"The NSA patent, granted on 10 August, is for a system of automatic topic spotting and labelling of data. The patent officially confirms for the first time that the NSA has been working on ways of automatically analysing human speech. The NSA's invention is intended automatically to sift through human speech transcripts in any language. The patent document specifically mentions "machine-transcribed speech" as a potential source.
Bruce Schneier, author of Applied Cryptography, a textbook on the science of keeping information secret, believes the NSA currently has the ability to use computers to transcribe voice conversations. 'One of the holy grails of the NSA is the ability automatically to search through voice traffic. They would have expended considerable effort on this capability, and this indicates it has been fruitful,' he said." You can find more details here.