Abstract:
A listening device for presenting at least one audio signal to a user comprises a first ear piece and a second ear piece, each of the first ear piece and the second ear piece including at least one speaker and each being adapted to block substantially all external sounds from entering an ear of a user. The device further comprises a microphone for sensing a first audio signal and a differential amplifier coupled to the microphone for amplifying the first audio signal. The differential amplifier is coupled to a first electrical ground. A switching arrangement coupled to and receiving a second audio signal from an external audio source and the external audio source having a second electrical ground that is electrically distinct from the first electrical ground. The switching arrangement is further coupled to the differential amplifier, the first ear piece, and the second ear piece, the switching arrangement being adapted to select at least one of the first audio signal and the second audio signal for transmission to the first ear piece and at least one of the first audio signal and the second audio signal for transmission to the second ear piece.

Description:
BACKGROUND OF THE INVENTION 
     The use of personal headsets with any of the various audio and communication devices, including music players and cell phones is common today among consumers. With the advent of in-the-ear versions that substantially seal to the ear and isolate the user from outside sounds, there is a communication gap when someone wants to interrupt the user or the user wants to interact with the outside environment. In this case, the user is forced to remove at least one ear bud to hear anything other than the audio source. One situation where this occurs is when a jogger is running while listening to a music player and does not want to be completely isolated from outside sounds like traffic noise. Another situation is on an airplane where the user is listening to music and needs to interact with another passenger or a flight attendant. It is desirable to provide multiple audio streams to a user on demand. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the disclosure, reference should be made to the following detailed description and accompanying drawings wherein: 
         FIG. 1  illustrates an exemplary listening device, in accordance with an embodiment of the present invention; 
         FIG. 2  illustrates an exemplary circuitry, in accordance with an embodiment of the present invention; 
         FIG. 3  illustrates another exemplary circuitry, in accordance with an embodiment of the present invention; 
         FIG. 4  illustrates another exemplary circuitry, in accordance with an embodiment of the present invention; and 
         FIG. 5  illustrates another exemplary circuitry, in accordance with an embodiment of the present invention. 
     
    
    
     Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity. It will further be appreciated that certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. It will also be understood that the terms and expressions used herein have the ordinary meaning as is accorded to such terms and expressions with respect to their corresponding respective areas of inquiry and study except where specific meanings have otherwise been set forth herein. 
     DETAILED DESCRIPTION 
     While the present disclosure is susceptible to various modifications and alternative forms, certain embodiments are shown by way of example in the drawings and these embodiments will be described in detail herein. It will be understood, however, that this disclosure is not intended to limit the invention to the particular forms described, but to the contrary, the invention is intended to cover all modifications, alternatives, and equivalents falling within the spirit and scope of the invention defined by the appended claims. 
       FIG. 1  illustrates an exemplary listening device  10 , in accordance with an embodiment of the present invention. The listening device  10  may be an earphone, an earplug, a headphone, a wireless earphone, a wireless headset, a wireless headphone, a hearing aid, an insert earphone and the like. The listening device  10  may be used with various types of audio and portable communication devices such as MP3 players, laptops, personal computers, tablet PCs, cellular phones, CD players and the like. The listening device  10  operatively coupled to the device may be a stereophonic device, a monophonic device, or combination thereof. The listening device  10  comprises left and right earphones  12 ,  14 , a user input device  20 , and a connecting cord  19  that is terminated in a plug  16 . The earphones  12 ,  14  may be electrically coupled to the user input device  20  via a cable  18 . At least a transducer (not shown) is encapsulated in the earphones  12 ,  14 . The transducer may be a receiver, a speaker, a combined receiver and microphone, or tandem receivers, depending on the desired applications. Normally, the left earphone  12  is placed in user&#39;s left ear and the right earphone  14  is placed in user&#39;s right ear. An ear mold or an ear tip (not shown) may be provided to increase the comfort seal in the ear and such ear mold can be identical to the conventional ear mold, which will not be discussed further. The plug  16  may be used to connect the earphones  12 ,  14  to the external device with an output port. The user input device  20  connected to the plug  16  via the connecting cord  19  may be utilized to select at least one audio signal. The user input device  20  comprises at least a switch arrangement (not shown) to selectively control between different modes to perform certain functions and will discussed in greater detail therein. 
