PATENT DOCUMENT

Publication Number: US-8942410-B2
Application Number: US-201213731973-A
Country: US
Kind Code: B2

Title: Magnetically biased electromagnet for audio applications

Abstract:
An electronic device having an enclosure having a top panel and a bottom panel. An electromagnet is mounted within the enclosure, the electromagnet having a core portion attached to the top panel and a coil connected to the core portion. An attractor plate is attached to the bottom panel, the attractor plate forming part of a magnetic circuit of the electromagnet such that when an electrical audio signal is applied to the electromagnet, the bottom panel vibrates and produces a sound. A permanent magnet is further attached to the core portion, the permanent magnet is configured to create a bias in the magnetic circuit so as to modify a distortion in the sound.

Claims:
What is claimed is: 
     
       1. An electronic device comprising:
 an enclosure having a top panel and a bottom panel; 
 an electromagnet mounted within the enclosure, the electromagnet having a core portion attached to the top panel and a coil connected to the core portion; 
 an attractor plate attached to the bottom panel, the attractor plate forming part of a magnetic circuit of the electromagnet such that input of an electrical audio signal to the electromagnet causes the bottom panel to move and produce an audible sound; and 
 a permanent magnet attached to the core portion, the permanent magnet made of a different material than the core portion and having a magnetic pole that faces the attractor plate such that the permanent magnet creates a bias in the magnetic circuit that modifies a distortion in the audible sound. 
 
     
     
       2. The electronic device of  claim 1  wherein the distortion is caused by a rectification of the electrical audio signal and biasing of the magnetic circuit allows the electrical audio signal to be recreated as a dynamic force without the rectification. 
     
     
       3. The electronic device of  claim 1  wherein the core portion comprises a coil support arm around which the coil is positioned, a first side arm and a second side arm, and wherein the permanent magnet comprises a first magnet and a second magnet, each of the first magnet and the second magnet positioned at ends of the first side arm and the second side arm, respectively, and having the same magnetic poles facing the attractor plate. 
     
     
       4. The electronic device of  claim 1  wherein the core portion comprises a base portion having a coil support arm around which the coil is positioned, a first side arm and a second side arm extending therefrom. 
     
     
       5. The electronic device of  claim 4  wherein the permanent magnet comprises a first magnet and a second magnet, each of the first magnet and the second magnet positioned at ends of the first side arm and the second side arm, respectively, and facing the attractor plate. 
     
     
       6. The electronic device of  claim 4  wherein the permanent magnet comprises a first magnet and a second magnet, each of the first magnet and the second magnet positioned at sides of the first side arm and the second side arm, respectively. 
     
     
       7. The electronic device of  claim 1  further comprising:
 a resilient spacer positioned within the magnetic circuit, between the attractor plate and core portion. 
 
     
     
       8. The electronic device of  claim 7  wherein the resilient spacer comprises a ferromagnetic material to improve an efficiency of the magnetic circuit. 
     
     
       9. The electronic device of  claim 1  wherein the attractor plate is fixedly attached to a side of the bottom panel facing the electromagnet. 
     
     
       10. The electronic device of  claim 1  wherein the attractor plate comprises a ferromagnetic material. 
     
     
       11. An electronic audio system comprising:
 an enclosure having a first panel operably connected to a second panel; 
 a transducer mounted within the enclosure, the transducer comprising:
 an electromagnet having a core portion mounted to the first panel and a coil positioned around the core portion; 
 an attractor plate mounted to a side of the second panel facing the first panel, the attractor plate forming part of a magnetic circuit produced by the electromagnet upon input of an electrical audio signal; and 
 a permanent magnet mounted to the core portion, the permanent magnet made of a different material than the core portion and configured to bias the magnetic circuit produced by the electromagnet such that a dynamic force between the first panel and the second panel is proportional to the electrical audio signal and results in an audible sound output; and 
 
 a processor in electrical communication with the transducer and coupled to a memory to execute an operating system program. 
 
     
     
       12. The electronic audio system of  claim 11  further comprising:
 a resilient spacer positioned within a gap between the electromagnet and the attractor plate. 
 
     
     
       13. The electronic audio system of  claim 11  wherein the transducer, the memory and the processor are contained within the enclosure. 
     
     
       14. The electronic audio system of  claim 11  wherein the dynamic force between the first panel and the second panel causes the second panel to move while the first panel having the electromagnet attached thereto remains substantially stationary. 
     
     
       15. The electronic audio system of  claim 11  wherein the dynamic force causes one of the first panel and the second panel to produce the audible sound output, and the audible sound output is at a frequency below 1 kilohertz such that it enhances a bass response of a speaker within the audio system. 
     
     
       16. A method of outputting sound from an electronic device comprising:
 generating an audible sound output by producing a dynamic force between a first panel and a second panel of an enclosure of an electronic device, wherein producing the dynamic force comprises applying an electrical audio signal to an electromagnet having a core portion and a coil attached to the first panel so as to create a magnetic circuit which attracts the second panel to the first panel; and 
 magnetically biasing the magnetic circuit so that 1) the dynamic force is proportional to the electrical audio signal and 2) the audible sound output enhances a bass response of the electronic device. 
 
     
     
       17. The method of  claim 16  wherein the magnetic circuit is biased by a permanent magnet positioned within the magnetic circuit so as to increase a magnetic force between the electromagnet and the second panel. 
     
     
       18. The method of  claim 16  wherein the magnetic circuit is biased using a direct current. 
     
     
       19. The method of  claim 16  wherein biasing the magnetic circuit modifies a rectification of the electrical audio signal so that the sound can be recreated from the electrical audio signal without distortion. 
     
