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(1 - 5 of 5)
- Title
- Noiseonomics: The relationship between ambient noise levels in the sea and global economic trends.
- Creator
- Frisk, George V.
- Abstract/Description
-
In recent years, the topic of noise in the sea and its effects on marine mammals has attracted considerable attention from both the scientific community and the general public. Since marine mammals rely heavily on acoustics as a primary means of communicating, navigating, and foraging in the ocean, any change in their acoustic environment may have an impact on their behavior. Specifically, a growing body of literature suggests that low-frequency, ambient noise levels in the open ocean...
Show moreIn recent years, the topic of noise in the sea and its effects on marine mammals has attracted considerable attention from both the scientific community and the general public. Since marine mammals rely heavily on acoustics as a primary means of communicating, navigating, and foraging in the ocean, any change in their acoustic environment may have an impact on their behavior. Specifically, a growing body of literature suggests that low-frequency, ambient noise levels in the open ocean increased approximately 3.3 dB per decade during the period 1950–2007. Here we show that this increase can be attributed primarily to commercial shipping activity, which in turn, can be linked to global economic growth. As a corollary, we conclude that ambient noise levels can be directly related to global economic conditions. We provide experimental evidence supporting this theory and discuss its implications for predicting future noise levels based on global economic trends.
Show less - Date Issued
- 2012-12-01
- PURL
- http://purl.flvc.org/fau/fd/FAUIR000018
- Format
- Citation
- Title
- Three-Dimensional Inversion Technique in Ocean Acoustics Using the Parabolic Equation Method.
- Creator
- Roa, Camilo Carlos, Frisk, George V., Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
A three-dimensional parabolic equation (PE) and perturbation approach is used to invert for the depth- and range-dependent geoacoustic characteristics of the seabed. The model assumes that the sound speed profile is the superposition of a known range-independent profile and an unknown depth- and range-dependent perturbation. Using a Green’s function approach, the total measured pressure field in the water column is decomposed into a background field, which is due to the range-independent...
Show moreA three-dimensional parabolic equation (PE) and perturbation approach is used to invert for the depth- and range-dependent geoacoustic characteristics of the seabed. The model assumes that the sound speed profile is the superposition of a known range-independent profile and an unknown depth- and range-dependent perturbation. Using a Green’s function approach, the total measured pressure field in the water column is decomposed into a background field, which is due to the range-independent profile, and a scattered field, which is due to the range-dependent perturbation. When the Born approximation is applied to the resulting integral equation, it can be solved for the range-dependent profile using linear inverse theory. Although the method is focused on inverting for the sound speed profile in the bottom, it can also invert for the sound speed profile in the water column. For simplicity, the sound speed profile in the water column was assumed to be known with a margin of error of ± 5 m/s. The range-dependent perturbation is added to the index of refraction squared n2(r), rather than the sound speed profile c(ro). The method is implemented in both Cartesian (x,y,z) and cylindrical (r,q,z) coordinates with the forward propagation of the field in x and r, respectively. Synthetic data are used to demonstrate the validity of the method [1]. Two inversion methods were combined, a Monte Carlo like algorithm, responsible for a starting approximation of the sound speed profile, and a steepest descent method, that fine-tuned the results. In simulations, the inversion algorithm is capable of inverting for the sound speed profile of a flat bottom. It was tested, for three different frequencies (50 Hz, 75 Hz, and 100 Hz), in a Pekeris waveguide, a range-independent layered medium, and a range-dependent medium, with errors in the inverted sound speed profile of less than 3%. Keywords: Three-dimensional parabolic equation method, geoacoustic inversion, range-dependent sound speed profile, linear inversion, Born approximation, Green’s functions.
Show less - Date Issued
- 2017
- PURL
- http://purl.flvc.org/fau/fd/FA00004868, http://purl.flvc.org/fau/fd/FA00004868
- Subject Headings
- Ocean tomography., Ocean bottom., Born approximation., Green's functions.
- Format
- Document (PDF)
- Title
- An Investigation into the Acoustic Variability and the Attenuation of an Acoustic Signal within a Port Environment Focusing on Port Everglades, Florida.
- Creator
- Sheahan, Daniel, Frisk, George V., Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
A methodology for characterizing the acoustical properties of a port environment, namely Port Everglades, has been proposed and carried out. This approach includes both a port-wide analysis of how the basic oceanographic features within the port impact the acoustic properties, and also a more focused sampling methodology within a small region of Port Everglades, allowing for the acoustic characteristics, including ambient noise, and an approximate signal absorption to be computed. The results...