       FIG. 2  illustrates a functional schematic of a listening device  100 , in accordance with an embodiment of the present invention. The listening device  100  comprises a left terminal  119   a , a right terminal  119   c , and a common terminal  119   b  formed in a connecting cord  119 . The listening device  100  further comprises a left terminal  118   a , a right terminal  118   c , and a common terminal  118   b  formed in a cable  118 . A first speaker  128  is disposed in a left earphone  112  and a second speaker  130  is disposed in a right earphone  114 . As shown, the first speaker  128  and the second speaker  130  shared the same common terminal  118   b  of the cable  118 . A user input device  120  comprises a switch arrangement  132 , a power source  138 , a microphone  122 , and a differential amplifier  124 . The microphone  122  picks up acoustic input as heard in the environment, converts the acoustic signal into a corresponding electrical signal, and is electrically coupled to an input of the differential amplifier  124 . The microphone  122  may be a silicon condenser microphone, an electret microphone, or a dynamic microphone, depending on the desired applications. The differential amplifier  124  may be integrated into the microphone  122 , defining a differential microphone unit  126 . The power source  138  may be a battery. The switch arrangement  132  comprises a left switch S 1 , a right switch S 2 , and a circuit switch S 3  which are ganged to select between two audio sources. S 1 , S 2 , and S 3  of the switch arrangement  132  may be mechanical switches such as toggle switches, slide switches, push button switches, rotary switches, or electronic (CMOS) switches and the like. A fixed end  132   a  of S 1  is connected to a plug  116  via the left terminal  119   a  of the connecting cord  119  and a fixed end  132   b  of S 1  is connected to a first output  134  of the differential amplifier  124 . A fixed end  132   c  of S 2  is connected to the plug  116  via the right terminal  119   c  of the connecting cord  119  and a fixed end  132   d  of S 2  is connected a second output  136  of the differential amplifier  124 . A movable end of S 1  is coupled to an input of the first speaker  128  via the left terminal  118   a  of the cable  118  and a movable end of S 2  is coupled to an input of the second speaker  130  via the right terminal  118   c  of the cable  118 . A fixed end  132   f  of S 3  is connected to the differential amplifier  124  and a movable end of S 3  is connected to the power source  138 . 
     The common terminal  118   b  of the cable  118  is electrically coupled to the common terminal  119   b  of the connecting cord  119  via the user input device  120  extending between the plug  116  and the first and second speakers  128 ,  130  of the earphones  112 ,  114 . When the switch arrangement  132  is in the first position, the movable end of S 1  is connected to the fixed end  132   a  and the movable end of S 2  is connected to the fixed end  132   c . The first and second speakers  128 ,  130  of the earphones  112 ,  114  are connected to the plug  116  to receive a first audio signal from an audio source  140 . The movable end of S 3  is connected to the fixed end  132   e  so that the power source  138  is disconnected from the differential amplifier  124 . When the switch arrangement  132  is in the second position, the movable end of S 1  is connected to the fixed end  132   b  and the movable end of S 2  is connected to the fixed end  132   d . The first and second speakers  128 ,  130  of the earphones  112 ,  114  are connected in series across the differential amplifier  124  to receive a second audio signal from the microphone  122 . The movable end of S 3  is connected to the fixed end  132   f  so that the power source  138  is connected to the differential amplifier  124 . In doing so, the differential amplifier  124  of the circuit  126  provides a gain and output impedance of a magnitude that allows the driving of the first and second speakers  128 ,  130  of the earphones  112 , 114 . One advantage of the device  100  is that, unlike the conventional circuits, the device  100  does not require any DC blocking capacitors between the outputs  134 ,  136  of the differential amplifier  124  and the speakers  128 ,  130  of the earphones  112 ,  114 . Further the device  100  does not require a connection between the ground of the circuit  126  and the ground of the external audio device  140 . 
