Whistle — NOAA PMEL equatorial hydrophone
Recorded July 7, 1997. Detected on a single hydrophone — no triangulation possible. NOAA notes similarity to volcanogenic sounds from the Mariana volcanic arc.
The Whistle was recorded on a single hydrophone — unlike the Bloop or Upsweep which were detected across multiple stations. This limits source triangulation. NOAA identified a spectral similarity to known volcanic signals from the Mariana arc, suggesting the sound may have traveled thousands of kilometres from its origin point before detection.
A brief, rapidly descending frequency signal of uncertain origin, captured on a single Pacific monitoring array in July 1997. Similar in profile to volcanogenic sounds from the Mariana volcanic arc.