These largest of animals have deep voices, in the frequency range (up to 100Hz) of the hydroacoustic stations of the CTBTO.  The CTBTO is one of the UN organizations located in Vienna. It is the verification branch of the Treaty outlawing any nuclear test, including in the oceans.

The hydroacoustic stations record the "noise" of large whales. What is noise for the standard processing to pick out possible nuclear explosions in the oceans is a melodious song to the whale specialists. A song that should allow us to know more about these still elusive and mysterious giants, monitor their population recovery since the stopping of large scale whaling in the 1970s, potentially identify individuals, locate them, and tell us about the acoustic characteristics of the oceans which, in turn, are a function of temperature.

The IMGW is collaborating on a project, www.baleakanta.org to study these signals. The project was presented at the recent Science and Technology meeting of the CTBTO, June 17-21 2013 (ctbto.org/specials/snt2013/).