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measurements a. Effects of barotropic tides Barotropic tides elevate or depress the sea surface, increasing or decreasing the total depth of the water column, which results in an increase or decrease in acoustic travel time, respectivly. If the sound speed is 1500 m s −1 , then a 1-m surface tide will cause a change in round-trip travel time of 1.3 × 10 −3 s. For our observation in the South China Sea, a millisecond travel time change is equivalent to a 24-m isopycnal displacement at the eigenfunction
measurements a. Effects of barotropic tides Barotropic tides elevate or depress the sea surface, increasing or decreasing the total depth of the water column, which results in an increase or decrease in acoustic travel time, respectivly. If the sound speed is 1500 m s −1 , then a 1-m surface tide will cause a change in round-trip travel time of 1.3 × 10 −3 s. For our observation in the South China Sea, a millisecond travel time change is equivalent to a 24-m isopycnal displacement at the eigenfunction
Using Acoustic Travel Time to Monitor the Heat Variability of Glacial Fjords-mounted acoustic devices. Bottom-to-surface round-trip acoustic travel time is an integrated measurement that depends on the depth and sound speed properties of the water column ( Del Grosso 1974 ). Since the speed of sound in seawater is primarily a function of temperature, acoustic travel time over a fixed depth is proportional to the integrated heat content of the overlying water ( Watts and Rossby 1977 ). In this study, we investigate the potential use of acoustic travel time to monitor fjord properties
-mounted acoustic devices. Bottom-to-surface round-trip acoustic travel time is an integrated measurement that depends on the depth and sound speed properties of the water column ( Del Grosso 1974 ). Since the speed of sound in seawater is primarily a function of temperature, acoustic travel time over a fixed depth is proportional to the integrated heat content of the overlying water ( Watts and Rossby 1977 ). In this study, we investigate the potential use of acoustic travel time to monitor fjord properties
acoustical extinction and includes both resonant and geometric effects. Geometric scattering is that due to the purely cross-sectional area of the bubble, separate from any resonant effects, and it increases as . In theory, if the attenuation with frequency is known, Eqs. (1) and (2) could be inverted to calculate n ( a ) da . Consequently, a single broadband measurement could be used to infer the bubble population over a wide radius range. Figure 1 shows two aspects of the extinction cross
acoustical extinction and includes both resonant and geometric effects. Geometric scattering is that due to the purely cross-sectional area of the bubble, separate from any resonant effects, and it increases as . In theory, if the attenuation with frequency is known, Eqs. (1) and (2) could be inverted to calculate n ( a ) da . Consequently, a single broadband measurement could be used to infer the bubble population over a wide radius range. Figure 1 shows two aspects of the extinction cross
An Acoustic Tomography Technique for Concurrently Observing the Structure of the Atmosphere and Water Bodiesusing real-time kinematic carrier phase differential GPS and microelectromechanical systems (MEMS) inertial navigation systems (INS). The natural acoustic signature of a manned or unmanned aircraft is monitored synchronously on board the platform and by the sensor sets on and under the water. The signal is assumed to travel only along the direct path ( Fig. 1 ), which is a transitory phenomenon that typically lasts only while the source is almost overhead. Still, as the attenuating effects of water
using real-time kinematic carrier phase differential GPS and microelectromechanical systems (MEMS) inertial navigation systems (INS). The natural acoustic signature of a manned or unmanned aircraft is monitored synchronously on board the platform and by the sensor sets on and under the water. The signal is assumed to travel only along the direct path ( Fig. 1 ), which is a transitory phenomenon that typically lasts only while the source is almost overhead. Still, as the attenuating effects of water
A Comparison of Vertical Atmospheric Wind Profiles Obtained from Monostatic Sodar and Unmanned Aerial Vehicle–Based Acoustic Tomographymasts), sodar, lidar, radio acoustic sounding system (RASS), radar, satellite-based techniques, and radiosondes. Each has benefits and drawbacks. Point-source observations from anemometers provide high wind velocity resolution and precision (0.01 and 0.05 m s −1 , respectively), but erection and maintenance costs for mast-based instruments become high as altitudes increase; and the presence of masts can obstruct or distort local wind flow ( Hasager et al. 2008 ). Measurements by remote sensing
masts), sodar, lidar, radio acoustic sounding system (RASS), radar, satellite-based techniques, and radiosondes. Each has benefits and drawbacks. Point-source observations from anemometers provide high wind velocity resolution and precision (0.01 and 0.05 m s −1 , respectively), but erection and maintenance costs for mast-based instruments become high as altitudes increase; and the presence of masts can obstruct or distort local wind flow ( Hasager et al. 2008 ). Measurements by remote sensing
