Abstract:
An external acoustic chamber ( 220 ) for attachment to a mobile device ( 200 ) is provided. The external acoustic chamber ( 220 ) optimizes the audio performance of the mobile device ( 200 ) thus reducing the need for signal equalization and/or hardware to amplify the sound signal. The mobile device ( 200 ) includes a loudspeaker ( 205 ) and a first acoustic chamber ( 207 ) acoustically coupled to the loudspeaker ( 205 ). The external acoustic chamber ( 220 ) comprises at feast a second acoustic chamber ( 222 ) which penetrates the first acoustic chamber ( 207 ) adding volume to the first acoustic chamber ( 207 ). The combined greater volume reduces the dampening of loudspeaker ( 205 ) caused by the pressure in the first acoustic chamber ( 207 ). The result is an improvement in the frequency response of loudspeaker ( 205 ) approaching the natural frequency response of loudspeaker ( 205 ). The at least second acoustic chamber ( 222 ) is sized and shaped so that a first exterior surface portion of the acoustic chamber ( 220 ) covers or is flush with the battery ( 214 ) installed in the housing ( 201 ) of the mobile device ( 200 ). The first, exterior surface portion is substantially aligned with a second exterior surface portion enclosing the at least second acoustic chamber ( 222 ).

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority to U.S. provisional patent application Ser. No. 60/867,990 filed on Nov. 30, 2006, which is incorporated by reference as if fully rewritten herein. 
    
    
     BACKGROUND OF THE INVENTION  
     Statement of the   Technical Field 
     The invention relates to accessories for mobile devices. More particularly, this invention relates to an attachable external acoustic chamber for mobile devices to improve the audio performance and define a seamless, aesthetically pleasing mobile device casement profile. 
     Background of the  Invention 
     The demand for mobile devices such as cellular telephones in recent years has been steadily increasing. As a result, the number of manufacturers of mobile devices and the competition among them has increased. This competition has forced mobile device designers to design mobile devices with additional features and capabilities to remain competitive. Typically, consumers prefer cellular telephones with longer talk time and standby time. The talk time and standby time depend on, among other things, the capacity of the battery that provides electrical power. There are many factors which determine the capacity of a battery for a mobile device. These factors include the materials used to manufacture the battery and the size of the battery. Accordingly, these factors affect the cost and weight of the battery. Mobile device designers must weigh all of these factors when selecting a battery for a mobile device for a particular model of mobile device. 
     One of the more recent popular features that have been incorporated into mobile devices is a loudspeaker. A loudspeaker allows the user to use the cellular telephone in a hands-free configuration without the use of headsets. Typically, in addition to the traditional mouthpiece and earpiece, a mobile device with a loudspeaker will have the loudspeaker in a front mounted or rear mounted configuration. The loudspeaker should have sufficient volume that it can be heard without holding the loudspeaker to the user&#39;s ear. Most mobile devices equipped with a loudspeaker feature have a switch which is depressed to activate the loudspeaker mode. 
     One drawback to incorporating the loudspeaker feature into a mobile device is that less volume is available for the loudspeaker in smaller sized mobile devices because of the smaller battery sizes that must be used. Thus, the function of the loudspeaker is less than optimal. One solution to this problem is for manufacturers of mobile devices to offer an aftermarket battery with greater power capacity that replaces the original battery. Such batteries are larger in size and are encased in a cover that typically extends further out of the battery chamber than the original battery. The result is a mobile device with an unsatisfactory casement profile. 
     Another drawback to a mobile device incorporating a loudspeaker is that the volume of the front or rear ported loudspeaker may not be optimal due to size constraints imposed on the phone ID. 
     There exists in the art an attempt to improve the audio performance of a cellular telephone. For example, in U.S. patent application no. 2005/0190941 A1, disclosed is a cellular telephone having a first opening for delivering voice on a shell. A printed circuit board (PCD) is disposed within an inner space enclosed by the shell and divides the inner space into a first acoustic room and a second acoustic room. A speaker is disposed within the first acoustic room and electrically connects the PCB. A through hole is formed on the PCB to communicate the first acoustic room and the second acoustic room to increase the size of total resonance chamber for improving resonance effect in low frequency voices. Furthermore, at least a second opening is formed on the shell to communicate the first acoustic room or the second acoustic room to the environment for flattening the resonance curve to improve the voice quality. However, the cellular phone disclosed does not have a loudspeaker and there is no attempt to improve the audio performance thereof. 
     Consequently, there exists a need in the art for a mobile device having an aesthetically pleasing casement profile when an extended capacity battery is installed in the battery cavity. There also exists a need in the art to improve the audio performance of a mobile device having a loudspeaker. 
