Physical Basis of Vibrational Behaviour: Channel Properties, Noise and Excitation Signal Extraction

Socially living insects rely on efficient and accurate communication and source localisation for survival. Insects communicate multimodally using visual, chemical or mechanical cues. Vibrations are often considered to be a primitive mode of exchanging information, but vibrations are independent of sight or airflow, and can reach the destination cryptically and reliably. However, other than in air or water, the vibration communication channel in nature is usually a heterogeneous substrate with nonlinear material properties. Communication is hindered by increased signal complexity under the influence of noise and distortion. This chapter gives an overview of biotremology on natural substrates and the difficulties associated with noise and heterogeneous materials. The noise control engineering principle is used to extract the excitation signal from substrate response vibrations and the communication channel properties. It is argued that in order to obtain insight into the role of vibrations in insect behaviour, the ability of insects to adapt to changed situations and environmental conditions by making use of the substrate as a filter needs to be studied by means of the excitation signal rather than the response signal alone.