- “Measurement of car cabin binaural impulse responses and auralization via convolution”, Felipe Ramos de Mello, Engenharia Acústica, Universidade Federal de Santa Maria:
- “Performance Weighted Blended Power Spectral Density Estimation” Jeff Tucker, PhD Student, George Mason University, and, Graduate Research Assistant, ECE Department, George Mason University
- “Atmospheric sound transmission loss uncertainties induced by sea roughness.” Andrea Vecchiotti,, PhD student at CUA.
- “Effects of crosslinking density on the acoustic properties of hydrogel scaffolds “. Megan Anderson, Catholic University of America, PhD Student.
- Felipe Ramos de Mello, Engenharia Acústica, Universidade Federal de Santa Maria:
Measurement of car cabin binaural impulse responses and auralization via convolution Authors: Felipe Ramos de Mello, William D’Andrea Fonseca, Davi Rocha Carvalho, Paulo Henrique Mareze e Olavo Silva Abstract Auralization is a well-known method used to create virtual acoustic scenarios. This work elaborates techniques for the Binaural Room Impulse Response (BRIR) extraction of the interior of a passenger car cabin. As a novelty, this study developed a binaural recorder based upon digital MEMS (micro-electro-mechanical system) microphones combined with an Arduino compatible microcontroller (Teensy). To improve the recordings, spectral corrections to the acquired data were carried out. The system is compact and cost-effective, creating an advantage for those measuring different source-receiver positions. For this paper, several combinations of BRIRs were tested, including combinations of binaural recordings for ambiance. Finally, equipped with the BRIRs database, it was possible to auralize different situations in real-time, for example, a conversation between two people (with the possibility to switch/tune background music and engine sound on and off). Furthermore, it was also possible to combine sources and receivers simultaneously with a contactless camera head tracker. Listening tests revealed that the spatial impression was preserved, rendering exceptional results as a virtual environment.
- “Performance Weighted Blended Power Spectral Density Estimation” , PhD Student – Jeff Tucker, PhD Student, George Mason University, and Graduate Research Assistant, ECE Department, George Mason University
- “Atmospheric sound transmission loss uncertainties induced by sea roughness.”,
A. Vecchiotti (1), T. J. Ryan (2), F. A. Cobb (2), J. F. Vignola (1), D. Turo (1)
(1). Mechanical Engineering, The Catholic University of America, Washington DC, DC, United States.
(2) Engineering, East Carolina University, Greenville, NC, United States.
Abstract: This work presents a numerical study conducted on atmospheric sound propagation over sea. In particular, it focuses on the sound pressure level prediction uncertainties induced by the water surface roughness. To quantify these uncertainties, the generalized terrain parabolic equation (GTPE) is used to model sound propagation above water surfaces at different sea states. Water roughness is pseudo-randomly generated using an ocean wave spectrum.
The GTPE predictions are compared with those obtained using the Crank-Nicholson parabolic equation (CNPE) solver. When using the CNPE the sea surface is flat and has a surface impedance equivalent to that of a rough surface. The use of the GTPE is less computationally efficient but provides insight on the detectability of an acoustic source at sea. This work presents relationships between fully developed sea states (up to sea state 4) and the uncertainties on sound pressure level predictions at distances up to 500 m from the source. These relationships are presented for typical diurnal and nocturnal thermal gradients and for different elevations from the water surface.
Effects of crosslinking density on the acoustic properties of hydrogel scaffolds
- Megan Anderson, Catholic University of America, PhD Student –
Abstract: Hydrogels are popular materials for various biomedical applications due to their large water content which resembles that of biological tissues. Given the relevance of hydrogels in therapeutic applications, non-invasive characterization of hydrogels is highly desirable for in vivo monitoring. Whereas traditional testing methods are destructive, ultrasound is a safe and readily available tool that could be used for non-invasive characterization. In the present study, gelatin methacrylate (GelMA) hydrogel scaffolds were produced with a range of crosslinking densities by varying both GelMA concentration and ultraviolet light curing time. These scaffolds were evaluated using pulse-echo ultrasound techniques, resulting in measurements for the speed of sound, acoustic impedance, and attenuation coefficient of each hydrogel. Compression testing was also performed. The stiffness of the hydrogels was found to be between 5 and 235 kPa, with an increase in GelMA concentration or an increase in ultraviolet light curing time corresponding to a stiffer hydrogel. The impact of stiffness and preparation parameters on the acoustic properties of the hydrogels will be discussed. Further knowledge on the effect of crosslinking density on acoustic properties will inform the use of acoustic techniques in characterizing hydrogels.