Distributed speech recognition system with multi-user input stations

A central dictation system includes a central server computer and a plurality of voice input stations connected to the server computer. Speaker-dependent speech recognition capabilities are provided at each voice input station, and any authorized user may use any station. When a user logs on to one of the stations, acoustic reference files to be used in recognizing the speech of the user are downloaded from the server to the station onto which the user has logged on. The down-loaded acoustic reference files are used to perform the speech recognition at the voice input station. A high bandwidth signal generated at the voice input station and used for speech recognition processing is transcoded at the input station to form a low bandwidth speech signal. The low bandwidth speech signal and the text document resulting from the speech recognition process are uploaded to the server computer.

FIELD OF THE INVENTION
 The present invention relates to document creation systems and, more
 particularly, to such systems in which speech recognition is performed to
 convert speech signals into text documents.
 BACKGROUND OF THE INVENTION
 Recent years have seen significant advances in practical applications of
 continuous speech recognition (CSR). For example, it is now possible to
 purchase commercially available CSR application software packages suitable
 for installation and use in a conventional personal computer for home or
 office.
 It has also been proposed to provide CSR as an additional feature of
 conventional central dictation systems.
 Known central dictation systems take a number of forms. In one typical
 variety of central dictation system, which is frequently used in
 hospitals, the hard disk drive or drives of a server computer is used as
 the central voice recording device. Dictate stations are provided at a
 number of locations in the hospital to permit physicians to dictate
 directly onto the central recorder. The dictate stations may be in the
 form of hand microphones or telephone-style handsets, and are connected by
 analog or digital signal paths to the central recorder. The dictate
 stations customarily include control switches which allow the authors to
 control conventional dictation functions, such as record, stop, rewind,
 fast forward, play, etc. In addition, the dictate stations typically
 include a keypad and/or bar code reader to permit the author to enter data
 to identify himself or herself as well as the patient to whom the dictated
 material is related.
 Typical central dictation systems also include a number of transcription
 stations connected to the central recorder. The transcription stations
 commonly include a personal computer which runs a word processing software
 package, as well as listening and playback-control devices which allow the
 transcriptionist listening access to voice files stored in the central
 recorder and control over playback functions. Dictation jobs awaiting
 transcription in the central recorder are assigned to transcriptionists
 according to conventional practices.
 It has been proposed to incorporate CSR functions in the central
 recorder/server of a central dictation system. The CSR function is applied
 at the server to a dictation file to generate a text document, and then
 the text document and voice file are made available to transcriptionists
 who edit and correct the text while reviewing the voice files. The
 preprocessing of the voice files by CSR can be expected to produce
 significant improvements in productivity for the transcription function.
 In a prior co-pending patent application Ser. No. 09/099,501, which is
 commonly assigned with the present application and entitled "Dictation
 System Employing Computer-To-Computer Transmission of Voice Files
 Controlled by Hand Microphone", it was proposed to provide a central
 dictation system utilizing networked computers. According to this
 proposal, some of the networked computers have hand microphones interfaced
 thereto and constitute dictation stations, whereas others of the networked
 personal computers have headsets and foot pedals interfaced thereto and
 constitute transcription stations. The e-mail system of the computer
 network is used to transport voice files from the dictation stations and
 to the transcription stations. In addition, the e-mail system may be used
 to forward dictation files into a central dictation recorder, from which
 transcriptions can play back the dictation files.
 It would be desirable to implement CSR functions in a central dictation
 system in a manner which increases capacity of the system and lessens
 burdens on the central recorder/server. It would also be desirable to
 provide an all-digital system in which the transmission bandwidth of the
 system is not unduly burdened.
 OBJECTS AND SUMMARY OF THE INVENTION
 It is an object of the invention to provide a central dictation system in
 which continuous speech recognition processing is employed.
 It is a further object of the invention to provide a central dictation
 system which makes speaker-independent CSR available at all input
 stations, while minimizing burdens upon transmission facilities and the
 central server computer of the system.
