Department of Evolution, Ecology, and Organismal Biology, University of California, Riverside, Riverside, CA 92521, USA
Department of Evolution, Ecology, and Organismal Biology, University of California, Riverside, Riverside, CA 92521, USA.
J Exp Biol. 2020 Oct 12;223(Pt 19):jeb214965. doi: 10.1242/jeb.214965.
Why do hummingbirds hum and insects whine when their wings flap in flight? Gutin proposed that a spinning propeller produces tonal sound because the location of the center of aerodynamic pressure on each blade oscillates relative to an external receiver. Animal wings also move, and in addition, aerodynamic force produced by animal wings fluctuates in magnitude and direction over the course of the wingbeat. Here, we modeled animal wing tone as the equal, opposite reaction to aerodynamic forces on the wing, using Lowson's equation for the sound field produced by a moving point force. Two assumptions of Lowson's equation were met: animal flight is low (<0.3) Mach and animals from albatrosses to mosquitoes are acoustically compact, meaning they have a small spatial extent relative to the wavelength of their wingbeat frequency. This model predicted the acoustic waveform of a hovering Costa's hummingbird (), which varies in the , and directions around the animal. We modeled the wing forces of a hovering animal as a sinusoid with an amplitude equal to body weight. This model predicted wing sound pressure levels below a hovering hummingbird and mosquito to within 2 dB; and that far-field mosquito wing tone attenuates to 20 dB within about 0.2 m of the animal, while hummingbird humming attenuates to 20 dB at about 10 m. Wing tone plays a role in communication of certain insects, such as mosquitoes, and influences predator-prey interactions, because it potentially reveals the predator's presence to its intended prey.
为什么蜂鸟在飞行时翅膀拍打会嗡嗡作响，昆虫在飞行时翅膀拍打会发出呜呜声？古廷提出，旋转的螺旋桨会产生音调声音，因为每个叶片上的空气动力压力中心的位置相对于外部接收器会发生振荡。动物的翅膀也会运动，此外，动物翅膀产生的空气动力在翅膀拍动过程中在大小和方向上波动。在这里，我们将动物翅膀的音调建模为与翅膀上的空气动力相等且相反的反应，使用洛森（Lowson）方程来描述运动点力产生的声场。洛森（Lowson）方程的两个假设得到了满足：动物飞行的马赫数较低（<0.3），并且从信天翁到蚊子的动物在声学上是紧凑的，这意味着它们相对于翅膀拍动频率的波长，其空间范围较小。该模型预测了悬停的 Costa 蜂鸟（）的声学波形，其在动物周围的 、 和 方向上变化。我们将悬停动物的翅膀力建模为振幅等于体重的正弦波。该模型预测的悬停蜂鸟和蚊子的翅膀声压级相差 2dB 以内；并且远场蚊子翅膀的音调在距动物约 0.2m 处衰减到 20dB，而蜂鸟的嗡嗡声在约 10m 处衰减到 20dB。翅膀的音调在某些昆虫（例如蚊子）的交流中起着作用，并影响捕食者-猎物的相互作用，因为它可能会将捕食者的存在暴露给其预期的猎物。
