Abstract:
Loudspeaker sounds in a communications handset may be amplified in predetermined frequency ranges through positioning the loudspeaker between ported and unported spaces. In one embodiment, an empty volume of space disposed in front of the loudspeaker is included to shape the frequency response of the loudspeaker. A port connecting this volume of space to the environment may be located at a longitudinal end of the handset. In one embodiment, the port may pass through a space formed by an antenna loop. An additional empty volume of space may be disposed behind the loudspeaker to further shape the frequency response of the loudspeaker.

Description:
BACKGROUND  
       [0001]     Wireless and cellular communications handsets are, by their very nature, mobile and used in a variety of locations. These locations include noisy environments such as public gatherings, construction sites, and areas where machinery is operated, such as airports or roadways. Thus, speaker loudness is an important consideration for users and manufacturers of these handsets. This may be particularly true for Push-To-Talk (PTT) type handsets, where incoming sounds may be broadcast either through an earpiece or a loudspeaker. When used in a speakerphone mode, incoming sounds may be directed through the loudspeaker. Thus, a user may position the PTT handset some nominal distance away from their ear during conversations with a remote caller. When used in this manner, the user should be able to distinguish sounds broadcast by the handset from other sounds generated around the user. That is, even with the noisiest of backgrounds, users should be able to recognize and identify communications broadcast by the handset.  
         [0002]     It is generally understood that speaker loudness is proportional to driver size. However, as is the case with many consumer electronics, communications handset designs are incorporating more features and more components into smaller packages. Thus, larger speakers or audio drivers may be an impractical solution to generating increased volume. Other factors, including speaker efficiency and the power with which the speaker is driven, may also contribute to higher volume. Unfortunately, these factors may be limited by cost and battery life considerations. Therefore, a passive approach for shaping or increasing handset loudness that does not adversely impact other system characteristics may be a desirable solution.  
       SUMMARY  
       [0003]     Embodiments of the present invention are directed to a mobile communications handset having a loudspeaker with an improved frequency response, particularly within a predetermined range of interest. The improved loudspeaker configuration may be implemented in a mobile communications handset having a housing and a wireless transceiver disposed within the housing for transmitting and receiving signals. A loudspeaker port may be disposed at one longitudinal end of the housing. This end may be a hinged end of a clamshell housing. The loudspeaker port emits sounds produced by a loudspeaker, with the output sounds shaped in part by a front acoustic volume disposed between the loudspeaker port and the loudspeaker. Generally, the acoustic volume and the loudspeaker port cooperate to excite resonant frequencies within a predetermined range when sounds are emitted from the loudspeaker.  
         [0004]     In one embodiment, the front acoustic volume is an open space of between about 1 to 2 cubic centimeters. In one embodiment, the handset also has a substantially sealed rear acoustic volume disposed behind the loudspeaker. In one embodiment, the predetermined frequency range is between about 2 KHz and about 4 KHz.  
         [0005]     In some embodiments, an antenna is coupled to the wireless transceiver and traverses an arcuate path from one lateral side of the housing to the opposite lateral side adjacent a longitudinal end of the housing. At some point along the arcuate path, the antenna is spaced from the housing. In at least one embodiment, the loudspeaker port passes through the space between the antenna and the housing. The loudspeaker port may extend substantially parallel or substantially perpendicular to a keypad on the handset.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]      FIG. 1  is a perspective view of a communications handset incorporating one embodiment of a loudspeaker configuration according to the present invention;  
         [0007]      FIG. 2  is a block diagram illustrating various components in a communications handset according to one embodiment of the present invention;  
         [0008]      FIG. 3  is a schematic representation illustrating an exemplary use of a communications handset incorporating one embodiment of a loudspeaker configuration according to the present invention;  
         [0009]      FIG. 4  is a side view, including a partial cutaway section of a communications handset incorporating one embodiment of a loudspeaker configuration according to the present invention;  
         [0010]      FIG. 5  is a schematic acoustic model representing one embodiment of a loudspeaker configuration according to the present invention;  
         [0011]      FIG. 6  is a graphical illustration representing frequency responses for various embodiments of a loudspeaker configuration according to the present invention; and  
         [0012]      FIG. 7  is a partial view of a communications handset incorporating one embodiment of a loudspeaker configuration according to the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0013]     The various embodiments disclosed herein are directed to methods and devices for shaping loudspeaker output in a communications handset. In general, the techniques disclosed herein provide a passive solution that uses acoustics to shape the loudspeaker output. The various embodiments may be implemented in a communications handset of the type indicated generally by the numeral  10  in  FIG. 1 . The exemplary communications handset  10  includes a clamshell design that is a common feature many communications handsets, including model Z520a available from Sony Ericsson Mobile Communications (USA) Inc. of Research Triangle Park, North Carolina. This type of handset design should not be construed as limiting since the teachings herein may be implemented in a variety of handset designs, including swivel action handsets such as model W600 or a fixed body handset such as model J300a, each also available from Sony Ericsson Mobile Communications.  