       FIG. 3  illustrates another functional schematic of a listening device  200 , in accordance with an embodiment of the present invention.  FIG. 3  is similar in construction to the device  100  in  FIG. 2  and like elements are identified with a like reference convention wherein, for example, element  120  corresponds to element  220 . In this embodiment, a switch arrangement  232  comprises a common switch S 1  and a circuit switch S 3  which are ganged to select between two audio sources. A fixed end  232   a  of S 1  is connected to a plug  216  via a common terminal  219   b  of a connecting cord  219  and a first output  234  of a differential amplifier  224 . A fixed end  232   b  of S 1  is connected to a second output  236  of the differential amplifier  224 . A movable end of S 1  is coupled to first and second speakers  228 ,  230  of the earphones  212 ,  214  via a common terminal  218   b  of a cable  218 . A fixed end  232   f  of S 3  is connected to the differential amplifier  224  and a movable end of S 3  is connected to a power source  238 . A left terminal  218   a  of the cable  218  being coupled to an input of the first speaker  228  is electrically coupled to a left terminal  219   a  of the connecting cord  219  via a user input device  220 . A right terminal  218   c  of the cable  218  being coupled to an input of the second speaker  230  is electrically coupled to a right terminal  219   c  of the connecting cord  219  via the user input device  220 . When the switch arrangement  232  is in the first position, the movable end of S 1  is connected to the fixed end  232   a . The common terminal  218   b  of the cable  218  between the first and second speakers  228 ,  230  of the earphones  212 ,  214  are connected to the common terminal  219   b  of the connecting cord  219  that is coupled to the plug  216  to receive a first audio signal from an audio source  240  and the movable end of S 3  is connected to the fixed end  232   e  so that the power source  238  is disconnected from the differential amplifier  224 . When the switch arrangement  232  is in the second position, the movable end of S 1  is connected to the fixed end  232   b . The common terminal  218   b  of the cable  218  between the first and second speakers  228 ,  230  of the earphones  212 ,  214  are connected to the output  236  of the differential amplifier  224  to receive a second audio signal from an microphone  222  and the movable end of S 3  is connected to the fixed end  232   f  so that the power source  238  is connected to the differential amplifier  224 . Since the second audio signal from the circuit  226  is in series with the first audio signal from the plug  216 , the first and second signals are mixed together and the mixed signals are transmitted to the earphones  212 ,  214  thereof. The device  200 , according to the present invention, allows the user an ability to simultaneously hear the electronically produced audio signal while at the same time hearing externally generated sound. One advantage of the device  200  is that, unlike the conventional circuits, the device  200  does not require any DC blocking capacitors between the outputs  234 ,  236  of the differential amplifier  224  and the speakers  228 ,  230  of the earphones  212 ,  214 . Further the device  200  does not require a connection between the ground of the circuit  226  and the ground of the external audio device  240 . 
