
Photoacoustic Effect - peter_d_sherman
https://en.wikipedia.org/wiki/Photoacoustic_effect
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thdrdt
A Dutch research group is using this to detect breast cancer. Currently the
method to detect breast cancer is very painful but with the photoacoustic
method it is painless.

The only con is that it can only 'see' 3cm deep.

[https://optics.org/news/6/7/13](https://optics.org/news/6/7/13)

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oneepic
That's a little over an inch, for us Americans. Either way it still seems
pretty good, especially if the person is skinny.

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peterwoerner
This is also how many silicon chip manufacturers check for defects. I remember
attending a seminar on it in graduate school. Used an ultra fast laser to
create a shock wave and then measured the reflections which came back.

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keanebean86
I was thinking recently that maybe we can use sound to control heat
dissipation. Heat is a manifestation of kinetic energy. If you could pulsate
pressure waves through an object you could massage the heat in a specif
direction.

My application would be for CPUs. You would pulsate heat towards the heatsink
using a tone generate on the underside of the socket.

A. I really don't have a strong mathematical grasp of the physics. B. I
imagine the frequency of the waves might damage the silicone lattice. C. Other
issues I don't have the knowledge to even consider.

This is just an idea that came to as I was walking home from work. I'm sure
it's absolute hogwash.

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peter_d_sherman
This is a fascinating idea... don't think of it as a tone generator for a
heatsink (well, not initially -- though that may be one use case)... think of
this as a research project... heat dissipation vs. temperature vs. vibrations
vs. material vs. shape...

In other words, the more materials you could test at different temperatures,
with different types of vibration going through them, the more you'd gain an
understanding of the phenomena... perhaps there's a new theory or discovery in
there... I can see the research paper or theory: "Heat dissipation via
pulsation in different materials at different frequencies".

Of course, you might fail... but you'd (have to!) learn a lot of things from
diverse areas of physics (and probably math too) in the process!

That would be a win, no matter what.

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wil421
Awesome video from Bell Labs. Watch it if this topic interests you.

[https://youtu.be/gf2J3HTYUHE](https://youtu.be/gf2J3HTYUHE)

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jagged-chisel
I don't think this is demonstrating the effect in the linked article.

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quadrature
related [https://lightcommands.com/](https://lightcommands.com/)

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haecceity
Reminds me of

[https://en.wikipedia.org/wiki/Crookes_radiometer](https://en.wikipedia.org/wiki/Crookes_radiometer)

People thought the motion was due to radiation pressure at first but the force
due to light is probably a few orders of magnitudes off. Turns out it was heat
causing the motion.

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peter_d_sherman
Excerpt:

"The photoacoustic effect or optoacoustic effect is the formation of sound
waves following light absorption in a material sample. In order to obtain this
effect the light intensity must vary, either periodically (modulated light) or
as a single flash (pulsed light).[1][page needed][2] The photoacoustic effect
is quantified by measuring the formed sound (pressure changes) with
appropriate detectors, such as microphones or piezoelectric sensors."

Related: Transducers

[https://en.wikipedia.org/wiki/Transducer](https://en.wikipedia.org/wiki/Transducer)

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wooptoo
This is linked from the above article:
[https://en.wikipedia.org/wiki/Microwave_auditory_effect](https://en.wikipedia.org/wiki/Microwave_auditory_effect)

Which further links to:
[https://en.wikipedia.org/wiki/Havana_syndrome](https://en.wikipedia.org/wiki/Havana_syndrome)

The photo-acoustic effect is studied in school to some degree and is pretty
well known. However the microwave auditory effect is lesser known and
incredibly interesting.

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hexa_storm
Thanks for posting this I am currently building a prism scanner and quickly
drafted some prior art in this field and did a quick patent analysis see
[https://hackaday.io/project/21933-open-hardware-fast-high-
re...](https://hackaday.io/project/21933-open-hardware-fast-high-resolution-
laser/log/170691-photoacoustic-effect)

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snvzz
Laser headphones would sell well to audiophiles.

Laser sharp imaging. Unlimited soundstage. Fast as light bass.

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ryanthedev
If sound propagation has a negative mass, couldn't this same effect muddy the
dark matter/energy numbers?

