Abstract:
A method and system for providing a moving-screen sound system for a portable communication device such as a cell phone employs a fixed, pivoted, or hinged display screen driven directly or indirectly by an audio actuator. While the frequency response of the screen may have defects that would negatively impact overall sound quality from the device, in embodiments a supplemental audio transducer is placed adjacent the screen or elsewhere on the device so as to supplement or correct the frequency response of the screen. In an embodiment, the supplemental audio transducer is driven to correct a notch or other defect in the screen response. In another embodiment, the supplemental audio transducer is driven to extend the bass response of the screen.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure is generally related to audio reproduction for mobile computing devices and, more particularly, to providing a moving-screen audio transducer while allowing enhanced clarity and frequency response of the audio system. 
       BACKGROUND 
       [0002]    Most mobile device users are aware that sophisticated hardware and software are used to drive their device display. However, far fewer users may realize that providing audio on such a device also raises daunting challenges. For users that employ earphones or headphones when listening to their device, the transduction of audio data into sound is left to the earphone or headphone manufacturer. However, for audio that needs to be projected directly from the device itself, e.g., during a hands-free call, the phone itself must be equipped for the transduction of audio data into sound. 
         [0003]    Traditionally, mobile devices have employed simple speaker technology. However, the continuing decrease in device size and weight have lead to an alternative speaker technique, namely, the use of the device display glass itself as a speaker membrane or surface. While this may be referred to as a moving-screen technology, it might more accurately be considered a vibrating-screen technology; these terms may be used interchangeably herein. 
         [0004]    In the moving-screen technique, the glass display acts as a transducer for an audio signal. This provides certain benefits, e.g., the user can place his ear essentially anywhere, during a hands-free or ordinary call, and still hear the conversation. However, there are also substantial drawbacks: Glass displays are designed primarily for visual display and not for audio transduction and thus do not inherently posses the properties required for high quality sound reproduction. 
         [0005]    Thus, for example, a single transducer applied to a display screen tends to have an audio response characterized by acoustic peaks and valleys. In addition, this type of moving-screen technology often results in poor reproduction of low-frequency audio. Moreover, since the display-screen production process is not adapted to test or control audio-response characteristics, there is substantial variation in frequency response from screen to screen. While these shortcomings can manifest themselves in the form of poor audio quality from the user&#39;s standpoint, they may also be severe enough to prevent industry certification or approval of the device. 
         [0006]    It will be appreciated that this Background section represents the observations of the inventors, and these observations are provided simply as a research guide to the reader. As such, nothing in this Background section is intended to represent, or to fully describe, any particular prior art. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0007]    While the appended claims set forth the features of the present techniques with particularity, these techniques, together with their objects and advantages, may be best understood from the following detailed description taken in conjunction with the accompanying drawings of which: 
           [0008]      FIG. 1  is a schematic diagram of a mobile computing device such as a smart phone, cell phone, etc., within which embodiments of the disclosed principles may be implemented; 
           [0009]      FIG. 2  is a perspective front view of a mobile computing device such as that shown in  FIG. 1 ; 
           [0010]      FIG. 3  is a partial cross-sectional view of a device in accordance with an embodiment of the disclosed principles; 
           [0011]      FIG. 4  is a frequency-response plot of a first audio transducer usable within an embodiment of the disclosed principles; 
           [0012]      FIG. 5  is a frequency-response plot of a second audio transducer usable within an embodiment of the disclosed principles; and 
           [0013]      FIG. 6  is a frequency-response plot showing a frequency-response plot of the first audio transducer, a modified frequency response of the second audio transducer, and a combined frequency response in keeping with an embodiment of the disclosed principles. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    Before providing a detailed discussion of the figures, a brief overview is given to guide the reader. In an embodiment, an audio-transducer system includes a first transducer formed with the display glass of a device and a second dynamic audio transducer near the top of the device. The second transducer supplements the sound output of the device while also compensating for frequency anomalies of the glass structure. Not only does this system provide an improved user experience, but it also allows the device to achieve adequate frequency response for Type Approval. In an embodiment, the second dynamic audio transducer is equalized so that the sum of its response and the glass&#39;s response meet the required mask. 
         [0015]    In an embodiment, the display movement near the perimeter is limited. In a further embodiment, the dynamic audio transducer is used to fill in notches in the glass response or to extend the bass response. 
         [0016]    Turning now to a more detailed discussion in conjunction with the attached figures, techniques of the present disclosure are illustrated as being implemented in a suitable environment. The following description is based on embodiments of the disclosed principles and should not be taken as limiting the claims with regard to alternative embodiments that are not explicitly described herein. 
         [0017]    The schematic diagram of  FIG. 1  shows an exemplary device within which aspects of the present disclosure may be implemented. In particular, the schematic diagram illustrates a user device  110  including several exemplary components. It will be appreciated that additional or alternative components may be used in a given implementation depending upon user preference, cost, and other considerations. 
         [0018]    In the illustrated embodiment, the components of the user device  110  include a display screen  120  having associated therewith a display-screen audio actuator  125 . These elements are discussed in greater detail later with reference to other figures. A dynamic audio transducer  130  is also included in the illustrated embodiment. The user device  110  further incorporates a processor  140 , a memory  150 , one or more audio drivers  160 , and one or more input components  170 . 
