Deploying the microphone array
The past month was very exciting for me. Five years ago, I was invited to a bachelor party in Oxford, England. As I was skipping along on a path in this city with its scholarly atmosphere, I had an idea for a project that finally comes to fruition now. I do not recall exactly where I was when I had my idea. I just wish I could say that I had the idea while playing croquet in the Masters Garden at Christ Church College, but I digress.
I had been studying the honey bee waggle dance to help out with a project that aims to understand how honey bees use the landscape at the time (you can read more about that on my wife's research page). For this, it is important to understand how exactly bees communicate to their nestmates where they have found food, and I was trying to improve the methods that are used to estimate where a bee had foraged based on videos of recorded dances. It occurred to me then that since bees are using a vibration signal for communicating in the dark of the hive, we should maybe better listen to the bees to understand where they forage instead of looking at them. The general idea was that if we used a microphone array, we could track bees' dances acoustically. Because I was a postdoc at the time, I did not have the resources to act on that idea.
Now I have had the good fortune to end up at Virginia Tech, where Ricardo Burdisso, an expert on acoustic source localization teaches and researches. Together with the help of undergraduate student Tianyu Zhao, Ricardo built a microphone array this summer, and it was finally time to deploy it. In mid-August undergrad research assistants Bethany McKenna and Keiran Zwirner helped Tianyu and me to install the Plexiglas panel with the microphone array in an observation hive.
The next day we set out to train bees to syrup feeders. Here, Bethany is seen monitoring the syrup feeder to mark any new recruits that arrive with small number tags.
After a couple of visits to the feeders, these marked recruits then advertised the food source to their nestmates when back in our observation hive. In the following video you can see such a marked dancer. In the bottom row of microphones, she is dancing right under the second microphone from the right:
Concurrently to recording the dances on videos, we measured the sound pressure using Ricardo's equipment:
Here is plot of the measurements from one of the microphones, with the portion of the recording that looks like a dance to us:
We are confident that we have some good recordings of dances (how exciting!). We will now further analyze the videos and acoustic data to improve on our experimental setup. The impeding cold is a perfect excuse to ditch the field work and go to the lab!