Jeroen Fransen, Dave Pye, Tony Robinson, Phil Woodland and Steve Young
Cambridge University Engineering Department (CUED) Speech Group Trumpington Street, Cambridge CB2 1PZ, UK
Introduction
The speech database described in this document is the UK English equivalent of a subset of the US American English WSJ0 database The WSJ0 corpus and associated wordlists and language models are available from the Linguistic Data Consortium, 441 Williams Hall, University of Pennsylvania, Philadelphia, PA 19104-6305, USA. Phone: +1 (215) 898-0464, Fax: +1 (215) 573-2175, e-mail: ldc@unagi.cis.upenn.edu. The name of the UK English version, WSJCAM0, represents the Wall Street Journal recorded at the University of CAMbridge (phase 0). It consists of speaker-independent (SI) read material, split into training, development test and evaluation test sets. There are 90 utterances from each of 92 speakers that are designated as training material for speech recognition algorithms. A further 48 speakers each read 40 sentences utterances containing only words from a fixed 5,000 word vocabulary of 40 sentences from the 64,000 word vocabulary, which will be used as testing material. Each of the total of 140 speakers also recorded a common set of 18 adaptation sentences. Recordings were made from two microphones: a far-field desk microphone and a head-mounted close-talking microphone.
All resulting waveforms will be distributed in compressed digitised form, accompanied by orthographic transcriptions and automatically generated phone and word alignments.
Recorded Material
All recorded sentences were taken from the Wall Street Journal (WSJ) text corpus. Since this text corpus had previously been recorded in American English for identical purposes, we could benefit from the materials used for that effort (see Paul Baker, 1992; also ftp: gov.nist.ncsl.jaguar). Therefore we could make use of existing conventions, utilities, vocabularies, and large selections of processed texts from a real newspaper. The main problems with recording British English talkers reading WSJ prompts came as a consequence of the US origin of the text. This posed an extra pronunciation problem to some speakers, which compounded the difficulties with WSJ's financial jargon and written style. Therefore a modified pronunciation dictionary had to be constructed that covered UK pronunciations for some US-specific words.
The recording text material was used as follows. A common set of 18 adaptation utterances were recorded at the start of the session for each speaker (see Appendix A for all sentences):
The training sentences were taken from the WSJ0 training subcorpus of about 10,000 sentences. Each training speaker read about 90 training sentences, selected randomly in paragraph units. It was found that this was the maximum number of sentences that could be recorded in a one hour session. The same sentences were allowed to occur in several speakers prompts, though never more than once per speaker.
Each test speaker read 80 sentences from the subcorpus originally designated for development testing in WSJ0, consisting of 40 sentences from the 5,000-word corpus (which contained a total of 2,000 sentences) and 40 sentences from the 64,000-word corpus (a total of 4,000 sentences). The test sentences were randomly selected and each test sentence was allowed to occur in only one speaker's prompt material. Since no sentence repetition between or within speakers was allowed for the testing portion of the corpus, this selection procedure exhausted the 5,000-word sentences almost completely (48 speakers by 40 sentences each). All sentences were taken from the non-verbalised pronunciation texts (i.e. there was no written punctuation words in the prompt material). All numerical data were written out in words in the prompts (i.e. so-called normalised texts were used).
Recording Room
All recordings were made in a quasi-soundproof room in the ECR Lab of the Engineering Department. This `quiet room' measured five metres by five metres. The room was closed off by double doors during recordings and its windows are double-glazed. Fresh air was blown in through sound-trapped ventilation.
Speakers sat on a chair in front of a desk. A fan-free workstation monitor that displayed the prompt texts was on the desk, along with the workstation keyboard and mouse. The actual workstation base-unit was placed outside the room to eliminate fan noise. The far-field desk microphone and a pre-amplifier for the close-talking microphone were placed to the left of the speaker. The close-talking microphone was attached to a pair of headphones which were worn by the speaker. The entire interactive recording process was co-ordinated by clicking on buttons on the workstation screen. More details of this procedure can be found in the recording session section of this report.
