README FILE FOR: Mixer 7 English Speech LDC CATALOG-ID: LDC2025S08 AUTHORS: Linda Brandschain, Kevin Walker, David Graff 1.0 Introduction The Mixer-7 English Speech Corpus comprises recordings made via the public telephone network (total of 2,784 calls) and multiple microphones in office-room settings (total of 629 sessions conducted by LDC staff). There are 222 distinct speakers including recruited speakers and LDC staff. All speakers were fluent English speakers with most being native speakers. Recordings took place between July 2010 and January 2011. The telephone audio portion of the corpus is similar to earlier Mixer collections: recruited speakers are connected through a robot operator to carry on casual conversations lasting up to 10 minutes, usually about a daily topic that is announced by the robot operator at the start of the call. The raw digital audio content for each call side is captured as a separate channel, and each full conversation is presented as a 2-channel interleaved audio file, with 8000 samples/second and u-law sample encoding. Each speaker was asked to complete 20 calls. The multi-microphone portion involves 14 distinct microphones set up identically in two distinct office rooms at the Linguistic Data Consortium. The same speakers who were taking part in the telephone collection were also brought in to record up to 4 sessions on distinct days, with each session lasting up to 90 minutes, typically producing 75 minutes of speech of various types. The 14 channels were recorded synchronously into separate single-channel files, using 16-bit PCM sample encoding at 16000 samples/second. Each multi-channel session was guided by an LDC staff person, who used specialized prompting and recording software to manage the session. Activities recorded in each session consisted of seven components: 1. Repeating questions - usually less than 1 minute 2. Informal conversation, "near" condition - 15 minutes 3. Telephone call, low or high vocal effort condition - 10 minutes 4. Transcript reading - 15 minutes 5. Telephone call, cell or speaker phone condition - 10 minutes 6. Informal conversation, "far" condition - 15 minutes 7. Telephone call, varied condition - 10 minutes More information about the session protocol is provided in the file "mx7_collection_doc.pdf". The recordings in this corpus were used in NIST Speaker Recognition Evaluation (SRE) test set for 2012. Researchers interested in applying those benchmark test sets should consult the respective NIST Evaluation Plans (available at http://nist.gov/itl/iad/mig/sre.cfm) for guidelines on allowable training data for those tests. 2.0 Directory Structure and Data Files The directory structure under data/ is as follows: ulaw_sphere/ -- contains 2784 2-channel, 8-kHz, NIST SPHERE files pcm_flac/ -- contains 14 directories, 1 microphone / directory: CH01/ - up to 4043 1-channel, 16-kHz, FLAC/ms-wav files ... - for each channel CH14/ All audio files have names that indicate the date and time when the recording began, along with other identifying information, as follows: ulaw_sphere/: {yyyymmdd}_{hrmnsc}_{callid}.sph pcm_flac/CH{nn}/: {yyyymmdd}_{hrmnsc}_{room}_{comp}_{subjid}_CH{nn}.flac where: yyyymmdd is the year, month and date of recording hrmnsc is the hour, minute and second when recording began callid is a unique, incremental number assigned to each call room is either "LDC" or "HRM", indicating which office was used comp is an abbreviated label for the interview component (see below) subjid is a numeric identifier assigned to the speaker nn is a two-digit microphone channel identifier (01-14) When the flac files are uncompressed, they become ms-wav/RIFF files (flac compression does not presently support SPHERE file format). For each 14-channel set of original full-length interview recordings, the various component segments have been extracted into separate audio files, leaving out the transition periods between components. As a result, within each CH{nn} directory, there is a set of up to seven files with the same "{yyyymmdd}_{hrmnsc}_{room}" and "{subjid}_CH{nn}" portions in their file names, and different strings for the "{comp}" portion, as follows: ivfr -- interview, "far" condition ivnr -- interview, "near" condition phce[12] -- phone call, "cell" condition phhv[12] -- phone call, "high vocal effort" condition phlv[12] -- phone call, "low vocal effort" condition phsp[123] -- phone call, "speaker-phone" condition rdtr -- transcript reading rptq -- repeating questions The digits appearing next to the various "ph.." labels reflect the relative order of the phone call component within the full session. The telephone audio is presented in SPHERE format because (a) this is consistent with other telephone audio releases from the LDC, and (b) flac does not support ulaw sample encoding. The current release of the open-source "sox" utility is able to handle both formats as input; other utilities are available for both flac and SPHERE formats. 3.0 Documentation The /docs directory contains the following files (along with this "README.txt" file); their various contents are explained in the subsections below: 1 mx7eng_subjects.csv 2 mx7eng_calls.csv 3 mx7eng_ivcomponents.csv 4 mx7_transcript_sentences.txt 5 mx7_collection_doc.pdf 6 ivchans_missing.tab 7 README.txt (this file) All the "*.csv" files are comma-delimited, plain-text "flat files". Care has been taken to ensure that no field values contain commas as part of the field data, so quotation marks are never used around field values, and nothing is done to mark or "escape" certain characters (such as apostrophes). Consecutive commas on a line of data indicate empty or null field values (which tends to be fairly common in the subjects table). 