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Acoustic propagation in seawater is an important aspect of scientific investigation. However, the impact of the THz scale frequencies for acoustic propagation is not included in the studies. Thus, a finite element analysis of such propagation in a seawater medium is presented in this paper applying THz frequencies. A transmitter (circular with a diameter of 14 mm, a thickness of 3 mm) and a rectangular receiver (20×10×0.5 mm3) are designed to trace the variations in the propagation mediums. A propagation medium of seawater (70×40×60 mm3) with ice and softwood is modelled. A scale of frequencies (1 kHz to 1 THz) is applied to trace the impact on the propagation pattern. It is found that THz range frequencies provide a very small wavelength. As a result, the potential propagation distance is very small. As such, the sound pressure level, displacements of the receiver and pressure field shows very rapid drops in the magnitude. This work considers only 70 mm as propagation distance, yet the sharp decrement of performance parameters suggests that it is rather inconvenient to achieve useful efficiency using THz frequencies for acoustic propagation.

Frequency-domain current signature analysis for fault detection on induction machines typically requires a very fine frequency resolution to distinguish between spectral components that differ from each other by multiples of the (usually very low) slip frequency. It is well known that if such a high resolution is not achieved, significant leakage errors may arise and misleading diagnostic information can be obtained from the measured current spectrum. This paper presents a leakage error compensation technique that allows accurate results even when the resolution is limited by the requirement of short observation time. This technique is based on the independent knowledge of the frequencies of the relevant components in the spectrum, which only depend on the power supply frequency and on the motor rotation speed, whose measurements are often available. The proposed method is here applied to the detection of rotor bar breakages and it is tested on simulated motor current waveforms

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