Acoustics of Marine Sediments
 
We seek to gain understanding of sound propagation and scattering in water saturated granular material, such as that found on sandy ocean bottoms.  In the laboratory, we measure the speed of sound and the attenuation in an impedance tube and in one-dimensional acoustic resonators, and use the measurements to guide and validate sound propagation models.  We also conduct experiments at sea, and infer acoustic properties of the sediment from ocean waveguide measurements.  The application is enhanced sonar operation and mine detection in shallow water.  [Sponsored by ONR]
 
Recent Publications:
 
D.P. Knobles, P.S. Wilson, S. Cho, and J.A. Goff, "Seabed acoustics of a sand ridge on the New Jersey continental shelf," J. Acoust. Soc. Am. 124, EL151–EL156 (2008).  link to file
 
T.F. Argo IV, M.D. Guild, P.S. Wilson, M. Schroter, C. Radin, and H.L. Swinney, "Sound speed and attenuation in water-saturated glass beads as a function of frequency and porosity," J. Acoust. Soc. Am. 129, EL101–107 (2011).  link to file
Acoustics of Gas-Bearing Sediments
 
We seek to gain understanding of sound propagation in ocean sediments that also contain gas bubbles.  This is a laboratory project and we measure the speed of sound and the attenuation in a one-dimensional acoustic resonator, and use contemporaneous micro x-ray computed tomography to obtain knowledge of the bubble size distribution and the volume of the gas content.  The application is enhanced sonar operation in shallow water and mine detection.  [Sponsored by ONR]
 
Recent Publications:
 
P.S. Wilson, A.H. Reed, W.T. Wood, and R.A. Roy, "The low-frequency sound speed of fluid-like gas-bearing sediments," J. Acoust. Soc. Am. 123, EL99–EL104 (2008).  link to file
 
P.S. Wilson, A.H. Reed, W.T. Wood, and R.A. Roy, "Low frequency sound speed measurements paired with computed x-ray tomography imaging in gas-bearing reconstituted natural sediments," in Proceedings of the 2nd International Conference and Exhibition on Underwater Acoustics Measurements:  Technologies and Results, J. S. Papadakis and L. Bjørnø, Eds. Heraklion, Greece, 2007, pp. 21–29, ISBN 978-960-88702-5-3.  link to file
Acoustics of Seagrass
 
This project is a collaboration with Dr. Kenneth Dunton, of the UT Marine Science Institute. The ultimate objective of this project is to develop an acoustic remote sensing technique to assess the health of estuarine environments.  The abundance of seagrass, one of the species that lives in estuarine environments, is a marker for the overall health of the environment.  Aerial photography is currently used to measure the abundance of seagrass, but is expensive, and only provides measurements at the time of the photography.  We seek to develop a remote sensing technique that would provide inexpensive, reliable long-term measurements by exploiting the fact that seagrass contains free gas within the tissue and respiration produces free gas bubbles on the leaves and in the local water column.  The current phase of the project involves measurements and of the effective acoustic properties of seagrass tissue and low frequency propagation model development.  [Sponsored by ONR, the UT Cockrell School of Engineering, and the Texas Sea Grant College Program]
 
Recent Publications:
 
P.S. Wilson and K.H. Dunton, "Laboratory investigation of the acoustic response of seagrass tissue in the frequency band 0.5–2.5 kHz," J. Acoust. Soc. Am. 125, 1951–1959 (2009).
         abstract
 
C.J. Wilson, P.S. Wilson, C.A. Greene and K.H. Dunton, "Seagrass leaves in 3-D: Using computed tomography and low-frequency acoustics to investigate the material properties of seagrass tissue," J. Exp. Marine Bio. 395, 128–134 (2010).
         abstract
 
The Acoustics of Bubbles and Bubbly Liquids
 
The presence of a small amount of gas bubbles in water greatly changes the acoustic properties of the medium.  Breaking waves at the surface of the ocean and in the surf zone create large numbers of bubbles, hence the performance of sonar in this environment is reduced.  We study the basic physics of sound propagation in this medium.  Bubbles are also used in medical applications such as lithotripsy (for the treatment of kidney stones) and as contrast agents for ultrasound diagnosis.  We study the dynamics of groups of bubbles interacting with themselves and with their surroundings.  Included in this work was a study of rectified diffusion, as it relates to the effects of naval sonar on marine mammals.  [Sponsored by ONR ]
 
Recent Publications:
 
Y.A. Ilinskii, P.S. Wilson, and M.F. Hamilton, "Bubble growth by rectified diffusion at high gas supersaturation levels," J. Acoust. Soc. Am. 124, 1950–1955 (2008).  abstract
 
T.F. Argo IV, P.S. Wilson, and V. Palan, "Measurement of the resonance frequency of single bubbles using a laser Doppler vibrometer," J. Acoust. Soc. Am. 123, EL121–EL125 (2008).  link to file
 
