Usually, acoustic partial discharge (PD) and vibration measurements take place on the outside tank wall of power transformers. This contribution determines new approaches for acoustic PD measurements within the oil volume of the transformer combined with electromagnetic in-oil measurements. Scope of the work is an acoustic and ultra-high frequency (UHF) detection of PD and additional recording ...

In recent years, the dynamic behavior of solid structure defects is extremely important as a small defect that is growing may well be more significant than a larger stable defect. Acoustic Emission (AE) is the method used to investigate the behavior of defects under stress. The importance of the AE is to determine the source location when it occurs. It is a real time monitoring technique. Ident...

High background noise is an impediment to signal detection and perception. We report the use of multiple solutions to improve signal perception in the acoustic and visual modality by the Bornean rock frog, Staurois parvus. We discovered that vocal communication was not impaired by continuous abiotic background noise characterised by fast-flowing water. Males modified amplitude, pitch, repetitio...

Lin H., Zhao J., Chen Q., Cai J., Zhou P. (2009): Eggshell crack detection based on acoustic impulse response and supervised pattern recognition. Czech J. Food Sci., 27: 393–402. A system based on acoustic resonance was developed for eggshell crack detection. It was achieved by the analysis of the measured frequency response of eggshell excited with a light mechanism. The response signal was pr...

Ultrasound-modulated optical tomography (UOT) detects ultrasonically modulated light to spatially localize multiply scattered photons in turbid media with the ultimate goal of imaging the optical properties in living subjects. A principal challenge of the technique is weak modulated signal strength. We discuss ways to push the limits of signal enhancement with intense acoustic bursts while conf...

Passive acoustic sensing has emerged as a powerful tool for quantifying anthropogenic impacts on biodiversity, especially for echolocating bat species. To better assess bat population trends there is a critical need for accurate, reliable, and open source tools that allow the detection and classification of bat calls in large collections of audio recordings. The majority of existing tools are c...

Application of the high-frequency acoustic emission (AE) technique in condition monitoring of rotating machinery has been growing over recent years. This is particularly true for bearing defect diagnosis and seal rubbing (Mba et al., 1999, 2003, 2005; Kim et al., 2007; Siores & Negro, 1997). The main drawback with the application of the AE technique is the attenuation of the signal and as such ...

We first describe the picosecond acoustic interferometry study of GaAs with twocolors pump-probe laser pulses. The dependence of the generation process on the pump wavelength and the detection process on the probe wavelength both can cause the shift in the phase of the Brillouin signal. Secondly, in order to distinguish the short high frequency wideband acoustic pulse from low frequency Brillou...

Subwavelength resolution in a transmission acoustic microscope configuration is demonstrated using optical fiber-tip sensors as small-sized acoustic probes. A slit with a width of 1/20 of the acoustic wavelength L representing the object was detected with a lateral resolution of the outer fiber diameter which was '1/10 L, and with a proper signal-to-noise ratio. Fiber preparation techniques may...