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As an expert in audio identification techniques his work brought him to the attention of the FBI, where he helped develop an eavesdropping technology to identify a speaker's location in a crowded room.
Using two closely spaced microphones, it was possible to separate and localise an arbitrary number of speakers. "So if you were in a room and 10 people were speaking, you could tell who said what, when," said Dr Rickard. "That is really important for the FBI - they have lots of recordings of people and they want to know what was said and who said it." (more)