     SUMMARY OF THE INVENTION 
     The invention concerns an external acoustic chamber for attachment to a wireless mobile electronic device. The wireless mobile electronic device comprises a first housing, a first acoustic chamber disposed within the first housing, a sound generator within the first housing acoustically coupled to the first acoustic chamber, a second housing defining at least a second acoustic chamber, the second housing is removably attached to the first housing, and at least a first acoustic port configured for acoustically coupling the first acoustic chamber to the second acoustic chamber when the second housing is attached to the first housing. 
     The at least first acoustic chamber further comprises at least a second acoustic port formed in the first housing for communicating audio from the sound generator to an exterior of the first and second housing. There is a third acoustic chamber disposed in the second housing, and a third acoustic port configured for acoustically coupling the sound generator to the third acoustic chamber. 
     In the exemplary embodiment of the invention, the at least first acoustic port defines an opening info the first acoustic chamber, the at least first acoustic port comprising a first mating structure configured for mating with a second mating structure of a second acoustic chamber exclusive of the first housing. The first mating structure comprises a socket formed on a portion of the first housing. The second mating structure is comprised of a hollow tubular structure extending from a portion of the second housing. The first mating structure or socket is sized and shaped for snugly mating with the second mating structure or hollow tubular structure when the second housing is attached to the first housing. The at least first acoustic port is configured for acoustically coupling the at least first acoustic chamber to the second acoustic chamber when the second housing is attached to the first housing. 
     There is a removable sealing member disposed in the opening of the at least first acoustic port for sealing the at least first acoustic port when the second housing is not attached to the first housing. 
     In the exemplary embodiment of the invention, the second housing further comprises a cover for a battery installed in the first housing of the wireless mobile electronic device. The battery is contained at least partially within the second housing. The battery has a size and shape which protrudes from the first housing, and the second acoustic chamber is sized and shaped so that a first exterior surface portion of the second housing covering the battery is substantially aligned with a second exterior surface portion of the second housing enclosing the second acoustic chamber. 
     In another embodiment of the invention, there is at least one sensing device configured for detecting when the second housing is attached to the first housing. There is an audio processing means configured to modify an amplitude of selected audio frequencies communicated to the sound generator responsive to the sensing device. The at least one sensing device is selected from the group consisting of a Hall effect sensor, a magnetic sensor, and a switch. 
     In another embodiment of the invention, the second housing further comprises first and second side portions which extend beyond peripheral edges of the first housing when the second housing is attached to the first housing. The first and second portions define a channel extending the third acoustic chamber beyond the peripheral edges of the first housing. The first and second side portions each define an opening configured for communicating audio from the sound generator to an exterior of the second housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments will be described with reference to the following drawing figures, in which like numerals represent like items throughout the figures, and in which: 
         FIG. 1A  is a perspective view of an exemplary prior art mobile device. 
         FIG. 1B  is a cross-sectional side view of the exemplary prior art mobile device of  FIG. 1A  taken along line  1 B- 1 B of  FIG. 1A  with a conventional thin battery and battery cover. 
         FIG. 1C  is a cross-sectional side view of the exemplary prior art mobile device of  FIG. 1A  taken along line  1 B- 1 B of  FIG. 1A  with an extended capacity battery and an extended capacity battery cover. 
         FIG. 2A  is a perspective view of an exemplary embodiment of a mobile device. 
         FIG. 2B  is an exploded perspective view of the exemplary embodiment of the mobile device shown in  FIG. 2A . 
         FIG. 2C  is a cross sectional side view of the exemplary embodiment of a mobile device shown in  FIG. 2A  taken along line  2 C- 2 C of  FIG. 2A  having an extended capacity battery, extended capacity battery cover, a rear ported loudspeaker, and an external acoustic chamber attached. 
         FIG. 2D  is an exploded cross-sectional side view of the mobile device of  FIG. 2C . 
         FIG. 2E  is a cross-sectional side view of another embodiment of the mobile device of  FIG. 2A  taken along line  2 C- 2 C of  FIG. 2A  having an extended capacity battery, extended capacity battery cover, front ported loudspeaker, and an external acoustic chamber attached. 
         FIG. 3A  is a front view of another embodiment of a mobile device. 
         FIG. 3B  is a cross-sectional side view of the embodiment of the mobile device of  FIG. 3A  taken along line  3 B- 3 B of  FIG. 3A  having an extended capacity battery, extended capacity battery cover, rear ported loudspeaker, and an external acoustic chamber attached. 
