Abstract:
A portable speakerphone having a housing, a receiving transducer, an electrical cable, a transmitting transducer, and a processor. The receiving transducer is affixed to the housing and is configured to receive a first electrical signal from a mobile device. The electrical cable is coupled to and extends from the housing. The transmitting transducer is affixed to the electrical cable, remote from the housing. Also, the transmitting transducer is configured to transmit a second electrical signal, and the second electrical signal is based in part on the first electrical signal. The processor is configured to suppress acoustic echo by modifying the second electrical signal. The processor is also configured to output the modified second electrical signal to the mobile device. A related method is also disclosed.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This patent application claims priority to and the benefit of U.S. Provisional Application No. 62/257,120, filed Nov. 18, 2015, which is incorporated in this patent application by this reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This disclosure relates to telecommunication, and, more particularly, to a system and methods for reducing echo in a speakerphone call. 
       BACKGROUND 
       [0003]    One purpose of a speakerphone system is to allow a user to conduct a phone call without having to hold a conventional handset. Thus, a speakerphone may allow the user&#39;s hands to be free, the user to move freely about the room while participating in the call, and multiple people to participate in the phone call from one location, such as a conference room. 
         [0004]    A conventional speakerphone system  100 , such as shown in  FIG. 1 , may include a speakerphone  101  and a far-side phone  102 . The speakerphone  101  may include a speakerphone housing  103 , having a microphone  104  and a loudspeaker  105  within the speakerphone housing  103  or supported by the speakerphone housing  103 . The speakerphone  101  may also include an acoustic echo cancellation (AEC) filter  106  and a non-linear processing (NLP) module  107 . 
         [0005]    In the context of speakerphone systems, the party speaking and listening through the speakerphone is typically called the near side, while the party calling into the speakerphone is typically called the far side. Hence the far-side party calls in through the far-side phone  102 . Additionally, a signal received from the far-side phone  102  propagates through a receive path (Rx-path) and is called an Rx-path signal  108 , while the signal received by the microphone  104  propagates through a transmit path (Tx-path) and is called a Tx-path signal  109 . 
         [0006]    Also, there are two common modes for a conventional speakerphone. In full-duplex mode, the Rx-path and the Tx-path are each fully active, or open, at any given time during the phone call. In half-duplex mode, however, only one of the two paths is open at a time. Thus, for example, if the far-side party is talking, the Rx-path is active and the Tx-path is muted. This helps to avoid echo at the far side. Yet, it also means that the inactive side, which is the side that is not speaking, cannot interrupt the active side, which is the side that is speaking, because the inactive side is muted. Accordingly, the half-duplex mode may lead to an unnatural experience for the parties, making it difficult to hold a conversation. 
         [0007]    One fundamental problem of conventional speakerphones is a loudspeaker-to-microphone bypass signal  110  on the near side. This bypass signal  110  is also called the acoustic echo path, and the far-side party may experience the bypass signal  110  as an echo. In other words, the far-side party may hear his or her own voice signal coming back, usually after a short delay. 
         [0008]    To overcome this problem, many conventional speakerphones implement an acoustic echo cancellation (AEC) signal-processing algorithm, for example, through the AEC filter  106 . In general, the AEC algorithm compares the incoming, receive-path signal  108  with the outgoing, transmit-path signal  109  and then subtracts the incoming signal  108  from the outgoing signal  109 . As a result, the processed transmit-path signal contains content from the near side, but not content received from the far side. Accordingly, the acoustic-echo-path signal  110  may be reduced or eliminated. 
         [0009]    The NLP module  107  may provide additional suppression of any remaining acoustic echo, particularly of any component of the acoustic echo that is non-linear. This is generally done by destructively removing a portion of the outgoing, transmit-path signal  109 , although this may damage the signal. 