Recording Equipment
Recordings were made with two microphones. The close-talking microphone (Sennheiser HMD414-6) fed directly into a separate pre-amplifier (Symetrix SX202) and then to the analogue line input of a workstation (Silicon Graphics Iris Indigo) which, in turn, was connected to the workstation's internal A/D converter. The desk microphone's signal (Canford C100PB) first fed into a built-in pre-amplifier and then into the analogue line input. The technical specifications of the recording equipment is given in Appendix B.
Speakers
Speakers were recruited by placing advertisements on computer bulletin boards, in the University student newspaper `Varsity', in the Engineering Department's newsletters, and on notice boards in common rooms throughout the University. The advertisement asked for native speakers of UK English who would like to contribute to speech research by reading out newspaper sentences for an hour. Each speaker was offered a reward of 5 for their efforts.
The age distribution of training speakers is displayed below. The age distribution of the test speaker population is similar. A concerted effort was made to attract as wide a range of regional accents as possible. However, we were obviously limited to those speakers who lived or worked in the Cambridge area.
Age Range Distribution of Training Speakers
Range Female Male 18-23 21 25 24-28 11 19 29-40 3 4 40+ 4 5Speaker Partitions for Evaluation and Development Test
The test material was recorded by 48 test speakers without making an a priori division of speakers into the development test and evaluation test groups. Two evaluation sets and a development set of speakers were defined, with the aim of obtaining balanced speaker groups. The procedure that placed speakers in the different test sets aimed to balance the number of male and female speakers in each set, then to balance the age distribution, and finally a coarsely calculated speaking rate measure. Therefore, each of the 3 test groups contain roughly the same proportion of speakers of the same sex and from the same age range. The speaking rate was computed for each test speaker by dividing the total number of samples per speaker by the number of words in the transcription .dot files. The adaptation material was not included in this computation as it was missing for one speaker. Within each age/sex group individual speakers with comparable speaking rates were then equally distributed over the test groups.
The development test speaker group comprises 18 speakers and is distributed with the training material. The two evaluation test sets contain data from 14 speakers that will be released at a later stage.
Recording Session
At the start of each recording session, the speaker was given some instructions to read. These instructions provided a general introduction to the project and a description of the task (reading US American English business newspaper sentences to a microphone). The speakers were asked to read each sentence through before recording it. They were also warned of the possibility of grammatical and spelling errors occurring, the financial business jargon and the written language style. The speakers were instructed to speak naturally and clearly in their usual accent at normal volume. Each speaker was given a short demonstration of how to use the recording setup.
The actual recording process for each sentence consisted of five steps, each co-ordinated by clicking on the on-scree buttons. First, the speaker silently read the sentence. When ready, the speaker would then click on record to start recording and then read the sentence aloud. The recording was terminated by clicking on the stop button. The user could check that the recording is satisfactory by using the play button to listen to what was recorded. If the speech was truncated or mispronounced it could be re-recorded by again using record. Speakers were advised to only utilise the play back and re-record facilities when not absolutely confident of the correctness of their utterance. When a speaker had finished with the current sentence, the continue button moved to the next sentence.
All speakers were first given the chance to practice on 4 sentences under supervision of the recording co-ordinator. Any problems detected in the process were corrected or explained. The practice phase was also used to set the recording levels. The results of the each practice phase were discarded.
In the adaptation phase all speakers first recorded 3 seconds of background noise. They then uttered 2 `phonetically rich' adaptation sentences, followed by the first 15 adaptation sentences from the WSJ0 adaptation corpus. During this phase the recording co-ordinator was always present and, where necessary, corrected speakers.
The main phase of each session consisted of the recording of either 90 training sentences or 80 test sentences. The recording co-ordinator was no longer present in the room during this period. Afterwards, a short anonymous questionnaire was completed by the speaker---the information from which can be found in the .ifo files.