         FIG. 4  is a cross-sectional side view of another embodiment of a mobile device similar to the mobile device of  FIG. 3A  taken along line  3 B- 3 B of the mobile device of  FIG. 3A  having a sensing device to detect the attachment of an external acoustic chamber. 
         FIG. 5  is a graph comparing the frequency response of a loudspeaker for a traditional mobile device to a loudspeaker for a mobile device with an external acoustic chamber attached. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to  FIG. 1A , shown is a front perspective view of an exemplary prior art mobile device  100 . The mobile device  100  could be any type of mobile device but the most typical application can include a cellular telephone. 
     Referring now to  FIG. 1B , shown is a cross-sectional side view of the exemplary prior art mobile device  100  shown in  FIG. 1A  taken along line  1 B- 1 B of  FIG. 1A . The prior art mobile device  100  can include a loudspeaker  105 . The loudspeaker  105  is useful for having a hands-free telephone conversation without having to hold the mobile device  100  close to the mouth and ears of the user. The loudspeaker  105  is also useful in hosting a conference call where more than one person can attend the conference call in the proximity of the mobile device  100 . 
     The loudspeaker  105  is rear ported resulting in the audio or front volume sound generated by loudspeaker  105  being directed out of the rear side of the mobile device  100 . The mobile device  100  also includes at the very least a shell  101  defining an interior space  102  housing a circuit board  103 , a battery  104  for providing electrical power to circuit board  103 , and the loudspeaker  105 . The circuit board  103  contains the operational electronics components comprising the mobile device  100  such as a numeric keypad, display, microprocessor, receiver/transmitter, microphone, and earpiece (none of which are shown). The loudspeaker  105  is connected to the circuit board  103 . Typically, the audio output of the earpiece (not shown) is muted and the sensitivity of the microphone (not shown) is increased when the loudspeaker  205  feature is activated. 
     The battery  104  is a “thin” battery design having only ordinary battery capacity as is known to one of ordinary skill in the art. The battery  104  could be inserted and housed in a recess  109  defined by a portion of shell  101  in the rear of shell  101 . A cover  110  could then be installed over the recess  109  to secure battery  104  in the recess  109 . The battery  104  could also be formed as part of the cover  110  and the composite assembly inserted into recess  109  and attached to the shell  101  of mobile device  100 . When battery  114  and cover  115  are installed on mobile device  100 , cover  115  fits into the contours of shell  101  such that a seamless, aesthetically pleasing mobile device  100  casement profile is defined. 
     The shell  101  is further comprised of an acoustic chamber  107  acoustically coupled to the rear side of loudspeaker  105 . An acoustic chamber is an enclosure that minimizes or attenuates noise. The acoustic chamber  107  absorbs the rear volume sound generated by loudspeaker  105 . The acoustic chamber  107  prevents the radiation of the rear volume sound of loudspeaker  105  to an outside area where it may interfere with other sound sensitive components of the mobile device  100 . 
     One or more ports  106  are formed in the sidewall  108  of shell  102  in the area in front of loudspeaker  105 . The ports  106  allow the front volume sound of loudspeaker  105  to be directed out of the rear side of the mobile device  100 . 
     Referring now to  FIG. 1C , shown is another cross-sectional side view of the exemplary prior art mobile device  100  of  FIGS. 1A and 1B . The mobile device  100  is identical to the mobile device  100  of  FIGS. 1A and 1B  except that an “extended” or “high” capacity battery  114  has been inserted into recess  109  and secured therein with a cover  115 . The battery  114  is termed an “extended” or “high capacity” battery because it has more electrical power available than traditional “thin” batteries used in a mobile device  100 . The additional electrical power provided by battery  114  gives the mobile device  100  heightened capabilities such as a longer talk time or standby time. 
     However, “extended” or “high capacity” type batteries are larger than traditional “thin” batteries and do not completely fit into the recess  109  of mobile device  100 . The way this has been resolved is to allow a portion of the battery  114  to protrude from recess  109  while a portion of battery  114  is inserted into recess  109 . This requires that the cover  115  also be designed to conform around the portion of battery  114  protruding from recess  109 . When battery  114  and cover  115  are installed on mobile device  100 , the cover  115  is discontinuous with the contours of shell  101  and distorts the seamless, aesthetically pleasing casement profile of mobile device  100  of  FIGS. 1A and 1B  to an otherwise aesthetically less than satisfactory mobile device  100  casement profile. 
