[supernova87a]

Hey, I heard about how utility pole inspecting helicopters are able to tell the good/rotten state of wooden telephone poles by the reverb pattern of sound waves coming off the poles from the rotors -- it seems to me the whole field of non-invasive sensing (and using existing/ambient emission sources) is getting pretty impressive.

[motorest]

> Hey, I heard about how utility pole inspecting helicopters are able to tell the good/rotten state of wooden telephone poles by the reverb pattern of sound waves coming off the poles from the rotors

There is a whole field dedicated to this, called non-destructive testing. Modal response (i.e., monitor how a structure vibrates in response to an excitation) is a basic technique that features in multiple areas such as structural health monitoring and service life estimations.

Some mechanics also do this by placing the tip of a screwdriver against a point in an engine and place their ear against the screwdriver's handle. If it's not sounding right, the engine has problems.

Even pottery. You should hear the sound of a pot after you tap it. If it's muffled then odds are it has internal cracks.

[bcrl]

In telecommunications construction we are taught to make ample use of the "hammer test" when working on and around poles. The difference in sound between a good pole, a marginal pole and a completely rotten pole is quite significant.

[klank]

In outdoor rock climbing smacking rocks is an integral part of ensuring the rock you're trusting your life with is in fact worth trusting your life with.

[jacquesm]

You could of course just bury your lines.

[bri3d]

Source article (2001!): https://electricenergyonline.com/energy/magazine/4/article/n...

I can’t tell if this ever became a reality; I know of more modern approaches attempting to use thermal and multi spectral imaging to achieve the same goal.

[nashashmi]

What kind of helicopter of what size are we talking about here that can actually get close to a utility pole with wires going across?

[gerdesj]

I live near a helicopter factory and when the spinning towers are in use, you hear all sorts of auditory patterns as you move around the town. When they are test flying - similar and the Police have one and there is an air ambulance too. My Dad's other staff car in the '80s was a Gazelle and in the '70s he whizzed around in a Sioux. I've seen and heard a lot of helos!

I have absolutely no doubt that with some funky signal processing you can do all sorts of things.

[privatelypublic]

HV transmission line inspection routinely has the linesmen crawl out of helicopters onto the lines and back. Granted, as far as I know its the highest skill and most difficult helicopter job.

[trenchpilgrim]

Look up "Helicopter tree trimming" and prepare to be amazed.

[trhway]

I think you can do it from a distance, just need to have directed microphone (or use laser “microphone”)

[Xmd5a]

A lot of value in machine learning is in establishing measures by proxy.

[odyssey7]

And yet CT scans that dose patients with radiation are still standard of care.

[_kb]

I don’t think having them stand under low flying aircraft is much safer.

[iancmceachern]

Do you have any other wavelenghts of radiation that pass through flesh but not bone and metal we can use instead? If so speak up please, otherwise we need to keep using x rays because, physics.

[nightfly]

You get a lot more detailed information out of a CT scan

[jacquesm]

Yes, what do those doctors know anyway... /s