     
       20. The method of  claim 16  further comprising:
 an attractor plate attached to a side of the second panel facing the electromagnet such that the attractor plate is within the magnetic circuit and an attractive force between the attractor plate and the electromagnet pulls the second panel toward the first panel.

Description:
FIELD 
     An embodiment of the invention is directed to a biased electromagnet for audio electronic devices. Other embodiments are also described and claimed. 
     BACKGROUND 
     In modern consumer electronics, audio capability is playing an increasingly larger role as improvements in digital audio signal processing and audio content delivery continue to happen. There is a range of consumer electronics devices that are not dedicated or specialized audio playback devices, yet can benefit from improved audio performance. For instance, portable computing devices such as laptops, notebooks, and tablet computers are ubiquitous, as are portable communications devices such as smart phones. These devices, however, do not have sufficient space to house high fidelity speakers. This is also true to a lesser extent for desktop personal computers and low profile television sets with built-in speakers. 
     Generally, as a speaker decreases in size it is able to move less volume and thus sound quality (or at least loudness) may decrease. This may be especially noticeable for sounds in the lower end of the audio spectrum, e.g., beneath 1 kHz. Furthermore, the available volume within an electronic device shrinks, which in turn provides less air for a speaker to react against and thus limits the audible response. Similarly, the sound level and frequencies able to be produced by a speaker may also decrease as the size of the speaker decreases. Thus, as electronic devices continue to decrease in size, detrimental effects may be experienced for audio produced by the devices. 
     SUMMARY 
     An embodiment of the invention is an electronic device including an enclosure having a top panel and a bottom panel. An electromagnet is mounted within the enclosure, the electromagnet includes a core portion attached to the top panel and a coil connected to the core portion. An attractor plate may be attached to the bottom panel. The attractor plate forms part of a magnetic circuit of the electromagnet such that the application of an electrical audio signal to the electromagnet causes the bottom panel to move and produce a sound. A permanent magnet is also attached to the core portion, the permanent magnet is configured to create a bias in the magnetic circuit so as to modify a distortion in the sound. 
     Another embodiment is directed to an electronic audio system including an enclosure having a first panel operably connected to a second panel. A transducer is mounted within the enclosure. The transducer includes an electromagnet having a core portion operably connected to the first panel and a coil operably connected to the core portion. The transducer further includes an attractor plate operably connected to the second panel, the attractor plate forms part of a magnetic circuit of the electromagnet such that an electrical audio signal input to the electromagnet creates a dynamic force between the first panel and the second panel so as to generate a sound. The transducer further includes a permanent magnet operably connected to the core portion, the permanent magnet is configured to create a biased force between the attractor plate and the electromagnet so as to modify a distortion in the sound. The electronic audio system further includes a memory to store an operating system program and a processor coupled to the memory to execute the operating system program. 
     In another embodiment, a method of outputting sound from an electronic device is disclosed. The method includes generating a sound by producing a dynamic force between a first panel and a second panel of an enclosure of an electronic device. Producing the dynamic force may include applying an electrical audio signal to an electromagnet associated with the first panel so as to create a magnetic circuit which attracts the second panel to the first panel. The method further including biasing the magnetic circuit so as to modify a distortion in the sound. 
     The above summary does not include an exhaustive list of all aspects of the present invention. It is contemplated that the invention includes all systems and methods that can be practiced from all suitable combinations of the various aspects summarized above, as well as those disclosed in the Detailed Description below and particularly pointed out in the claims filed with the application. Such combinations have particular advantages not specifically recited in the above summary. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments are illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and they mean at least one. 
         FIG. 1A  is a cross-sectional side view of one embodiment of a magnetically biased electromagnet. 
         FIG. 1B  is a bottom perspective exploded view of the magnetically biased electromagnet of  FIG. 1A . 
         FIG. 2A  is one embodiment of an audio signal waveform. 
         FIG. 2B  is one embodiment of a rectified audio signal waveform. 
         FIG. 2C  is one embodiment of a biased audio signal waveform associated with a sound produced by an electronic device within which a magnetically biased electromagnet is implemented. 
         FIG. 3  is a cross-sectional side view of another embodiment of a magnetically biased electromagnet. 
         FIG. 4  is a cross-sectional side view of another embodiment of a magnetically biased electromagnet. 
         FIG. 5  is a cross-sectional side view of another embodiment of a magnetically biased electromagnet. 
         FIG. 6A  is a perspective view of one embodiment of an electronic device within which the magnetically biased electromagnet may be implemented. 
         FIG. 6B  is a block diagram of certain embodiments of the electronic device illustrated in  FIG. 6A . 
         FIG. 7  is an exploded view of a bottom enclosure of the electronic device. 
         FIG. 8  is a perspective view of another embodiment of an electronic device within which the magnetically biased electromagnet may be implemented. 
     
    
    