         [0010]    While AEC algorithms generally work well, one challenge with implementing them is the close proximity of the microphone  104  to the loudspeaker  105  in a conventional speakerphone system  100 . That is, as the microphone  104  is positioned closer to the loudspeaker  105 , the incoming signal picked up by the microphone  104  becomes louder, or stronger. The desired signal from the party talking at the near side, however, typically originates much farther from the microphone  104  than the loudspeaker  105  is from the microphone  104 . Hence, the desired signal presents a significantly quieter, or weaker, signal to the microphone  104  relative to the Rx-path signal  108  rendered by the loudspeaker  105 . 
         [0011]    The ratio between the desired signal from the party talking at the near side and the acoustic echo path  110  can be quantified as a signal-to-echo ratio. As a conventional rule of thumb, a signal-to-echo ratio of down to about −20 or −25 dB can be managed by a conventional AEC algorithm. This means that the AEC algorithm is effective at canceling the acoustic echo up to about that ratio. For ratios smaller than about −20 or −25 dB, echo cancellation may be much less effective, meaning that the far-side party may perceive an echo, or a partial echo, of that party&#39;s own voice because all or some of the acoustic echo may bleed through the AEC filter  106 . A high-quality system is one that provides full duplex support and no echo at the far side. At a signal-to-echo ratio of less than about −25 dB, however, that goal generally cannot be achieved. 
         [0012]    Additionally, the signal-to-echo ratio can be a significant problem in small speakerphones, where the smaller size means that the loudspeaker  105  must be closer to the microphone  104 . Mathematically, halving the distance between the loudspeaker  105  and the microphone  104  results in a 6 dB decrease in the signal-to-echo ratio. For example, if the signal-to-echo ratio is −15 dB at a distance of 30 mm, halving the distance between the loudspeaker  105  and the microphone  104  to 15 mm results in a signal-to-echo ratio of −21 dB. Likewise, doubling the distance between the loudspeaker  105  and the microphone  104  results in a 6 dB increase in the signal-to-echo ratio. Thus, high-quality speakerphone systems tend to be relatively large to provide a favorable distance between the microphone  104  and the loudspeaker  105 . 
         [0013]    Furthermore, while the main portion of the acoustic echo path signal  110  travels through the air, a portion of the acoustic echo path signal  110  may be conducted structurally, through the coupling between the loudspeaker  105  and the microphone  104 . For example, a plastic housing component may rattle at the loudspeaker&#39;s frequency, and the rattling may be transmitted through structural conduction to the microphone  104  where it is sensed. Additionally, this structurally conducted sound has a transfer function that is typically non-linear. Conventional speakerphones may address such unwanted structural sound by including suspension mechanisms, such as rubber sleeves or springs, to isolate the mechanical vibration. Those solutions, however, increase the cost and complexity of the speakerphone system. Also, those solutions might not effectively reduce the structural sound at some frequencies. 
         [0014]    Embodiments of the invention address these and other issues in the prior art. 
       SUMMARY OF THE DISCLOSURE 
       [0015]    Embodiments of the disclosed subject matter provide a speakerphone with a relatively small form factor but an improved signal-to-echo ratio over existing small speakerphones. Accordingly, embodiments include a loudspeaker in a housing and a microphone that is remote from the housing, on a cable or on a connector at a distal end of the cable. Thus, relative to conventional designs with the microphone and loudspeaker in the same housing, the microphone and the loudspeaker are farther apart and mechanically isolated from each other, both without increasing the form factor of the housing. 
         [0016]    Accordingly, at least some embodiments of a portable speakerphone may include a housing, a receiving transducer, an electrical cable, a transmitting transducer, and a processor. The receiving transducer is affixed to the housing and is configured to receive a first electrical signal from a mobile device. The electrical cable is coupled to and extends from the housing. The transmitting transducer is affixed to the electrical cable, remote from the housing. Also, the transmitting transducer is configured to transmit a second electrical signal, and the second electrical signal is based in part on the first electrical signal. The processor is configured to suppress acoustic echo by modifying the second electrical signal. The processor is also configured to output the modified second electrical signal to the mobile device. 
         [0017]    In another aspect, in at least some embodiments of the speakerphone, the receiving transducer is a loudspeaker. 
