Abstract:
A telecommunication device is disclosed, comprising: a microphone array comprising a plurality of microphones, wherein each microphone receives an analogue acoustic signal; a position sensing device for determining how the telecommunication device is positioned in three-dimensions with respect to a user&#39;s mouth; at least one analogue/digital converter for converting each analogue acoustic signal into a digital signal; a digital signal processor for performing signal processing on the received digital signals comprising a controller, a plurality of delay circuits for delaying each received signal based on an input from the controller and a plurality of preamplifiers for adjusting the gain of each received signal based on a gain input from the controller, wherein the controller selects the appropriate delay and gain values applied to each received signal to remove noise from the received signals based on the determined position of the telecommunication device. A method for creating and controlling a location of a virtual microphone near a telecommunication device so as to reduce background noise in a speech signal is also disclosed.

Description:
TECHNICAL FIELD 
       [0001]    The present invention generally relates to generating uplink noise cancellation in a telecommunication device. In particular, the present invention relates to a method and apparatus for changing the location of a sensitivity lobe of a microphone array based on how the telecommunication device is being held. 
       BACKGROUND 
       [0002]    The use of wireless or telecommunication devices such as a cellular phone has greatly increased through the years. As a result, these telecommunication devices are being used in a large variety of environments ranging from inside moving vehicles, to crowded cafes, to windy beaches. Many of these environments are noisy environments which pose special problems for service providers to provide acceptable signal quality to their users. 
         [0003]    For many conventional telecommunication devices, a microphone is placed near a speaking user&#39;s mouth and will pick up speech signals. Unfortunately, the microphone will also pick up background noise, which can greatly degrade the quality of the speech signal transmitted to all of the parties involved in the call. Many noise cancellation methods have been developed for single microphone systems, but they tend to still result in substandard quality when used in noisy conditions. 
         [0004]    Better noise cancellation can be achieved using multiple microphones located on the telecommunication device. The multiple microphone techniques exploit spatial selectivity and can suppress non-stationary noises such as babbling noise produced by people talking in the background. However, many of these systems still assume a standard location of the microphones in relation to the speaker&#39;s mouth. A problem occurs when the speaker does not hold the communication device in the standard configuration. 
         [0005]    One system designed to overcome such problems is disclosed in U.S. Patent Application No. 2007/0230712. In this system, two microphones are used to capture an acoustic signal including the desired voice signal and an unwanted noise signal. The telecommunication device includes an orientation sensor for measuring a one dimensional orientation of the communication device, i.e., how the telecommunication device is being held along the user&#39;s cheek, while the acoustic signal is being captured. An audio processing unit then processes the acoustic signal to remove some of the noise based on the measured orientation of the telecommunication device. 
         [0006]    One problem with the disclosed multiple microphone technique is that the noise cancellation system relies only on the one dimensional orientation measurement along the cheek of the user. Unfortunately, different users hold their telecommunication devices in a variety of ways, which results on various distances between the user&#39;s mouth and the telecommunication device and distances between the user&#39;s ear and the telecommunication device. Thus, there is a need for a method and apparatus for providing noise cancellation in a received acoustic signal based on a three dimensional orientation measurement of the telecommunication device. 
       SUMMARY 
       [0007]    The present invention provides noise cancellation for acoustic signals received by a plurality of microphones wherein the three-dimensional position of the telecommunication device is determined and then used by a digital signal processor to remove the noise component from the acoustic signal. 
         [0008]    According to a first aspect, there is provided a telecommunication device, comprising: a microphone array comprising a plurality of microphones, wherein each microphone receives an analogue acoustic signal; a position sensing device for determining how the telecommunication device is positioned in three-dimensions with respect to a user&#39;s mouth; at least one analogue/digital converter for converting each analogue acoustic signal into a digital signal; a digital signal processor for performing signal processing on the received digital signals comprising a controller, a plurality of delay circuits for delaying each received signal based on an input from the controller and a plurality of preamplifiers for adjusting the gain of each received signal based on a gain input from the controller, wherein the controller selects the appropriate delay and gain values applied to each received signal to remove noise from the received signals based on the determined position of the telecommunication device. 
