This sound was repeatedly recorded during summer, 1997 on the Equatorial Pacific Ocean autonomous hydrophone array. The sound rises rapidly in frequency over about one minute and was of sufficient amplitude to be heard on multiple sensors, at a range of over 5,000 km.  It yields a general location near 50^oS; 100^oW. The origin of the sound is unknown. 

Click on spectrogram for full-sized image.

162K wav file(The recorded signal has been sped up 16 times)