BackgroundDetect() — Plays a file in the background and detects talking
Similar to Background(), but attempts to detect
      talking.
During the playback of the file, audio is monitored in the receive
      direction. If a period of non-silence that is greater than
      min milliseconds yet less than
      max milliseconds and is followed by silence
      for at least sil milliseconds occurs, the
      audio playback is aborted and processing jumps to the talk extension, if available.
If unspecified, sil,
      min, and max
      default to 1,000 ms, 100 ms, and infinity, respectively.
exten => 123,1,BackgroundDetect(tt-monkeys)
exten => 123,2,Playback(im-sorry)
exten => talk,1,Playback(yes-dear)