       FIG. 4  illustrates yet another functional schematic of a listening device  300 , in accordance with an embodiment of the present invention.  FIG. 4  is similar in construction to the device  200  in  FIG. 3  and like elements are identified with a like reference convention wherein, for example, element  220  corresponds to element  320 . The listening device  300  comprises a left terminal  319   a , a right terminal  319   c , and a common terminal  319   b  formed in a connecting cord  319 . The listening device  300  further comprises a left terminal  318   a , a right terminal  318   c , and a common terminal  318   b . A first speaker  328  is disposed in a left earphone  312  and a second speaker  330  is disposed in a right earphone  314 . The first and second speakers  328 ,  330  of the earphones  312 ,  314  shared the same common terminal  318   b  of the cable  318 . A user input device  320  comprises a first switch arrangement  332 , a second switch arrangement  342 , a power source  338 , a microphone  322 , and a differential amplifier  324 . As shown, the first switch arrangement  332  comprises a common switch S 1  and a circuit switch S 3  which are ganged together to operate in unison. The second switch arrangement  342  comprises a left switch S 4  and a right switch S 5  which are ganged together to operate in unison. A fixed end  342   a  of S 4  is connected to a plug  316  via the left terminal  319   a  of the connecting cord  319 . A fixed end  342   c  of S 5  is connected to the plug  316  via the right terminal  319   c  of the connecting cord  319 . Fixed ends  342   b ,  342   d  of S 4 , S 5  are connected to the plug  316  via the common terminal  319   b . A movable end of S 4  is connected to an input of the first speaker  328  via the left terminal  318   a  of the cable  318 . A movable end of S 5  is connected to an input of the second speaker  330  via the right terminal  318   c  of the cable  318 . A fixed end  332   a  of S 1  is connected to the plug  316  via the common terminal  319   b  of the connecting cord  319 . The fixed end  332   a  of S 1  is further connected to a first output  334  of the differential amplifier  324 . A fixed end  332   b  of S 1  is connected to a second output  336  of the different amplifier  324 . A movable end of S 1  is connected to the first and second speakers  328 ,  330  of the earphones  312 ,  314  via the common terminal  318   b  of the cable  318 . A fixed end  332   f  of S 3  is connected to the differential amplifier  324  and a movable end of S 3  is connected to the power source  338 . 
     When the switch arrangements  332 ,  342  are in the first mode, the movable ends of S 1 , S 3 , S 4 , S 5  are connected to the fixed ends  332   a ,  332   e ,  342   a ,  342   c , the first and second speakers  328 ,  330  are connected to the plug  316  to receive a first audio signal from an external device  340  and the power source  338  is disconnected from the differential amplifier  324 . When the switch arrangements  332 ,  342  are in the second mode, the movable ends of S 1 , S 3 , S 4 , S 5  are connected to the fixed ends  332   b ,  332   f ,  342   a ,  342   c , the first audio signal from the external device  340  via the plug  316  and a second audio signal from the microphone  322 , defining a mixed first and second audio signals are received by the first and second speakers  328 ,  330 . The power source  338  is connected to the differential amplifier  324  in the second mode. When the switch arrangements  332 ,  342  are in the third mode, the movable ends of S 1 , S 3 , S 4 , S 5  are connected to the fixed ends  332   b ,  332   f ,  342   b ,  342   d , only the second audio signal received by the microphone  322  is transmitted to the first and second speakers  328 ,  330  of the earphones  312 ,  314  and the power source  338  is connected to the differential amplifier  324 . When the switch arrangements  332 ,  342  are in the fourth mode, the movable ends of S 1 , S 3 , S 4 , S 5  are connected to the fixed ends  332   a ,  332   e ,  342   b ,  342   d , no signal is presented to the first and second speakers  328 ,  330  of the earphones  312 ,  314  and thus silence is heard by the user. The power source  338  may be a unipolar supply which is advantageous from a manufacturing standpoint. Other examples of power source  338  are possible. In this embodiment, the DC level of the signals from differential amplifier  324  is between approximately 0.7V and Vdd-0.7V, where Vdd is the voltage of the power source  338 . The power source  338  may be used to power CMOS switches used to implement switch arrangements  332  and  334  as the signals being switched are at an optimum voltage level. 