     DETAILED DESCRIPTION 
     In this section we shall explain several preferred embodiments of this invention with reference to the appended drawings. Whenever the shapes, relative positions and other aspects of the parts described in the embodiments are not clearly defined, the scope of the invention is not limited only to the parts shown, which are meant merely for the purpose of illustration. Also, while numerous details are set forth, it is understood that some embodiments of the invention may be practiced without these details. In other instances, well-known structures and techniques have not been shown in detail so as not to obscure the understanding of this description. 
       FIG. 1A  illustrates a cross-sectional side view of one embodiment of a magnetically biased electromagnet.  FIG. 1B  illustrates an exploded perspective view of the electromagnet of  FIG. 1A . Electromagnet  100  may act as a transducer that can be used to produce a dynamic force between two or more components in order to generate sound using an applied electrical current. In one embodiment, the components may be opposing panels of an enclosure for an electronic audio device, for example, a top panel  106  and a bottom panel  108 . Top panel  106  and bottom panel  108  may be connected by sidewalls such that they can contain components of the audio device, for example, a keyboard housing of a laptop computer. 
     Electromagnet  100  may drive movement of top panel  106  or bottom panel  108  with respect to the other in order to generate a sound. To do so, in one embodiment, electromagnet  100  may be attached to top panel  106  and an attractor plate  110  may be attached to bottom panel  108 . In this embodiment, electromagnet  100  and attractor plate  110  are separate and independent structures which are separately attached to their associated panels. Attractor plate  110  may be a substantially planar structure such that it does not substantially affect a Z-height of the overall enclosure (e.g. a thickness or vertical height of the enclosure as viewed in  FIG. 1A ). In one embodiment, attractor plate  110  may be made of a ferromagnetic material (e.g., iron) and mounted to a surface of bottom panel  108  which faces electromagnet  100 . A gap  112  may be formed between electromagnet  100  and attractor plate  110  such that they have space to move vertically with respect to one another. Application of an electrical audio signal to electromagnet  100  creates one or more of magnetic circuits  114 A and  114 B between electromagnet  100  and attractor plate  110 . Magnetic circuits  114 A and  114 B create an attractive dynamic force between electromagnet  100  and attractor plate  110  as illustrated by arrows  116  and  118 . In one embodiment, top panel  106  is a substantially stationary structure and bottom panel  108  is moveable. In this aspect, the attractive force pulls attractor plate  110  toward electromagnet  100  and in turn pulls bottom panel  108  toward top panel  106 . In some cases, the entire bottom panel  108  moves, while in others a portion of the bottom panel  108  attached to attractor plate  110  bows out toward electromagnet  100 . Electromagnet  100  may be used to move the bottom panel  108  toward and away from electromagnet  100  such that bottom panel  108  serves essentially as a diaphragm which can be used to generate a sound to enhance an acoustic performance of the associated electronic device. 
     It should be understood, however, that although electromagnet  100  is described as being attached to a stationary top panel  106  while attractor plate  110  is attached to a movable bottom panel  108 , other configurations are possible depending upon which of the associated components are to be moved. For example, in some embodiments, top panel  106  may be movable while bottom panel  108  is stationary such that the electromagnet  100  and attractor plate  110  move top panel  106  while bottom panel  108  remains stationary. In another example, electromagnet  100  may be attached to a movable panel (panel  108 ) while attractor plate  110  is attached to a stationary panel (panel  106 ) such that the panel attached to electromagnet  100  moves while the panel attached to attractor plate  110  remains stationary. Also, although the terms “top panel” and “bottom panel” are used herein, it does not necessarily mean that one panel is on top of the other, and in some cases the bottom panel may form a top or side of the enclosure or the top panel may form a bottom or side of the enclosure, for example, where the electronic device is flipped over or flipped on its side. In addition, although electromagnet  100  and attractor plate  110  are described as being attached to top panel  106  and bottom panel  108 , respectively, they may be attached to any type of component or structure where movement of one with respect to the other is desired. 
     It should further be understood that an advantage of using electromagnet  100  and attractor plate  110  to produce a dynamic force between top panel  106  and bottom panel  108 , as compared to a typical moving coil design, is that the electromagnet  100  sits on one component (top panel  106  in this case) and only a passive attractor plate  110  sits on the other component (bottom panel  108  in this case). This allows the transducer to be tolerant of relative positioning (e.g. horizontal positioning) of one component with respect to the other. This is in contrast to a moving coil configuration in which the magnet and the coil are attached to separate components and therefore have to be accurately aligned in both the horizontal and vertical directions. 
     Referring in more detail to electromagnet  100 , electromagnet  100  includes a core portion  102  and associated coil  120 . Coil  120  may be made of an electrically conductive material such that transmission of an electrical current through coil  120  creates a magnetic field which can be concentrated within core portion  102 . In one embodiment, the core portion  102  may include a base portion  122  which is a substantially planar member which is mounted within the enclosure, on or near top panel  106 . A coil support arm  124  and side arms  126  and  128  extend from base portion  122  in a direction of bottom panel  108 . Side arms  126  and  128  are spaced a distance from opposing sides of coil support arm  124  such that coil  120  can be positioned around coil support arm  124 . Although three arms are shown extending from base portion  122 , it is contemplated that core portion  102  may include any number of arms sufficient to support the associated coil and allow for attachment of a component such as top panel  106 . In some embodiments, core portion  102  and the associated coil  120  are attached directly to top panel  106 , such as by a bolt, screw or the like through base portion  122 , while in other embodiments, a bracket assembly may be used to attach core portion  102  and the associated coil  120  to top panel  106 . Core portion  102  may be one integrally formed structure made of any material suitable for forming an electromagnet core (e.g., a ferromagnetic material such as iron). 