         [0014]     In the exemplary embodiment shown in  FIG. 1 , the handset  10  comprises a first body portion  12  that is pivotally attached to a second body portion  14  at a hinge  16 . The first body portion includes a substantially planar back surface  13 . Similar to other conventional handsets, the first body portion  12  may comprise features such as a keypad (not visible in  FIG. 1 ) that is substantially parallel to the back surface  13  while the second body portion  14  may include one or more displays (also not visible in  FIG. 1 ). One or more of these displays may be visible when the handset  10  is closed as illustrated in  FIG. 1 . The first body portion  12  also includes various control buttons  26  providing access to one or more control functions and loudness control buttons  28 .  
         [0015]     The handset has a generally rectangular shape, with the distance between lateral side  18  and lateral side  22  defining a lateral dimension. The perpendicular longitudinal direction is generally defined between a first longitudinal end  24  and a second longitudinal end  25 . In one embodiment, the longitudinal dimension is greater than the lateral dimension. The exemplary handset  10  includes a loudspeaker port  20  disposed at the first longitudinal end  24  of the first body portion  12 . In addition, the handset  10  comprises a built-in antenna loop  30  that traverses a substantially arcuate path from the first lateral side  18  of the first body portion  12  to the opposite lateral side  22  of the first body portion  12 . In the illustrated embodiment, the loudspeaker port  20  is disposed between the antenna loop  30  and the hinge  16 . With the configuration shown, even as the handset  10  is opened and the second body portion  14  is flipped away from the first body portion  12 , the loudspeaker port  20  advantageously remains unobstructed (see, e.g.,  FIG. 3 ).  
         [0016]     As suggested above, the handset  10  may include other features not visible in the orientation shown in  FIG. 1 . Accordingly,  FIG. 2  provides a block diagram showing various internal and external components of the exemplary handset  10 . The handset  10  comprises a microprocessor  32 , program memory  34 , input/output circuit  36 , transceiver  38 , audio processing circuit  40 , user interface  42 , image sensor  44 , image processor  46 , and optical system  48 . The microprocessor  32  controls the operation of the handset  10  according to programs stored in program memory  34 . Input/output circuits  36  manage interaction between the microprocessor  32  and the user interface  42 , transceiver  38 , audio processing circuit  40 , and image processing circuit  46 . The audio processing circuit  20  provides basic analog output signals to the speakers  50 ,  60  and accepts analog audio inputs from the microphone  52 . The transceiver  18  is coupled to the aforementioned antenna  30  for receiving and transmitting signals on a suitable communications network (not shown).  
         [0017]     The user interface  42  comprises a keypad  54  and a display  56 . The keypad  54  allows the operator to dial numbers, enter commands, and select options. They keypad  54  may include a conventional 0-9 alphanumeric pad as well as various other input keys or buttons, including side-mounted button  26  and volume buttons  28 , described above. The display  56  allows the operator to see dialed digits, call status, images or other media, and other service information. As indicated above, one or more additional displays  58  may be disposed on an exterior surface of first body portion  12  or second body portion  14  to allow handset operators to view graphical information if the clamshell device is closed. In certain alternative mobile handsets, a touchpad display combines user input and output functions.  