Pronunciation Dictionary
In constructing a speech recognition system, pronunciation information must be provided for all words spoken in both test and training data. A British English Example Pronunciation Dictionary (BEEP) has recently been developed for large vocabulary speech recognition with the WSJCAM0 corpus in mind. Two thirds of this dictionary stem from a combination of two sources: the MRC Psycholinguistic Database and CUVOALD (the Computer Usable Oxford Advanced Learners Dictionary). These databases have been publicly available for a number of years. In addition, a considerable number of new pronunciations have been provided from sources in Durham and Cambridge Universities.
The set of new symbols specific to British English were defined as follows, /oh/ for the vowel in ``pot'', and /ia/, /ea/ and /ua/ for the diphthongs in ``peer'', ``pair'' and ``poor'' respectively. The complete phone set used is shown in Appendix C of this document.
The accumulation of these diverse sources into a single standardised format produced over 100,000 word pronunciations. However, this process failed to cover 2,700 words of the 20,000 word lexicon evaluation task. The process of constructing pronunciations for these additional words proceeded in a number of stages. First, a tool was written to automatically derive word pronunciations for inflected words, by looking-up their stem pronunciations and appending that of the correct inflection from morphological rules of English . This functioned for words with the following suffixes:
[-es, -s, -'s, -', -ed, -d, -er, -r, -est, -ing]
This worked by considering each member of the 20,000 word list (having a suffix in the above set) and searching for their stems from the current pronunciation directory. As a result, several hundred new words were found. The remaining words needed for the 20k evaluation task (currently around 2,000) were taken from the CMU pronunciation dictionary. This source was used as a last resort, since since they are US pronunciations. However, it is hoped to reduce the number of them in subsequent releases of the pronunciation dictionary. Finally, fifty seven words were not found in the CMU dictionary, and the pronunciations for these were manually entered into the dictionary.
The pronunciation dictionary on first release contains over 96,000 word definitions. Its format has been designed with machine readability a primary factor. It is thus unashamedly simple and an extract is included below.
OUIJA-BOARDS 3cm w iy1 jh ax b ao d z OUIJAS w iy1 jh ax z OUNCE aw n s OUNCES aw1 n s ih z OUR aw1 ax OUR aw1 ax r OURS aw1 ax z OURSELF aw ax s eh l f OURSELVES aw ax s eh l v zThe dictionary is freely available for non-commercial use by Internet FTP from host svr-ftp.eng.cam.ac.uk with file name /pub/comp.speech/data/beep-0.3.tar.Z.
Data Formats
The primary file format for all waveforms is NIST's SPHERE format, the DOT file format is used for transcriptions and the original prompt files are in PTX format. In addition, an information file about each speaker (.ifo) is part of the distribution. The format specifications as described below are taken from the document wsj-format-spec.doc at the NIST ftp site: gov.nist.ncsl.jaguar.
File Naming Formats
Data types are differentiated by unique filename extensions. All files associated with the same utterance have the same basename. All filenames are unique across all WSJCAM and ARPA-collected WSJ corpora. Utterance IDs (basenames) will not be re-used. The filename format is as follows:
<UTTERANCE-ID>.<XXX>where,
UTTERANCE-ID ::=<SSS><T><EE><UU>where,
SSS ::= 001 ... zzz (base-36 speaker ID) T ::= (speech type code) c (Common read no verbal punctuation) a (Adaptation read) EE ::= 01 ... zz (base-36 session ID; 01 for all adaptation; 02 for main session for training speakers and 5k for test speakers; 03 for 20+k for test speakers) UU ::= 01 ... zz (base-36 within-session sequential speaker utterance code)We were allocated the use of speaker IDs c00-czz. Speaker IDs c00-c2z were used for training speakers, speaker IDs c30-c4z were used for test speakers (both development and evaluation).
