Patent Publication Number: US-2010128883-A1

Title: System And Method Of Calibrating An Echo Canceller Using Preemptive Tone Sequencing

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is related to copending patent application Ser. No. 11/497,886 entitled “System and Method for Managing Virtual Collaboration Systems,” filed on Aug. 2, 2006 and assigned to the same assignee as the present application, the disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND 
     Media conferencing is becoming more commonplace as technological advancements enable the real-time or near real-time transmission of bandwidth-intensive media, such as video and audio, between geographically-dispersed nodes. An exemplary conferencing system may include audio communication between two or more nodes, each utilizing a conference speakerphone or a separate speaker and microphone. One problem that may arise in the conferencing system is echo, which results from the microphone picking up sound from the speaker as the sound reflects off other objects, such as the walls of a room. 
     A number of echo cancellers have been created to minimize the presence of echo to users. An echo canceller may be initiated and calibrated using an audio input. For example, the echo canceller may be initiated and calibrated as a user begins speaking into a microphone. However, the echo canceller may not properly calibrate if the user&#39;s voice is not of sufficient vocal quality, for example, if the user&#39;s voice is too low in volume. This is particularly relevant for children, the elderly, sick individuals (e.g., with a cold or flu), and other people with vocal deficiencies. A consequence of an improperly calibrated echo canceller may be that the echo becomes so prevalent that the conference is deemed unusable. 
     For these and other reasons, there is a need for the present invention. 
     SUMMARY 
     One embodiment provides a system for calibrating an echo canceller using a preemptive tone sequence. The system includes a node and a tone sequence management unit operatively connected to the node. The node includes a speaker, a microphone, and the echo canceller operatively connected to the microphone. The tone sequence management unit transmits a digital tone sequence to the speaker. The speaker plays the digital tone sequence. The microphone records an output of the speaker, converts the output into a digital data segment, and transmits the digital data segment to the echo canceller. The echo canceller is calibrated based on the digital data segment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide a further understanding of the present invention and are incorporated in and constitute a part of this specification. The drawings illustrate the embodiments of the present invention and together with the description serve to explain the principles of the invention. Other embodiments of the present invention and many of the intended advantages of the present invention will be readily appreciated as they become better understood by reference to the following detailed description. The elements of the drawings are not necessarily to scale relative to each other. Like reference numerals designate corresponding similar parts. 
         FIG. 1  illustrates a block diagram of a system for calibrating an echo canceller using a preemptive tone sequence, in accordance with one embodiment. 
         FIG. 2  illustrates another block diagram of a system for calibrating an echo canceller using a preemptive tone sequence, in accordance with one embodiment. 
         FIG. 3  illustrates a flow diagram of a method of calibrating an echo canceller using a preemptive tone sequence, in accordance with one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     In the following Detailed Description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. In this regard, directional terminology, such as “top,” “bottom,” “front,” “back,” “leading,” “trailing,” etc., is used with reference to the orientation of the Figure(s) being described. Because components of embodiments of the present invention can be positioned in a number of different orientations, the directional terminology is used for purposes of illustration and is in no way limiting. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims. 
     As used herein, the term “media” includes text, audio, video, sounds, images, or other suitable digital data capable of being transmitted over a network. 
     As used herein, the term “node device” includes processor-based devices, input/output devices, or other suitable devices for facilitating communications among remote users. Examples of node devices include fax machines, video cameras, telephones, printers, scanners, displays, personal computers, microphones, and speakers. 
     As used herein, the term “node” includes any suitable environment or system configured to transmit and/or receive media via one or more node devices. In one embodiment, the environment is a collaborative environment, which enables remote users to share media across one or more node devices. A collaborative environment will enable, for example, a presenter to simultaneously give a multimedia presentation to an audience not only in the presenter&#39;s location but also in one or more remote locations. The collaborative environment may further enable the audience in the remote locations to participate in the presentation as the audience in the presenter&#39;s location would participate (e.g., ask questions to the presenter). 
     As used herein, the term “event” refers to a connection of a plurality of nodes such that one or more node devices of one node are configured to transmit media to and/or receive media from one or more node devices of another node. 
     Embodiments of a system and method of calibrating an echo canceller using a preemptive tone sequence are described herein. A preemptive tone sequence is played to calibrate the echo canceller at each node. In one embodiment, the preemptive tone sequence is played at the beginning of an event. In one embodiment, the preemptive tone sequence includes a number of consecutive, polyphonic chimes. In one embodiment, different preemptive tone sequences serve as different indicators. For example, a tone sequence may be used to instruct users to begin the event. In one embodiment, the preemptive tone sequence covers a frequency range similar to the frequency range of a human voice. 
       FIG. 1  illustrates a block diagram of a system  100  for calibrating an echo canceller using a preemptive tone sequence, in accordance with one embodiment.  FIG. 2  illustrates another block diagram of system  100  for calibrating an echo canceller using a preemptive tone sequence, in accordance with one embodiment. Referring to  FIGS. 1 and 2 , system  100  includes an event manager  102 , a first node  104   a , and a second node  104   b . Event manager  102  is operatively connected to first node  104   a  and second node  104   b  (collectively referred to as nodes  104 ) via network  106 . First node  104   a  is capable of communicating with second node  104   b  over network  106 . In one embodiment, nodes  104  are geographically-dispersed. Network  106  includes any suitable network, such as a local area network (LAN) or the Internet. 