         [0018]    In yet another aspect, in at least some embodiments of the speakerphone, the transmitting transducer is a microphone. 
         [0019]    In still another aspect, in at least some embodiments of the speakerphone, the electrical cable has a connector at a distal end of the electrical cable, opposite a proximal end of the electrical cable coupled to the housing, and the transmitting transducer is a microphone located along the electrical cable, between the proximal end of the electrical cable and the connector. In other embodiments, the transmitting transducer is a microphone affixed to the connector or substantially enclosed within the connector. 
         [0020]    In another aspect, at least some embodiments of a method of calibrating a distance between a loudspeaker and a microphone in a speakerphone may include receiving, at a loudspeaker affixed to a housing, a receive-path signal from a far-side device; transmitting, by a microphone remote from the housing and affixed to a distal end of an electrical cable that is coupled to and extends from the housing at a proximal end of the electrical cable, a transmit-path signal, the transmit-path signal being based in part on the receive-path signal; determining, by a processor, a signal-to-echo ratio of the second electrical signal; increasing a length of the electrical cable until the determined signal-to-echo ratio is greater than a minimum desired ratio, the minimum desired ratio being about −25 dB; modifying, by the processor, the transmit-path signal; and outputting the modified transmit-path signal to the far-side device. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  is a functional block diagram showing signal paths in a conventional speakerphone system. 
           [0022]      FIG. 2  is a front, perspective view of a speakerphone with an on-cable microphone, according to embodiments of the invention. 
           [0023]      FIG. 3  is a functional block diagram showing signal paths in a system incorporating a speakerphone with an on-cable microphone, according to embodiments of the invention. 
           [0024]      FIG. 4  is a functional block diagram showing signal paths in a system incorporating a speakerphone with an on-cable microphone, according to embodiments of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    As described herein, embodiments of the invention are directed to an apparatus providing a speakerphone with a relatively small form factor but an improved signal-to-echo ratio over existing small speakerphones. Accordingly, embodiments of the invention include a loudspeaker in a housing and a microphone that is remote from the housing, on a cable or on a connector at a distal end of the cable. In this way, the microphone and the loudspeaker may be separated at a distance without increasing the form factor of the housing. Also, in a mechanical sense, the microphone and the loudspeaker are substantially isolated from each other because the microphone is remote from the housing. This helps to reduce or eliminate the structural transmission of sound waves, without the need for additional structures, such as suspension mechanisms, to isolate the mechanical vibration from the sound waves. 
         [0026]    As used in this disclosure, a “small form factor” with respect to a speakerphone housing means that, if a microphone and a loudspeaker were both integrated in the housing, the distance between the microphone and the loudspeaker would be less than about 100 mm (about 4 inches). To put it another way, the housing and the electrical cable may be configured to separate the microphone and the loudspeaker by more than about four inches, with the microphone being outside of the housing. Thus, for example, if the housing is essentially box-shaped, such as the loudspeaker housing  203  of  FIG. 2 , then “small form factor” means that the length, the width, and the height of the housing each do not exceed about four inches. To generalize this further, including for housings that are not box-shaped, “small form factor” means that the distance between the microphone and the loudspeaker is greater than maximum external dimension of the housing. Accordingly, the microphone is farther away from the loudspeaker than it would be if the microphone were within the speakerphone housing, and the microphone is structurally isolated from the housing, and likewise the loudspeaker, by the cable. The distances are measured with the cable fully extended away from the speakerphone housing. 
         [0027]      FIG. 2  is a front, perspective view showing material portions of a speakerphone  201  with an on-cable microphone according to embodiments of the invention. As illustrated in  FIG. 2 , a speakerphone  201  with an on-cable microphone may include a loudspeaker housing  203 , a cable  211 , a connector  212 , a receiving transducer  205 , and a transmitting transducer  204 . 
         [0028]    The receiving transducer  205  is configured to receive an electrical signal. For example, the receiving transducer  205  may be a loudspeaker that is configured to receive and render an audio signal. 
