Spectral Kurtosis based system for transients´ detection: Application to termite targeting

In this paper we present the operation results of a portable computer-based measurement equipment conceived to perform non-destructive testing of suspicious termite infestations. Its signal processing module is based in the Spectral Kurtosis (SK) and it can be applied to numerous kinds of transients´ detection. We introduce the de-noising complement of the discrete wavelet transform (DWT) and we study how can it serves to reduce subjectiveness. The SK pattern allows the targeting of alarms and activity signals. The DWT complements the SK, by keeping the successive approximations of the termite emissions, supposed more non-Gaussian (less noisy) and with less entropy than the detail approximations. For a given mother wavelet, the maximum acceptable level, in the wavelet decomposition tree, which preserves the insects´ emissions features, depends on the comparative evolution of the approximations details´ entropies, and the value of the global spectral kurtosis associated to the approximation of the separated signals. The paper explains the detection criterion by showing different types of real-life recordings (alarms, activity, and background).