         [0019]    The processor  140  can be any of a microprocessor, microcomputer, application-specific integrated circuit, or the like. For example, the processor  140  can be implemented by one or more microprocessors or controllers from any desired family or manufacturer. Similarly, the memory  150  may reside on the same integrated circuit as the processor  140 . Additionally or alternatively, the memory  150  may be accessed via a network, e.g., via cloud-based storage. The memory  150  may include a random-access memory. Additionally or alternatively, the memory  150  may include a read-only memory (i.e., a hard drive, flash memory, or any other desired type of memory device). 
         [0020]    The information that is stored by the memory  150  can include code associated with one or more operating systems or applications as well as informational data, e.g., program parameters, process data, etc. The operating system and applications are typically implemented via executable instructions stored in a non-transitory computer- readable medium (e.g., memory  150 ) to control basic functions of the electronic device  110 . Such functions may include, for example, interaction among various internal components and storage and retrieval of applications and data to and from the memory  150 . 
         [0021]    The device  110  may also include a component interface  180  to provide a direct connection to auxiliary components or accessories and a power supply  190 , such as a battery, for providing power to the device components. In an embodiment, all or some of the internal components communicate with one another by way of one or more internal communication links  195 , such as an internal bus. 
         [0022]    Further with respect to the applications, these typically utilize the operating system to provide more specific functionality, such as file-system service and handling of protected and unprotected data stored in the memory  150 . Although many applications may govern standard or required functionality of the user device  110 , in many cases applications govern optional or specialized functionality, which can be provided, in some cases, by third-party vendors unrelated to the device manufacturer. 
         [0023]    Finally, with respect to informational data, e.g., program parameters and process data, this non-executable information can be referenced, manipulated, or written by the operating system or an application. Such informational data can include, for example, data that are preprogrammed into the device  110  during manufacture, data that are created by the device  110 , or any of a variety of types of information uploaded to, downloaded from, or otherwise accessed at servers or other devices with which the device  110  is in communication during its ongoing operation. 
         [0024]    In an embodiment, the device  110  is programmed such that the processor  140  and memory  150  interact with the other components of the device  110  to perform a variety of functions. The processor  140  may include or implement various modules and execute programs for initiating different activities such as launching an application, transferring data, and toggling through various graphical user-interface objects (e.g., toggling through various icons that are linked to executable applications). 
         [0025]      FIG. 2  presents a simplified perspective illustration of an example user device  200  within which embodiments of the disclosed principles may be implemented. As shown, the user device  200  generally includes a body or case  201  that allows a user to hold and handle the device  200 . In addition, the case  201  serves to protect the internal components of the device  200  and to provide an anchor for external interface ports and components such as headphone jacks and hardware buttons  202 ,  203 ,  204 . 
         [0026]    The illustrated device also includes a display screen  205 , which is a touch screen in an embodiment. Although not visible in  FIG. 2 , the display screen  205  is movable, e.g., via its inherent flexibility or through a hinged or other movable attachment to the case  201 . An audio actuator, also not visible in  FIG. 2 , is linked to an underside of the display screen  205 . The audio actuator may be affixed directly to the underside of the display screen  205  or may be attached to a link or lever that is itself attached to or otherwise in contact with the display screen  205 . 
         [0027]    As shown in  FIG. 2 , the illustrated device  200  also includes a speaker outlet  206 . The speaker outlet  206  provides a port usable by a sound source (not visible in  FIG. 2 ) to project sound out of the device  200 . The sound source may include one or more individual sources and may employ a dynamic speaker or another type of sound source. 
         [0028]    Within the context of a device such as that described with reference to  FIGS. 1 and 2 , or a similar device having a display as well as audio capabilities,  FIG. 3  illustrates in greater detail a simplified schematic of an audio transduction system in accordance with the disclosed principles. In particular,  FIG. 3  shows a simplified schematic illustration of an exemplary audio system of such a device. 
         [0029]    In the illustrated embodiment, the audio system  300  includes an audio decoding or decompression module  301 . The decoding or decompression module  301  provides a digital input  302  to an audio-driver module  303  which creates one or more driving signals  304 ,  305 . While the driving signals  304 ,  305  are shown in  FIG. 3  as one-way signals, it will be appreciated by those of skill in the art that the audio-driver module  303  may be capable of monitoring impedance to further adjust its output. The driving signals  304 ,  305  drive a plurality of audio transducers  306 ,  307  respectively. 
         [0030]    In an embodiment, the first audio transducer  306  comprises a moving-screen transducer comprising an actuator  308  and a screen  205 , which may be the display screen of the host device. The actuator  308  may be of any suitable type capable of causing a vibration of the screen  205  at human-audible frequencies and suitable amplitudes. Suitable actuators include piezo-electric actuators, electromagnetic actuators, and the like. 
