A multi-year study of acoustic propagation and ambient sound in a Thalassia testudinum seagrass meadow in a shallow sub-tropical lagoona).

Seagrasses provide a multitude of ecosystem services and act as important carbon sinks. However, seagrass habitats are declining globally, and they are among the most threatened ecosystems on earth. For these reasons, long-term and continuous measurements of seagrass parameters are of primary importance for ecosystem health assessment and sustainable management.

Direct measurements of sediment geoacoustic properties in the New England Mud Patch and shelf breaka).

This paper reports on an original set of direct sound speed measurements collected with the acoustic coring system in the New England Mud Patch (NEMP) and shelf break area to the south. Cores collected within the NEMP show range-dependence of the mud with slower sound speed and lower attenuation on the west side. In the shelf break region, the highest sound speeds are observed between the 200- and 350-m isobaths.

Pediatric Postoperative Outcomes for Severe and Very Severe Obstructive Sleep Apnea Syndrome.

Objective: To determine if increasing obstructive sleep apnea syndrome (OSAS) severity, as determined by preoperative polysomnography data, is an independent risk for respiratory complications and level of follow-up care after adenotonsillectomy or tonsillectomy.

Methods: A retrospective analysis of patients ≤21 years of age with severe OSAS (obstructive apnea-hypopnea index [OAHI] >10) undergoing adenotonsillectomy or tonsillectomy. Patients were categorized based on preoperative polysomnography data (PSG).

Out-of-plane arrivals recorded by drifting hydrophones during the Northern Ocean Rapid Surface Evolution Experiment.

This paper reports on an observation of three-dimensional (3D) arrivals for which the change in the direction of horizontally refracted sound is nearly 180°. The experimental site is Jan Mayen Channel (JMCh), which connects the Greenland and Norwegian Seas. During the experiment, signals from a moored source transmitting a 500-1500 Hz sweep every 4 h were recorded by three surface drifters equipped with hydrophone arrays.

Evaluating machine learning architectures for sound event detection for signals with variable signal-to-noise-ratios in the Beaufort Sea.

This paper explores the challenging polyphonic sound event detection problem using machine learning architectures applied to data recorded in the Beaufort Sea during the Canada Basin Acoustic Propagation Experiment. Four candidate architectures were investigated and evaluated on nine classes of signals broadcast from moored sources that were recorded on a vertical line array of hydrophones over the course of the yearlong experiment. These signals represent a high degree of variability with respect to time-frequency characteristics, changes in signal-to-noise ratio (SNR) associated with varying signal levels as well as fluctuating ambient sound levels, and variable distributions, which resulted in class imbalances.

Evaluation of Parental Perspectives and Concerns about Pediatric Cochlear Implantation: A Social Media Analysis.

Objective: Parents often experience uncertainty during decision-making for their child's cochlear implantation (CI) surgery, and online forums provide insight on parental opinions that might not be expressed in clinic. This study aims to evaluate parental perspectives and concerns about pediatric CI using social media analysis.

Study Design: Qualitative study.

Characterizing the acoustic response of Thalassia testudinum leaves using resonator measurements and finite element modeling.

Seagrasses play an important role in coastal ecosystems and serve as important marine carbon stores. Acoustic monitoring techniques exploit the sensitivity of underwater sound to bubbles, which are produced as a byproduct of photosynthesis and present within the seagrass tissue. To make accurate assessments of seagrass biomass and productivity, a model is needed to describe acoustic propagation through the seagrass meadow that includes the effects of gas contained within the seagrass leaves.

Inter-seasonal comparison of acoustic propagation in a Thalassia testudinum seagrass meadow in a shallow sub-tropical lagoon.

Acoustic propagation measurements were collected in a seagrass meadow in a shallow lagoon for periods of over 65 h in winter and 93 h in summer. A bottom-deployed sound source transmitted chirps (0.1-100 kHz) every 10 min that were received on a four-receiver horizontal hydrophone array.

Model-data comparison of sound propagation in a glacierized fjord with a simulated brash ice surface.

Glacier ice loss impacts sound propagation within Arctic fjords. Regular calving events contribute to a collection of floating ice fragments, known as brash ice, at the ocean surface that obstruct the natural and anthropogenic acoustic signals, yet are difficult to characterize. Transmission loss measurements using a maximum length sequence (m-sequence) signal were conducted in September 2017 near Hansbreen glacier in Hornsund Fjord, Svalbard with dense brash ice present at the water surface.

Clustering analysis of a yearlong record of ambient sound on the Chukchi Shelf in the 40 Hz to 4 kHz frequency range.

Changes in the Arctic environment with regard to declining sea ice are expected to alter the ambient sound field, affecting both the sound generating processes and the sound propagation. This paper presents acoustic recordings collected on the 150-m isobath on the Chukchi Shelf over a yearlong period spanning October 2016 to October 2017. The analysis uses sections of recordings approximately 12 min long collected six times daily.

Temporal and spatial dependence of a yearlong record of sound propagation from the Canada Basin to the Chukchi Shelf.

The Pacific Arctic Region has experienced decadal changes in atmospheric conditions, seasonal sea-ice coverage, and thermohaline structure that have consequences for underwater sound propagation. To better understand Arctic acoustics, a set of experiments known as the deep-water Canada Basin acoustic propagation experiment and the shallow-water Canada Basin acoustic propagation experiment was conducted in the Canada Basin and on the Chukchi Shelf from summer 2016 to summer 2017. During the experiments, low-frequency signals from five tomographic sources located in the deep basin were recorded by an array of hydrophones located on the shelf.

Application of acoustical remote sensing techniques for ecosystem monitoring of a seagrass meadow.

