Case file · High strangeness
'Train' and 'Whistle', the 1997 sounds
In 1997 NOAA's Pacific hydrophones recorded two further unexplained signals, a steady rumble like a passing train (4 March) and a single wavering 'whistle' (7 July).
1997 CE · -71.50, 171.00 · status: explained
The account
Train was traced to a very large iceberg dragging its keel on the seafloor in the Ross Sea near Cape Adare. Whistle, heard only on the hydrophone moored at 8°N, 110°W, resembles the sound of erupting submarine arc volcanoes, but its source could not be located. Position approximate.
The sceptical view
Both are explained, or tentatively explained, as natural ice or volcanic noise.