     Referring now to  FIGS. 2A and 28 , shown are rear perspective and exploded rear perspective views of an exemplary embodiment of a mobile device  200  having an extended capacity battery  214  and battery cover  215  attached to the rear of the mobile device  200 . Also shown is an external acoustic chamber  220  attached to the rear side of mobile device  200  beneath the battery cover  215 . The mobile device  200  could be a cellular telephone but the invention is not limited in this regard. In the embodiment shown, the loudspeaker  205  is rear ported so that the audio or front volume sound of loudspeaker  205  is directed out the rear of mobile device  205 . 
     Referring now to  FIGS. 2C and 2D  and still to  FIGS. 2A and 2B , shown are cross-sectional side and exploded cross-sectional side views of the mobile device  200 . Both the cross-sectional side view of  FIG. 2C  and the exploded cross-sectional side view of  FIG. 2D  are taken along line  2 C- 2 C of  FIG. 2A . The mobile device  200  is similar to the prior art mobile device of  FIGS. 1A-1C . The mobile device  200  includes at the very least a first housing or shell  201  defining an interior-space  202  housing a circuit board  203 , a battery  214  for providing electrical power to circuit board  203 , and a sound generator such as loudspeaker  205 . The circuit board  203  contains the operational electronics components comprising the mobile device  200  such as a numeric keypad, display, microprocessor, receiver/transmitter, microphone, and earpiece (none of which are shown). The loudspeaker  205  is connected to the circuit board  203 . The loudspeaker  205  is acoustically coupled to a first acoustic chamber  207 . 
     The battery  214  is of the extended or high capacity type and consequently has an extended profile when installed in a recess  209  defined in a portion of shell  201 . A cover  215  is fitted over battery  214  and encases battery  214  in recess  209 . Alternately, battery  214  and cover  215  can be integrally formed and inserted as a composite arrangement into recess  109 . Similar to the prior art mobile device  100  in  FIG. 1C , when battery  214  is installed in recess  209  a portion of battery  214  protrudes from recess  209  and cover  215  is fitted over the protruding portion. The result is a less than satisfactory aesthetic mobile device  200  casement profile. 
     One other problem associated with a loudspeaker  205  in a mobile device  200  such as the rear ported loudspeaker  205  shown in  FIGS. 2C and 2D  is that the audio performance of the loudspeaker  205  is usually less than desired or less than it could be. For example, in the prior art mobile device  100  of  FIGS. 1A-1C , the audio or front volume sound of the loudspeaker  105  is directed out the rear of the mobile device  100  through the one or more ports  106 . The natural frequency response of loudspeaker  105  is dampened by the pressure in the acoustic chamber  107  disposed within the shell  201  and acoustically coupled to loudspeaker  105 . In the prior art mobile device  100  of  FIGS. 1A-1C , this loss of the natural frequency response is somewhat compensated for electronically by equalization (EQ). Still, this compensation is less than the natural frequency response of loudspeaker  105  would be if loudspeaker  105  was not dampened by the pressure in acoustic chamber  107 . 
     The present invention solves this problem by attaching an external acoustic chamber  220  to the rear of the mobile device  200 . The external acoustic chamber  220  is defined by a second housing  221  that attaches to the sidewall  208  of shell  201 . The second housing  221  could be attached to shell  201  directly beneath battery  214  and cover  215 . However, the invention is not limited in this regard as the external acoustic chamber  220  could be attached at other locations on the mobile device  200 . The external acoustic chamber  220  is comprised of at least one second acoustic chamber  222  and a third acoustic chamber  227 . At least one sidewall  229  divides the external acoustic chamber  220  into the at least one second acoustic chamber  222  and the third acoustic chamber  227 . 
     When battery  214  is installed in recess  209  and cover  215  and external acoustic chamber  220  are attached to the rear of mobile device  200 , the result is a seamless, aesthetically pleasing mobile device  200  casement profile (best seen in  FIG. 2A ). Alternately, external acoustic chamber  220  could be integrally formed with battery  214  and cover  215  so that the composite arrangement could be attached to the rear of mobile device  200 . The composite arrangement also provides a seamless, aesthetically pleasing mobile device  200  casement profile when installed on mobile device  200 . 
     It is envisioned that the external acoustic chamber  220  could be sold separately as an aftermarket product to consumers who wish to improve the audio performance of their mobile device  200 . This may especially appeal to consumers who have already purchased a high capacity battery  214  and cover  215  which results in the mobile device  200  having a less than satisfactory aesthetic profile. The addition of the external acoustic chamber  220  beneath the battery  214  and cover  215  results in a seamless, aesthetically pleasing mobile device  200  casement profile. 
