This GCHQ experiment profile from March 2010 proposes a test of the effectiveness of GCHQ and NSA voice recognition systems: see the Intercept article Finding Your Voice, 19 January 2018.
This GCHQ research report dated 20 September 2011, cowritten by researchers at Heilbronn Institute for Mathematical Research based at the University of Bristol, concerns the use of data mining techniques to develop usable intelligence as well as the contradictions that arise from the use of algorithms to identify wrong doers, or potential wrong doers. The paper also provides a great deal of background information on GCHQ operations and the detailed discussion of network theory demonstrates the power of metadata collection: see the Boing Boing article Doxxing Sherlock, 2 February 2016.
This 6 September 2011 post from the NSA’s internal SIDToday newsletter describes progress in the agency’s speech-to-text capability over the course of the year: see the Intercept article The Computers are Listening: How the NSA Converts Spoken Words Into Searchable Text, 5 May 2015.
This undated presentation from the NSA’s European Cryptologic Center explains some of the activities of the agency’s main European base: see the Der Spiegel article Terrorverdächtige: NSA nutzte Erkenntnisse aus Deutschland-Filiale für Tötungen, 15 June 2014.