J. Cui, M.F. Hamilton, P.S. Wilson, and E.A. Zabolotskaya, "Bubble pulsation between parallel plates," J. Acoust. Soc. Am. 119, 2067–2072 (2006).  abstract
 
P.S. Wilson, R.A. Roy, and W.M. Carey, "Phase speed and attenuation in bubbly liquids inferred from impedance measurements near the individual bubble resonance frequency," J. Acoust. Soc. Am. 117, 1895–1910 (2005).  abstract
Vocal Production and Sound Radiation by the Túngara Frog
 
This is a collaboration with Professor Michael J. Ryan in the Section of Integrative Biology at UT Austin.  We seek to understand the sound radiation pattern produced by the male túngara frog.  These calls are used to attract mates, but they also attract parasites (biting flies) and predators (frog eating bats), hence they are an evolutionarily interesting.  We found that their calls are preferentially directed away from prospective mates and toward the predators and parasites, in an apparent evolutionary paradox, as of yet unexplained.  [Sponsored by NSF]
 
Recent Publications:
 
X.E. Bernal, R.A. Page, M.J. Ryan, T.F. Argo Iv, and P.S. Wilson, "Acoustic radiation patterns of mating calls of the túngara frog (Physalaemus pustulosus): Implications for multiple receivers," J. Acoust. Soc. Am., 126, 2757-2767 (2009).  link to file
 
Selected research areas are highlighted below.  Links to articles or abstracts are provided. Additional research is described in the CV.
 
Acoustics of Methane Hydrates
 
Methane hydrate is a naturally occurring material that appears on and within the sediment layers of the ocean bottom.  Interest in the material is due to its potential use as a fuel, and because it also contributes to the green house gases in the atmosphere.  At times, it can naturally release gaseous methane, which rises up through the water column and enters the atmosphere.  We study the acoustic properties of methane hydrate in the laboratory through the use of a pressure vessel (shown at right) that simulates the ocean depths at which methane hydrate can occur. Increased knowledge of these properties can be exploited to facilitate remote detection of methane hydrate via seismic ocean surveys.
 
We also participated in a field expedition, Methane in the Arctic Shelf (MITAS 2009) in September 2009, onboard the Coast Guard icebreaker Polar Sea, pictured at right.  You can read a news item about the cruise here, and also visit the official MITAS weblog here.  [Sponsored by ONR]
 
Recent Publications:
 
C. Greene, P.S. Wilson, and R.B. Coffin, "Laboratory measurements on gas hydrates and bubbly liquids using active and passive low-frequency acoustic techniques," POMA 12, 045001-8 (2011).  link to file
 
Underwater Noise Abatement Using Freely Rising Bubbles and
Tethered Encapsulated Bubbles
 
It has long been known that bubbles attenuate underwater sound.  We are now using them in a unique way to abate noise from underwater drilling and construction activities, such as pile driving. [Sponsored by Shell Global Solutions]
 
Recent Publications:
 
K. Lee, K. Hinojosa, M. Wochner, T. Argo Iv, P. Wilson, and R. Mercier, "Attenuation of low-frequency underwater sound using bubble resonance phenomena and acoustic impedance mismatching," POMA 11, pp. 005001).  link to file
New Materials with Increased Sound and Vibration Absorption Capacity Using Negative Stiffness Elements  
 
One can minimize the transmission of sound and vibration through structures by using a buckled beam that provides a negative stiffness.  [Sponsored by DARPA]
 
Recent Publications:
 
Lia Kashdan, Carolyn C. Seepersad, Michael R. Haberman, Preston S. Wilson, "Design, fabrication, and evaluation of negative stiffness elements using SLS," Rapid Prototyping Journal, in press (2011).  link to file
 
Analysis and Optimization of Personal Alarm Safety System (PASS) for Fire Fighters

The PASS device is worn by fire fighters when entering a burning building.  The device sounds an acoustic alarm when the fire fighter becomes immobilized.  Although in use for many years, improvement is sought.  We are conducting the first acoustically-based analysis and optimization of the PASS signal, device and its use in the fire fighting environment.  [Sponsored by US Dept. Homeland Security]

Recent Publications:
new project, just started Fall 2011....see for now:  link to press release 

Lia Kashdan, Carolyn C. Seepersad, Michael R. Haberman, Preston S. Wilson, "Design, fabrication, and evaluation of negative stiffness elements using SLS," Rapid Prototyping Journal, in press (2011).  link to file
http://www.nfpa.org/newsReleaseDetails.asp?categoryid=488&itemId=52608&cookie%5Ftest=1Research_files/Kashdan_SFFpaper11_1.pdfshapeimage_12_link_0shapeimage_12_link_1