
             
             
                 
                 
               (DIN) 
             
             
               152 
               Microphone 
               Input Impedance: Greater than 3k 
             
             
                 
               Preamplifier 
               ohms 
             
             
                 
                 
               Frequency Response: 20-20 
             
             
                 
                 
               kHz, +0, −1 dB 
             
             
                 
                 
               THD: [0.01% (1 kHz, +24 dBm 
             
             
                 
                 
               Gain, 600 ohms, balanced out) 
             
             
                 
                 
               Maximum gain 66 dB, Minimum gain 
             
             
                 
                 
               26 dB 
             
             
                 
                 
               UL ®-Listed 
             
             
               154 
               Equalizer 
               Frequency Bands: ⅔ - 
             
             
                 
                 
               Octave ISO Spacing from 25 Hz to 
             
             
                 
                 
               16 kHz 
             
             
                 
                 
               Type: Constant Q 
             
             
                 
                 
               Accuracy: 3% center frequency 
             
             
                 
                 
               Frequency response: 20-60 
             
             
                 
                 
               kHz; +0/−3 dB 
             
             
                 
                 
               THD + Noise: .009%; +/−.002%; +4 
             
             
                 
                 
               dBu, 20-20 kHz 
             
             
                 
                 
               IM Distortion (SMPTE): 
             
             
                 
                 
               .005%, +/−.003%; 60 Hz/7 kHz, 
             
             
                 
                 
               4:1, +4 dBu, 20 kHz bandwidth 
             
             
                 
                 
               Signal-to-Noise: 108/92 dB +/− 2 
             
             
                 
                 
               dB; re +20 dBu/+4 dBu; Slider 
             
             
                 
                 
               Centered, Unity gain 
             
             
                 
                 
               UL ®-Listed and CSA-approved 
             
             
               156 
               Digital 
               Frequency response: 
             
             
                 
               Signal 
               Unprocessed Channels 10 Hz-100 
             
             
                 
               Processor 
               kHz, +1 dB, −3 dB, Ref. 1 kHz 
             
             
                 
                 
               Processed Channels 10-18 kHz, +1 
             
             
                 
                 
               dB, −3 dB, Ref. 1 kHz 
             
             
                 
                 
               THD + Noise: &lt;0.05% @ 1 kHz 
             
             
                 
                 
               maximum level 
             
             
                 
                 
               Signal-to-Noise ratio: 90 dB min., 
             
             
                 
                 
               A-weighted, Ref. 1 kHz level 
             
             
                 
                 
               UL ®-Listed, CSA-approved 
             
             
               158 
               Audio 
               Output power: 45 watt @ 4 ohms, 
             
             
                 
               Amplifier 
               20-20 kHz, 0.1% THD 
             
             
                 
                 
               Frequency Response: 20-20 
             
             
                 
                 
               kHz, +0, −1 dB at 1 watt 
             
             
                 
                 
               Slew rate: 6 V/us 
             
             
                 
                 
               Damping factor: Greater than 400 from 
             
             
                 
                 
               DC to 400 Hz 
             
             
                 
                 
               Signal-to-Noise: 106 dB from 20 Hz to 
             
             
                 
                 
               20 kHz @ 45 W 
             
             
                 
                 
               Total Harmonic Distortion 
             
             
                 
                 
               (THD): &gt;0.001% @ 45 W from 20 Hz 
             
             
                 
                 
               to 400 Hz increasing linearly to 0.03% 
             
             
                 
                 
               at 20 kHz 
             
             
                 
                 
               UL ®-Listed, CSA-approved 
             
             
                 
             
           
        
       
     
   
