Air-coupled ultrasound (ACU) is used in through transmission to detect delamination, rot, and cracks in wood without altering the structure permanently. Novel ferroelectret transducers with a high signal-to-noise ratio enable high-precision structure recognition. Transducers made of cellular ...
We experimentally demonstrate and theoretically analyze high Q-factor (~107) capillary-based optical ring resonators for non-contact detection of air-coupled ultrasound. Noise equivalent pressures in air as low as 215 mPa/√Hz and 41 mPa/√Hz at 50
The good agreement between the air-coupled ultrasonic results and those obtained by the rheological analysis demonstrated the reliability of air-coupled ultrasound in monitoring the changes of viscoelastic properties at gelation and vitrification. The position of the transducers on the same side of the ...
The falling cost of embedded sensor systems has opened up the possibility of in-transit air-coupled ultrasound interior imaging of shipping container cargo. This new technology could allow for real-time cargo integrity verification and improved shipping and transportation security. This paper takes the...
In the case of non-linear air-coupled ultrasound, the sample is excited at frequencies that have the centre frequency of the air-coupled narrow band receiver as an overtone. When the receiver scans across the sample, it responds selectively to the higher harmonics.In this study, high ...
Air-coupled ultrasound was used for assessing natural defects in wood boards by through-transmission scanning measurements. Gas matrix piezoelectric (GMP) and ferroelectret (FE) transducers were studied. The study also included tests with additional bias voltage with the ferroelectret receivers. Signal ...
or otherwise be destroyed. Additionally, air-coupled ultrasound offers the benefit of low, highly penetrating frequency ultrasound combined with the short wavelength in air. This allows the nondestructive inspection of previously untestable composits like thick, multilayer honeycombs, foam cores or green...
Air-coupled ultrasound as an accurate and reproducible method for bonding assessment of glued timber Wood Sci. Technol. (2011) M. Castaings et al. The generation, propagation, and detection of lamb waves in plates using air-coupled ultrasonic transducers J. Acoust. Soc. Am. (1996) There are...
Using the above mentioned transducers and broadband ultrasound sources allows a quantitative comparison of estimation of the location of an ultrasonic wave source with the use of broadband modulated signals (modelled on bats' echolocation signals) to be performed. During the laboratory research the team...
Passive focusing devices for Air-Coupled Ultrasound (ACU) transducers provide simple methods to concentrate the sound beam into a focus. This helps to improve lateral resolution and increase sensitivity. This work analyzed both theoretical and experimentally the behavior of three passive focusing devices...