Many male hummingbirds produce loud sounds with their tail-feathers during their courtship displays. Collaborator Chris Clark studies the aeroacoustics of how feathers flutter to produce sound. Using Scanning Doppler Laser Vibrometer, we measured the vibrations of a series of hummingbird feathers in a wind tunnel, documenting how they vibrated as a function of feather size, shape, and airspeed. It turns out that feathers can produce a wide variety of sounds, ranging in frequency, loudness, and harmonic structure. Interestingly, a vibrating feather can also interact with its neighboring feathers. These interactions can amplify the sound, or they can produce interaction frequencies, if the feathers flutter at different frequencies.
