Making Sense of the Cacophony
January 8, 2024
The seas were calm but the Humpbacks were not for Friday’s Wake Up with the Whales Cruise from Anaeho’omalu Bay.
We spent most of the trip drifting with an interested Humpback at our stern. This whale surfaced multiple times right behind the boat, and in between his surfacings, we were able to hear him singing loud and clear. We also got to watch a couple of Humpbacks breach just about 120 yards from us — HUGE splashes from them.
Guests on Saturday’s Mid-Morning Whale Watch from Kawaihae had to keep their heads on a swivel as we watched FIVE different pods of Humpbacks spread out just outside of Kawaihae Harbor. The pods were either duos or trios, and all of them seemed to be on 12 minute dive cycles (which meant we were almost always watching someone either spouting or lifting his or her flukes to dive). When we deployed the hydrophone we were astounded by how many whale voices we could hear at the same time. Our naturalist DJ suspects we were picking up sounds from around a dozen Humpbacks in our area — quipping that it was actually “over-stimulating” (not that anyone was complaining).
On Sunday’s Mid-Morning Whale Watch Cruise we got to know Momma Humpback and her very little calf. At first, both of them were really calm. Baby was interested in our boat, and Mom allowed him to venture within about 50 yards of us. While we were intently watching the calf (who couldn’t hold his breath very long at all) two separate adult duos surfaced about 200 yards from us. One of the pairs made a b-line over to check out Momma and her calf — which must have caused Mom’s aggressive instincts to kick in, as she head-lunged 5 times, aiming that aggression towards those other interested adults. Of course we couldn’t be sure if Mom was attempting to keep those adults away from her little one or if she knew that those Humpbacks were both males looking to mate, and she was expressing her total disinterest in that activity.
Ocean Sports Whale Fact of the Day: You know how when you’re talking to someone at a crowded party, not only can you focus on one particular voice, but you can tell from which direction the speaker is speaking relative to you? Well, that’s because your ears and brain are adapted to interpreting sounds traveling through the air. When you’re underwater, or when you’re listening to underwater sounds through a traditional hydrophone, the sound waves are moving so fast that you’re unable to pinpoint a directional source or often even a particular “speaker” (or in the case of the Humpbacks, a “singer”) — and this is what led DJ to feel overstimulated listening to the cacophony of sounds picked up by our hydrophone on Saturday.
To address that very issue, this past summer, researcher James Crutchfield and his colleagues from UC, Davis developed a hydrophone capable of recording the full three-dimensional nature of marine sound fields. This “hydroambiphone” consists of a steel sphere with 4 regular hydrophones attached to it, pointing in different directions. Since the sphere blocks the sounds coming from behind each of the single hydrophones, this hydropambiphone is able to record sounds coming from each direction, and the researchers can then isolate each recorded sound field to figure out where the sounds originate.
The researchers posit that whales and other cetaceans are naturally able to interpret sounds directionally and most likely can focus on single auditory sources for information. Humans listening to recordings made through the hydroambiphone are better able to understand the auditory world in which the cetaceans live. You can read more about this research here, and listen in to some Humpbacks recorded through the hydroambiphone here.