Search results for "ACOUSTIC"

Facepiece filtering respirators with exhalation valve should not be used in the community to limit SARS-CoV-2 diffusion.

2020

Reverberation reduction in capacitive micromachined ultrasonic transducers (CMUTs) by front-face reflectivity minimization

2015

Abstract Front-face acoustic reflectivity of ultrasonic imaging transducers, due to acoustic impedance mismatch with the propagation medium, may cause reverberation phenomena during wideband pulse-echo operation. Front-face reflectivity may be reduced by promoting the transmission of the echoes, received from the medium, to the transducer backing, and by maximizing the mechanical-to-electrical energy conversion and dissipation by tuning the electrical load impedance connected to the transducer. In Capacitive Micromachined Ultrasonic Transducers (CMUTs), the energy transfer from the medium to the backing is very low due to the large impedance mismatch between the medium and the transducer su…

A Bayesian direction-of-arrival model for an undetermined number of sources using a two-microphone array.

2014

Sound source localization using a two-microphone array is an active area of research, with considerable potential for use with video conferencing, mobile devices, and robotics. Based on the observed time-differences of arrival between sound signals, a probability distribution of the location of the sources is considered to estimate the actual source positions. However, these algorithms assume a given number of sound sources. This paper describes an updated research account on the solution presented in Escolano et al. [J. Acoust. Am. Soc. 132(3), 1257-1260 (2012)], where nested sampling is used to explore a probability distribution of the source position using a Laplacian mixture model, whic…

Real-time Sound Source Localization on Graphics Processing Units

2013

Abstract Sound source localization is an important topic in microphone array signal processing applications, such as camera steering systems, human-machine interaction or surveillance systems. The Steered Response Power with Phase Transform (SRP- PHAT) algorithm is one of the most well-known approaches for sound source localization due to its good performance in noisy and reverberant environments. The algorithm analyzes the sound power captured by a microphone array on a grid of spatial points in a given room. While localization accuracy can be improved by using a high resolution spatial grid and a high number of microphones, performing the localization task in these circumstances requires …

Automatic Detection and Characterization of Acoustic Plane-Wave Reflections Using Circular Microphone Arrays

2013

The spatial characteristics of the sound field inside a room can be meaningfully described by means of microphone array processing techniques. In this context, the set of impulse responses sampled by a microphone array can be seen as an image made of acoustic plane-wave footprints. Due to the circular geometry of the microphone array, these footprints have a cosine-like shape that can be fully described as a function of the direction of arrival (DOA) of the impinging plane wave. This paper proposes a Hough-transform-based approach to plane-wave detection in microphone array multi-trace impulse responses. Experiments using a set of real microphone recordings are described, showing the potent…

0264: How to Address the Treatment of Idiopathic Plantar Fasciitis with Mini-Invasive Techniques: HRUS Criterion

2009

Modeling of Vehicle-to-Vehicle Channels in the Presence of Moving Scatterers

2012

In this paper, we derive a vehicle-to-vehicle~(V2V) channel model assuming a typical propagation scenario in which the local scatterers move with random velocities in random directions. The complex channel gain of the proposed V2V channel model is provided. Subsequently, for different scatterer velocity distributions, the corresponding autocorrelation functions~(ACFs) are derived, illustrated, and compared with the classical ACF derived under the assumption of fixed scatterers. Furthermore, under specific conditions, highly accurate approximations for the ACFs are provided in closed form. Since the proposed V2V channel model covers several communication scenarios as special cases, including…

On the moving load problem in Euler–Bernoulli uniform beams with viscoelastic supports and joints

2016

This paper concerns the vibration response under moving loads of Euler–Bernoulli uniform beams with translational supports and rotational joints, featuring Kelvin–Voigt viscoelastic behaviour. Using the theory of generalized functions to handle the discontinuities of the response variables at the support/joint locations, exact beam modes are obtained from a characteristic equation built as determinant of a (Formula presented.) matrix, for any number of supports/joints. Based on pertinent orthogonality conditions for the deflection modes, the response under moving loads is built in the time domain by modal superposition. Remarkably, all response variables are built in a closed analytical for…

A theoretical basis for the high-frequency performance of the outer hair cell’s receptor potential

1997

The frequency response of the outer hair cell (OHC) was studied theoretically. An electrical model of the OHC was analyzed mathematically, taking into account the effect of its inherent voltage-dependent capacitance. It was found that the variations of the capacitance dependent on the membrane potential could enhance the high-frequency response of the OHC, so that its cutoff frequency could be extended into the audio range. It was found further that the enhancement of the frequency response of the OHC was strongly dependent on its resting potential and on the ratio of the maximum voltage-dependent capacitance to the membrane linear capacitance.

Intraosseous monitoring of drilling in lumbar vertebrae by ultrasound: An experimental feasibility study.

2016

The rationale for this project is to evaluate the efficiency of a novel sonographic method for measurements of interosseous distances. The method utilizes a propagating ultrasonic beam through aqueous milieu which is directed as a jet into a drilled tract. We used a plastic model of human L5 vertebra and ex vivo specimen of L5 porcine vertebra and generated 2 mm in diameter tracts in vertebral pedicles. The tracts were created in the "desired" central direction and in the "wrong" medial and lateral directions. The drilled tracts and the residual, up to opposite cortex, distances were measured sonographically and mechanically and compared statistically. We show that "true" mechanical measure…