Greybeard was developed by the Linguistic Data Consortium (LDC) and is comprised of approximately 590 hours of English telephone conversation speech collected in October and November 2008 by LDC. The goal was to record new telephone conversations among subjects who had participated in one or more previous LDC telephone collections, from Switchboard-1 (1991) through the Mixer studies (2006).
A total of 172 subjects were enrolled in the Greybeard collection, all of whom had participated in one of the following:
- Switchboard-1 (LDC97S62) 1991-1992: 2 subjects
- Switchboard-2 (LDC98S75, LDC99S79, LDC2002S06) 1996-1997: 16 subjects
- Mixer 1 and 2 2003-2005: 103 subjects
- Mixer 3 2006: 51 subjects
Most Greybeard participants completed 12 calls. Some subjects completed up to 24 calls. Calls were made or received via an automatic operator system at LDC which connected two participants and announced a topic for discussion.
This releases consists of 4680 calls -- the complete set of calls recorded during the Greybeard collection (1098 calls) as well as all calls from the legacy collections that involved the Greybeard speakers.
The audio from each call was captured digitally by the operator system and stored in a separate file as raw mu-law sample data. As the recordings were uploaded daily from the robot operator to network disk storage, automated processes reformatted the audio into a 2-channel SPHERE-format file for each conversation and queued the recordings for manual audit to verify speaker identification and to check other aspects of the recording. Auditors provided impressionistic judgments on overall audio quality, presence of background noise and cross-channel echo and any other technical difficulty with the call, in addition to confirming the speaker-ID on each channel. These auditor decisions are provided in the call_info tables, described in more detail in the included documentation.
For this release, each 2-channel recording was converted from SPHERE to MS-WAV file format and compressed using FLAC. All audio files are 2-channel, 8 KHz, 16-bit PCM sample data, in FLAC-compressed form (http://flac.sourceforge.net). When uncompressed, they have MS-WAV/RIFF headers.
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