Scale effects as constraints in insect sound communication

Abstract

Calling insects have problems of optimizing range and maintaining the specificity of the call. Higher frequencies are more easily refracted and reflected by objects in the environment. Smaller insects have less muscle power and also, because of the small sound source size, higher frequencies are radiated more efficiently than lower frequencies. In open air or water, the sound spreads spherically and decays by the inverse square law. If the sound can be confined to a sheet it decays as the inverse of range while within a rod it decays due to viscous losses; such calls are usually rather simple pulses and rely on initial time of arrival because of multiple pathlengths in the environment. With airborne sounds, those in the range from 1 to 10 kHz tend to have sustained pure-tone components and a specific pattern of pulses which propagates well; but with higher frequencies pulses tend to become briefer and, once again, to rely on time of arrival of the onset.