       FIG. 5  illustrates still another functional schematic of a listening device  400 , in accordance with an embodiment of the present invention.  FIG. 5  is similar in construction to the device  300  in  FIG. 4  and like elements are identified with a like reference convention wherein, for example, element  320  corresponds to element  420 . The listening device  400  comprises a left terminal  419   a , a common terminal  419   b , a right terminal  419   c , and a microphone terminal  419   d  collectively disposed in a connecting cord  419 . The listening device  400  further comprises a left terminal  418   a , a common terminal  418   b , and a right terminal  418   c  collectively disposed in a cable  418 . A user input device  420  comprises a switch arrangement  432 , a power source  438 , a microphone  422 , and a differential amplifier  424 . The switch arrangement  432  comprises a left switch S 1 , a first common switch S 2 , a second common switch S 3 , a right switch S 4 , and a circuit switch S 5 . A fixed end  432   a  of S 1  is connected to a plug  416  via the left terminal  419   a  of the connecting cord  419  and a fixed end  432   b  of S 1  is connected to both the common terminal  419   b  of the connecting cord  419  and a first output  434  of the differential amplifier  424 . A movable end of S 1  is connected to an input of the first speaker  428  via the left terminal  418   a  of the cable  418 . A fixed end  432   d  of S 2  is connected to both the common terminal  419   b  of the connecting cord  419  and a first output  434  of the differential amplifier  424 . A fixed end  432   f  of S 3  is connected to a second output  436  of the differential amplifier  424 , and the microphone terminal  419   d  of the connecting cord  419  via the coupling capacitor  450 . Movable ends of S 2  and S 3  are connected to the first and second speakers  428 ,  430  via the common terminal  418   b . A fixed end  432   g  of S 4  is connected to the right terminal  419   c  of the connecting cord  419 . A fixed end  432   h  of S 4  is connected to both an output  436  of the differential amplifier  424  and the microphone terminal  419   d  of the connecting cord  419  via coupling capacitor  450 . A movable end of S 4  is connected to an input of the second speaker  430  via the right terminal  418   c  of the cable  418 . A fixed end  432   j  of S 5  is connected to the differential amplifier  424  and the movable end of S 5  is connected to the power source  438 . 
     It is contemplated that the external device  440  is a cell phone with stereo MP3 functionality. When the switch arrangement  432  is in the first mode, also known as cell mode, the movable ends of S 1 , S 2 , S 3 , S 4 , and S 5  are connected to fixed ends  432   a ,  432   d ,  432   e ,  432   g , and  432   j  respectively, the first and second speakers  428 ,  430  are connected to the plug  416  via the terminals  419   a ,  419   b ,  419   c ,  418   a ,  418   b ,  418   c  to receive a first audio signal from an external device  440  while the power source  438  is connected to the circuit  426 . Microphone  422  provides a signal to the external device  440  microphone input through the terminal  419   d  and the coupling capacitor  450 . When the switch arrangement  432  is in the second mode, also known as MP3 mode, the movable ends of S 1 , S 2 , S 3 , S 4 , and S 5  are connected to fixed ends  432   a ,  432   d ,  432   e ,  432   g , and  432   i  respectively, the first and second speakers  428 ,  430  are connected to the plug  416  via the terminals  419   a ,  419   b ,  419   c ,  418   a ,  418   b ,  418   c  to receive the first audio signal from an external device  440  but no current is provided to the circuit  426 . When the switch arrangement  432  is in the third mode, also known as mix mode, the movable ends of S 1 , S 2 , S 3 , S 4 , and S 5  are connected to fixed ends  432   a ,  432   c ,  432   f ,  432   g , and  432   j  respectively, and a mixed first and second audio signals from the external device  440  via the plug  416  and the microphone  422  of the circuit  426  are received by the first and second speakers  428 ,  430  via the terminals  419   a ,  419   b ,  419   c ,  418   a ,  418   b ,  418   c  while the power source  438  is connected to the circuit  426 . When the switch arrangement  432  is in the fourth mode, also known as microphone mode, the movable ends of S 1 , S 2 , S 3 , S 4 , and S 5  are connected to fixed ends  432   b ,  432   c ,  432   e ,  432   h , and  432   j , only the second audio signal received by the microphone  422  of the circuit  426  is transmitted to the first and second speakers  428 ,  430  while the current from the power source  458  is supplied to the differential amplifier  424 . 
     To conserve the life of the power source when the microphone  422  is activated to receive audio signal as heard from the environment, an optional control member (not shown) is provided to the circuit  426  to set a predetermined time limit. The device  400  enters a sleep mode and thus a power switch is not required. 
     All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extend as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein. 
     The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. 
     Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. It should be understood that the illustrated embodiments are exemplary only, and should not be taken as limiting the scope of the invention.