         [0029]    The transmitting transducer  204  is configured to transmit an electrical signal. For example, the transmitting transducer  204  may be a microphone, and the transmitting transducer  204  may be configured to transmit a microphone signal. The transmitting transducer  204  may include, as examples, an electret condenser microphone (ECM), a microelectromechanical system (MEMS) microphone, or a dynamic microphone capsule. As another example, the transmitting transducer  204  may be an accelerometer, such as an accelerometer to detect sound vibrations. Other types of transmitting transducers may also be used. 
         [0030]    The connector  212  may be any connector configured to connect to an electronic device, such as a mobile device. As examples, the mobile device may be a cellular telephone, a smartphone, or a tablet computer. The connector  212  may be, for example, a universal serial bus (USB) connector. In embodiments, such as shown in  FIG. 2 , the transmitting transducer  204  may be integrated into the connector  212  by being substantially enclosed within the connector  212 . In such embodiments, the connector  212  may include an aperture  213  to permit sound waves, for example, to be sensed by the transmitting transducer  204 . Alternatively, the transmitting transducer  204  may be attached, or affixed, to the connector  212 . When the connector  212  is connected to the electronic device, the speakerphone  201  may signal the electronic device to deactivate the electronic device&#39;s microphone or loudspeaker or both. 
         [0031]    The loudspeaker housing  203  may substantially enclose or otherwise support the receiving transducer  205 . The loudspeaker housing  203  may have one or more substantially flat outer surfaces configured to rest on a horizontal support surface, such as a desk or table. 
         [0032]    The loudspeaker housing  203  may be made from plastic, metal, or another rigid or semi-rigid material. 
         [0033]    The cable  211  extends from the loudspeaker housing  203  and physically connects the connector  212  to the loudspeaker housing  203 . The cable  211  may be any cable, such as a flexible, electrical cable, configured to carry an electrical signal between the connector  212  and the loudspeaker housing  203 . In some embodiments, the transmitting transducer  204  may be located along the cable  211  rather than at the connector  212 . In such embodiments, the transmitting transducer  204  may be substantially enclosed within a transducer housing. The transducer housing may be configured to protect the transmitting transducer  204 , and it may be configured to channel a signal, such as a sound wave, to the transmitting transducer  204 . The cable  211  may be permanently attached to the loudspeaker housing  203 , or the cable  211  may be detachably connected to the loudspeaker housing  203 , such as with a second electrical connector. 
         [0034]    The cable  211  may be of any suitable length, although the cable  211  preferably has a length between about 3 inches (about 80 mm) and about 3 feet (about 0.9 m). More preferably, the cable  211  has a length between about 5 inches (about 130 mm) and about 2 feet (about 0.6 m). In this context, a “suitable length” is a length that results in there being a distance between the receiving transducer  205  and the transmitting transducer  204  such that the signal-to-echo ratio is no less than about −25 dB (decibels) or, more preferably, no less than about −20 dB. 
         [0035]    In some embodiments, there may be more than one transmitting transducer  204 . For example, one or more transmitting transducers  204  may be located at the connector  212 , and one or more transmitting transducers  204  may be located on the cable  211 , or both, to form an array of transmitting transducers  204 . The array of transmitting transducers  204  may form, for example, a beamforming array. As another example, in embodiments where the transmitting transducer  204  is a microphone, the array of microphones may be configured as a directional microphone. 
         [0036]      FIG. 3  is a functional block diagram showing material portions of signal paths in a system  300  incorporating a speakerphone with an on-cable microphone. As illustrated in  FIG. 3 , a system  300  incorporating a speakerphone with an on-cable microphone may include a speakerphone  301  and the ability to connect to a far-side device  302 . The speakerphone  301  may include a transmitting transducer  304 , a receiving transducer  305 , an acoustic echo cancellation (AEC) processor  306 , a non-linear processing (NLP) module  307 , and a mixer  314 . The speakerphone  301  may also include other signal processing configured to enhance signal quality. 
