Excess attenuation at the beach: a model validation. Andrea Vecchiotti
This work presents a comparison between experimental results and numerical modelling of atmospheric sound transmission loss across a range that includes water and a sandy shore. This work is part of a larger project developing a numerical model of long-range (~3 km) atmospheric acoustic propagation in littoral or riverine environments with a near-shore acoustic source and on-shore receivers. The narrow angle parabolic equation method used in this work accounts for wind and temperature variation with elevation along the acoustic propagation path. The beach is modelled as an equivalent fluid employing the Johnson-Champoux-Allard-Pride-Lafarge (JCAPL) model. This eight-parameters model is reduced to a one parameter model by considering the sand is randomly packed spherical particles. The single parameter is the grain size. Measured grain size distributions of the sand and its change in water content with the distance from the water inform model development of the beach. Sound pressure levels predicted by three model variations are compared with measurements. Advantages and drawbacks of model complexity are presented. We show that short spans of saturated sand are effectively modelled with a fully reflective surface whereas longer spans of sand require varying levels of sound absorption.
“Acoustic Noise Measurements During Neonatal MR Scans”. Hannah Kurdila, Tayeb Zaidi, Subha Maruvada, Sunder Rajan
The magnetic resonance (MR) scan is a standard means to image the human body that produces significant sound pressure levels. Steps have been taken to explore and mitigate this threat for the adult patient, but now, it is becoming standard practice to use MR scanners on neonates, who are believed to be more sensitive than adults to loud sounds. We present: (1) a survey of the neonatal MR practices of hospitals in the DC area, (2) details of the sound levels produced during neonatal scan protocols, and (3) an appraisal of the threat level to the neonatal patient based on our findings and the current literature surrounding neonatal hearing.