         [0009]    According to second aspect, there is provided a method for creating and controlling a location of a virtual microphone near a telecommunication device so as to reduce background noise in a speech signal, comprising the steps of: receiving acoustic signals containing a speech signal and a noise signal at a plurality of microphones located on the telecommunication device; determining a three-dimensional position of the telecommunication device with reference to a user&#39;s mouth; and adjusting delay and gain values applied to the received acoustic signals from each microphone based on the determined position of the telecommunication device to reduce the noise signal in the received acoustic signal. 
         [0010]    According to a third aspect, there is provide a computer program comprising instructions which when executed on a processor of a telecommunication device cause the telecommunication device to perform the method according to the second aspect. 
         [0011]    Other objectives, features and advantages of the present invention will appear from the following detailed disclosure, from the attached dependent claims as well as from the drawings. Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to “a/an/the [element, device, component, means, step, etc]” are to be interpreted openly as referring to at least one instance of said element, device, component, means, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The above, as well as additional objects, features and advantages of the present invention, will be better understood through the following illustrative and non-limiting detailed description of preferred embodiments of the present invention, with reference to the appended drawings. 
           [0013]      FIG. 1  schematically illustrates a telecommunication device according to one embodiment of the invention. 
           [0014]      FIG. 2  illustrates further features of the telecommunication device illustrated in  FIG. 1  according to one embodiment of the invention. 
           [0015]      FIG. 3  illustrates a microphone array with signal processing devices according to one embodiment of the invention. 
           [0016]      FIG. 4  is a flow chart illustrating a method for noise cancellation according to one embodiment of the invention. 
           [0017]      FIG. 5A  illustrates a telecommunication device being held in a first position according to one embodiment of the invention. 
           [0018]      FIG. 5B  illustrates a telecommunication device being held in a second position according to one embodiment of the invention. 
           [0019]      FIG. 5C  illustrates a telecommunication device being held in a third position according to one embodiment of the invention. 
           [0020]      FIG. 5D  illustrates a telecommunication device being held in a fourth position according to one embodiment of the invention. 
           [0021]      FIG. 6  schematically illustrates a computer readable medium and a processing device, wherein a computer program is stored on the computer readable medium, the computer program comprising instructions which when executed on the processor of a telecommunication device cause the method of  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0022]      FIG. 1  is a diagram of a telecommunication device  100  according to an implementation consistent with principles of the invention. As shown in  FIG. 1  the telecommunication device  100  may include a housing  110 , a speaker  120 , a display  130 , control buttons  140 , a keypad  150 , a plurality of microphones  160 ,  161 ,  162 , and an imaging unit  170 . The housing  110  may support the components of the telecommunication device  100 . The speaker  120  may provide audible information to the user of the telecommunication device  100 . The display  130  may provide visual information to a user of the telecommunication device  100 . For example, the display  130  may render media information, such as image frames and/or video, and/or function as a viewfinder in connection with the operation of the imaging unit  170 . The control buttons  140  may permit the user to interact with the communication device  100  to cause the telecommunication device  100  to perform one or more operations. The keypad  150  may include a standard telephone keypad. The microphones  160 ,  161 ,  162  can be unidirectional microphones and arranged in an array which creates a virtual microphone which receives audible information from the user. As will be explained below in more detail the location of the virtual microphone can be changed by adjusting the delay and gain of the acoustic signals captured by the plurality of microphones. The microphones can be arranged symmetrically or asymmetrically around the telecommunication device  100 . Furthermore, the location of each microphone on the communication device  100  and the number of microphones used in the array can be varied from the layout shown in  FIG. 1  and the invention is not limited thereto. The imaging unit  170  may enable the user to capture and store video and/or images. 
         [0023]    Referring now to  FIG. 2 , an exemplary telecommunication device  100 , in accordance with one embodiment of the invention, comprises a microphone array comprised of three microphones  160 ,  161 ,  162 , a keypad  150 , one or more speakers  120 , the display  130 , a transceiver  125 , a memory  155  that communicates with a processor  135 , an imaging unit  170  and an position sensing device  195 . The transceiver  125  comprises a transmitter circuit  180  and a receiver circuit  145 , which respectively transmit outgoing radio frequency signals to base station transceivers and receive incoming radio frequency signals from the base station transceivers via an antenna  115 . 
