Background: I am still new to acoustics research and I am hoping to get some advice on integrating a directional microphone with an ultrasonic recorder. I am trying to collect acoustic data from small, nocturnal, and arboreal primates (both sonic and ultrasonic calls). I want to connect behaviors with vocalizations so it is crucial that I am able to say that my focal individual is the one producing the call.
Query: I want to use a Wildlife Acoustics Song Meter Mini Bat 2AA, since I have used it before for PAM, but I am trying to find a way to make it directional instead of omnidirectional. Does anyone have any experience with or suggestions regarding attaching a directional microphone to a Song Meter Mini bat recorder?
Any and all information would be greatly appreciated! Thank you so much!
30 April 2024 4:28pm
Hi Luke, sounds like an interesting project! One thing to note is the ultrasonic Wildlife Acoustics unit you're looking at is already fairly directional. Take a look at the horizontal directionality plot towards the bottom:
You can see that for the relevant frequencies for slow lorises ultrasonic calls (40-60 kHz), there is 25-30 dB difference between 0 and 180 horizontal degrees. It's not perfect, but is close to some directional mics, and if it works well enough for your project it would save a lot of time and testing!
If you do choose to integrate an external directional microphone, be careful with microphone placement to avoid potential ultrasonic reflections from any hard flat surface like a tree trunk, water surface, or the instrument housing itself. Here's an example of some echo calls from reflective surfaces from bat vocalizations:
Tips for Siting Bat Detectors
Deploying detectors is more involved than simply picking up an “approved” ultrasonic recorder and sticking it out in the woods and turning it on to record. Properly siting a bat detector is every bit as important as properly siting a mist net . . . maybe more so. After all, it’s easy for us to visualize how bats might travel thru a flyway and how best to intercept them. It’s more difficult perhaps for us to conceptualize how bats use echolocation to navigate thru their habitats, and how that high-frequency sound travels thru air and is impacted by physical, environmental, and anthropogenic structures. First and foremost . . . Don’t put detectors on the ground. Bats don’t often fly within 1-2 meters of the ground. And if they do, they will be producing those undesirable approach-phase echolocation call characteristics that are less diagnostic. The ground
Bat Conservation and Management, Inc.It would be helpful to hear how you plan on obtaining behavioral information (and what kind) to correlate with vocalizations? Observations, cameras, biologgers, etc.? This could inform responses a bit more.
Jesse Turner
Colorado State University