The file extensions are interpreted as follows: \begin{verbatim} XXX ::= (data type) .wv1 (channel 1 - Sennheiser waveform) .wv2 (channel 2 - Canford waveform) .ptx (prompting text) .dot (detailed orthographic transcription) .ifo (information file about speaker) .phn (TIMIT style phone alignments) .wrd (TIMIT style word alignments) \end{verbatim} The NIST file format: waveforms (.wv1, .wv2) The waveforms are SPHERE-headered, digitised, zero-meaned (using NIST's bias), and compressed (using NIST's transparent shorten algorithm wencode).
The filename extension for the waveforms will contain the characters, ``wv'', followed by a 1-character code to identify the channel. The 1024-byte NIST header for each waveform contains the following fields/types:
Field Type Description - Probable defaults marked ()
speaker_id string 3-char. speaker ID from filename
speaking_mode string speaking mode ("read-common",
"read-adaptation")
recording_site string recording site
recording_date string beginning of recording date stamp of the
form DD-MMM-YYYY.
recording_time -s11 string beginning of recording time stamp of the
form HH:MM:SS.HH.
recording_environment string text description of recording environment
microphone string microphone description
utterance_id string utterance ID from filename of the form
SSSTEEUU as described in the filenames
section above.
prompt_id string WSJ source sentence text ID - see .ptx
description below for format
database_id string database (corpus) identifier
database_version string database (corpus) revision ("1.0")
channel_count integer number of channels in waveform ("1")
speaker_session_number string 2-char. base-36 session ID from filename
sample_count integer number of samples in waveform
sample_max integer maximum sample value in waveform
sample_min integer minimum sample value in waveform
sample_rate integer waveform sampling rate ("16000")
sample_n_bytes integer number of bytes per sample ("2")
sample_byte_format string byte order (MSB/LSB -> "10",
LSB/MSB -> "01")
sample_coding string waveform encoding
sample_checksum integer checksum obtained by the addition of all
(uncompressed) samples into an unsigned
16-bit (short) and discarding overflow.
sample_sig_bits integer number of significant bits in each sample
("16")
session_utterance_number string 2-char. base-36 utterance number within
session from the filename
end_head none end of header identifier
Example Header
NIST_1A 1024 speaker_id -s3 c2e speaking_mode -s11 read-common recording_site -s4 CUED recording_date -s11 09-Feb-1994 recording_time -s11 11:01:22.00 recording_environment -s14 ECR_Quiet_Room microphone -s17 Sennheiser_HMD414 utterance_id -s8 c2ec0202 prompt_id -s22 87.034.861205-0013.1.2 database_id -s7 WSJCAM0 database_version -s3 1.0 channel_count -i 1 speaker_session_number -s2 02 sample_count -i 103500 sample_max -i 23478 sample_min -i -23889 sample_rate -i 16000 sample_n_bytes -i 2 sample_byte_format -s2 10 sample_sig_bits -i 16 session_utterance_number -s2 02 sample_coding -s26 pcm,embedded-shorten-v1.09 sample_checksum -i 34559 end_headDetailed Orthographic Transcription (.dot): The transcriptions for all utterances in a session are concatenated into a single file of the form, <SSS><T><EE>00.dot and include the utterance-ID codes. The format for a single utterance transcription entry in this table is as follows:
<TRANSCRIPTION-TEXT> (<UTTERANCE-ID>) <NEW-LINE>
An example sentence illustrating this format is given below:
The December contract rose one point oh seven cents a pound to sixty eight point six two cents at the Chicago Mercantile Exchange (c13c020l)
There is one .dot file for each speaker-session. It should be noted that the conventions used during transcription were slightly different from those used in WSJ0 and can be found in the section on `WSJCAM0 Detailed Orthographic Transcription (.dot) Specification'.