         [0018]     The exemplary handset  10  may also function as a camera phone. In such cases, an image sensor  44  captures images formed by light impacting on the surface of the image sensor  44 . The image sensor  44  may be any conventional image sensor  44 , such as a charge-coupled device (CCD) or complementary metal oxide semiconductor (CMOS) image sensor. Incoming light energy may be focused on the sensor  44  by an integrated optical system  48  comprising one or more optical elements. Image processor  46  processes raw image data collected by the image sensor  44  for subsequent output to the display  56 ,  58 , storage in memory  34 , or for transmission by the transceiver  38 .  
         [0019]     The exemplary handset  10  also includes a microphone  52 , an ear speaker  50 , and a loudspeaker  60 . The microphone  52  converts input sounds, including the user&#39;s speech, into electrical audio signals. The ear speaker  50  and loudspeaker  60  convert electrical signals into audible signals that can be heard by the user. The ear speaker  50  allows the user to use the handset as a conventional phone while holding the handset  10  to their ear and listening to output sounds through the ear speaker  50 . Alternatively, the user may hear the output sounds through the loudspeaker  60  by placing the handset in a speakerphone mode. This latter mode of use is often employed while communicating in a PTT conversation. The term “speaker” as used herein, is intended to encompass a general class of electro-acoustic transducers that include inductive coil drivers, reed drivers, electrostatic drivers, and other audio output devices known in the art capable of converting electrical audio signals into sounds.  
         [0020]      FIG. 3  shows one exemplary use of the handset  10  illustrated in  FIG. 1 . As demonstrated, the handset  10  is secured to a user&#39;s arm, with the loudspeaker port  20  facing upward. As oriented, sound waves, identified in  FIG. 3  as a series of parallel arcs  62 , emanate from the loudspeaker port  20  in the direction of the user&#39;s head. This illustrated example is not intended to insinuate that sounds are only heard if the loudspeaker port  20  points in the direction of the user&#39;s ears. In fact, certain frequencies emitted by the loudspeaker  60  through the loudspeaker port  20  may be considered directionless in the sense that their wavelength are larger than the distance between the handset  10  and the user&#39;s ears. For example, at frequencies of about 1000 Hz and below, the wavelength of audible sounds is in excess of about 34 cm or 13 in. Thus, for these sounds, the orientation of the handset  10  may be less important.  
         [0021]     However, for other frequencies, including those in the range of between about 1000 Hz and 4000 Hz, the wavelengths fall to a within a range between about 8-34 cm or 3-13 inches. Therefore, the example shown in  FIG. 3  illustrates one possible advantage to placement of the loudspeaker port  20  at a longitudinal end  24  of the handset  10 . With this orientation, sounds with shorter wavelengths, sometimes termed directional sounds, may be directed towards the user&#39;s ears due to the positioning of the loudspeaker port  20 .  
         [0022]      FIG. 4  provides a side view of the exemplary handset  10 .  FIG. 4  also includes a partial cutaway section illustrating the configuration of loudspeaker  60  and loudspeaker port  20 . The loudspeaker port  20  exits the handset at the hinged longitudinal end  24  of the handset and in a direction that is roughly parallel to the back surface  13 . As indicated above, the loudspeaker port  20  passes under the antenna loop  30 .  FIG. 4  specifically shows the loudspeaker port  20  passing between antenna conductors  75  and other portions of the handset  10 , including hinge  16 , second body portion  14 , and the loudspeaker  60 . The antenna conductors  75  may comprise rigid or flexible conductors that generally traverse a path similar to the antenna loop  30  shown in  FIG. 1 . The antenna conductors  75  may be coupled at both ends of the antenna loop  30  to form a “loop antenna” as is known in the art or may be coupled to the transceiver  38  at a proximal end and simply terminate at a distal end.  
