We verified today our prior acoustic observation of bowhead whales. The whales seem still to be far away but we were able to extract a spectrogram of their weak song from our recordings.
To be very precise, a sound source underwater (or above water for that matter) can not be 100% verified until the source has been localised and identified. Localisation can only occur with 3 or more hydrophones allowing cross correlation of the time of arrival difference of the signal into the different receivers. This is an important notion to bear in mind and one of the things that makes studies of acoustic behaviour of aquatic animals so difficult. However, in Disko Bay we are lucky to have only few seal and whale species present at this time and the acoustic repertoires and frequency ranges are fairly well described for all of the species. To aid one in learning to distinguish the different species sound examples of most of animals can be accessed through different sound libraries such as Macaulay library or from the net. So based on our previous experience and in the knowledge of the sounds that the other species make, we feel certain to conclude that the sounds we record stem from bowhead whales.