Vibration attenuation performance of long-eared owl plumage

A comparative study of vibration attenuation behaviour of primary remex with lateral branches from the long-eared owl (a silent flying bird), golden eagle and pigeon (two noisy flying birds) was conducted in order to investigate the damping ability of owl's primary remex. Amplitude variation of the measurement points on the rachis with vane structures was measured by a laser displacement sensor, and vibration process of the observation point on the barb with lateral barbules was recorded by a high-speed camera. Amplitude-time analysis results indicate that loss factors of long-eared owl's complete primary feathers and barbs are higher than those of the golden eagle and pigeon feathers. Thus, vibration amplitudes of the long-eared owl feathers and their barbs decay much faster, showing a superior vibration-damping characteristic. Consequently, mechanical noise caused by the relative motion of the owl primary feather structures during flight may be effectively suppressed. Vibration reduction principle of the long-eared owl primary feather was briefly discussed based on the damping-by-branching mechanism at last.