         [0037]    In operation, a call is initiated by either the far-side device  302  or the speakerphone  301 . When a call is active, the transmitting transducer  304  transmits a transmit-path signal  309  that is received by the AEC processor  306  and the mixer  314 . Also, the receiving transducer  305  and the AEC processor  306  receive a receive-path signal  308  from the far-side device  302 . The AEC processor  306  outputs an AEC signal  315  to the mixer  314 , and the mixer  314  combines the AEC signal  315  and the transmit-path signal  309  to output a reduced echo-path signal  316  to the NLP module  307 . The NLP module  307  receives the reduced echo-path signal  316  and outputs a processed signal  317  that is transmitted to the far-side device  302 . 
         [0038]    The transmitting transducer  304  and the receiving transducer  305  may be generally as described above for  FIG. 2 . Thus, the transmitting transducer  304  may be a microphone, and the receiving transducer  305  may be a loudspeaker. The transmitting transducer  304  is separated from the receiving transducer  305  by a cable  311  to structurally isolate the transmitting transducer  304  from the receiving transducer  305  and to cause the transmitting transducer  304  and the receiving transducer  305  to be separated at a distance. As discussed above, because of this distance, the signal-to-echo ratio improves over what the ratio would be at a closer distance. Since the cable  311  may have a variety of suitable lengths, such as those described above for the cable  211 , the cable  311  is shown in  FIG. 3  with break lines. 
         [0039]    The AEC processor  306  and the NLP module  307  operate generally as discussed above for  FIG. 1 , and the AEC processor  306  may include an AEC filter or an AEC adaptive filter. That is, the AEC processor  306  may include a signal-processing algorithm that compares the incoming, receive-path signal  308  with the outgoing, transmit-path signal  309  and then subtracts the incoming signal from the outgoing signal. The subtracting of the receive-path signal  308  from the transmit-path signal  309  may be in combination with the mixer  314 . 
         [0040]    The telephone functionality for the near side may be integrated into the speakerphone  301 , or the telephone functionality may be provided by an external device, such as a traditional, wired telephone; a cellular telephone; or a Voice over Internet Protocol (VoIP) telephone or device, including a computer or mobile device operating over the Internet, for example. If the telephone functionality is provided by an external device, the external device may mediate between the speakerphone  301  and the far-side device  302 . An example of this is shown in  FIG. 4 . 
         [0041]    Returning to  FIG. 3 , the far-side device  302  may be a communication device, such as a traditional, wired telephone; a cellular telephone; or a Voice over Internet Protocol (VoIP) telephone or device, including a computer or mobile device operating over the Internet, for example. 
         [0042]    One or more of the AEC processor  306 , the NLP module  307 , and the mixer  314  may be located in a loudspeaker housing  303 , such as the loudspeaker housing  203  of  FIG. 2 . Alternatively, one or more of those components may be located in a connector, such as the connector  212  of  FIG. 2 . 
         [0043]      FIG. 4  is a functional block diagram showing material portions of signal paths in a system  400  incorporating a speakerphone with an on-cable microphone. As illustrated in  FIG. 4 , a system  400  incorporating a speakerphone with an on-cable microphone may include a speakerphone accessory  401 , a near-side device  418 , and the ability to connect to a far-side device  402 . The ability to connect to a far-side device  402  may be wireless, as illustrated in  FIG. 4 , or the ability to connect may be wired or a combination of wired and wireless connections. The speakerphone accessory  401  may be the speakerphone  201  of  FIG. 2 . In the system  400  of  FIG. 4 , though, the term “accessory” is used because the speakerphone accessory  401  connects to the near-side device  418 , which may provide the telephone functionality for the near side. 
         [0044]    Thus, the speakerphone accessory  401  may include a transmitting transducer  404 , a receiving transducer  405 , an acoustic echo cancellation (AEC) processor  406 , a non-linear processing (NLP) module  407 , and a mixer  414 . The speakerphone accessory  401  may also include other signal processing configured to enhance signal quality. 
