《In situ measurements of sediment acoustic properties in Currituck Sound and comparison to models》
In situmeasurements of compressional and shear wave speed and attenuation were collected 30 cm below the water-sediment interface in Currituck Sound, North Carolina at two field locations having distinctly different sediment types: medium-to-fine-grained sand and fine-grained sand with approximately 10% mud content. Shear wave measurements were performed with bimorph transducers to generate and receive horizontally polarized shear waves in the 300 Hz to 1 kHz band, and compressional wave measurements were performed using hydrophones operated in the 5 kHz to 100 kHz band. Sediment samples were collected at both measurement sites and later analyzed in the laboratory to characterize the sediment grain size distribution for each field location. Compressional and shear wave speed and attenuation were estimated from the acoustic measurements, and preliminary comparisons to the extended Biot model by Chotiros and Isakson [J. Acoust. Soc. 135, 3264–3279 (2014)] and the viscous grain-shearing theory by Buckingham [J. Acoust. Soc. 136, 2478–2488 (2014)] were performed.
The middle ear efficiently transmits sound from the ear canal into the inner ear through a broad range of frequencies. Thus, understanding middle-ear transmission characteristics is essential in the study of hearing mechanics. Two models of the chinchilla middle ear are presented. In the first model, the middle ear is modeled as a lumped parameter system with elements that represent the ossicular chain and the middle-ear cavity. Parameters of this model are fit using available experimental data of two-port transmission matrix parameters. In an effort to improve agreement between model simulations and the phase of published experimental measurements for the forward pressure transfer function at high frequencies, a second model in which a lossless transmission line model of the tympanic membrane is appended to the original model is proposed. Two-port transmission matrix parameter results from this second model were compared with results from previously developed models of the guinea pig, cat, and human middle ears. Model results and published experimental data for the two-port transmission matrix parameters are found to be qualitatively similar between species. Quantitative differences in the two-port transmission matrix parameters suggest that the ossicular chains of chinchillas, cats, and guinea pigs are less flexible than in humans.
Illustration of the exciton of TiO2 interacting with a propagating coherent acoustic wave. Credit: Adriel Dominguez (Max Planck Institute, Hamburg)Physicists from Switzerland, Germany, and France have found that large-amplitude acoustic waves, launched by ultrashort laser pulses, can dynamically manipulate the optical response of semiconductors..