Prompting Text (.ptx):
The prompting texts for all read Wall Street Journal utterances in a session including the utterances' utterance-IDs and prompt IDs have been concatenated into a single file of the form, <SSS><T><EE>00.ptx. The format for a single prompting text entry in the .ptx file is as follows:
<PROMPTING-TEXT> (<UTTERANCE-ID> <PROMPT-ID>)
The prompt ID is the sentence index designed by Doug Paul to reference the Wall Street Journal texts in the ACL/DCI CD-ROM. The format for this index is:
<YEAR>.<FILE-NUMBER>.<ARTICLE-NUMBER> <PARAGRAPH-NUMBER>.<SENTENCE-NUMBER>
and an example sentence:
The December contract rose one point oh seven cents a pound to sixty-eight point six two cents at the Chicago Mercantile Exchange (c13c020l 87.120.871013-0032.14.2)
The inclusion of both the utterance ID and prompt ID allows the utterance to be traced to its source sentence text and surrounding paragraph. There is one .ptx file for each speaker-session.
Phone and Word Alignments (.phn, .wrd)
An automatic alignment procedure was used to provide alignments of utterances at both the word and phone levels. Each alignment file is named in the following format <SSS><T><EE><UU>.<XXX>; where the suffix XXX is either phn for phone level alignments or wrd at the word level. The alignment files adopt the standard NIST format where each line (of a word file) has the following structure:
<START> &+ltEND> <WORD> <NEW-LINE>
Example:
8960 13568 today 13568 15616 the 15616 23040 chairmen 23040 24064 are 24064 27648 net 27648 36096 losersOne .wrd and a corresponding .phn file exist for each utterance.
Directory Structure
The following depicts the directory structure and default partitioning proposed for the subcorpora on different discs. Subcorpora categories are denoted by the directory names in level 2. Different subcorpora will reside on different discs unless specified otherwise below. Training and development test data will probably be distributed together on one series of discs.
top level: wsjcam0/ corpus 2nd level: README a brief summary of the file structure doc/ on-line documentation etc/ official training and development test sets sitr/ SI, training, 90-100 WSJ sentences SI, adaptation, 1 3-second recording of background noise, 2 `rich', 15 WSJ sentences sidt/ SI, dev. test, 40 WSJ sentences, 20K voc. SI, adaptation, 1 3-second recording of background noise, 2 `rich', 15 WSJ sentences SI, dev. test, 40 WSJ sentences, 5K voc. siet[12]/SI, eval. test, 40 WSJ sentences, 20K voc. SI, adaptation, 1 3-second recording of background noise, 2 `rich', 15 WSJ sentences SI, eval. test, 40 WSJ sentences, 5K voc. 3rd level: <XXX>/ (speaker-ID, where XXX = ``001'' to ``zzz'', base 36) 4th level: <FILES> (corpora files, see previous chapters for format and types)The different files for the 5k and 20+k test speakers can be distinguished between by means of the session number in the filename (see also section on File Naming Formats): 01 for all adaptation; 02 for the main session for training speakers; 02 for 5k for test speakers; 03 for 20+k for test speakers)
WSJCAM0 Detailed Orthographic Transcription (.dot) Specification
This is a modified version of the CSR WSJ0 Detailed Orthographic Transcription Specification as it was proposed by the CCCC Transcription Subcommittee (12/12/91) which was revised 01/05/93 by John Garofolo to relax rules requiring prosodic markings and capitalisation per the CCCC conference call 11/24/92.
The current revision is by Jeroen Fransen. It includes minor adaptations that were needed to deal with the specific characteristics of the WSJCAM0 situation. These consist of additions to the types of non-speech events that occur. Also, the first adaptation sentence for each speaker will be a waveform containing background noise only. The transcription for this will be defined as a space followed by the usual utterance id.
The Detailed Orthographic Transcription (.dot) file will contain a case-sensitive transcription consisting of markings for an utterance's orthography, some prosodics, disfluencies and non-speech events.
Orthography
The lexical tokens in the transcription were generated without special regard to case and capitalisation. Appropriate capitalisation was used most of the time but was not strictly adhered to. Grammatical punctuation has been excluded except for periods (), used specifically in abbreviations, and apostrophes (). Non alpha- numeric characters such as these, which are part of a lexical item, have been prefaced by the escape character, ().
