The long term goals of this research activity are to significantly increase the performance and affordability of small AUV systems by eliminating their need for expensive navigation equipment by providing exact position updates through an acoustic uplink system with a geographically positioned ASV. The mobile surface acoustic link shall also allow the AUV to communicate data while in transit an...

This paper addresses typical problems encountered with hands-free equipment in the context of GSM radiotelephony. We first summarise some important characteristics of the noise field in moving vehicles, and we also describe the acoustical echo phenomenon. We show that, in order to provide sufficiently high speech quality, these hands-free equipments should include noise reduction (NR) and acous...

The present paper presents the design and development results of a system setup for measuring Young’s modulus of thin films by laser-induced surface acoustic waves based on the integration of two detection methods, namely, piezoelectric transducer detection and differential confocal detection, which may be used for conducting consecutive or simultaneous measurements. After demonstrating the cap...

Acoustic emission tests are highly relevant among nondestructive tests applied in equipment for the petroleum industry. This paper presents methodologies for the classification of acoustic emission patterns obtained in tests to identify propagation of defects in pressurized tubes. This work is a continuation of previous research. However, to estimate the accuracy of the classification and give ...

This paper discusses principal component analysis (PCA) of integral transforms (spectra and autocovariance functions) of time-domain signals. It is illustrated using acoustic emissions from mechanical equipment. It was found that acoustic signals from different stages of operation appeared as distinct clusters in the PCA analysis. The clusters moved when machinery faults were present and the mo...

New materials and light-weight structures call for new concepts of reliability assurance and maintenance. The progress in micro-electronics and micro-electromechanical systems (MEMS) allows development of highly integrated smart systems in large quantities at low costs that combine signal generation, data pre-processing and wireless communication accompanied by energy harvesting mechanisms, thu...

A selective acoustic activation of defects based on the concept of Local Defect Resonance (LDR) enables to enhance considerably the intensity of defect vibrations and makes it possible to reduce the input acoustic powers to the levels permissible for noncontact nondestructive inspection. Since for cm-size defects in composite materials, the LDR frequencies lie in the low kHz-range the resonant ...

Non-Destructive testing is useful in rail, pipeline and aerospace industries for maintenance of equipment, such as thickness measurements, corrosion and defect detection in materials. In this work a finite element analysis of an Electromagnetic acoustic transducer is presented. EMAT is an emerging technology that provides a non contact process of testing materials compared to ultrasonic sensors...