         [0045]    The near-side device  418  may be a communication device, such as a traditional, wired telephone; a cellular telephone; or a Voice over Internet Protocol (VoIP) telephone or device, including a computer or mobile device operating over the Internet, for example. 
         [0046]    In operation, a call is initiated by either the far-side device  402  or the near-side device  418 . When a call is active, the transmitting transducer  404  transmits a transmit-path signal  409  that is received by the AEC processor  406  and the mixer  414 . Also, the receiving transducer  405  and the AEC processor  406  receive a receive-path signal  408  from the far-side device  402 , through near-side device  418 . The AEC processor  406  outputs an AEC signal  415  to the mixer  414 , and the mixer  414  combines the AEC signal  415  and the transmit-path signal  409  to output a reduced echo-path signal  416  to the NLP module  407 . The NLP module  407  receives the reduced echo-path signal  416  and outputs a processed signal  417  that is transmitted to the far-side device  402 . 
         [0047]    The transmitting transducer  404  and the receiving transducer  405  may be generally as described above for  FIG. 2 . Thus, the transmitting transducer  404  may be a microphone, and the receiving transducer  405  may be a loudspeaker. The transmitting transducer  404  may be integrated into a connector  412 , such as shown diagrammatically in  FIG. 4 , or the transmitting transducer  404  may be located along a cable  411 . A representative segment of the cable  411  is shown diagrammatically in  FIG. 4 . The transmitting transducer  404  is separated from the receiving transducer  405  by the cable  411  to structurally isolate the transmitting transducer  404  from the receiving transducer  405  and to cause the transmitting transducer  404  and the receiving transducer  405  to be separated at a distance. As discussed above, because of this distance, the signal-to-echo ratio improves over what the ratio would be at a closer distance. The cable  411  may have a variety of suitable lengths, such as those described above for the cable  211 . 
         [0048]    The AEC processor  406  and the NLP module  407  operate generally as discussed above for  FIG. 1 , and the AEC processor  406  may include an AEC filter or an AEC adaptive filter. That is, the AEC processor  406  may include a signal-processing algorithm that compares the incoming, receive-path signal  408  with the outgoing, transmit-path signal  409  and then subtracts the incoming signal from the outgoing signal. The subtracting of the receive-path signal  408  from the transmit-path signal  409  may be in combination with the mixer  414 . 
         [0049]    Thus, embodiments of the invention may be implemented as an accessory to an existing speakerphone system in a near-side device  418 , such as a speakerphone system built in to a mobile device. When connected to the near-side device  418 , the speakerphone accessory  401  may supplement or replace the existing system. Also, when connected to the near-side device  418 , the speakerphone accessory  401  may signal the near-side device  418  to deactivate the microphone or loudspeaker or both of the near-side device  418 . 
         [0050]    Accordingly, embodiments of the invention provide a speakerphone with a relatively small form factor but an improved signal-to-echo ratio over conventional small speakerphones by, for example, locating the transmitting transducer remotely from the speakerphone housing containing the receiving transducer. Thus, the transmitting transducer may be located on a connector or a connector cable extending from the housing. In this way, the microphone and the loudspeaker may be separated at a distance without increasing the form factor of the housing. This separation also helps to reduce or eliminate the structural transmission of sound waves that may propagate through the housing. Accordingly, embodiments of the invention may improve the performance of a conventional AEC filter and a conventional NLP module used within the disclosed system. 
         [0051]    The previously described versions of the disclosed subject matter have many advantages that were either described or would be apparent to a person of ordinary skill. Even so, all of these advantages or features are not required in all versions of the disclosed apparatus, systems, or methods. 
         [0052]    Additionally, this written description makes reference to particular features. It is to be understood that the disclosure in this specification includes all possible combinations of those particular features. For example, where a particular feature is disclosed in the context of a particular aspect or embodiment, that feature can also be used, to the extent possible, in the context of other aspects and embodiments. 
         [0053]    Although specific embodiments of the invention have been illustrated and described for purposes of illustration, it will be understood that various modifications may be made without departing from the spirit and scope of the invention.