 According to an aspect of the invention, there is provided a method of
 operating a document creation system, the system including a plurality of
 voice input stations and a server computer connected to exchange data
 signals with the voice input stations, the method including the steps of
 logging on to one of the voice input stations; placing the one of the
 voice input stations in a training mode for training a speech recognition
 algorithm; dictating into the one of the voice input stations to generate
 speech signals; analyzing the speech signals to generate acoustic
 reference files; and uploading the acoustic reference files to the server
 computer.
 According to further aspects of the invention, the logging-on step includes
 inputting ID data for identifying a person who is performing the
 logging-on step, and the method further includes the step of uploading the
 ID data to the server together with the acoustic reference files.
 According to further aspects of the invention, the method further includes
 second logging-on to a second one of the voice input stations, the second
 logging-on step including inputting author ID data for identifying an
 author who is performing the second logging-on step, the author being the
 person who performed the logging-on step previously referred to in
 connection with the training mode; transmitting to the server computer the
 author ID data inputted in the second logging-on step; in response to the
 transmitting step, downloading from the server computer to the second one
 of the voice input stations the acoustic reference files uploaded to the
 server computer in the uploading step; dictating into the second one of
 the voice input stations to generate second speech signals; and applying a
 speech recognition algorithm to the second speech signals at the second
 one of the voice input stations by using the downloaded acoustic reference
 files, to generate text document data from the second speech signals.
 According to still further aspects of the invention, the second speech
 signals are digital signals generated at a first data rate, and the method
 of the present invention further includes transcoding the second speech
 signals to form transcoded speech signals which have a second data rate
 which is lower than the first data rate. For example, the first data rate
 is preferably on the order of 22 kilobytes per second, which is high
 enough to support satisfactory performance of the speech recognition
 algorithm. After or in parallel with the speech recognition processing,
 the speech signals are transcoded down to, say, one kilobyte per second.
 At the lower data rate, although some fidelity is lost, the sound quality
 is still adequate for the purposes of audibly reviewing the transcoded
 voice file. The transcoded voice file is uploaded to the server computer
 along with the text document created by applying the voice recognition
 algorithm to the high bandwidth speech signals.
 According to other aspects of the invention, the document creation system
 includes a plurality of document review stations (which may also be
 regarded as transcription stations). The method of the invention
 preferably includes downloading the transcoded speech signals, the text
 document data and author ID data from the server computer to one of the
 document review stations to which a particular dictation job has been
 assigned. The text document is then edited and corrected at the document
 review station by the transcriptionist, who audibly plays back and reviews
 the transcoded speech signals and compares the text document which
 resulted from the speech recognition algorithm with the transcoded speech
 signals.
 According to another aspect of the invention, there is provided a central
 dictation system, including a server computer, a plurality of voice input
 stations, and a data communication network connecting the voice input
 stations to the server computer. Further in accordance with this aspect of
 the invention, the voice input stations, which are preferably constituted
 by personal computers having hand microphones interfaced thereto, are
 programmed to perform speech recognition with respect to speech signals
 inputted into the voice input stations, where the speech recognition is
 performed on the basis of acoustic reference files downloaded to the voice
 input stations from the server computer. Preferably the voice input
 stations also are programmed to transcode the speech signals inputted into
 the voice input stations from a first data rate to a second data rate
 which is lower than the first data rate, and the transcoded speech signals
 are uploaded from the voice input stations to the server computer along
 with text documents created at the voice input stations by application of
 speech recognition at the voice input stations.
 According to further aspects of the invention, the central dictation system
 includes a plurality of document review stations connected to the server
 computer by the data communication network; and text documents created by
 the speech recognition performed at the voice input stations are
 downloaded along with the transcoded speech signals from the server to
 document review stations.
 The central dictation system and document creation method, as provided in
 accordance with the invention and summarily described above, allows every
 author to use every one of the voice input stations and provides
 speaker-independent speech recognition processing at each of the input
 stations. Consequently, the central server is not burdened by speech
 recognition processing, and the capacity of the system, in terms of number
 of authors who may be simultaneously served, may be the same as the number
 of voice input stations. This is in contrast to previously proposed
 systems, in which the number of authors who could be served simultaneously
 by speech recognition processing was relatively few, being limited by the
 processing capacity of the central server. Furthermore, because the high
 bandwidth speech signals required for satisfactory speech recognition
 processing need not be transmitted to the central system, only low
 bandwidth (transcoded) speech signals are transmitted, thereby minimizing
 burdens on the transmission bandwidth of the system.