Coupling of Wave Data and Underwater Acoustic Measurements in a Maritime High-Traffic Coastal Area: A Case Study in the Strait of Sicily. Therefore, in the development of a noise-monitoring plan in marine shallow waters, a comparative study coupling wave data and underwater acoustic measurements contributes to distinguishing the main natural abiotic underwater noise from anthropogenic noise ( Buscaino et al. 2016 ). X-band marine radars are useful active microwave remote sensing systems for sea-state monitoring either offshore or close to the coastline. Sea surface analyses by marine radar are based on the acquisition of consecutive radar
. Therefore, in the development of a noise-monitoring plan in marine shallow waters, a comparative study coupling wave data and underwater acoustic measurements contributes to distinguishing the main natural abiotic underwater noise from anthropogenic noise ( Buscaino et al. 2016 ). X-band marine radars are useful active microwave remote sensing systems for sea-state monitoring either offshore or close to the coastline. Sea surface analyses by marine radar are based on the acquisition of consecutive radar
Effect of Acoustic Doppler Velocimeter Sampling Volume Size on Measurements of Turbulence1. Introduction Acoustic Doppler velocimeters (ADVs) have been extensively used for both laboratory and field research over the past decades. The ability of ADVs to make nonintrusive, three-dimensional velocity measurements—even in nonclean environments—and their relatively low cost make them a compelling choice in many circumstances. The precision and sources of error of ADVs in the measurements of the mean and higher-order statistics of turbulent flows have been quantified. More precisely, it
1. Introduction Acoustic Doppler velocimeters (ADVs) have been extensively used for both laboratory and field research over the past decades. The ability of ADVs to make nonintrusive, three-dimensional velocity measurements—even in nonclean environments—and their relatively low cost make them a compelling choice in many circumstances. The precision and sources of error of ADVs in the measurements of the mean and higher-order statistics of turbulent flows have been quantified. More precisely, it
seismic reflection images. Our study includes full-wavefield synthetic tests of the sensitivity of seismic data in the k x domain, an analysis of the effects of random and shot-generated noise, and the first corroboration of seismically derived turbulence estimates against measurements from collocated, in situ oceanographic data. Using new approaches to estimate horizontal wavenumber content directly from the seismic data and via tracked reflections, we show that seismically derived horizontal slope
seismic reflection images. Our study includes full-wavefield synthetic tests of the sensitivity of seismic data in the k x domain, an analysis of the effects of random and shot-generated noise, and the first corroboration of seismically derived turbulence estimates against measurements from collocated, in situ oceanographic data. Using new approaches to estimate horizontal wavenumber content directly from the seismic data and via tracked reflections, we show that seismically derived horizontal slope
Comparison and Validation of Acoustic Response Models for Wind Noise Reduction Pipe Arrayspropagation effects within the pipe array structure. To validate the results provided by the two models in agreement, a field experiment was conducted. The measurements recorded by the system under test and the reference system were compared through a series of processing steps developed specifically for the purpose of this experiment. The modeled and measured acoustic responses appeared to fit extremely well for the six pipe array configurations. This showed that the models developed by Alcoverro and Le
propagation effects within the pipe array structure. To validate the results provided by the two models in agreement, a field experiment was conducted. The measurements recorded by the system under test and the reference system were compared through a series of processing steps developed specifically for the purpose of this experiment. The modeled and measured acoustic responses appeared to fit extremely well for the six pipe array configurations. This showed that the models developed by Alcoverro and Le
observations are, in particular, the underwater acoustic propagation measurements. Oceanic and acoustic measurements may provide complementary information to be exploited in the context of operational analyses and forecasts. The link between oceanic and acoustic variables is provided by the sound propagation in the ocean, which strongly depends on space–time sound speed fields, and thus seawater temperature and, to a lesser extent, salinity. The underwater acoustic propagation is sensitive to oceanic
observations are, in particular, the underwater acoustic propagation measurements. Oceanic and acoustic measurements may provide complementary information to be exploited in the context of operational analyses and forecasts. The link between oceanic and acoustic variables is provided by the sound propagation in the ocean, which strongly depends on space–time sound speed fields, and thus seawater temperature and, to a lesser extent, salinity. The underwater acoustic propagation is sensitive to oceanic