     In some embodiments, permanent magnets  104 A and  104 B are attached to the ends of side arms  126  and  128 , respectively, facing attractor plate  110 . In one embodiment, side arms  126  and  128  may have a length which is less than coil support arm  124  so as not to increase an overall height of electromagnet  100  when permanent magnets  104 A and  104 B are attached thereto. Such a configuration also helps to maintain the spacing of gap  112  between electromagnet  100  and attractor plate  110 . Permanent magnets  104 A and  104 B are used to create a bias force between attractor plate  110  and electromagnet  100 . This bias force is important to the acoustic performance of the device because it allows the sound created by movement of the bottom panel  108  to be accurately recreated from the dynamic input electrical audio signal without distortion. In particular, as previously discussed, electromagnet  100  creates an attractive force with attractor plate  110 . Since only attractive forces are possible, the input electrical audio signal is rectified and therefore any corresponding dynamic force produced by the audio signal is not proportional to the audio signal (i.e. any audio signal current below zero is output as a positive dynamic force). This, in turn, results in a distorted sound output. 
     The concepts of a bias force and rectification of the audio signal may be better understood in reference to  FIG. 2A ,  FIG. 2B  and  FIG. 2C . In particular,  FIG. 2A  illustrates an undistorted audio signal waveform  202  in which the Y-axis represents the current (Amps) and the X-axis represents time. It can be seen that the current levels change with time and alternate between positive values and negative values. In the absence of the biased force created by permanent magnets  104 A and  104 B, these negative values are output as positive forces (i.e., rectified), thus distorting the sound.  FIG. 2B  illustrates the rectified dynamic force waveform  204 , which corresponds to audio signal waveform  202  when the bias force is not present. The Y-axis represents the force (N) and the X-axis represents time. From waveform  204 , it can be seen that when force (N) is greater than 0, as is the case when only attractive forces are possible, the negative portions of audio signal waveform  202  illustrated in  FIG. 2A  are rectified as shown in  FIG. 2B  and thus the audio signal  202  is distorted.  FIG. 2C  illustrates the audio signal of  FIG. 2A  when the biased force is created between attractor plate  110  and electromagnet  100  by permanent magnets  104 A and  104 B. The biased force  208 , in this case approximately 1.5N, biases the signal waveform  206  in a positive direction so that the entire audio signal waveform  202  of  FIG. 2A  is above zero and can therefore be recreated as a dynamic force without the distortion. In other words, as a result of the biased force  208 , the dynamic force produced by the electromagnet is proportional to the dynamic input audio signal. Although a bias force of approximately 1.5N is illustrated, it is to be understood that any bias force necessary to reduce the distortions may be used. For example, the bias force may be from about 0.5N to about 2.5N, for example, from about 1N to about 1.5N. 
     With the foregoing in mind, the manner in which permanent magnets  104 A and  104 B create the biased force and allow for the sound created by bottom panel  108  to be recreated from the dynamic audio signal without distortion will now be described in more detail. Representatively, referring back to  FIG. 1A , when an electrical audio signal is applied to coil  120  of electromagnet  100  in a direction of arrow  130 , magnetic circuits  114 A and  114 B are created. Magnetic circuits  114 A and  114 B create an attractive force between electromagnet  100  and attractor plate  110 . This attractive force pulls attractor plate  110 , and the associated bottom panel  108 , toward electromagnet  100 . Permanent magnets  104 A and  104 B are positioned within magnetic circuits  114 A and  114 B, respectively, such that sometimes the magnetic circuits created by coil  120  are with (i.e., add to) the magnetic force created by permanent magnets  104 A and  104 B and sometimes they are against (i.e., subtract from) the magnetic force of permanent magnets  104 A and  104 B. When magnetic circuits  114 A and  114 B are with the magnetic force, the bottom panel  108  is pulled closer to the electromagnet  100 , i.e., panel  108  moves or bows in a direction of electromagnet  100 . When the circuits  114 A and  114 B are against the magnetic force, the bottom panel  108  is pulled less close to the electromagnet  100 , i.e., panel  108  returns to the resting, non-bowed or less bowed configuration. In either case, there is always a biased force between attractor plate  110  and electromagnet  100  due to permanent magnets  104 A and  104 B such that the dynamic force, which drives movement of panel  108 , is proportional to the input electrical audio signal (as illustrated by  FIG. 2C ) and therefore the resulting sound can be recreated without distortion. 
     It is noted that the distance the attractor plate  110 , and in turn bottom panel  108 , travel to or from electromagnet  100  may be varied by varying the electrical charge to which coil  120  is subjected. In this manner, attractor plate  110  may be driven by electromagnet  100  in precise motions depending upon the strength and duration of the electrical current applied to the coil. The motion of the corresponding panel, in this case bottom panel  108 , produces audible sound waves which can enhance an acoustic response of the overall audio device. Thus the attractor plate  110  in combination with electromagnet  100  essentially serves as a transducer in which bottom panel  108  operates similar to the diaphragm found in the conventional audio transducer. 
     In some embodiments, bottom panel  108  may produce audible low frequency sound waves (e.g., sound waves of below 1 kilohertz frequency) as well as other audio frequency sounds. Bottom panel  108  may have a greater surface area than a diaphragm of a typical speaker that may be contained within the electronic device, as such, it may move more air and thus produce more (and possibly clearer) audio. That is, because the bottom panel  108  may have a larger surface area than other speakers installed within the electronic device, the sound produced by causing the bottom panel  108  to move may be louder than traditional speakers. Also, because the electromagnet  100  utilizes the whole enclosure to move most of the air, the actual size of the transducer assembly (i.e., electromagnet  100  and attractor plate  110 ) may be quite small in comparison to a traditional speaker capable of outputting the same volume of audio. This is beneficial due to the limited space within typical electronic device enclosures. Thus, the transducer assembly may save space, while producing a loud sound often not achievable by ordinary speakers within the space constrains of the enclosure(s). 