Seagrasses provide a multitude of ecosystem services and serve as important organic carbon stores. However, seagrass habitats are declining worldwide, threatened by global climate change and regional shifts in water quality. Acoustical methods have been applied to assess changes in oxygen production of seagrass meadows since sound propagation is sensitive to the presence of bubbles, which exist both within the plant tissue and freely floating the water as byproducts of photosynthesis.

Impacts of simulated infaunal activities on acoustic wave propagation in marine sediments.

The activities of infaunal organisms, including feeding, locomotion, and home building, alter sediment physical properties including grain size and sorting, porosity, bulk density, permeability, packing, tortuosity, and consolidation behavior. These activities are also known to affect the acoustic properties of marine sediments, although previous studies have demonstrated complicated relationships between infaunal activities and geoacoustic properties. To avoid difficulties associated with real animals, whose exact locations and activities are unknown, this work uses artificial burrows and simulates infaunal activities such as irrigation, compaction, and tube building in controlled laboratory experiments.

Three-dimensional acoustic propagation effects induced by the sea ice canopy.

This work examines three-dimensional (3D) propagation caused by interaction with the sea ice canopy using an approximate normal mode/parabolic equation hybrid model. The effects of horizontal refraction are assessed through comparison of two-dimensional (2D) and 3D solutions for the modal amplitudes and depth-averaged transmission loss. The following 3D effects are described: diffraction of sound into shadow zones behind ice keels, horizontal defocusing of sound behind ice keels, and horizontal focusing of sound that has propagated between ice keels.

Broadband sound propagation in a seagrass meadow throughout a diurnal cycle.

Acoustic propagation measurements were conducted in a Thalassia testudinum meadow in the Lower Laguna Madre, a shallow bay on the Texas Gulf of Mexico coast. A piezoelectric source transmitted frequency-modulated chirps (0.1 to 100 kHz) over a 24-h period during which oceanographic probes measured environmental parameters including dissolved oxygen and solar irradiance.

Progressive Dominant Hearing Loss (Autosomal Dominant Deafness-41) and P2RX2 Gene Mutations: A Phenotype-Genotype Study.

Objectives/hypothesis: P2RX2 encoding P2X purinoreceptor 2 has been identified as the gene responsible for autosomal dominant deafness-41 (DFNA41) as well as mediating vulnerability to noise-induced hearing loss (NIHL). The objective of this study was to investigate the audiological and molecular characteristics of P2RX2-related deafness, with emphasis on its role in NIHL by determining the audiological characteristics of a previously reported six-generation DFNA41 family with a 10-year follow-up. We have also summarized phenotype-genotype correlations of P2RX2-related deafness in human and mouse models.

Measurements and modeling of acoustic propagation in a scale model canyon.

Two scale-model acoustic propagation experiments were conducted in a laboratory tank to investigate three-dimensional (3D) propagation effects induced by range-dependent bathymetry. The model bathymetry, patterned after measured bathymetric data, represents a portion of the Hudson Canyon at 1:7500 scale. The bottom condition in the scale model is nearly pressure release, and as a result, the bottom reflection and backscattering are stronger than that of the real ocean environment.

Scale model observations of coupled vertical modes in a translationally invariant wedge.

Scale-model tank experiments offer a controlled environment in which to make underwater acoustic propagation measurements that can provide high-quality data for comparison with numerical models. This paper presents results from a scale model experiment for a translationally invariant wedge with a 10° slope fabricated from closed-cell polyurethane foam to investigate three-dimensional (3-D) propagation effects. A computer controlled positioning system accurately located a receiving hydrophone in 3-D space to create a dense field of synthetic vertical line arrays, which are subsequently used to mode filter the measured pressure field.

Observation of out-of-plane ambient noise on two vector sensor moorings in Lake Travis.

Two Autonomous Underwater Multi-Dimensional Acoustic Recorders (AUMDAR) were deployed in the southeastern part of Lake Travis during the summer of 2018. Each AUMDAR system possessed a three-axis acoustic vector sensor capable of estimating the azimuthal and vertical arrival angles from discrete sound sources. A unique and complicated propagation environment existed during the experiment due to the mooring locations and the range-dependent lake bathymetry.

A comparison between directly measured and inferred wave speeds from an acoustic propagation experiment in Currituck Sound.

An acoustic propagation experiment was conducted in Currituck Sound to characterize low-frequency propagation in a very-shallow-water estuarine environment. The water column properties were homogeneous over the study area, and the emphasis of this work is on understanding the propagation effects induced by the estuarine bed. During the experiment, low-frequency sound propagation measurements of waterborne sound and interface waves were acquired, and direct measurements of the compressional and shear wave properties were obtained at high frequencies.

Sound speed and attenuation measurements within a seagrass meadow from the water column into the seabed.

In situ measurements of sound speed and attenuation at 50 kHz were conducted in a Thalassia testudium meadow. Measurements were obtained at discrete depths in the water column, in the seagrass canopy, and in the sediment beneath the seagrass. Measurements were also obtained in bare sediment located a few meters away.

Examining the effects of microstructure on geoacoustic parameters in fine-grained sediments.

This paper presents a set of controlled laboratory experiments designed to develop a basis for understanding the relationship between microscopic and macroscopic properties of fine-grained sediments. Two samples of kaolinite platelets were selected for this study, and effects of sediment microstructure on geoacoustic properties are deduced from a comparison of the measured properties. To provide additional interpretation of the acoustic measurements, compressional and shear wave properties are compared to predicted values from sediment-acoustic models.

In situ measurements of sediment acoustic properties in Currituck Sound and comparison to models.

In situ measurements 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.