DESCRIPTION OF PREFERRED EMBODIMENTS
 A preferred embodiment of the invention will now be described, initially
 with reference to FIG. 1. In FIG. 1, reference numeral 10 generally
 indicates a central dictation system provided in accordance with the
 invention. The major components of the central dictation system 10 are a
 central server computer 12, voice input (dictation) stations 14, document
 review (transcription) stations 16, and a data communication network 18
 which connects the voice input stations 14 and the document review
 stations 16 to the server 12.
 All of the components shown in FIG. 1 may be constituted by standard
 hardware. Preferably the communication network 18 is a conventional local
 area network (LAN). The voice input stations 14 are each preferably
 constituted by a conventional personal computer 20 which runs both known
 software packages as well as software provided in accordance with the
 invention. Each of the voice input stations 14 also includes a hand
 microphone 22 which is interfaced to the respective PC 20 to permit input
 of voice signals into the PC 20. The hand microphones 22 may be of the
 type commercially marketed by the assignee of the present application
 under the trademark "BOOMERANG".
 Each of the document review stations 16 also preferably includes a
 conventional PC (reference numerals 24). Interfaced to each of the PC's 24
 is a headset 26 and a foot pedal 28. As is well known to those who are
 skilled in the art, the foot pedals 28 permit the transcriptionist to
 control playback functions of a voice file that is being reviewed by the
 transcriptionist, and the headsets 26 include small speakers or ear plugs
 which permit the transcriptionist to hear the audible reproduction of the
 voice file under review. Both the headsets 26 and the foot pedals 28 made
 be of the types commercially marketed by the assignee of the present
 invention under the trademark "BOOMERANG".
 It should be understood that each of the PC's 20 and 24 also include other
 peripheral devices not separately shown in FIG. 4. These peripherals may
 include a display, a keyboard, a mouse and a barcode reader. The PC's
 should also include a conventional sound card such as is installed in many
 of the personal computers that are now commercially available.
 FIG. 1A is a schematic representation of software which is loaded into and
 controls operation of the PC's 20.
 The software for the PC's 20 include operating system software 40, which
 may be a conventional operating system such as Windows NT. The software
 loaded in the PC's 20 also includes a program 42 which manages input and
 recording of speech signals dictated into the hand microphone 22. The
 program 42 also manages storage of speech signals as voice files in the PC
 20 as well as reproduction of the voice files.
 Another software package stored in the PC 20 is a speech recognition
 package 44. The speech recognition software 44 may be any one of a number
 of conventional CSR packages. Another program loaded in the PC's 20 is a
 speech transcoding application 46 which carries out a bandwidth-reduction
 algorithm with respect to the speech signals stored in the PC 20.
 Reference numeral 47 indicates software in the PC 20 which enables it to
 interface properly with the local area network 18, and reference numeral
 48 represents other software loaded in the PC 20, such as conventional
 device driver software, and other applications which run on the PC 20.
 The software installed in the PC's 24 of the document review stations 16
 may be similar to that illustrated in FIG. 1A, except that no voice
 transcoding software is required in the PC's 24, and the "other
 applications" represented by reference numeral 48 preferably include a
 word processing software application.
 The administrative server computer is programmed to perform the
 conventional functions carried out by the central computer of a central
 dictation system. In addition, the server computer carries out additional
 functions which are described below.
 Operation of the system of FIG. 1 for the purpose of initializing or
 "training" the speech recognition capabilities of the system will now be
 described with reference to FIG. 2.