         [0024]    The processor  135  communicates with the memory  155  via an address/data bus. The processor  135  may be, for example, a commercially available or custom microprocessor. The memory  155  is representative of the one or more memory devices containing software and data used to provide audible feedback to a user through the speaker  120 . The memory  155  may include, but is not limited to, the following types of devices: cache, ROM, PROM, EPROM, EEPROM, flash, SRAM and DRAM. 
         [0025]    The memory  155  may contain various categories of software and/or data. For example, as illustrated in  FIG. 2 , the memory  155  may comprise an operating system  190 . The operating system  190  generally controls the operation of the telecommunication device  100 . In particular, the operating system  190  may manage the telecommunication device&#39;s software and/or hardware resources and may coordinate execution of programs by the processor  135 . Although  FIG. 2  illustrates an exemplary software and hardware architecture that may be used to provide noise cancellation and other operations of a telecommunication device, it will be understood that the present invention is not limited to such a configuration but is intended to encompass any configuration capable of carrying out the operations described herein. 
         [0026]    According to one embodiment of the invention, the processor  135  may be comprised of or operate like various components comprising but not limited thereto at least Digital Signal Processor (DSP) hardware including one analogue/digital converter  205 ,  205 ′,  205 ″, at least one delay element  210 ,  210 ′,  210 ″ and at least one preamplifier  215 ,  215 ′,  215 ″ and the controller  220  as illustrated in  FIG. 3 . In this embodiment, each microphone has its own A/D converter, delay element and preamplifier but the invention is not limited thereto. The controller  220  can control the microphone array comprised of microphones  160 ,  161 ,  162  by adjusting the delay and gain values that are applied to the acoustic signals received by each microphone. 
         [0027]    As mentioned above, the microphone array creates a virtual microphone using known control techniques. The virtual microphone has sensitivity lobes from which acoustic signals are received and null sections from which no or limited acoustic signal are received or dampened. The location of the virtual microphone can be moved by adjusting the delay, gain, and frequency response values applied to the received signals. Thus, the best location for recording speech signals can be moved around the telecommunication device  100  by adjusting the delay and gain values applied during processing. 
         [0028]    According to one embodiment of the invention, a position sensing device  195  is incorporated into the telecommunication device  100 . The position sensing device  195  is used to determine how the user is holding the telecommunication device  100  in relation to the user&#39;s head. In this embodiment of the invention, the position sensing device is an accelerometer but the invention is not limited thereto. For example, any device which can sense or determine how the telecommunication device is being held in a three-dimensional way can be used in the present invention. In this embodiment, the accelerometer  195  can create an [x,y,z] system, wherein the three sub-vectors are orthogonal in relation to each other, and the resulting vector v determined by the accelerometer  195  always points to the ground. 
         [0029]    As a result of the position information obtained from the accelerometer  195 , the controller  220  can determine the location of the virtual microphone to be able to receive acoustic signals in an approximate direction of the user&#39;s mouth. The controller  220  can then change the location of the virtual microphone to correspond to the determined position of the user&#39;s mouth. This will increase the speech component in the processed acoustic signal while decreasing the noise component, thus increasing the quality of the speech component. 
         [0030]    According to one embodiment of the invention, the controller  220  can store various delay, gain, and frequency shape values for various predetermined positions of the telecommunication device. As a result, the controller  220  can quickly apply the appropriate delay and gain values to the acoustic signals from the microphone array once the position of the telecommunication device is determined. The user may turn the device  100  in different directions illustrated, but not limited to, the arrows a, b, and c as shown in  FIG. 5A . 
         [0031]    For example, a first set of delay and gain values can be stored for use when the telecommunication device is being held in a standard manner as illustrated in  FIG. 5A , The location of the virtual microphone can be moved by adjusting the delay, gain, and frequency response values applied to the received signals. Thus, the best location for recording speech signals can be moved in a direction illustrated by the dashed lines and oval forming a virtual microphone lobe  500   a  of a virtual microphone. 