   Generally, the portable acoustic shell system  100  of the present invention is used by first assembling the portable acoustic shell  104 . Based on the desired shape and size of portable acoustic shell  104 , the appropriate number of vertical panel assemblies  120  are positioned in a side-by-side arrangement. Typically, each vertical frame  130  will include a combination attachment/locking mechanism allowing adjacent vertical panel assemblies  120  to be interconnected and locked into position. Once the portable acoustic shell  104  is assembled, the electronic acoustical assembly  102  is wired to the portable acoustic shell  104  such that the electronic acoustical assembly  102  is in electrical communication with the microphone assembly  134  and the speaker assemblies  144   a ,  144   b . For purposes of assembling the portable acoustic shell system  100 , the location of electronic acoustical assembly  102  in comparison to the portable acoustic shell  104  is unimportant. Generally, the only requirement for positioning the electronic acoustical assembly  102  is that it be in an electrically safe environment and that a power supply is readily available. 
   Use of the portable acoustic shell system  100  during a performance is described with reference to  FIG. 13 . Once the portable acoustic shell system  100  is assembled, a performance step  160  can commence. Performance step  160  can include any type of performance that includes an audio portion such as speeches, concerts, plays and other forms of performances. Once performance step  160  has begun, a capture step  162  is initiated, whereby the microphone assemblies  134  capture the audio portion of the performance step  160 . Depending upon the size and configuration of the portable acoustic shell  104 , a plurality of microphone assemblies  134  can be used to ensure complete and accurate capture of the audio portions. Once the microphone assembly  134  captures the audio portions, the captured audio signal is amplified by the microphone preamplifier  152  in a preamplification step  164 . The amplified signal is then filtered through the equalizer  154  in a filter step  166 . The filtered signal is then processed by the digital signal processor  156  in a processing step  168 . In processing step  168 , the filtered signal is tuned and adjusted according to the desired audio characteristics that have been input by a user. By changing these desired audio characteristics within digital signal processor  156 , a user can selectively process, modify and/or enhance the filtered signal. The desired audio characteristics can be modified at any time, including between performances, or “on the fly” during an actual performance. The digital signal processor  156  processes the signal into four outputs, which are fed to the audio amplifier  158  in an audio amplification step  170 . Audio amplification step  170  amplifies the four outputs to create four channels of audio amplified signals. The four channels of audio amplified signals are then fed to the speaker assemblies  144   a ,  144   b  in a transmission step  172 . In transmission step  172 , the audio amplified signals are fed to speaker assemblies  144   a ,  144   b  in an interleaving pattern, such that adjacent speakers are never on the same audio/processing channel. Finally, the speaker assemblies  144   a ,  144   b  reflect/diffuse the audio amplified signals back to the musicians/audience in a broadcast step  174 . 
   Canopy panel  128  and vertical panel assembly  120  define an acoustic reflective zone in performance area  106 . Sounds made by a performer in the acoustic reflective zone are received by microphone assembly  134 . This sound is processed by electronic acoustic system  102  and returned to the performer by way of speaker assemblies  144   a ,  144   b . Absorber panel  142  is mounted between the speaker assemblies  144   a ,  144   b  and performance area  106  so that absorber panel  142  provides a semi-anechoic zone within the reflective zone described above. Speaker assemblies  144   a ,  144   b  are oriented away from performance area  106  and toward vertical panel assembly  120  and the sound they produce reaches a performer in the performance area indirectly. This configuration and the creation of a semi-anechoic zone between speaker assemblies  144   a ,  144   b  by way of absorber panel  142 , provides acoustic feedback to a performer in performance area  106  that can be optimized to a particular piece or ensemble, and which is reproducible at different set up sites. Accordingly, a performer practicing in one space, and performing in a different space, will not have to adapt “on the fly” to the varying acoustics of different performance spaces. 
   Although various embodiments of the present invention have been disclosed here for purposes of illustration, it should be understood that a variety of changes, modifications and substitutions may be incorporated without departing from either the spirit or scope of the present invention. For example, the vertical panel assemblies can include additional speaker assemblies, for example, in canopy panel  128 , to further enhance the performance of the portable acoustic shell system  100  of the present invention. In other embodiments, microphone assemblies  134  can be positioned in alternative locations, such as in front of the portable acoustic shell  104 , within the performance area  106  or even being handheld by the performers themselves.

Summary:
An electroacoustic shell system adapted create a performance area where sound created by a performer is received, processed, and returned to the performer in the performance area. The system broadly includes an electroacoustic shell with a vertical panel and a canopy, a microphone and a speaker operably coupled to the shell, and an electronics processing assembly connected to the microphones and speakers for recording, broadcasting, and simulating sound.