         [0023]      FIG. 4  also shows a rear acoustic volume  70  behind the loudspeaker  60  and a front acoustic volume  80  in front of the loudspeaker  60 . In the illustrated embodiment, the loudspeaker  60  is covered by a grill  66 . In addition, a seal  64  is disposed at the loudspeaker  60  mounting surface. Therefore, the rear acoustic  70  volume may be isolated from the front acoustic volume  80 . Further, the rear acoustic volume  70  may be substantially sealed. In other embodiments, the rear acoustic volume may be ported in a manner similar to the porting of the front acoustic volume  80  through loudspeaker port  20 . In yet another embodiment, the loudspeaker  60  may be inverted so that it faces into the rear acoustic volume  70 . Each of these various configurations may shape the perceived and measurable loudness and frequency response of the loudspeaker  60 .  
         [0024]     To the extent the rear acoustic volume  70  may be sealed, the enclosed space behind the loudspeaker may help prevent out-of-phase sound waves from the rear of the loudspeaker  60  from combining with the positive phase sound waves from the front of the loudspeaker  60 , which would result in interference patterns. These interference patterns tend to cancel one another, causing the efficiency of the loudspeaker  60  to be compromised, particularly in the low frequencies where the wavelengths are large enough that interference will affect the listening area in the vicinity of the handset  10 .  
         [0025]     The front acoustic volume  80  uses a port  20  that is open to the environment to increase loudness and sound pressure as compared to a similar sealed enclosure or to configurations where the loudspeaker  60  fires into open air. In speaker design, ports are often known as a specifically tuned opening in an enclosure that allows audio output generated from a speaker driver to move air and produce sound waves. The port allows air inside the enclosure to move to the outside of the enclosure in order to improve sound output. In the configuration shown in  FIG. 4 , the front acoustic volume  80  works in conjunction with the loudspeaker  60  and the rear acoustic volume  70  to produce an amplification of a range of frequencies emanated from the loudspeaker  60 .  
         [0026]     A simplified representation of the loudspeaker configuration is provided in  FIG. 5 . An acoustic component model is shown in  FIG. 5 . In this model, box  70   a  represents a rear acoustic volume analogous to the rear acoustic volume  70  shown in the exemplary handset  10  in  FIG. 4 . Similarly, box  80   a  represents a front acoustic volume analogous to the front acoustic volume  80 , speaker  60   a  is representative of the loudspeaker  60 , and the radiating port  20   a  is representative of the loudspeaker port  20 .  
         [0027]      FIG. 6  shows actual and alternative frequency response curves for various embodiments of the loudspeaker  60  configuration. The horizontal axis in  FIG. 6  represents the frequency of loudspeaker  60  output sounds while the vertical axis represents the loudness in decibels, dB. The loudness may be measured using a Sound Pressure Level (SPL) meter. In one embodiment, the results illustrated may be obtained through measurement at a distance of 20 cm from the handset. This distance approximates a representative handset-to-ear distance during speakerphone use.  
         [0028]     In  FIG. 6 , various dashed lines are shown to illustrate the flexibility offered by changing the size of the relevant acoustic volumes  70 ,  80 . It is generally understood that the frequency response that is produced through changes in these volumes  70 ,  80  may be predicted using a Thiele-Small analysis. The Thiele-Small approach analyzes the electromechanical behavior of a speaker voice coil, magnet, and cone, interacting with the cone suspension and the air in and outside of an enclosure. This analysis considers such variables as the size of the driver, the axial movement range of the driver, the resonant frequency of the driver, chamber volumes, power used to drive the speaker, and dimensionless variables known in the art simply as Q factors. An alternative form of analysis uses a lumped component model, where certain physical components with acoustical properties may be approximated as behaving similarly to standard electronic components or simple combinations of components. These and other types of analyses known in the art may be used to predict the loudspeaker  60  frequency response.  