 In an initial step 50 of FIG. 2, an individual who is an authorized user of
 the system, but for whom the speech recognition capabilities have not yet
 been initialized, logs onto one of the voice input stations 14. As will be
 understood by those of ordinary skill in the art, the log-in process
 preferably includes entry of data which identifies the user, and may also
 include entry of a password and/or another step for verifying the user's
 identity or authorization to use the system. Thus, instead of or in
 addition to entering a password, other security measures such as a
 biometric scan or use of an access card may be required.
 The voice input stations 14 may be arranged so that the speech recognition
 application 44 is automatically invoked upon completion of a log-in
 procedure; alternatively, the speech recognition program may be available
 to be invoked by the user upon completion of log-in. In either case, it
 will be assumed for the purposes of FIG. 2 that the speech recognition
 application is invoked. The user then has the option of placing the speech
 recognition program in a "training" mode, which is done according to step
 52 in FIG. 2. The user is then instructed by the voice input station 14 to
 dictate predetermined text into the hand microphone 22. The text to be
 dictated may conveniently be displayed on a display screen (not separately
 shown) of the PC 20, as is done when training conventional CSR software.
 As the user dictates into the microphone 22, the PC 20, running the speech
 recognition software, stores and analyzes the resulting voice signals to
 generate files which are indicative of the results of the analysis of the
 user's speech. This analysis is performed in accordance with conventional
 practices for speech recognition algorithms, and the resulting files are
 customarily referred to as "acoustic reference files." The generation of
 such files is indicated at step 54 in FIG. 2.
 Following step 54 is step 56. At step 56 the acoustic reference files
 generated at the voice input station in step 54 are uploaded from the
 voice input station to the central server, together with information which
 identifies the author who performed the training procedure. The uploaded
 acoustic reference files are then stored in the server and are indexed
 according to the author identifying information.
 FIG. 3 is a flow chart which illustrates operation of the central dictation
 system of FIG. 1 in connection with dictation and voice recognition
 processing of a document dictated by an author.
 According to a first step 60 in FIG. 3, an author logs on to one of the
 voice input stations. The voice input station to which the author logs on
 need not be the same as the station which the author had previously used
 to carry out the CSR training procedure. That is, the voice input station
 may be any one of the voice input stations included in the system 10.
 After the log-on process is complete, the speech recognition application is
 invoked, either automatically or by action of the author. The author then
 places the voice input station in a mode to carry out speech recognition
 of voice input to be dictated by the author (step 62). The voice input
 station then communicates with the server computer to request downloading
 of the acoustic reference files for the author which had previously been
 stored in the server computer, and the acoustic reference files are
 downloaded from the server computer to the voice input station to which
 the author logged on at step 60 (step 64). Alternatively, the downloading
 of the acoustic reference files may occur automatically during or upon
 completion of the log-on process, and before the recognition software is
 invoked or placed in recognition mode.
 Following step 64 is step 66, at which the author proceeds to dictate into
 the hand microphone of the voice input station in order to create a
 document. Although not separately indicated in step 66, the author may
 also use conventional practices to identify the subject matter of the
 document. For example, a bar code on a patient's chart may be scanned by a
 bar code reader to enter data which indicates that the document to be
 dictated relates to the patient in question.
 As the author dictates into the hand microphone, the resulting analog
 electrical signal is converted into a digital speech signal at a data rate
 that is sufficiently high to permit satisfactory application of the speech
 recognition algorithm to be carried out by the speech recognition
 software. According to a preferred embodiment of the invention, the speech
 recognition software is either one of the speech recognition packages
 provided by Philips Electronics or IBM (the latter being distributed under
 the trademark "Via Voice"). For proper operation of those speech
 recognition software packages, a data rate of 22 kilobytes per second is
 appropriate. The resulting high bandwidth digitized speech signals are
 processed by the speech recognition algorithm to generate a text document.
 At the same time, the high bandwidth speech signals are stored in the mass
 storage device of the voice input station. When the author indicates that
 dictation of the document is complete, the high bandwidth signal is
 transcoded by a conventional technique to yield a low bandwidth signal
 (step 68). For example, the low bandwidth signal may have a data rate of 1
 kilobyte/sec, in compliance with the well known "True Speech" standard.