     Event manager  102  includes a tone sequence management unit  108 . First node  104   a  includes a first speaker  110   a , a first microphone  112   a , and a first echo canceller  114   a  operatively connected to first microphone  112   a . Second node  104   b  includes a second speaker  110   b , a second microphone  112   b , and a second echo canceller  114   b  operatively connected to second microphone  112   b . Tone management unit  108  transmits a digital tone sequence over network  106  to first speaker  110   a  and second speaker  110   b  (collectively referred to as speakers  110 ). Speakers  110  output an analog tone sequence based on the digital tone sequence. 
     First microphone  112   a  and second microphone  112   b  (collectively referred to as microphones  112 ) record the analog tone sequence output by speakers  110 , convert the analog tone sequence into a digital data segment, and transmit the digital data segment to first echo canceller  114   a  and second echo canceller  114   b  (collectively referred to as echo cancellers  114 ), respectively. 
     Echo cancellers  114  minimize echo created within nodes  104 . Echo cancellers  114  may include any suitable echo canceller capable of minimizing echo in an audio signal. In one embodiment, echo cancellers  114  are initiated after receiving the digital data segment from microphones  112  and are calibrated based on the digital data segment. 
     In one embodiment, echo cancellers  114  are calibrated by comparing the digital data segment with the digital tone sequence to determine an echo to be eliminated from future recordings of microphones  114 . In other embodiments, echo cancellers  114  are calibrated using any suitable process as contemplated by those skilled in the art. 
     In one embodiment, nodes  104  are enclosed or partially-enclosed rooms, which are capable of creating echo. In one embodiment, microphones  112  are boundary microphones. In one embodiment, speakers  110  that output the analog tone sequence are positioned near microphones  112  such that microphones  112  can effectively record the analog tone sequence. In one embodiment, each corresponding speaker  110  and microphone  112  pair are included within a single unit, such as a speakerphone. 
     Tone sequence management unit  108  manages one or more tone sequences played by speakers  110 . The tone sequence is recorded by microphones  112  and used to calibrate echo cancellers  114 . In one embodiment, a tone sequence is a plurality of consecutive, polyphonic chimes. In one embodiment, the plurality of polyphonic chimes are selected based on pleasantly sounding note combinations (i.e., a melody) in accordance with music theory as contemplated by those skilled in the art. In one example, the tone sequence may be created to follow a chord progression. 
     The tone sequence is of a suitable length and volume, and each chime is of a suitable frequency to properly calibrate echo cancellers  114 . In one embodiment, each tone in the tone sequence is about a half-second. In one embodiment, the tone sequence is of a frequency range similar to the frequency range of a human voice. In one embodiment, the tone sequence is of an ascending frequency range. For example, a tone sequence may include a sequence of four audio tones: a 400 Hz tone, a 1000 Hz tone, a 2000 Hz tone, and a 3750 Hz tone. In one embodiment, the delay between each tone is about 500 ms. In other embodiments, the length of each tone, the time between each tone, the volume of the tones, and the melody of the tones are suitably selected for optimal calibration of echo cancellers  114 . 
     In one embodiment, the tone sequence is played by speakers  110  at the beginning of an event (e.g., a teleconference). In one embodiment, the tone sequence is played at the end of an event. In one embodiment, the tone sequence is played when a user joins and/or leaves an event. In other embodiments, the tone sequence is played at any suitable time within the event. 
     In one embodiment, the tone sequence serves as an indicator, relaying information regarding the event to the users. In one example, the tone sequence may serve as an indicator to begin an event (e.g., to indicate that users may begin speaking). In another example, the tone sequence may serve as an indicator of a user joining or leaving an event. In one embodiment, different tone sequences are used to represent different indicators. 
       FIG. 3  illustrates a flow diagram of a method  140  of calibrating an echo canceller using a preemptive tone sequence, in accordance with one embodiment. Referring to  FIGS. 1 ,  2  and  3 , tone sequence management unit  108  transmits (at  142 ) a digital tone sequence to speakers  110 . As previously described, a tone sequence is a plurality of consecutive, polyphonic chimes. Speakers  110  play (at  144 ) the digital tone sequence. The digital tone sequence is output from speakers  110  as an analog tone sequence. Microphones  112  record (at  146 ) the analog tone sequence along with other sounds present in nodes  104 . The recorded analog tone sequence is converted (at  148 ) to a digital data segment, and the digital data segment is transmitted (at  150 ) to echo cancellers  114 . In one embodiment, echo cancellers  114  are initiated after receiving the digital segment. Echo cancellers  114  are calibrated (at  152 ) based on the digital data segment. 
     Embodiments described and illustrated with reference to the Figures provide systems and methods of calibrating an echo canceller using a preemptive tone sequence. It is to be understood that not all components and/or steps described and illustrated with reference to the Figures are required for all embodiments. In one embodiment, one or more of the illustrative methods are preferably implemented as an application comprising program instructions that are tangibly embodied on one or more program storage devices (e.g., hard disk, magnetic floppy disk, RAM, ROM, CD ROM, etc.) and executable by any device or machine comprising suitable architecture, such as a general purpose digital computer having a processor, memory, and input/output interfaces. 
     Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific embodiments shown and described without departing from the scope of the present invention. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this invention be limited only by the claims and the equivalents thereof.