Point taken on the deep water ping progagation.
But the spectrum/waterfall of the
recorded pings looked pretty clean. Except that the detected frequency was so offset by 4.2 kHz from 37.5 kHz.
The area searched was about 15 NM x 15 NM around the ping that was heard for 2 hours and 20 mins(!!). Do you think propagation can go beyond this?