With Halloween upon us, there is a lot of talk about scary things. Ghosts, witches and skeletons decorate shop windows and front yards. Creepy sounds are part of the landscape as well — strange moanings and cacklings that are eerie and other worldly. Perhaps they are sounds from underground. But what does it sound like underwater? These sounds can be somewhat spooky as well, and new technology is helping us to hear them more clearly.

You may already be familiar with efforts to identify bird songs and may have used an app like “Merlin Bird ID” to help you to learn them. This app was created by Cornell University scientists and it is a fun and easy tool that you can use to identify what species you’re hearing and to learn more about it. Recently, Cornell, in collaboration with the FishEye Collaborative, has created a similar tool — this one to listen to sounds under water. This is much more complicated than identifying sounds on land. Under water, sound travels really quickly — more than four times as quickly! Sound under water can also get scattered and muffled easily by the motion of waves or bubbles under the surface. Add to that the fact that human ears aren’t made to listen under water and you have to come up with a different system for identifying these sounds.

Acoustic instruments used to listen to undersea sounds are not new. Hydrophones, for example, are type of microphone that you can stick under water with a big umbrella around it that helps to focus the sound. With larger marine animals like whales and dolphins, the sound-source connection is fairly straightforward. But for many other marine species, tracing these sounds to a specific source has been a challenge. New technology that combines a microphone with underwater videography is now allowing scientists to make more of these species-specific connections.

Whereas, previously, the underwater world was a jumbled chorus of popping and crackling, the Omnidirectional Underwater Passive Acoustic Camera (UPAC-360) can help tease out individual sounds. What scientists using this tool are discovering is helpful in understanding what lives where as well as more about the behaviors of those species. It’s also identifying sounds made from fish that they never thought made sounds. Fish use a variety of body parts to make sounds, including those as simple as slapping their fins to those that are more complex like rattling bones together or squeezing air in and out of their swim bladders. Some of these sounds may be just for fun and others more purposeful, like warning other fish about a nearby predator or showing off for a mate. Some of these more subtle sounds are now being attributed to species thanks to this technology.

While I think sounds under water are odd but lovely, they can definitely give off a creepy vibe. I bet if you broadcast some of these on your stoop, you’d scare a few trick-or-treaters. Regardless, they are worth listening to in order to get a sense of how diverse sound is under water. To listen to the sound library, go to fisheyecollaborative.org/library, and to see the videos that led to their identification, go to bit.ly/45GjMss.

Susan Olcott is the director of strategic partnerships at Maine Coast Fishermen’s Association.