     It is also envisioned that a composite external acoustic chamber  220  and high capacity battery  214  and cover  215  arrangement could be sold as an aftermarket product. This product would appeal to consumers who wish to improve the capability of their mobile device  200  while simultaneously improving the audio performance of the loudspeaker  205 . This arrangement is especially desirable since the composite arrangement provides a seamless, aesthetically pleasing mobile device  200  casement profile. 
     The external acoustic chamber  220  improves the audio performance of the mobile device  200  by penetrating the first acoustic chamber  207  acoustically coupled to loudspeaker  205 . The volume of first acoustic chamber  207  is acoustically coupled to the volume of the at least one second acoustic chamber  222  to improve the low end frequency response of loudspeaker  205 . The greater combined volume or acoustic space reduces the dampening of loudspeaker  205  caused by the pressure within the first acoustic chamber  207 . The result is a frequency response of loudspeaker  205  that approaches the natural frequency response of loudspeaker  205 . 
     The external acoustic chamber  220  penetrates the volume of the first acoustic chamber  207  by one or more acoustic plugs or tubes  223  that acoustically couples the at least one second acoustic chamber  222  to the first acoustic chamber  207 . The one or more tubes  223  are inserted into complementary respective one or more sockets  212  ( FIG. 2B ) defined in sidewall  208  ( FIG. 2B ) of shell  201 . The one or more tubes  223  and one or more sockets  212  serve as one or more ports acoustically coupling the first acoustic chamber  207  and the at least one second acoustic chamber  222 . A seal  213  may also be provided in each of the one or more sockets  212  to seal the one or more tubes  224  when inserted into the respective socket  212 . The seal  213  could also be used to seal the one or more sockets  212  and the first acoustic chamber  207  before the external acoustic chamber  220  is attached to mobile device  200 . Each of the one or more sockets  212  define an opening into a channel  210  formed in a cylindrical boss  211 . The one or more tubes  223  are seated in the channel  210  in the cylindrical boss  211  in a frictional type fit. Each of the one or more tubes  223  define a channel  224  that is connected to one of the second acoustic chambers  222 . It should be understood that the acoustic plugs or tubes  223  and the boss  211  are cylindrical in the exemplary embodiment. However, the invention is not limited in this regard as the tubes  223  and the boss  211  could be any cross-sectional shape such as square, elliptical, octagonal or other shape known to one of ordinary skill in the art. 
     The audio or front volume sound of loudspeaker  205  passes through a plurality of ports  206  formed in sidewall  208  of shell  202 . When the acoustic chamber  220  is attached to the rear of mobile device  200 , the plurality of ports  206  are aligned with a plurality of ports  226  formed on a first sidewall of second housing  221  to allow the front volume sound of loudspeaker  205  to enter the third acoustic chamber  227 . The front volume sound then exits the third acoustic chamber  227  through a plurality of ports  228  on a second sidewall of second housing  221  opposed from said first sidewall. 
     As discussed, the additional volume provided by the external acoustic chamber  220  acoustically coupled to the first acoustic chamber  207  improves the low end frequency response of loudspeaker  205 . For example, shown in  FIG. 5  is a graph of the improved low end frequency response of loudspeaker  205  for a mobile device  200 . The solid line represents the frequency response of a traditional prior art mobile device  100  without an external acoustic chamber  220 . The dashed lines represents the frequency response of a mobile device  200  of the present invention with an external acoustic chamber  220  attached. As can be seen, there is an improvement in the sound pressure level (SPL) in the low end frequency response under the frequency of approximately 900 hertz. There is an average 7 db gain for the mobile device  200  with the external acoustic chamber  220  attached in the frequency range from 200 to 1000 hertz. The improvement of the frequency response of loudspeaker  205  depends on factors such as the size of the loudspeaker  205 , the number of tubes  223  and sockets  212 , the volume of the first acoustic chamber  207 , and the volume of the at least one second acoustic chamber  222 . 
     Referring now to  FIG. 2E , shown is a cross-sectional side view of another embodiment of a mobile device  200  similar to the one shown in  FIGS. 2A-2D . For the purposes of illustration, the cross-sectional side view of  FIG. 2E  is taken along line  2 C- 2 C of the mobile device  200  shown in  FIG. 2A  since the embodiment shown is similar to the embodiment of the mobile device  200  shown in  FIG. 2A . 
