Hughes Derke R, Nuttall Albert H, Katz Richard A, Carter G Clifford
Naval Undersea Warfare Center Division, Newport, Newport, Rhode Island 02841-1708, USA.
J Acoust Soc Am. 2009 Feb;125(2):958-67. doi: 10.1121/1.3050258.
An analysis of cicada mating calls, measured in field experiments, indicates that the very high levels of acoustic energy radiated by this relatively small insect are mainly attributed to the nonlinear characteristics of the signal. The cicada emits one of the loudest sounds in all of the insect population with a sound production system occupying a physical space typically less than 3 cc. The sounds made by tymbals are amplified by the hollow abdomen, functioning as a tuned resonator, but models of the signal based solely on linear techniques do not fully account for a sound radiation capability that is so disproportionate to the insect's size. The nonlinear behavior of the cicada signal is demonstrated by combining the mutual information and surrogate data techniques; the results obtained indicate decorrelation when the phase-randomized and non-phase-randomized data separate. The Volterra expansion technique is used to fit the nonlinearity in the insect's call. The second-order Volterra estimate provides further evidence that the cicada mating calls are dominated by nonlinear characteristics and also suggests that the medium contributes to the cicada's efficient sound propagation. Application of the same principles has the potential to improve radiated sound levels for sonar applications.
一项对在野外实验中测量的蝉交配叫声的分析表明，这种相对较小的昆虫所辐射出的极高声能主要归因于信号的非线性特征。蝉在所有昆虫中发出的声音是最响亮的之一，其发声系统占据的物理空间通常小于3立方厘米。鼓膜发出的声音通过中空的腹部得到放大，腹部起到调谐谐振器的作用，但仅基于线性技术的信号模型并不能完全解释与昆虫体型如此不相称的声音辐射能力。通过结合互信息和替代数据技术证明了蝉信号的非线性行为；所得结果表明，当相位随机化数据和非相位随机化数据分离时会出现去相关。沃尔泰拉展开技术用于拟合昆虫叫声中的非线性。二阶沃尔泰拉估计进一步证明了蝉交配叫声由非线性特征主导，也表明介质有助于蝉的高效声音传播。应用相同原理有可能提高声纳应用中的辐射声级。
