Wavelets and Wavelet Packets Applied to Termite Detection

Abstract

In this paper we present an study which shows the possibility of using wavelets and wavelet packets to detect transients produced by termites. Identification has been developed by means of analyzing the impulse response of three sensors undergoing natural excitations. Denoising exhibits good performance up to SNR=-30 dB, in the presence of white Gaussian noise. The test can be extended to similar vibratory or acoustic signals resulting from impulse responses.

Higher-order spectra measurement techniques of termite emissions. A characterization framework

“…When the instrument fails to detect a pulse within a specified timeout, the detector circuit turns off and stores the pulses in the measuring time as a hit. 3 The former AE types are found in real situations in miscellaneous forms, with noise background. Spiky continuous noise characterizes turbulence in fluid or gas flow systems and voltage fluctuations in high tension lines.…”

“…This energy travels through the material as a stress or strain wave and is typically detected using a piezoelectric transducer, which converts the surface displacement (vibrations) to an electrical signal [3,8,9].…”

Third-Order Spectral Characterization of Termite’s Emission Track

“…AE is defined as the class of phenomena whereby transient elastic waves are generated by the rapid (and spontaneous) release of energy from localized sources within a material, or the transient elastic wave(s) so generated. This energy travels through the material as a stress wave and is typically detected using a piezoelectric transducer, which converts the surface displacement (vibrations) to an electrical signal [4].…”

“…Termites use a sophisticated system of vibratory long distance alarm described, among others in, [1]. In [4] is is shown one of the impulses within a typical four-impulse burst (alarm signals) and its associated power spectrum of the specie (reticulitermes lucifugus). The carrier frequency of the drumming signal is defined as the main spectral component.…”

“…Other prior-art second-order tools, like wavelets and wavelet packets (timedependent technique) concentrate on transients and non-stationary movements, making possible the detection of singularities and sharp transitions, by means of sub-band decomposition. The method has been proved under controlled laboratory conditions, up to a SNR=-30 dB [4].…”