     The mobile device  200  includes at the very least a first housing or shell  201  defining an interior space  202  housing a circuit board  203 , an extended capacity battery  214  for providing electrical power to circuit board  203 , and a loudspeaker  205 . The circuit board  203  contains the operational electronics components comprising the mobile device  200  such as a numeric keypad, display, microprocessor, receiver/transmitter, microphone, and earpiece (none of which are shown). The loudspeaker  205  is connected to the circuit board  203 . The loudspeaker  205  is acoustically coupled to a first acoustic chamber  207 . The loudspeaker  205  is front ported so that the front volume sound of loudspeaker  205  is directed to the front of the mobile device  200  through a plurality of ports  206  defined in sidewall  208  of shell  201 . An external acoustic chamber  250  is removably attached to the rear of mobile device  200  underneath the protruding portion of battery  214  and cover  215 . 
     The external acoustic chamber  250  is defined by a second housing  251  and a second acoustic chamber  252 . The external acoustic chamber  250  penetrates the volume of the first acoustic chamber  207  by one or more acoustic plugs or tubes  255  which extend from within the second acoustic chamber  252  and from second housing  251 . The one or more tubes  255  fit info complementary respective one or more sockets  212  formed in the sidewall  208  of shell  201  (similar to the embodiment shown in  FIG. 2B ). The one or more tubes  265  and one or more sockets  212  serve as at least one port acoustically coupling the first acoustic chamber  207  and the second acoustic chamber  252 . The one or more sockets  212  ( FIG. 2B ) receive the one or more tubes  255  when the second housing  251  is attached to sidewall  208  of shell  201 . The one or more sockets  212  ( FIG. 2B ) define an opening for a channel  210  (similar to the embodiment shown in  FIG. 2D ) that acoustically couples to the first acoustic chamber  207 . The channel  210  ( FIG. 2D ) is defined by a tubular sidewall  211  ( FIG. 2D ). The one or more tubes  255  are received in the channel  210  ( FIG. 2D ) of boss  211  ( FIG. 2D ) in a frictional type fit. In the exemplary embodiment of the invention, the tubes  255  and boss  211  are cylindrical. However, the invention is not limited in this regard and as the cross-sectional shape of tubes  255  and boss  211  could be of any cross-sectional shape known to one of ordinary skill in the art. 
     A seal  213  ( FIG. 2B ) may also be provided to seal the one or more tubes  255  in the one or more sockets  212  ( FIG. 2B ). The seal  213  ( FIG. 2B ) could also be used to seal the one or more sockets  212  ( FIG. 2B ) and the first acoustic chamber  207  before acoustic chamber  250  and the second housing  251  are attached to mobile device  200 . 
     The frequency response of the loudspeaker  205  is improved because the additional volume of the second acoustic chamber  252  is added to the volume of the first acoustic chamber  207 . The greater combined volume or acoustic space reduces the dampening of loudspeaker  205  caused by the pressure within the first acoustic chamber  207 . The result is an improved frequency response of loudspeaker  205  that approaches the natural frequency response of loudspeaker  205 . 
     Referring now to  FIG. 3A , shown is a front view of another embodiment of a mobile device  200  similar to the embodiment shown in  FIGS. 2A-2D . The mobile device  200  has an external acoustic chamber  270  removably attached for improving the audio performance of a loudspeaker  205  ( FIG. 3B ). 
     Referring now to  FIG. 3B  and still to  FIG. 3A , shown is a cross-sectional side view of the embodiment of a mobile device  200  shown in  FIG. 3A . The cross-sectional side view of  FIG. 3A  is taken along line  3 B- 3 B of  FIG. 3A . The mobile device  200  is comprised of at least a first housing or shell  201  defining an interior space  202  housing a circuit board  203 , an extended capacity battery  214  for providing electrical power to circuit board  203 , and a loudspeaker  205 . The circuit board  203  contains the operational electronics components comprising the mobile device  200  such as a numeric keypad, display, microprocessor, receiver/transmitter, microphone, and earpiece (none of which are shown). The loudspeaker  205  is connected to the circuit board  203 . The loudspeaker  205  is acoustically coupled to a first acoustic chamber  207 . The loudspeaker  205  is rear ported so that the front volume sound of loudspeaker  205  is normally directed to the rear side of the mobile device  200  through a plurality of ports  206  defined in sidewall  208  of shell  201  similar to the rear ported loudspeaker  105  of  FIGS. 1A-1C  and  2 B- 2 D. 
     In certain instances, it may be desirable to redirect the audio or front volume sound generated by loudspeaker  205  to the front side of the mobile device  200 . For example, sound directed towards the listener is considered to be of a higher perceived quality than sound directed away from the listener. 
     In the present invention, this is done with an external acoustic chamber  270  which is attached to the rear side of mobile device  200  underneath the protruding portion of battery  214  and cover  215 . The external acoustic chamber  270  penetrates the volume of the first acoustic chamber  207  to improve the frequency response of loudspeaker  205  in the manner previously discussed. The external acoustic chamber  270  also redirects the front volume sound of loudspeaker  205  to the front side of mobile device  200 . 