     Returning now to the configuration of permanent magnets, in one embodiment, permanent magnets  104 A and  104 B may be attached (e.g., chemically attached, welded, screwed, or the like) to an end of side arms  126  and  128 , respectively, such that they face attractor plate  110  and are within the magnetic circuit created by electromagnet  100 . Permanent magnets  104 A and  104 B may be positioned such that their poles face the same direction. In other words, both permanent magnets  104 A and  104 B are oriented so that their South poles face attractor plate  110  or so that their North poles face attractor plate  110 . Permanent magnets  104 A and  104 B may extend along the entire length of side arms  126  and  128  as illustrated by the exploded view of  FIG. 1B . In other embodiments, one or more of permanent magnets  104 A and  104 B may extend along only a portion of the length of side arms  126  and  128 . Permanent magnets  104 A and  104 B may be made of any material suitable for forming permanent magnets having the desired biasing force, for example, a hard ferromagnetic material such as alnico or ferrite. 
       FIG. 3  illustrates a cross-sectional side view of another embodiment of a magnetically biased electromagnet. Each of the aspects of electromagnet  100 , attractor plate  110  and permanent magnets  104 A,  104 B illustrated in this view are substantially the same as those discussed in reference to  FIG. 1A . In addition the previously discussed aspects, resilient spacers  302 A,  302 B and  302 C are provided within gap  112  between electromagnet  100  and attractor plate  110 . Resilient spacers  302 A- 302 C may allow for more accurate vertical alignment of electromagnet  100  with respect to attractor plate  110  as well as allow some relative misalignment in the horizontal direction. In addition, resilient spacers  302 A- 302 C may create a push force between electromagnet  100  and attractor plate  110 . As previously discussed, the force created between electromagnet  100  and attractor plate  110  is only an attractive or pull force. Resilient spacers  302 A- 302 C may therefore add a push force which helps with movement of attractor plate  110  and the associated panel  108  with respect to electromagnet  100 . In this aspect, resilient spacers  302 A- 302 C may be dimensioned to fit within the gap  112  provided between electromagnet  100  and attractor plate  110  so that a relatively consistent vertical spacing range may be maintained between electromagnet  100  and attractor plate  110 . In one embodiment, resilient spacers  302 A- 302 C may be dimensioned so that they are always slightly compressed between electromagnet  100  and attractor plate  110  and more compressed when an electrical current  130  is applied to electromagnet  100 . In other words, when the electromagnet  100  and attractor plate  110  are in a rest position (e.g., applied electrical current is zero), resilient spacers  302 A- 302 C are slightly compressed such that they apply a push force which wants to push attractor plate  110  away from electromagnet  100 . In an actuated position (e.g., electrical current is greater than zero), resilient spacers  302 A- 302 C are compressed even further as attractor plate  110  is pulled toward electromagnet  100  by the magnetic circuits  114 A,  114 B. 
     Resilient spacers  302 A- 302 C may be attached to the ends of, and run along an entire length of, each of side arms  126 ,  128  and coil support arm  124 . Alternatively, resilient spacers  302 A- 302 C may run along only a portion of the arms, or be attached to less than each of side arms  126 ,  128  and coil support arm  124  as illustrated. Still further, it is contemplated that one or more of resilient spacers  302 A- 302 C may be omitted such that they are attached to less than each of each of side arms  126 ,  128  and coil support arm  124 . 
     Resilient spacers  302 A- 302 C may be made of any resilient structure or material suitable for maintaining a vertical alignment and/or enhancing movement between electromagnet  100  and attractor plate  110 . For example, one or more of resilient spacers  302 A- 302 C could be made of a block of resilient or elastic material such as a rubber or foam material. Alternatively, resilient spacers  302 A- 302 C could be made of a spring or other resilient structure. In some embodiments, resilient spacers  302 A- 302 C may contain a ferromagnetic material such that they help to improve an efficiency of the magnetic circuit. Representatively, resilient spacers  302 A- 302 C may be made entirely of a ferromagnetic material (e.g., an iron spring) or they may be made of a composite of a resilient material such as a rubber or elastic material which is embedded with or otherwise contains a ferromagnetic material (e.g., filings) in an amount sufficient to improve the efficiency of the magnetic circuit. 
       FIG. 4  illustrates a cross-sectional side view of another embodiment of a magnetically biased electromagnet. Each of the aspects of electromagnet  100  and attractor plate  110  are substantially the same as those discussed in reference to  FIG. 1A  except that in this embodiment, permanent magnets  404 A and  404 B are attached (e.g., welded, bolted or the like) along the side walls of side arms  126  and  128 , respectively, of core portion  102 . In this aspect, magnetic circuits  414 A and  414 B are created which extend outside of side arms  126  and  128  and through permanent magnets  404 A and  404 B. Permanent magnets  404 A and  404 B may extend along the entire length of side arms  126  and  128  or only a portion of the side arms. In any case, permanent magnets  404 A and  404 B may have any shape or dimensions sufficient to bias magnetic circuits  414 A and  414 B and modify a distortion in the audio signal as in the manner previously discussed. 
       FIG. 5  illustrates a cross-sectional side view of another embodiment of a magnetically biased electromagnet. Each of the aspects of electromagnet  100  and attractor plate  110  are substantially the same as those discussed in reference to  FIG. 1A  except that in this embodiment, permanent magnet  504  is attached (e.g., welded, bolted or the like) to an end of coil support arm  124  facing attractor plate  110 . Permanent magnet  504  may extend along an entire length of coil support arm  124  or only a portion of coil support arm  124 . In this aspect, magnetic circuits  514 A and  514 B are created which extend along side arms  126  and  128  and through permanent magnet  504  as shown. Permanent magnet  504  may have any shape or dimensions sufficient to bias magnetic circuits  514 A and  514 B and modify an acoustic distortion in the manner previously discussed. 
     It is to be understood that although the previously discussed permanent magnets are shown at specific locations along electromagnet  100 , it is contemplated that the permanent magnets may be positioned at any location within the magnetic circuit created by electromagnet  100 . Moreover, a single permanent magnet may be positioned within the magnetic circuit or more than one permanent magnet may be positioned within the magnetic circuit, for example, three permanent magnets may be positioned within the magnetic circuit, e.g., one at each end of arms  124 ,  126  and  128 . Moreover, although core portion  102  of electromagnet  100  is shown having three arms  124 ,  126  and  128 , any number of arms sufficient to create a magnetic circuit between electromagnet  100  and attractor plate  120  may be provided. For example, more or fewer than three arms may extend from base portion  122 . Representatively, in one embodiment, two arms may extend from base portion  122  and coil  120  positioned around one of the arms or the base portion between the arms. In another embodiment, the arms may be omitted and coil  120  may be positioned around the base portion  122 . 