         [0032]    A second set of delay and gain values can be stored to be used when the telecommunication device is being held in the manner illustrated in  FIG. 5B . In this example, the stored values would move the location of the virtual microphone down, forming a virtual microphone lobe  500   b , since the telecommunication device is being held above the user&#39;s mouth. 
         [0033]    A third set of delay and gain values can be stored to be used when the telecommunication device is being held in the manner illustrated in  FIG. 5C . In this example, the stored values would move the location of the virtual microphone in a direction from the telecommunication device forming a virtual microphone lobe  500   c , since the telecommunication device is being held above and away from the user&#39;s mouth. 
         [0034]    A fourth set of delay and gain values can be stored to be used when the telecommunication device is being held in the manner illustrated in  FIG. 5D . In this example, the stored values would move the location of the virtual microphone up forming a virtual microphone lobe  500   d  since the user most likely be lying and thus the telecommunication device is being held in a standard matter in relation to the user&#39;s mouth. The decision to form a virtual microphone lobe in a direction illustrated in  FIG. 5D  may be based on a reasonableness analysis performed by the controller based on the position information received from the accelerometer  195  about the device  100 . 
         [0035]    This change of direction of the virtual microphone, as illustrated in  FIG. 5D , may be delayed, because the device  100  may just be temporary moved into this position and than back to a normal position where the user sits or stands. In this case the virtual microphone lobe will be directed according to the location illustrated in  FIG. 5A . 
         [0036]    The operation of the processor  135  will now be described with reference to  FIG. 4  according to one embodiment of the invention. In step  401 , each microphone of the microphone array receives a plurality of acoustic signals. In step  403 , the controller  220  receives information from the accelerometer  195  to determine the position of the telecommunication device in relation to the user&#39;s head. The controller  220  either calculates the needed delay and gain values for each received acoustic signal or simply retrieves stored delay and gain values from memory  155  for the determined position of the telecommunication device  100  in step  405 . The controller  220  then applies the selected delay and gain values to the delay elements  210  and the preamplifiers  215  in step  407 . The controller then processes the acoustic signals in a known manner using the applied delay and gain values after they have been converted into digital signals by the A/D converters  205  to produce an output signal in step  409 . The output signals can then be sent to the transceiver  180  for broadcast. 
         [0037]    According to another embodiment of the invention, the controller  220  sends the output signals as a side tone to the ear speaker  120  of the telecommunication device  100  so that the user can hear his/her part of the conversation. In this embodiment, the controller  220  can adjust the strength of the side tone based on the determined position of the telecommunication device. For example, the strength of the side tone can be increased when it is determined that the telecommunication device is being held away from the user&#39;s ear. 
         [0038]    The method according to the present invention is suitable for implementation with aid of processing means, such as computers and/or processors. Further especially, the feature of processing digital signals are particularly suitable to be performed in a Digital Signal Processor (DSP) hardware or other dedicated hardware. 
         [0039]    Therefore, there is provided computer programs, comprising instructions arranged to cause the processing means, processor, or computer to perform the steps of any of the methods according to any of the embodiments described with reference to  FIG. 4 . The computer programs preferably comprise program code which is stored on a computer readable medium  1000 , as illustrated in  FIG. 6 , which can be loaded and executed by a processing means, processor, or computer  1002  to cause it to perform the methods, respectively, according to embodiments of the present invention, preferably as any of the embodiments described with reference to  FIG. 4 . The computer  1002  and computer program product  1000  can be arranged to execute the program code sequentially where actions of the any of the methods are performed stepwise. The processing means, processor, or computer  1002  is preferably what normally is referred to as an embedded system. Thus, the depicted computer readable medium  1000  and computer  1002  in  FIG. 6  should be construed to be for illustrative purposes only to provide understanding of the principle, and not to be construed as any direct illustration of the elements. 
         [0040]    The invention has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the invention, as defined by the appended patent claims. 
         [0041]    For example, the microphone array may be comprised of at least three or more microphones in other embodiments.