         [0031]    In an embodiment, the driving signals  304 ,  305  convey essentially identical audio data, with the exception of possible differences in the format, amplitude, and frequency envelope of the data. For example, depending upon the actuators used, the first driving signal  304  may be a current signal with an amplitude and envelope configured to drive an electromagnetic actuator  308  affixed to a screen  205 , the system having a response notch in the middle of the audible range. In contrast, the second driving signal  305  may be a voltage signal with an amplitude and envelope configured to drive an isolated piezo actuator having a flat response. Nevertheless, the outputs of the first and second transducers  306 ,  307  may sound essentially the same to the user, with minor differences in overall amplitude and frequency response. It will be appreciated that there is no requirement for any signal to be of any particular type, e.g., voltage or current, and that the foregoing examples are simply given for illustrative purposes. 
         [0032]    In an alternative embodiment, the driving signals  304 ,  305  are identical, and are thus not configured to account for the frequency response of the relevant transducers  306 ,  307 . 
         [0033]    As noted above, the combined frequency response of a screen and its actuator may be inherently poor. For example, this system may have significant notching in its frequency response. Furthermore, the placement of the screen against the user&#39;s cheek during a call may also affect the system&#39;s frequency response, e.g., by damping certain frequencies or frequency ranges. 
         [0034]    To this end, in an embodiment, the second transducer  307  is an electrodynamic speaker, that is, a speaker that uses a driven coil to move a coil or magnet that is connected to a diaphragm (e.g., a speaker cone). The driven coil is selectively energized within a magnetic field to oscillate the speaker cone in a manner that reproduces a sound of interest. The magnetic field may be provided by a permanent magnet or by a field coil. In a further embodiment the electrodynamic speaker is driven in a manner calculated to at least partially offset frequency notches in the response of the screen  205  (acting as part of the audio transducer  306 ). 
         [0035]      FIG. 4  is a simulated response plot  400  showing a possible frequency response of a driven display screen, that is, the system&#39;s response to an excitation wave of constant amplitude that is swept through the relevant frequency range. As can be seen, in the illustrated example the frequency response of the screen is irregular, showing poor bass response  401  and a notch  402  that would affect the user-perceived sound quality. Not shown in  FIG. 4  are additional notches and peaks typically associated with driven displays. These artifacts in the response would also likely be considered sufficient to prevent type of approval of the system. 
         [0036]    Continuing,  FIG. 5  is a simulated response plot  500  showing a possible frequency response of the second transducer  307 , which as noted above may be an electrodynamic speaker. As can be seen in the illustrated example, the response of the second transducer  307  conforms to a standard smooth response curve, with a roll-on region  501  from the low-frequency cut off and a relatively flat midrange response region  502 . 
         [0037]    While the pleasant response of the second transducer  307  may somewhat mask the poor response of the first transducer  306 , the defects in the response of the screen-based first transducer  306  may still be audible. To that end, in an embodiment, the response of the second transducer  307  is artificially modified to offset the defects in the response of the first transducer  306 . 
         [0038]      FIG. 6  shows a set  600  of example plots, including a first plot  601  corresponding to the response of the first transducer  306 , a second plot  602  corresponding to the response of the second transducer  307 , and a third plot  603  corresponding to the combined response of both transducers  306 ,  307 . In the illustrated example, the frequency response  602  of the second transducer  307  has been modified, by selective scaling or other techniques, to offset the response  601  of the first transducer  306 , such that the combined response from the transducers  306 ,  307  is as shown in response  603 . In particular, the combined response  603  is smooth with no significant peaks or notches that would disrupt the user experience. 
         [0039]    In an embodiment, the modification of the response of the second transducer  307  is performed via a mapping executed before the communications device is sold at retail. In a further embodiment, a user may perform an initial or subsequent mapping using an application or function loaded on the device. Depending upon the consistency of response among various screen-based transducers such as transducer  306 , it is also possible for the same response mapping to be applied by the manufacturer on each device that uses the same screen. 
         [0040]    In an embodiment, one or both transducers  306 ,  307  are selectively disabled depending upon the usage mode of the device. For example, during a hands-free call, both transducers  306 ,  307  may be active. However, when the device is held to the user&#39;s ear during a call, the first transducer  306  may be disabled. In addition, the sound volume from the second transducer  307  may be reduced in this situation. 
         [0041]    In an embodiment, the second transducer  307  is equalized so that the sum of its response and the glass&#39;s response meet a specified mask. In another embodiment, the display movement near the perimeter is limited. In yet another embodiment, the second transducer  307  is used to extend the bass response of the device. Although the examples given show the second transducer  307  on the front face of the device near the top, the second transducer  307  may be placed at another location if desired. Further, a third, fourth, or subsequent transducer may also be used without departing from the scope of the disclosed principles. 
         [0042]    It will be appreciated that the disclosed principles allow the use of a screen-based transducer to produce sound with respect to a mobile device, while also allowing the manufacturer to provide acceptable frequency response for the device as a whole. However, in view of the many possible embodiments to which the principles of the present discussion may be applied, it should be recognized that the embodiments described herein with respect to the drawing figures are meant to be illustrative only and should not be taken as limiting the scope of the claims. Therefore, the techniques as described herein contemplate all such embodiments as may come within the scope of the following claims and equivalents thereof.