Show moreA methodology for characterizing the acoustical properties of a port environment, namely Port Everglades, has been proposed and carried out. This approach includes both a port-wide analysis of how the basic oceanographic features within the port impact the acoustic properties, and also a more focused sampling methodology within a small region of Port Everglades, allowing for the acoustic characteristics, including ambient noise, and an approximate signal absorption to be computed. The results documented through the duration of this research indicate that the temperature variation throughout the port is the principal contributor to the characteristics of the sound velocity profile. Ambient noise measurements have revealed high levels of background noise within the sub-5 kHz region, owing likely to consistent port traffic. The calculation of absorption indicates that high frequency systems, i.e. > 100 kHz, may encounter problems when transmitting over a considerable distance. These are important factors for consideration when implementing a successful underwater acoustic system.
Show less - Date Issued
- 2007
- PURL
- http://purl.flvc.org/fau/fd/FA00012553
- Subject Headings
- Underwater acoustics--Measurement, Port Everglades (Fort Lauderdale, Fla), Harbors--Environmental aspects--Florida--Fort Lauderdale, Acoustic surface waves--Measurement
- Format
- Document (PDF)
- Title
- Optical Characterization ofPort Everglades Focusing on Underwater Visibility.
- Creator
- Whipple, Dustin E., Frisk, George V., Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
The development of an unmanned underwater vehicle at Florida Atlantic University with onboard optical sensors has prompted the temporal and spatial optical characterization of Port Everglades, with in-situ measurements of the turbidity, conductivity, and temperature. Water samples were collected for laboratory analysis where attenuation and absorption were measured with a bench top spectrometer. All of the measurements showed a high degree of variability within the port on a temporal and...
Show moreThe development of an unmanned underwater vehicle at Florida Atlantic University with onboard optical sensors has prompted the temporal and spatial optical characterization of Port Everglades, with in-situ measurements of the turbidity, conductivity, and temperature. Water samples were collected for laboratory analysis where attenuation and absorption were measured with a bench top spectrometer. All of the measurements showed a high degree of variability within the port on a temporal and spatial basis. Correlations were researched between the measured properties as well as tide and current. Temporal variations showed a high correlation to tidal height but no relation was found between turbidity and current, or salinity. Spatial variations were primarily determined by proximity to the port inlet. Proportionality constants were discovered to relate turbidity to scattering and absorption coefficients. These constants along with future turbidity measurements will allow the optimization of any underwater camera system working within these waters.
Show less - Date Issued
- 2007
- PURL
- http://purl.flvc.org/fau/fd/FA00012569
- Subject Headings
- Oceanographic submersibles--Mathematical models, Image processing--Digital techniques, Optical pattern recognition, Port Everglades (Fort Lauderdale, Fla)
- Format
- Document (PDF)
- Title
- FAU Climate Change Initiative Priority Theme: Research, Engineering, and Adaption to a Change Climate.
- Creator
- Berry, Leonard, Koch, Marguerite, Center for Environmental Studies, Benscoter, Brian, Comas, Xavier, Devlin, Donna, Fadiman, Maria, Gerstein, E., Herzing, Denise L., Hindle, Tobin, Milton, Sarah L., Oleinik, Anton E., Proffitt, C. Edward, Restrepo, Jorge I., Root, Tara L., Wyneken, Jeanette, Xie, Zhixiao, Zhang, Xing-Hai, Esnard, Ann-Margaret, Mitsova, Diana, Murley, J., Vos, J., Escaleras, Monica, Mehallis, M., Shaw, Eric H., Hardman, Guillermo [John], Lambert, Julie, Thomas, G., Arockiasamy, Madasamy, Bloetscher, Frederick, Carvalho, G., Dhanak, Manhar R., Frisk, George V., Kaisar, Evangelos I., Kalva, Hari, Meeroff, Daniel E., Rodriguez, Jarice, Scarlatos, Panagiotis (Pete) D., Shankar, Ravi, Teegavarapu, Ramesh, Brown, Clifford T., McAfee, Francis, Widener, Patricia, Dalgleish, Fraser R., Hanisak, M. Dennis, McMulloch, S., O'Corry-Crowe, Gregory, Pomponi, Shirley A., Reed, John K., Scarpa, John, Voss, Joshua, Heimlich, Barry N., Alvarez, R., Jolley, J., Edwards, A., Charles E. Schmidt College of Science, Harbor Branch Oceanographic Institute, College of Business, Dorothy F. Schmidt College of Arts and Letters, College of Education, College of Engineering and Computer Science
- Date Issued
- 2010
- PURL
- http://purl.flvc.org/fau/fd/FA00003457
- Format
- Citation