3.1 Subjects table (mx7eng_subjects.csv) Each row in this table provides demographic information about one of the speakers in the collection. LDC staffers who led the interview sessions and were involved in many of the phone calls that were conducted during those sessions are included in this table. 1 subjid - numeric identifier, links to calls and interviews 2 sex - M or F 3 yob - year of birth 4 edu_years - years of formal education 5 edu_degree - highest education degree earned 6 edu_deg_yr - year in which highest degree was earned 7 edu_contig - Y or N: were all edu_years spent contiguously? 8 esl_age - for ESL speakers, age when English was learned 9 ntv_lg - native language 10 oth_lgs - other languages ('/'-separated) 11 occup - occupation 12 cntry_born - country where born 13 state_born - state where born 14 city_born - city where born 15 cntry_rsd - country where raised 16 state_rsd - state where raised 17 city_rsd - city where raised 18 ethnic - ethnicity 19 smoker - Y or N 20 ht_cm - height in centimeters 21 wt_kg - weight in kilograms 22 mother_born - country (state city) where mother was born 23 mother_raised - country (state city) where mother was raised 24 mother_lang - mother's native language 25 mother_edu - mother's years of formal education 26 father_born - country (state city) where father was born 27 father_raised - country (state city) where father was raised 28 father_lang - father's native language 29 father_edu - father's years of formal education 3.2 Calls table (mx7eng_calls.csv) Each row in this table provides the available information about a 2-channel telephone conversation. A couple of fields ("lang", "eng_stat") are actually irrelevant here, because this was an English-only collection, but the field inventory is fixed in order to provide consistency with other telephone corpus releases from the LDC. 1 call_id - numeric identifier, links to audio file name 2 call_date - links to audio file name 3 lang - language in which the conversation was conducted (always ENG) 4 eng_stat - not used in this corpus (always empty) 5 sid_a - subjid of the speaker on channel A (may be marked by "*" or "?"; see 4.5 below) 6 phid_a - telephone ID on channel A 7 ph_categ_a - one of: M (main phone), O (other phone) 8 phtyp_a - one of: 1 (cell phone), 2 (cordless), 3 (standard) 9 phmic_a - one of: 1 (spkr-phone), 2 (headset), 3 (earbud), 4 (handheld) 10 cnvq_a - audit judgment of conversation quality (Good,Acceptable,Unsuitable) 11 sigq_a - audit judgment of signal quality (Good,Acceptable,Unsuitable) 12 tbug_a - Y or N: auditor found a technical problem channel A 13-20 - same as 5-12, applied to channel B 21 topic - numeric ID of the topic announced to the callers 3.3 Interview components table (mx7eng_ivcomponents.csv) Each row in this table provide time stamps for partitioning a single in-office multi-channel recording session into its distinct components. The time stamps provided for the call components are all based on careful alignment between the 10-minute ulaw telephone audio and the 45-minute session recording, so when the call portions of the session audio files are extracted using the stated time stamps, the resulting excerpt should align within a few milliseconds with the corresponding ulaw channel. The time stamps for the other components (rptq, intv, rdtr) are based on session log files (or have been set by manual annotation, in some cases where log files were not available). The time stamps from log files are prone to having varying margins of accuracy relative to the actual start and end of the given component. (See the discussion in section 4.2 below about the "rdtr" time stamps.) 1 comp_type - one of: rptq, ivnr, ivfr, phce, phsp, phhv, phlv, rdtr 2 date - 8-digit year-month-day (YYYYMMDD) 3 iv_bgntime 6-digit hour-minute-second (HRMNSC) 4 place - recording-room, one of: HRM, LDC 5 comp_id - same as comp_type, incl. one-digit ID# for ph.. types (e.g. "phce1") 6 subj_id - six-digit ID# references col.1 in mx7eng_subjects.csv 7 duration - in seconds 8 interlocutor_id - six-digit ID# references col.1 in mx7eng_subjects.csv 9 language - ENG, SPA or MXD 10 call_id - for ph.. types, 4-digit ID# references col.1 in mx7spa_calls.csv 11 call_side - for ph.. types, "1" (= channel A) or "2" (= channel B) 12 ivchans_missing - semi-colon-delimited list of missing channels, if any Columns 2-6 can be concatenated with underscore characters to form the file-ID (minus the channel specification) for the corresponding set of pcm_flac audio files -- e.g. taking the first row following the table header: ivfr,20100712,145113,HRM,ivfr,120537,1336.6,120904,ENG,,,all_present columns 2-6 can be joined as follows to form the file-ID: 20100712_145113_HRM_ivfr_120537 Since column 12 in that row shows "all_present", we can locate 14 channel files for this interview component ("far interview" for subj_id 120537) as follows: ./data/pcm_flac/CH*/20100712_145113_HRM_ivfr_120537* In cases where one or more channels are missing (due to problems in the recording session), the missing channels are listed in column 12; if more than one channel is missing for a given component, the missing channels are conjoined with semi-colons in ascending order (e.g. "CH08;CH11;CH13"). 