"Three-wattled Bell-bird" is a recording of an unidentified bird,
followed by the "bonk" of the Bell-bird. If you have SoundEdit or
similar software, try listening 2 octaves lower (1/4 speed). Based on
limited spectral analysis, I believe the Bell-bird makes its unusual
anvil-like sound by singing up to three notes simultaneously. This is
a trick which takes the young birds a while to perfect. This one seems
to be producing pitches of roughly 1280, 1365, and 1450 Hz, approximately
E6, F6, and F-sharp6 in the musical scale. These three notes, each a
semi-tone apart, produce a very rough, dissonant sound. (Try generating sine
waves with these pitches on a synthesizer or in SoundEdit, and
compare the result to the Bell-bird sound - it's quite similar.) This
recording was made in a cloud forest in Costa Rica in 1988 or '89 by
Earl Vickers.
 
This sample is from "It's a JUNGLE in There", a 60-minute binaural (3D)
cassette (no longer available) of tropical rainforest sounds.
 
If you isolate one of the bonks, it makes a good Macintosh beep.