     The external acoustic chamber  270  is defined by a second housing  271 , at least one second acoustic chamber  272 , and a third acoustic chamber  277 . One or more sidewalls  278  divide the external acoustic chamber  270  into the at least one second acoustic chamber  272  and third acoustic chamber  277 . One or more ports  276  align with the ports holes  206  for allowing the front volume sound of loudspeaker  205  to enter into the third acoustic chamber  277 . The second housing  271  attaches to the rear side of mobile device  200  and has side portions  279 ,  280  that extend beyond the peripheral edges of shell  201 . The side portions  279 ,  280  extend beyond the peripheral edges of shell  201  so that portions of the third acoustic chamber  277  also extend beyond the peripheral edges of shell  201 . The side portions  279 ,  280  also define openings  281 ,  282  so that the front volume sound of loudspeaker  205  can exit from within the third acoustic chamber  277  and be directed to the front side of mobile device  200 . 
     The external acoustic chamber  270  penetrates the volume of the first acoustic chamber  207  by one or more acoustic plugs or tubes  273  that are acoustically coupled to the at least one second acoustic chamber  272 . The one or more tubes  273  fit into complementary respective one or more sockets  212  (like the embodiment shown in  FIG. 2B ) formed in the sidewall  208  of shell  201 . The one or more tubes  273  and one or more sockets  212  ( FIG. 2B ) serve as at least one port acoustically coupling the first acoustic chamber  207  and the at least one second acoustic chamber  272 . 
     The one or more sockets  212  ( FIG. 2B ) receive the one or more tubes  273  when the second housing  271  is attached to sidewall  208  of shell  201 . The one or more sockets  212  ( FIG. 2B ) define an opening for a channel  210  ( FIG. 2D ) that acoustically couples to the first acoustic chamber  207 . The channel  210  ( FIG. 2D ) is defined by a boss  211  ( FIG. 2D ). Thus, the one or more tubes  273  are received in the channel  210  ( FIG. 2D ) of boss  211  ( FIG. 2D ) in a frictional type fit. 
     A removable seal  213  ( FIG. 2B ) may also be disposed in the one or more sockets  212  ( FIG. 2B ) to seal the one or more tubes  273 . The seal  213  ( FIG. 2B ) could also be used to seal the sockets  212  ( FIG. 2B ) and the first acoustic chamber  207  before the external acoustic chamber  270  is attached to mobile device  200 . In the exemplary embodiment of the invention, the tubes  273  and boss  211  are cylindrical. However, the invention is not limited in this regard and as the cross-sectional shape of tubes  273  and boss  211  could be of any cross-sectional shape known to one of ordinary skill in the art. 
     The frequency response of the loudspeaker  205  is improved because the additional volume of the at least one second acoustic chamber  272  is acoustically coupled to the volume of the first acoustic chamber  207 . The greater combined volume reduces the dampening of loudspeaker  205  caused by the pressure within the first acoustic chamber  207 . The result is an improved frequency response of loudspeaker  205  that approaches the natural frequency response of loudspeaker  205 . 
     Referring now to  FIG. 4 , shown is cross-sectional side view of another embodiment of a mobile device  200  similar to the mobile device  200  shown in any one of  FIGS. 2A-3D  or  FIGS. 3A-3B . For illustrative purposes, the cross-sectional side view of  FIG. 4  is taken along line  2 C- 2 C of the mobile device  200  of  FIG. 2A  since the embodiment shown is similar to the embodiment of the mobile device  200  shown in  FIG. 4 . 
     The mobile device  200  is comprised of at least a shell  201  defining an interior space  202  housing a circuit board  203 , a battery  214  for providing electrical power to circuit board  203 , and a loudspeaker  205 . The circuit board  203  contains the operational electronics components comprising the mobile device  200  such as a numeric keypad, display, microprocessor, receiver/transmitter, microphone, and earpiece (none of which are shown). The loudspeaker  205  is connected to the circuit board  203 . The loudspeaker  205  is acoustically coupled to a first acoustic chamber  207 . The mobile device  200  could have a loudspeaker  205  that is rear ported like the mobile device  200  in  FIGS. 2B-2D  and  FIGS. 3A-3B  or front ported like the mobile device  200  in  FIG. 2E . 
     An external acoustic chamber  290  could be attached to the rear of the mobile device  200  to improve the audio performance of the loudspeaker  205 . The external acoustic chamber  290  further defines at least one second acoustic chamber  292  and a third acoustic chamber  297 . At least one sidewall  298  divides the external acoustic chamber  290  into the at least one second acoustic chamber  292  and the third acoustic chamber  297 . 
