1. Pressure-particle velocity coherence Environmental effects on coherence of pressure–vertical particle velocity David Dall’Osto and Peter H. Dahl Applied Physics Laboratory University of Washington Pacific Rim Underwater Acoustics Conference 2011 5-7 October 2011 Jeju Island, Korea

2. Radar overlay of ISW: Luo, et. al JASA EL 2008 WHOI Temp. Array MORAY R/V Knorr (200 m) VLA Bottom model from: Choi, et. al JASA EL 2008 SSP from WHOI Temp. Array 200 m 40 m 25 m 50 m R/V Knorr 77 m Experimental Overview: SW06 Source suspended at 40 m depth (1 kHz, 4 ms pulses) Pressure measurements on 2 short VLA (25 m and 50 m depth) SSP and Bottom Model for PE Simulation

3. Data: Finite Difference Approximation real-valued “measured” signals complex hilbert transform pair d = 20 cm Instantaneous Intensity PE simulation : (hilbert transform) vertical instantaneous intensity horizontal instantaneous intensity pressurehorizontal velocityvertical velocity vertical instantaneous intensity ^

4. Complex Intensity active and reactive intensity envelopes ActiveReactive pressure magnitude squared gradients non-propagating energy phase gradients propagating energy flux PE simulation Data

5. 4 min No focusing SSP Dependent Focusing Nearby Pressure Maxima 25 m 50 m Focusing of rays due to refraction (creates pressure magnitude gradients beyond spherical spreading) Active intensity envelope indicates arrival angle Reactive intensity envelope indicates region of focused sound energy PE simulation Data Scalar intensity, proportional to magnitude pressure squared, is steady No focusing

6. 25 m depth - 20 pings (loss of coherence on DP) Pressure-Particle Velocity Coherence DP SP BPR vertical intensity (25 m) p-v z coherence (25 m) Real Part Imaginary Part Absolute Value scalar intensity (log space) DP SP BP R

7. Summary Instantaneous complex intensity describes: –Active direction of propagating energy –Reactive focusing of energy: soundspeed profile constructive/destructive interference Pressure-vertical particle velocity coherence effected by waveguide focusing effects –Real part signifies direction of propagating intensity –Imaginary part indicates degree of focusing/interference