I'm interested in understanding if is possible and feasible to detect and record underwater sound without touching the water, e.g. with a laser interferometer like those used to record sounds by detecting the vibrations of a surface like a glass window.
I think that it is not possible: an interferometric quality glass window is homogeneous in roughness at least at the level of the used wavelength. Water surface is not an optical grade surface.
https://fas.org/nuke/guide/usa/slbm/detection.pdf
forse ti può essere di aiuto !
I see this is an old question but it popped up on my feed - it is absolutely possible. you can also actively image the sea floor and the water column using active interferometrics.
Wouldn't the impedance differences at the air-water interface make this impossible?
no, not at all. you're relying on the LDV to tell you acoustically what is happening, not directly on the acoustics. I can tell you from experience that when you turn a Benthos acoustic modem up (transmitting in A band, ~=8-14KHz) underwater it is possible to hear it from very far away out of the water. so in a simple way the acoustics translate out of the water and into the air. I've seen thermal inversions introduce non-linearities to the travel path as well. if I can find a paper from JASA (Opto-Acoustic Hybrid) I'll share, we built a laser system here that pinged the water and acoustically observed particle displacement rather than vibration, or something to that effect. we were able to image 2-liter soda bottles many meters below the water.
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