How oscillating aerodynamic forces explain the timbre of the hummingbird’s hum and other animals in flapping flight
Abstract
How hummingbirds hum is not fully understood, but its biophysical origin is encoded in the acoustic nearfield. Hence, we studied six freely hovering Anna’s hummingbirds, performing acoustic nearfield holography using a 2176 microphone array in vivo, while also directly measuring the 3D aerodynamic forces using a new aerodynamic force platform. We corroborate the acoustic measurements by developing an idealized acoustic model that integrates the aerodynamic forces with wing kinematics, which shows how the timbre of the hummingbird’s hum arises from the oscillating lift and drag forces on each wing. Comparing birds and insects, we find that the characteristic humming timbre and radiated power of their flapping wings originates from the higher harmonics in the aerodynamic forces that support their bodyweight. Our model analysis across insects and birds shows that allometric deviation makes larger birds quieter and elongated flies louder, while also clarifying complex bioacoustic behavior.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Mar 16, 2021
- Source ID
- 10.7554/elife.63107
Entities
People
- Ben J Hightower
- Daniel Shorr
- David Lentink
- Diana D. Chin
- Jade Nguyen
- Patrick Wa Wijnings
- Rick Scholte
- Rivers Ingersoll
Organizations
- Dutch Research Council
- Eindhoven University of Technology
- National Science Foundation
- Stanford University