Normal lexical items were represented as they are in the prompt text used to elicit the speech.
Hyphenated words
Hyphens were removed in the transcription. The vocabulary file wfl-64 was checked to see the if word occurred without the hyphen. Otherwise it was broken up into separate words. e.g.:
compound in wfl-64:
Nonstop -> Non-stop
compound not in wfl-64:
hard-headed -> hard headed
Misquotations
Where an utterance differs from its prompt text yet remains fluent and linguistically valid, the DOT transcription represents the actual spoken utterance. This utterance text may consist of deletions, transpositions, substitutions and (theoretically unlikely) insertions of words from the original prompt text. This approach increases the quantity of testing and training data at the expense of losing consistency with the newspaper text.
Mispronunciations
Mispronounced but intelligible words in utterances not satisfying the misquotation criteria have been delimited with a ``*''. If the prompt read, ``He grew up in Belair.'' and the subject said, ``He grew up in Blair.'' then the utterance was transcribed: ``He grew up in *Belair*''
False Starts and Spoken Word Fragments
Incompletely spoken words were transcribed using the following notation:
Pauses
Only conspicuous pauses were marked with a single ``.'' indicating the location of the pause.
Emphatic Stress
Emphatic stress is indicated by prepending a ``!'' to the word or syllable which was stressed. This only includes stress which would not normally occur due to lexical and syntactic factors.
Lengthening
Lengthening is transcribed by appending a ``:'' to the lengthened sound. This only includes lengthening which would not normally occur due to lexical and syntactic factors.
Descriptive Markings of Speech and Non-Speech Events
Non-speech Events
Non-speech events are indicated by a descriptor enclosed in square brackets ``[]''. The descriptor contains only alphabetic characters and underscores and was drawn from the following list:
AH CHAIRSQUEAK COUGH CROSSTALK DOORSLAM ER GRUNT LAUGHTER LIPSMACK LOUDBREATH MM PAPERRUSTLE PHONERING SIGH THROATCLEAR TONGUECLICK UH UNINTELLIGIBLE UM MOUSECLICK (specific to WSJCAM) MIKEOVERLOAD (specific to WSJCAM)An example file:
The doctor said [throatclear] open wide
Descriptor Placement and Concurrent Events
A descriptor was placed in the orthography at the point at which the non-speech event occurs. If a non-speech event overlaps with a spoken lexical item, the descriptor was placed next to the lexical item it co-occurred with and the character, ``'' or ``'' was appended or prepended to the descriptor depending on whether it is placed to the left or right of the co-occurring lexical item:
The escaped convict [ <doorslam] ran for his life
and
The escaped [>doorslam ] convict ran for his life
are roughly equivalent.
If a phenomenon was noted throughout, or co-occurred with, more than one lexical item, then the phenomenon's descriptor is used in the following notation to bound the lexical items it spans:
[DESCRIPTOR/] WORD WORD ... WORD [/DESCRIPTOR]
Example: [crosstalk/] The plane narrowly escaped disaster [/crosstalk] as it took off
Bad Recording
If the recording quality of an utterance was so bad that it defies transcription, then the flag, ``[badrecording]'', was substituted for the transcription in the .dot file and the utterance will be viewed as unusable.
[badrecording] (c05c021b)
Waveform Truncation
If a waveform file was truncated due to a recording error by the system or by the failure of the speaker to press the record button at the proper times, the following notation in the corresponding transcription file was used:
Utterance Identification
The 8-character utterance ID from the filename (minus extension) was placed at the end of each transcription string in parentheses immediately followed by a new-line character. The parenthesised utterance ID was separated from the transcription string by one space character.
TEXT TEXT TEXT (UTTERANCE-ID) <NEW-LINE>
Example: Los Angeles based Government Funding is used to picking up where banks leave off (c04c0202)