**Introduction** Mixer 7 English Speech (LDC2025S08) was developed by the Linguistic Data Consortium (LDC) and contains 12,321 hours of audio recordings of interviews, transcript readings, and conversational telephone speech involving 222 distinct English speakers. This material was collected by LDC in 2010 and 2011 as part of the Mixer project. The recordings in this corpus were used in the 2012 NIST Speaker Recognition Evaluation test set. The speech data in this release was collected by LDC at its Human Subjects Collection facilities in Philadelphia. The telephone collection protocol was similar to other LDC Mixer collections: recruited speakers were connected through a robot operator to carry on casual conversations lasting up to 10 minutes, usually about a daily topic announced by the robot operator at the start of the call. The raw audio content for each call side was 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 of the collection utilized 14 distinct microphones set up identically in two multi-channel audio recording rooms at LDC. Each session was guided by collection staff using prompting and recording software to conduct the following activities: (1) repeat questions (less than one minute); (2) informal conversation, "near" condition (15 minutes); (3) telephone call, low or high vocal effort (10 minutes); (4) transcript reading (15 minutes); (5) telephone call, cell or speaker phone (10 minutes); (6) informal conversation, "far" condition (15 minutes); and (7) telephone call, varied condition ( 10 minutes). Speakers recorded up to four 75-minute sessions on distinct days. The 14 channels were recorded synchronously into separate single-channel files, using 16-bit PCM sample encoding at 16000 samples/second. **Data** The collection contains 2,784 recordings made via the public telephone network and 629 sessions of multiple microphone recordings in office-room settings. The telephone recordings are presented as 2-channel interleaved NIST SPH files, with 8000 samples/second and u-law sample encoding, and the microphone recordings are presented as 16-KHz 1-channel flac/ms-wav files. When the flac files are uncompressed, they become ms-wav/RIFF files (flac compression does not presently support SPHERE file format). The telephone audio is presented in SPHERE format because (a) this is consistent with other telephone audio releases from 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. **Updates** No updates at this time.

Creator(s)

Linda Brandschain, David Graff, Kevin Walker

Distributor(s)

Linguistic Data Consortium

Right Holder(s)

Linguistic Data Consortium