     In addition, it is contemplated that in some embodiments attractor plate  110  may be omitted and instead, the enclosure opposite the electromagnet  100  and coil  120 , which is used to generate the sound (e.g., bottom panel  108 ), may be made of a material similar to attractor plate  110  (e.g., a ferromagnetic material). In this aspect, the attractive force created by electromagnet  100  pulls the enclosure panel toward electromagnet  100  in the absence of attractor plate  110 . 
     In another embodiment, the bias force between electromagnet  100  and attractor plate  110  may be created by using a direct current (DC) (i.e., bias current) to create the bias instead of permanent magnets and the permanent magnets may be omitted. Representatively, the audio signal may be tracked and the bias signal varied slowly over time such that only a sufficient bias is used in a given section of the audio signal (e.g., a desired section of a song) to stop the force from dropping to zero resulting in signal rectification. 
       FIG. 6A  illustrates a perspective view of one embodiment of an electronic device in which the biased electromagnet described herein may be implemented.  FIG. 6B  illustrates a block diagram of one embodiment of the electronic device of  FIG. 6A . Electronic device  600  may include a top enclosure  614  and a bottom enclosure  612 . The enclosures  612 ,  614  generally surround or enclose the internal components of the electronic device  600 , although apertures and the like may be formed into one or both of the enclosures. The electronic device  600  may include a keyboard  618 , a display screen  616 , a speaker  620 , and optional feet  622 . Also, the electronic device  600  generally includes an audio transducer assembly  626  (i.e., magnetically biased electromagnet and attractor plate), as shown in  FIG. 7 , encased within or affixed to one or both of the enclosures  612 ,  614 . 
     Electronic device  600  may be capable of storing and/or processing signals such as those used to produce images and/or sound. In some embodiments, electronic device  600  may be a laptop computer, a handheld electronic device, a mobile telephone, a tablet electronic device, an audio playback device, such as an MP3 player, and the like. A keyboard  618  and mouse (or touch pad)  650  may be coupled to the electronic device  600  via a system bus  640  (see  FIG. 6B ). Additionally, in some embodiments, the keyboard  618  and the mouse  650  may be integrated into one of the enclosures  612 ,  614  as shown in  FIG. 6A . In other embodiments the keyboard  618  and mouse  650  may be external to the electronic device  600 . 
     The keyboard  618  and the mouse  650 , in one example, may provide user input to the electronic device  600 ; this user input may be communicated to a processor  638  through suitable communications interfaces, buses and the like. Other suitable input devices may be used in addition to, or in place of, the mouse  650  and the keyboard  618 . For example, in some embodiments the electronic device  600  may be a smart phone, tablet computer or the like and include a touch screen (e.g., a capacitive screen) in addition to or in replace of either the keyboard  618 , the mouse  650  or both. An input/output unit  636  (I/O) coupled to the system bus  640  represents such I/O elements as a printer, stylus, audio/video I/O, and so on. For example, external speakers may be electrically coupled to the electronic device  600  via an input/outlet connection (not shown). 
     The electronic device  600  may also include a video memory  642 , a main memory  644  and a mass storage  648 , all coupled to the system bus  640  along with the keyboard  618 , the mouse  650  and the processor  638 . In some embodiments, main memory  644  may store an operating system program, which may include instructions for operating electronic device  600 . Processor  638  may be configured to execute the operating system program. Processor  638  may be any suitable microprocessor or microcomputer. The mass storage  648  may include both fixed and removable media, such as magnetic, optical or magnetic optical storage systems and any other available mass storage technology. The system bus  640  may contain, for example, address lines for addressing the video memory  642  or the main memory  644 . 
     The system bus  640  also may include a data bus for transferring data between and among the components, such as the processor  638 , the main memory  644 , the video memory  642  and the mass storage  648 . The video memory  642  may be, for example, a dual-ported video random access memory or any other suitable memory. One port of the video memory  642 , in one example, is coupled to a video amplifier  634  which is used to drive a display screen  616 . The display screen  616  may be any type of screen suitable for displaying graphic images, such as a liquid crystal display, cathode ray tube monitor, flat panel, plasma, or any other suitable data presentation device. Furthermore, in some embodiments the display screen  616  may include touch screen features, for example, the display screen  616  may be capacitive. These embodiments allow a user to enter input into the display screen  16  directly. 
     The electronic device  600  also may include a communication interface  646  coupled to the system bus  640 . The communication interface  646  provides a two-way data communication coupling via a network link. For example, the communication interface  646  may be a satellite link, a local area network (LAN) card, a cable modem, and/or wireless interface. In any such implementation, the communication interface  646  sends and receives electrical, electromagnetic or optical signals that carry digital data streams representing various types of information. 
     Code and/or other information (e.g. an operating system program) received by the electronic device  600  may be executed by the processor  638  as the code is received. Code may likewise be stored in the mass storage  648 , or other non-volatile storage for later execution. In this manner, the electronic device  600  may obtain program code in a variety of forms and from a variety of sources. Program code may be embodied in any form of computer program product such as a medium configured to store or transport computer readable code or data, or in which computer readable code or data may be embedded. Examples of computer program products include CD-ROM discs, ROM cards, floppy disks, magnetic tapes, computer hard drives, servers on a network, and solid state memory devices. 