     When the external acoustic chamber  290  is attached to mobile device  200 , the at least one second acoustic chamber  292  penetrates the first acoustic chamber  207  so that the volume of the at least one second acoustic chamber  292  is acoustically coupled to the volume of the first acoustic chamber  207 . The frequency response of the loudspeaker  205  is improved with the additional volume of the at least one second acoustic chamber  292  acoustically coupled to the volume of the first acoustic chamber  207 . The greater combined volume reduces the dampening of loudspeaker  206  caused by the pressure within the first acoustic chamber  207 . The result is an improved frequency response of loudspeaker  205  that approaches the natural frequency response of loudspeaker  205 . 
     The one or more tubes  291  extending from the at least one second acoustic chamber  292  are inserted into complementary respective one or more sockets  212  (similar to the embodiment shown in  FIG. 2B ) in the sidewall  208  of shell  201 . The one or more tubes  273  and one or more sockets  212  ( FIG. 2B ) serve as at least one port acoustically coupling the first acoustic chamber  207  and the at least one second acoustic chamber  292 . 
     The sockets  212  ( FIG. 2B ) receive the one or more tubes  291  when the external acoustic chamber  290  is attached to sidewall  208  of shell  201 . The sockets  212  ( FIG. 2B ) define an opening for a channel  210  ( FIG. 2D ) that connects to the first acoustic chamber  207 . The channel  210  ( FIG. 2D ) is defined by a cylindrical boss  211  ( FIG. 2D ). Thus, the one or more tubes  291  are received in the channel  210  ( FIG. 2D ) of boss  211  ( FIG. 2D ) in a fictional type fit. 
     A removable seal  213  ( FIG. 2B ) may also be disposed in the one or more sockets  212  to seal the one or more tubes  291 . The seal  213  ( FIG. 2B ) could also be used to seal the one or more sockets  212  ( FIG. 2B ) and the first acoustic chamber  207  before the external acoustic chamber  290  is attached to mobile device  200 . In the exemplary embodiment of the invention, the tubes  291  and boss  211  are cylindrical. However, the invention is not limited in this regard and as the cross-sectional shape of tubes  291  and boss  211  could be of any cross-sectional shape known to one of ordinary skill in the art. 
     The front volume sound of loudspeaker  205  could be directed into the third acoustic chamber  297  for allowing the front volume sound to pass through the external acoustic chamber  290  out the rear side of the mobile device like the mobile device  200  in  FIGS. 2B-2D . Alternately, the front volume sound of loudspeaker  205  could be directed into the third acoustic chamber  297  and then further directed to the front side of the mobile device  200  as in  FIGS. 3A-3B . 
     A sensing device  295  could be disposed in shell  201  in the proximal area where the external acoustic chamber  290  is attached to mobile device  200 . The sensing device  295  is for detecting when the external acoustic chamber  290  is attached to mobile device  200 . The sensing device  295  is connected to the circuit board  203  to notify the onboard electronics (not shown) that the external acoustic chamber  290  is attached. The electronics (not shown) on circuit board  203  could electronically adjust the equalization (EQ) to use less frequency boost to compensate for the improved natural frequency response due to the external acoustic chamber  290  being attached to mobile device  200 . 
     The sensing device  295  could be a Hall Effect sensor, magnetic sensor, or a mechanical switch. However, the invention is not limited in this regard as any sensing device known to one of ordinary skill In the art could be used to detect when the external acoustic chamber  290  is attached to mobile device  200 . 
     The external acoustic chamber  280  could be provided as an aftermarket product by itself or manufactured as a composite arrangement with the extended battery  214  and extended battery cover  215 . The external acoustic chamber  290  when installed as a unitary product on mobile device  200  beneath battery  214  and battery cover  215  is designed to define a seamless, aesthetically pleasing mobile device  200  casement profile (see  FIG. 2A ). Similarly, the external acoustic chamber  290  when formed as a composite arrangement with the extended battery  214  and extended battery cover  215  installed on mobile device  200  define a seamless, aesthetically pleasing mobile device  200  casement profile (see  FIG. 2A ). 
     All of the apparatus, methods and algorithms disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure. While the invention has been described in terms of preferred embodiments, it will be apparent to those of skill in the art that variations may be applied to the apparatus, methods and sequence of steps of the method without departing from the concept, spirit and scope of the invention. More specifically, if will be apparent that certain components may be added to, combined with, or substituted for the components described herein while the same or similar results would be achieved. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and concept of the invention as defined.