         [0029]     In one embodiment, a 16 mm loudspeaker  60  may be used in conjunction with a rear acoustic volume of about 2 cubic centimeters and a front acoustic volume of between about 1 and 2 cubic centimeters to produce an elevated response between about 2 KHz and 4 KHz as identified by the portion of the curve in  FIG. 6  labeled  100 . This elevated response reflects about 3-5 dB increase over the curve labeled  102  that is representative of the loudspeaker  60  without the front acoustic volume  80  and the loudspeaker port  20 . Depending on the size of the driver used and the amount of space available, resonance type gains of up to 10 dB or more may be achievable. Given this improved frequency response over a certain frequency range, this configuration may be referred to as a bandpass configuration, with the amplified sounds exiting from a bandpass port  20 . Note also that the response at lower frequencies (i.e., less than about 1 KHz) identified by the portion of the curve labeled  104  is elevated relative to the dashed curve labeled  106 . This particular increase in loudness may be attributable to the enclosed rear acoustic volume  70 . The trailing response at higher frequencies indicated by dashed curve  108  is representative of mechanical and resonance limitations of the loudspeaker  60 .  
         [0030]     As indicated, the elevated loudness identified by curve portion  100  represents an increase in loudness for sounds that are in the 2 KHz to 4 KHz range. This range represents an range of sounds that is important in speech perception and in identifying audible tones and other sounds produced by the handset  10 . Speech and other sounds can be described in terms of formant frequencies. A formant is a peak in an acoustic frequency spectrum which results from the resonant frequencies of any acoustical system. Sounds in human speech are distinguishable because different sounds have different formant frequencies. In general, the formant with the lowest frequency is called f 1 , the second f 2 , and the third f 3 . Typically, the two first formants, f 1  and f 2 , are enough to disambiguate a vowel. However, greater intelligibility, both of sound and speaker identity, may be achieved through recognition of higher order formants. Many vowel sounds in the American English language include first formants that are below about 800 Hz. For certain sounds, the second formants are close to the first formant and occur below about 1 KHz. For others, the separation is greater, with the second formant occurring between about 1500 KHz and 3500 KHz. Also relevant to human sound perception is the knowledge that trained singers are able to produce a clear formant around 3000 Hz that allows the singers to be heard and understood over an orchestra. Thus, amplification of sounds in or around these frequency ranges may help handset  10  users distinguish speech and sounds transmitted by the loudspeaker  60  from surrounding background noises.  
         [0031]     As suggested above, the size of the acoustic volumes  70 ,  80 , and various other parameters may be adjusted to shape the frequency response of the loudspeaker  60  system. Specifically, the parameters may be adjusted to shift the amplified region up (as in curve  110 ) or down (as in curves  112 ,  114 ) in frequency. Furthermore, the range of elevated frequency may also be wider or narrower than those illustrated based in part upon space constraints and the type of driver used.  
         [0032]     The present invention may be carried out in other specific ways than those herein set forth without departing from the scope and essential characteristics of the invention. For example, one embodiment of handset  10  is provided illustrating a front acoustic volume  80  and a loudspeaker port  20  disposed near a hinged longitudinal end  24  of the handset  10 . In other embodiments, the front acoustic volume and loudspeaker port may disposed at the longitudinal end opposite the hinge  16 . For fixed-body handsets, the front acoustic volume and loudspeaker port may be disposed at a longitudinal end above the display or at the opposite end below the keypad. As an example of an alternative embodiment, a handset  200  is shown in  FIG. 7 . In this embodiment, the loudspeaker port  120  is disposed at a longitudinal end  124  of the handset  200  that below the keypad  154 , opposite to the hinged end (not shown in  FIG. 7 ). Note also, that in the exemplary handset  200  illustrated in  FIG. 7 , the loudspeaker port  120  also exits through an antenna loop  130 . Further, the loudspeaker port  120  exits in a direction that is substantially perpendicular to the keypad  154 . This configuration may advantageously direct sounds away from a surface on which the handset  200  rests. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.