 Following step 68 is step 70. At step 70, the voice input station uploads
 to the server computer both the text document generated at step 66 and the
 transcoded (low bandwidth) digital speech signals generated at step 68.
 The text document and the speech signals may also be retained at the voice
 input station, or may be deleted from the mass storage device of the voice
 input station.
 It will be noted that the total quantity of data to be transmitted from the
 voice input station to the server computer is relatively low, since only
 the low bandwidth speech signals, and not the originally recorded high
 bandwidth speech signals, are transmitted to the server together with the
 text document. Of course, the text document itself typically consists of a
 rather small quantity of data, on the order of one kilobyte per page.
 At this point, both the low bandwidth digital speech signals and the
 unedited text document may be made available for review by authorized
 users of the system. In addition, the text document and the low bandwidth
 speech signals are transmitted from the server computer to one of the
 document review stations 16, either immediately upon uploading of those
 items to the server, or at a subsequent time when the task of reviewing
 and editing the text document is assigned to a transcriptionist who uses
 the document review station (step 72).
 FIG. 4 is a flow chart which illustrates a process for editing the text
 document which was downloaded to the text document review station at step
 72 of FIG. 3.
 As indicated in step 80 of FIG. 4, the transcriptionist causes the
 downloaded low bandwidth speech signals to be played back and reviews the
 reproduced speech while also reviewing the text document and making such
 corrections to the text document as are required. The main purpose of this
 step is for the transcriptionist to detect and correct errors made by the
 CSR software in creating the text document. The transcriptionist does this
 by listening to the reproduced low bandwidth speech signals and comparing
 them to the text document. The transcriptionist corrects the text document
 so that it matches the speech signals dictated by the author.
 When the transcriptionist has finished editing the text document, the
 resulting corrected text document is then transmitted back to the server
 12 for distribution to the intended recipients. (step 82).
 In addition, suitable speech recognition software at the document review
 station notes the corrections made by the transcriptionists, compares the
 corrections with corresponding speech signals and generates updated
 acoustic reference files. These updated acoustic reference files are then
 uploaded to and stored in the server computer. By updating the author's
 acoustic reference files, subsequent performance of the speech recognition
 function for that author is improved.
 In the document creation/central dictation system described above, and
 provided in accordance with the invention, speaker-dependent speech
 recognition processes are made available at each one of voice input
 stations included in the system. The speech recognition process is carried
 out by the voice input station itself, so that the processing requirements
 for speech recognition do not burden the server computer. Any author may
 use any one of the voice input stations, because the acoustic reference
 files for the author are downloaded as required from the central server to
 the voice input station currently in use by the author. Digital speech
 signals are initially generated at a high bandwidth data rate that is
 suitable for speech recognition processing. Before the speech signals are
 transmitted within the dictation system, the signals are transcoded to a
 low bandwidth data rate that is adequate for subsequent audible review of
 the voice file but does not unduly burden the data transmission capacity
 of the system.
 Although the foregoing description assumes that the author's speech signals
 were inputted into the voice input stations via a hand microphone included
 in the voice input station, there are alternative possibilities. For
 example, the author's dictation may be telephoned in to the voice input
 station. The speech signal provided to the voice input station may be
 either analog or digital. As another alternative, the dictation may
 initially be dictated into a separate recorder such as a portable recorder
 which utilizes a digital memory card as a recording medium. The dictation
 may then be transferred to the voice input station by interfacing the
 portable recorder to the voice input station, or by interfacing the
 digital memory card itself to the voice input station.
 It is preferred that, as discussed above, the "training" of the CSR
 software be performed at the voice input stations. However, it is also
 within the contemplation of the invention that training of the CSR
 software be performed by the server computer on the basis of high
 bandwidth speech signals transmitted from a voice input station.
 It is to be understood that the above description may indicate to those
 skilled in the art additional ways in which the principles of this
 invention may be used without departing from the spirit of the invention.
 The particularly preferred methods and apparatus are thus intended in an
 illustrative and not limiting sense. The true spirit and scope of the
 invention are set forth in the following claims.