Vibro-Acoustic Signatures of Various Insects in Stored Products.

Stored products, such as grains and processed foods, are susceptible to infestation by various insects. The early detection of insects in the supply chain is crucial, as introducing invasive pests to new environments may cause disproportionate harm. The STAR Center at Stevens Institute of Technology developed the Acoustic Stored Product Insect Detection System (A-SPIDS) to detect pests in stored products.

Towards an Automated Acoustic Detection Algorithm for Wood-Boring Beetle Larvae (Coleoptera: Cerambycidae and Buprestidae).

The development of acoustic systems for detection of wood-boring larvae requires knowledge of the features of signals produced both by insects and background noise. This paper presents analysis of acoustic/vibrational signals recorded in tests using tree bolts infested with Anoplophora glabripennis (Motschulsky) (Coleoptera: Cerambycidae) (Asian longhorn beetle) and Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) (emerald ash borer) larvae. Based on features found, an algorithm for automated insect signal detection was developed.

Modulation of high frequency noise by engine tones of small boats.

The effect of modulation of high frequency ship noise by propeller rotation frequencies is well known. This modulation is observed with the Detection of Envelope Modulation on Noise (DEMON) algorithm. Analysis of the DEMON spectrum allows the revolutions per minute and number of blades of the propeller to be determined.

Acoustic ship signature measurements by cross-correlation method.

Cross-correlation methods were applied for the estimation of the power spectral density and modulation spectrum of underwater noise generated by moving vessels. The cross-correlation of the signal from two hydrophones allows the separation of vessel acoustic signatures in a busy estuary. Experimental data recorded in the Hudson River are used for demonstration that cross-correlation method measured the same ship noise and ship noise modulation spectra as conventional methods.

Time reversal acoustic focusing with a catheter balloon.

The ability to deliver configurable myocardial lesions was noted as a critical factor to the success of atrial fibrillation (AF) treatment. This article considers the implementation of time reversal acoustics (TRA) principles for ultrasound focusing using an AF cardiac catheter developed for pulmonary vein isolation. Experiments conducted with a single transmitting channel demonstrated that a catheter balloon could be used as an acoustic reverberator to enable focusing and steering of ultrasound short pulses in the TRA mode.

Wideband nonlinear time reversal seismo-acoustic method for landmine detection.

Acoustic and seismic waves provide a method to localize compliant mines by vibrating the top plate and a thin soil layer above the mine. This vibration is mostly linear, but also includes a small nonlinear deviation. The main goal of this paper is to introduce a method of processing that uses phase-inversion to observe nonlinear effects in a wide frequency band.

Determination of acoustic attenuation in the Hudson River Estuary by means of ship noise observations.

Analysis of sound propagation in a complex urban estuary has application to underwater threat detection systems, underwater communication, and acoustic tomography. One of the most important acoustic parameters, sound attenuation, was analyzed in the Hudson River near Manhattan using measurements of acoustic noise generated by passing ships and recorded by a fixed hydrophone. Analysis of the ship noise level for varying distances allowed estimation of the sound attenuation in the frequency band of 10-80 kHz.

Radiation force and shear motions in inhomogeneous media.

An action of radiation force induced by ultrasonic beam in waterlike media such as biological tissues (where the shear modulus is small as compared to the bulk compressibility) is considered. A new, nondissipative mechanism of generation of shear displacement due to a smooth (nonreflecting) medium inhomogeneity is suggested, and the corresponding medium displacement is evaluated. It is shown that a linear primary acoustic field in nondissipative, isotropic elastic medium cannot excite a nonpotential radiation force and, hence, a shear motion, whereas even smooth inhomogeneity makes this effect possible.

Nonlinear resonant ultrasound spectroscopy (NRUS) applied to damage assessment in bone.

Nonlinear resonant ultrasound spectroscopy (NRUS) is a resonance-based technique exploiting the significant nonlinear behavior of damaged materials. In NRUS, the resonant frequency(ies) of an object is studied as a function of the excitation level. As the excitation level increases, the elastic nonlinearity is manifest by a shift in the resonance frequency.

Slow dynamics and anomalous nonlinear fast dynamics in diverse solids.

Results are reported of the first systematic study of anomalous nonlinear fast dynamics and slow dynamics in a number of solids. Observations are presented from seven diverse materials showing that anomalous nonlinear fast dynamics (ANFD) and slow dynamics (SD) occur together, significantly expanding the nonlinear mesoscopic elasticity class. The materials include samples of gray iron, alumina ceramic, quartzite, cracked Pyrex, marble, sintered metal, and perovskite ceramic.

Nonlinear scattering of acoustic waves by natural and artificially generated subsurface bubble layers in sea.

The paper describes nonlinear effects due to a biharmonic acoustic signal scattering from air bubbles in the sea. The results of field experiments in a shallow sea are presented. Two waves radiated at frequencies 30 and 31-37 kHz generated backscattered signals at sum and difference frequencies in a bubble layer.