This work presents a numerical study on atmospheric sound propagation over rough water surfaces with the aim of improving predictions of sound propagation over long distances. A method for generating pseudorandom sea profiles consistent with sea wave spectra is presented. The proposed method is suited for capturing the logarithmic nature of the energy distribution of the waves. Sea profiles representing fully developed seas for sea states 2, 3, 4, and 5 are generated from the Elfouhaily et al. (ECKV) sea wave spectra. Excess attenuation caused by refraction and surface roughness is predicted with a parabolic equation (PE) solver. A novel method for estimating equivalent effective impedance based on PE predictions at different sea states is presented. Parametric expressions using acoustic frequency and significant wave height are developed for effective surface impedances. In this work, sea surface roughness is on a scale comparable with the acoustic wavelength. Under this condition, the acoustic scattering is primarily incoherent. This work shows the limitations of using an equivalent surface impedance in such incoherent scattering cases.

This work presents a case study of atmospheric acoustic transmission loss measurements over a mixed domain of water and sand. The aim of this paper is a detailed description of the measurement system and data handling approach. This effort is part of an ongoing project modeling atmospheric acoustic transmission loss in littoral or riverine environments. The goal of the presented experiment is the evaluation of the excess attenuation introduced by a sandy shore. The site is a small pond with a man-made sandy beach area. An acoustic source is placed on the opposite edge of the pond and three 7-microphone arrays are placed in line at ranges of 126 m (water’s edge), 146 m and 166 m. Data is presented in order to highlight the design of the measurement system and post-processing approach. Sound pressure levels predicted by a numerical model, which is presented in detail in a companion work, are included as an illustrative case.

The aim of this work is to describe a rich set of acoustic transmission loss observations that were completed in a coastal environment. The data library, enumerated in detail and publicly posted, is comprised of pitch-catch acoustic transmission loss measurements along with concurrent high spatial resolution meteorological observations. The meteorological parameters include near-surface temperature profiles, vertical wind speed profiles in the acoustic propagation direction, and significant wave height estimates. The acoustic source is positioned on an anchored vessel such that the first several hundred meters of the acoustic range is over open water with one microphone array positioned at the shore. A second microphone array is placed several hundred meters inland along the same source-to-receiver heading. The path between the two acoustic arrays is uniform salt marsh vegetation. Observations were made during seven sessions, which represent a variety of atmospheric conditions. That variety of conditions allows for some experimental generalizations about transmission loss as a function of meteorological observations. These include (1) the relationship between vertical effective sound speed profile and transmission loss, and (2) the variability of acoustic pressure with turbulence over time and elevation.

Factors that must be considered in the study of long-range atmospheric sound propagation include surface characteristics like ground geometry and surface impeda

The aim of the paper is to describe a portable, modular, and scaleable system for measuring concurrent acoustic transmission loss and atmospheric characteristics. This system has been developed specifically to inform an effort to improve the ability to implement high fidelity numerical predictions of acoustic transmission loss, particularly in acoustically complex outdoor ranges, such as those that occur in coastal areas. Such a system has broad possible applicability in many outdoor atmospheric acoustic monitoring scenarios.