3.4 List of Transcript sentences (mx7_transcript_sentences.txt) This is simply a list of the 335 sentence prompts displayed to speakers in order to be read aloud. All the sentences are in English, and have been drawn from transcripts of spontaneous conversations in earlier LDC data collections. In every session, the transcript-reading component always presented this list in the order shown (one sentence at a time), and always started at the first sentence. If the speaker got to the end of the list quickly, with time remaining in the session schedule for transcript reading, the list was simply presented again, starting over at the first sentence. (So, some sessions may contain more than 335 sentence readings in this component, and in this case, sentences at the start of the list will have been read twice.) 3.5 Corpus collection specifications (mx7_collection_doc.pdf) This pdf file provides more detailed information about the Mixer 7 collection project: the procedures for recruiting and recording, microphone specifications, interview and auditing protocols, etc. 3.6 Missing channels (ivchans_missing.tab) This is a list of missing channels as detailed in the mx7eng_ivcomponents.csv table (col.12, "ivchans_missing"). There were a number of sessions where one or more channels failed to record as intended. 4.0 Known Problems and Difficulties The following subsections list some issues where the data being published fall short of expectations. 4.1 Some channels missing from some in-office recording sessions As detailed in the mx7eng_ivcomponents.csv table (col.12, "ivchans_missing"), there were a number of sessions where one or more channels failed to record as intended. In some cases a channel failure occurred mid-session, such that all channels were recorded for initial components in the session, and some were missing for later components. 4.2 Variable performance in transcript reading task While reading transcript sentences aloud, speakers would sometimes stumble, restart, or misread the prompt text (adding, skipping or substituting one or more words); there were also some cases where speakers interjected a remark or question in between the sentence prompts. Another issue was a relatively low level of English reading proficiency among some native Spanish speakers, causing the transcript reading task to be difficult and error-prone. The recording process would not be stopped for problems of this sort, and no attempt has been made to edit them out of the audio files. As a result, there will be some difficulty in trying to align the sentence prompt text with the corresponding audio portion in some number of sessions. 4.3 Relatively low recording levels in some channels or some sessions Some of the microphones in the recording rooms were purposefully set at distances beyond the stated performance specifications for the given mic. This was done to cause some channels to serve as "stress tests" for relevant speech technologies. In addition, there were difficulties with other channels in balancing between conflicting goals: (a) always maintain a constant gain setting on each channel across all sessions; (b) take as much care as possible in setting levels in order to avoid clipping; (c) employ techniques during the phone call components to explicitly evoke both unusually loud and unusually soft speech. Of course, there are also wide differences among speakers in terms of their intrinsic loudness, and during informal conversation, they would often cover a wide dynamic range. Taken together, these factors tended to lead to relatively lower gain settings than would have been optimal in many cases. 4.4 Resampling applied to multi-channel recordings The 14 channels presented in the "pcm_flac" directory were originally recorded via matched pairs of 8-channel A/D converters, running from a common clock signal. But relative to the 8KHz ulaw telephone channel (recorded via the public telephone network), and a pair of "reserved" channels recorded via a separate, 22KHz A/D device, it was found that the nominal 16000Hz sample rate applied to channels 01-14 was actually closer to 15899 Hz. This was measured and confirmed over numerous sessions, and we also manually confirmed that, by doing a digital resampling from 15899 to 16000, the alignment of channels 01-14 to both the 8KHz ulaw and 22KHz signals was correct. This resampling has been applied to all the pcm_flac data, and should have no more than a negligible effect on signal analysis. 4.5 Some call-side speaker-IDs not fully confirmed by audits As indicated above in the description of the mx7spa_calls table, some rows have a question mark or asterisk ("?" or "*") attached to the A- or B-side subj_id value. These are cases where the given call side was not audited at all (question mark), or the auditor judged that the voice on the given channel did not match the individual associated with the given subject-ID (asterisk). In total, 717 call-sides have "?", and 3 have "*". 4.6 Single annotator with multiple subject IDs One annotator used two different PINs and as a result has two different subject IDs. The subject IDs 110226 and 120996 are the same subject, with two separate rows in subjids-ldcstaff.txt and mx7eng_subjects.csv. 4.7 Incorrect number of microphones given In Section A, pg. 1 of the Mixer 7 Specification ("mx7_collection_doc.pdf".), it incorrectly states that the on-site interview sessions were recorded via 16 microphones - this should be 14. 5.0 Copyright © 2010-2011 Trustees of the University of Pennsylvania ------- README prepared 2022-04-08 by David Graff updated 2025-04-04 by Summer Ploegman