     The electronic device  600  may also include an audio transducer  626 . The audio transducer  626  may be coupled to the system bus  640 , which may in turn electrically connect the audio transducer  626  to any of the processor  638 , main memory  644 , mass storage  648  and the like. The audio transducer  626  is an output device that produces sound waves in response to electrical signals. The audio transducer  626  may be encased within or otherwise affixed to one of the enclosures  612 ,  614  and may be used alone or in combination with other output devices (such as an external speaker) to produce sound. Additionally, the audio transducer assembly  626  may mechanically vibrate other surfaces, such as the enclosures  612 ,  614  and/or a supporting surface on which the device rests, to produce a louder sound. Thus, as the audio transducer  626  responds to the electrical signal it vibrates the enclosure  612 ,  614 , which in turn disturbs air particles and produces sound waves. 
       FIG. 7  will now be described and embodiments discussed with respect thereto.  FIG. 7  illustrates an exploded view of the bottom enclosure  612 , showing certain elements of the aforementioned computer device (although some are omitted for clarity). Although audio transducer  626  is shown installed in bottom enclosure  612 , it may also be installed in the upper enclosure  614 . In certain embodiments, the lower enclosure  612  may include a top panel  728  and a bottom panel  752 . The top panel  728  may form the top surface of the bottom enclosure  612  and, in some embodiments, surround the keyboard  618 , mouse  650 , touch screen (not shown) or other input device, and the like. The bottom panel  752  may form the bottom surface of the bottom enclosure  612  and electronic device  600 . Typically, the top panel  728  forms the top surface of the enclosure and may provide access to the keyboard  618  and/or mouse  650 . In tablet-style devices, there may be a single enclosure defined by the top and bottom panels. 
     The enclosures  612 ,  614  may be constructed out of a variety of materials and, depending on the type electronic device  600 , may be constructed in a variety of different shapes. In some embodiments, the enclosures  612 ,  614  may be constructed out of carbon fiber, aluminum, glass and other similar, relatively stiff materials. The material for the enclosures  612 ,  614  in some embodiments may improve the sound volume and/or quality produced by the audio transducer  626 . This is because in some embodiments the enclosure  612 ,  614  mechanically vibrates due to vibrations produced by the audio transducer  626 , producing sound waves. Thus, the material may be altered to be more responsive to the vibrations and/or more easily move, increasing the sound quality/volume. Additionally, it should be noted that the bottom enclosure  612  and the top enclosure  614  may be constructed out of different materials from each other. Furthermore, in some embodiments the electronic device  600  may only include one of the enclosures  612 ,  614 . For instance, if the electronic device display  616  includes a touch screen or other display device that also accepts input, then the bottom enclosure  612  may be omitted as the keyboard  618  and mouse  650  may be integrated into the top enclosure  614 . 
     The enclosures  612 ,  614  in some embodiments may be water and/or air-tight. This is because the audio transducer  626 , as discussed in more detail below, may not require an air-opening (e.g., a grille or screen) in order for a user to hear sound waves produced by the audio transducer  626 . The audio transducer  626  uses the enclosures  612 ,  614  and/or supporting surface to produce sound waves, as opposed to a diaphragm within a traditional speaker that must be open to the air in order for the sound waves to be heard. Therefore, the enclosures  612 ,  614  and thus the electronic device  600  may be completely sealed from water and/or air. This may permit the electronic device  600  to be waterproof, more versatile, and allows the electronic device  600  to have a refined, smooth outer appearance. However, as the electronic device  600 , may include a combination of an audio transducer  626  and a speaker  620 , in other embodiments the enclosures  612 ,  614  may include a grill/screen. 
     The bottom panel  752  and the top panel  728  may be connected together in a variety of ways. In the embodiment illustrated in  FIG. 7 , the top panel  728  and the bottom panel  752  are attached via fasteners  725 . The fasteners  725  may be inserted in apertures  727  on both panels  728 ,  752 . Additionally, in some embodiments the fasteners  725  may be used to attach the feet  622  to the bottom panel  752 . The top enclosure  614  may be similarly secured to together, including an upper and bottom panel (not shown). In other embodiments, the enclosures  612 ,  614  may be glued together or otherwise secured. In still other embodiments, the top panel  728  and the bottom panel  758  may include a seal disposed between to create a waterproof, air tight connection. The seal helps prevent elements from entering into the inner cavity of the enclosures  612 ,  614  when the panels  728 ,  752  are secured together. 
     The internal elements described above with regard to  FIG. 6B  are represented by the circuit boards  757 ,  759 , which are shown in a representative fashion only. More or fewer circuit boards or other circuitry may be present and the shape of the boards/circuitry may vary from what is shown. The circuit boards  757 ,  759  may include a combination of the elements described above with respect to  FIG. 6B , such as main memory  644 , video memory  642 , mass storage  648 , the processor  638  and the like. The circuit boards  757 ,  759  may be electrically connected to the audio transducer  626  via the system bus  640  or another electrical connection. Furthermore, the circuit boards  757 ,  759  may be secured to the enclosures  612 ,  614  and enclosed inside. 
     The audio transducer  626  may be installed in such a manner that one of the electromagnet  100  and the attractor plate  110  is attached to the top panel  728  while the other is attached to the bottom panel  752 . In some instances, the electromagnet  100  may be operably connected to the top panel  728  while the attractor plate  110  is operably connected to the bottom panel  752 , but in other embodiments the electromagnet  100  may be operably connected to the bottom panel  752  while the attractor plate  110  is operably connected to the top panel  728 . In still other embodiments, the electromagnet  100  may be connected to a circuit boards  757 ,  759 , for instance a motherboard, logic board or the like. Thus, in different embodiments the electromagnet  100  may be connected to either of the panels  728 ,  752  or either of the circuit boards  757 ,  759 . 
