Helmholtz Equation Least Squares Based Near-Field Acoustic Holography With Laser

This dissertation presents the HELS based NAH with laser and use normal surface velocity as input in near-field acoustic holography. The conventional HELS based NAH uses acoustic pressure as input to reconstruct sound field quantities, while this modified HELS based NAH with laser utilizes the normal surface velocities measured by LDV to reconstruct the acoustic quantities at interested positions. Theoretical principles of the HELS based NAH with laser have been fully developed and the method has been verified in theoretical perspective. Two theoretical examples verify that HELS based NAH with laser can obtain exactly the same results as analytic solution. The error analysis shows that the magnitudes of errors are bounded and the HELS based NAH with laser is robust and reliable. Numerical simulations have been conducted on ideal sound sources. Another numerical study has been conducted on some special cases of a transverse vibration problem of thin plates. The reconstructed acoustic field is compared with the theoretical values, and it testifies that HELS based NAH with laser is also applicable to both ideal sound sources and complex sound sources. Experimental validation was finished by reconstructing acoustic pressure generated by a subwoofer. Through comparing the reconstructed sound pressure at 4 different positions with measured values from microphones, it demonstrates that the HELS based NAH with laser demonstrates succeed in reconstructing sound pressure based on normal surface velocity input

Proceedings of the International Workshop on Medical Ultrasound Tomography: 1.- 3. Nov. 2017, Speyer, Germany

Ultrasound Tomography is an emerging technology for medical imaging that is quickly approaching its clinical utility. Research groups around the globe are engaged in research spanning from theory to practical applications. The International Workshop on Medical Ultrasound Tomography (1.-3. November 2017, Speyer, Germany) brought together scientists to exchange their knowledge and discuss new ideas and results in order to boost the research in Ultrasound Tomography

Modelling, Simulation and Data Analysis in Acoustical Problems

Modelling and simulation in acoustics is currently gaining importance. In fact, with the development and improvement of innovative computational techniques and with the growing need for predictive models, an impressive boost has been observed in several research and application areas, such as noise control, indoor acoustics, and industrial applications. This led us to the proposal of a special issue about “Modelling, Simulation and Data Analysis in Acoustical Problems”, as we believe in the importance of these topics in modern acoustics’ studies. In total, 81 papers were submitted and 33 of them were published, with an acceptance rate of 37.5%. According to the number of papers submitted, it can be affirmed that this is a trending topic in the scientific and academic community and this special issue will try to provide a future reference for the research that will be developed in coming years

Investigating the build-up of precedence effect using reflection masking

The auditory processing level involved in the build‐up of precedence [Freyman et al., J. Acoust. Soc. Am. 90, 874–884 (1991)] has been investigated here by employing reflection masked threshold (RMT) techniques. Given that RMT techniques are generally assumed to address lower levels of the auditory signal processing, such an approach represents a bottom‐up approach to the buildup of precedence. Three conditioner configurations measuring a possible buildup of reflection suppression were compared to the baseline RMT for four reflection delays ranging from 2.5–15 ms. No buildup of reflection suppression was observed for any of the conditioner configurations. Buildup of template (decrease in RMT for two of the conditioners), on the other hand, was found to be delay dependent. For five of six listeners, with reflection delay=2.5 and 15 ms, RMT decreased relative to the baseline. For 5‐ and 10‐ms delay, no change in threshold was observed. It is concluded that the low‐level auditory processing involved in RMT is not sufficient to realize a buildup of reflection suppression. This confirms suggestions that higher level processing is involved in PE buildup. The observed enhancement of reflection detection (RMT) may contribute to active suppression at higher processing levels