Passive acoustic measurements of wind velocity and sound speed in air

2014 ◽  
Vol 135 (2) ◽  
pp. EL68-EL74 ◽  
Author(s):  
Oleg A. Godin ◽  
Vladimir G. Irisov ◽  
Mikhail I. Charnotskii
Keyword(s):  
Wind Velocity ◽  
Sound Speed ◽  
Acoustic Measurements ◽  
Passive Acoustic

scholarly journals PRELIMINARY EVALUATION OF ATMOSPHERIC TEMPERATURE AND WIND PROFILES OBTAINED USING UNMANNED AERIAL VEHICLE BASED ACOUSTIC TOMOGRAPHY

2019 ◽  
Vol XLII-2/W13 ◽  
pp. 283-287 ◽  
Author(s):  
A. Finn ◽  
K. Rogers ◽  
J. Meade ◽  
J. Skinner ◽  
A. Zargarian
Keyword(s):  
Wind Velocity ◽  
Unmanned Aerial Vehicle ◽  
Sound Speed ◽  
Three Dimensional ◽  
Atmospheric Temperature ◽  
Preliminary Evaluation ◽  
Sound Fields ◽  
Aerial Vehicle ◽  
Wind Profiles ◽  
Virtual Temperature

<p><strong>Abstract.</strong> An acoustic signature generated by an unmanned aerial vehicle is used in conjunction with tomography to remotely sense temperature and wind profiles within a volume of atmosphere up to an altitude of 120&amp;thinsp;m and over an area of 300&amp;thinsp;m&amp;thinsp;&amp;times;&amp;thinsp;300&amp;thinsp;m. Sound fields recorded onboard the aircraft and by an array of microphones on the ground are compared and converted to sound speed estimates for the ray paths intersecting the intervening medium. Tomographic inversion is then used to transform these sound speed values into three-dimensional profiles of virtual temperature and wind velocity, which enables the atmosphere to be visualised and monitored over time. The wind and temperature estimates obtained using this method are compared to independent measurements taken by a co-located mid-range ZephIR LIDAR and sensors onboard the aircraft. These comparisons show correspondences to better than 0.5&amp;thinsp;&amp;deg;C and 0.3&amp;thinsp;m/s for temperature and wind velocity, respectively.</p>

scholarly journals Passive underwater acoustic evolution of a calving event

2012 ◽  
Vol 53 (60) ◽  
pp. 113-122 ◽  
Author(s):  
Erin C. Pettit
Keyword(s):  
Spectral Characteristics ◽  
Low Frequency ◽  
Acoustic Measurements ◽  
Dynamic Nature ◽  
High Frequencies ◽  
Direct Measurements ◽  
Audible Sound ◽  
Passive Acoustic ◽  
Remotely Sense ◽  
Ocean Boundary

AbstractDirect measurements of processes occurring at the ice–ocean boundary are difficult to acquire because of the dangerous and dynamic nature of the boundary, yet these processes are among the least well understood in glaciology. Because sound travels well through water, passive underwater acoustics offers a method to remotely sense activity at this boundary. Here we present passive acoustic measurements and spectral analysis of the evolution of a subaerial calving event and the subsequent mini-tsunami and seiche at Meares Glacier, Alaska, USA. Using two hydrophones to record sound from 1 to 40 000 Hz, we find that each phase of a calving event has distinctive spectral characteristics. An event begins with an infrasound rumble (1–20 Hz), then the ice fractures (20–100 Hz), falls and impacts the water (200–600 Hz). High-frequency (>10 000 Hz) sound increases in intensity quickly as the iceberg oscillates, creating turbulence, spray and waves. Within 10 s, the low-frequency audible sound dissipates and the mini-tsunami and seiche sounds dominate (infrasound plus high frequencies) and continue for over 10 min. The specific frequencies and duration of each phase of a calving event depend on its size and location and the glacier and fjord characteristics.

Seabed sound speed and attenuation from broadband acoustic measurements in the Shallow Water 2006 experiment.

2009 ◽  
Vol 126 (4) ◽  
pp. 2193
Author(s):  
Lin Wan ◽  
Ji-Xun Zhou ◽  
Peter H. Rogers ◽  
David P. Knobles
Keyword(s):  
Shallow Water ◽  
Sound Speed ◽  
Acoustic Measurements

Characterization of the Content of the Cavity Behind a High-Speed Supercavitating Body

2006 ◽  
Vol 129 (2) ◽  
pp. 136-145 ◽  
Author(s):  
Xiongjun Wu ◽  
Georges L. Chahine
Keyword(s):  
Sound Speed ◽  
High Speed ◽  
Test Facility ◽  
Direct Visualization ◽  
Acoustic Measurements ◽  
Supercavitating Flow ◽  
Flow Test ◽  
High Sound ◽  
Very High

A high speed/high flow test facility was designed and implemented to study experimentally the supercavitating flow behind a projectile nose in a controlled laboratory setting. The simulated projectile nose was held in position in the flow and the cavity interior was made visible by having the walls of the visualization facility “cut through” the supercavity. Direct visualization of the cavity interior and measurements of the properties of the cavity contents were made. Transducers were positioned in the test section within the supercavitation volume to enable measurement of the sound speed and attenuation as a function of the flow and geometry parameters. These characterized indirectly the content of the cavity. Photography, high speed videos, and acoustic measurements were used to investigate the contents of the cavity. A side sampling cell was also used to sample in real time the contents of the cavity and measure the properties. Calibration tests conducted in parallel in a vapor cell enabled confirmation that, in absence of air injection, the properties of the supercavity medium match those of a mixture of water vapor and water droplets. Such a mixture has a very high sound speed with strong sound attenuation. Injection of air was also found to significantly decrease sound speed and to increase transmission.

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