     The concepts described here, however, need not be limited to portable audio devices such as laptop computers. For example, as seen in  FIG. 8 , the biased electromagnetic transducer may be implemented within a mobile communications device  800  such as a smart phone. Mobile communications device  800  may include an enclosure  802  defining or closing off a chamber in which the constituent electronic components of the communications device  800  are housed. Enclosure  802  may include a front or top panel  804  and a rear or bottom panel  806 , which are connected by a sidewall portion  808 . The top panel  804  may be considered a display side of the device in that it may include a touch screen display  828  that serves as an input and a display output for the device. The touch screen display  828  may be a touch sensor (e.g., those used in a typical touch screen display such as found in an iPhone® device by Apple Inc.). Although the touch screen is illustrated on top panel  804 , if desired, it may be mounted on the bottom panel  806  of device  800 , on a side wall portion  808  of device  800 , on a flip-up portion of device  800  that is attached to a main body portion of device  800  by a hinge (for example), or using any other suitable mounting arrangement. The bottom panel  806  may form a back side of the device, which can be held by the user during operation of device  800 . 
     To further enable its use as a mobile communications device, device  800  may include various acoustic openings or ports at different locations within enclosure  802  to allow for transmission of acoustic signals to and from device  800 . Representatively, enclosure  802  may have formed therein a speaker acoustic port  810 , a receiver acoustic port  812  and microphone acoustic ports  816 ,  818 ,  820 . Although the acoustic ports are illustrated as separate ports, it is contemplated that any one or more of the illustrated ports may be combined into one port such that, for example, the transducers associated with the illustrated receiver or microphone ports may instead share the same port. In one embodiment, the receiver acoustic port  812  is formed within top panel  804  of enclosure  802  and speaker acoustic port  810  is formed within an end portion of sidewall portion  808 . It is contemplated, however, that each of these ports may be formed in other portions of enclosure  802 , for example, speaker acoustic port  810  may be on the top panel  804  or bottom panel  806  while receiver acoustic port  812  is along the sidewall. Each of these ports may consist of multiple holes clustered together or alternatively a single, large hole as shown. 
     Each of the speaker acoustic port  810 , receiver acoustic port  812  and microphone acoustic ports  816 ,  818  and  820  may be associated with one or more transducers, which are mounted within enclosure  802 . In the case of the microphone acoustic ports  816 ,  818  and  820 , the transducer is an acoustic-to-electric transducer such as a microphone that converts sound into an electrical signal. The microphone may be any type of microphone capable of receiving acoustic energy, for example sound through the associated port, and converting it into an electrical signal. For example, in one embodiment, the microphone may be a micro-electro-mechanical systems (MEMS) microphone, also referred to as a microphone chip or silicon microphone. In this aspect, various features of the microphone such as the pressure-sensitive diaphragm, are etched directly into a silicon chip by MEMS techniques. 
     Camera  822  may further be mounted to enclosure  802  to capture still and/or video images of objects of interest. Enclosure  802  may further include other input-output devices such as an earphone port (not shown) to receive an earphone plug, docking port  814  and command button  826 . Docking port  814  may sometimes be referred to as a dock connector,  30 -pin data port connector, input-output port, or bus connector, and may be used as an input-output port (e.g., when connecting device  800  to a mating dock connected to a computer or other electronic device). Command button  826  may be, for example, a menu button or any other device that can be used to supply an input to and/or operate device  800 . 
     A transducer having a magnetically biased electromagnet as previously discussed in reference to  FIG. 1A  to  FIG. 5 , may be implemented within communications device  800 , for example, by operably connecting the electromagnet  100  and associated coil  120  to the top panel  804  and operably connecting the attractor plate  110  to the bottom panel  806 . In this aspect, during operation, the transducer may produce a dynamic force between top panel  804  and bottom panel  806  such that the bottom panel  806  acts as a diaphragm and vibrates thereby generating sound waves which can be emitted to the user to enhance an audio performance of device  800 . 
     While certain embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that the invention is not limited to the specific constructions and arrangements shown and described, since various other modifications may occur to those of ordinary skill in the art. For example, although the transducer assembly (e.g., electromagnet  100  (including coil  120 ) and attractor plate  110 ) is described as serving essentially as a “subwoofer,” which enhances a performance of existing speakers within the electronic device, the assembly may operate in such a manner that it provides a near full-range response frequency. For example the transducer assembly may output both low and mid-range frequencies. In such embodiments, the transducer assembly may output not only bass range frequencies (e.g., about 20-500 Hz), but also mid-frequencies (e.g., about 500-1500 Hz or higher). The transducer assembly may therefore be combined with other speakers in an electronic device such as a laptop, tablet or handheld computing device, or used instead of other speakers, to enhance or produce sound which can be output from the electronic device to a user without distortion. 
     Although embodiments described herein have generally been discussed with respect to standalone electronic devices (many of which may be portable), it should be appreciated that the embodiments disclosed herein may be applied in a variety of other fashions. For example, the audio transducer described herein may be integrated into conventional speakers and operate with the woofers and tweeters of the conventional speaker. Likewise, an audio transducer of the type disclosed herein may be incorporated into a seat or chair as part of a home theater experience. The audio transducer may vibrate not only the chair but the person sitting in the chair under certain circumstances, thereby providing not only audible but also tactile feedback if desired. As still another example, the audio transducer may be combined with a capacitive or touch-based input so that motions of a user&#39;s hands on a device enclosure may act to increase or decrease the output of the audio transducer. The description is thus to be regarded as illustrative instead of limiting.

Metadata:
Filing Date: 20121231
Publication Date: 20150127
Grant Date: 20150127
Priority Date: 20121231
Inventors: WILK CHRISTOPHER R.
JOHNSON MARTIN E.
KESSLER PATRICK
JOHANNINGSMEIER NATHAN A.
Assignee: APPLE INC
CPC Classifications: [{"code": "H04R9/025", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04R9/025", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04R9/025", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04R2499/11", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R2499/11", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 51017252