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Photoacoustic Effect (wikipedia.org)
63 points by peter_d_sherman on Nov 5, 2019 | hide | past | favorite | 17 comments

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.


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

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.

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.

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.

I'll be interested to read your upcoming initial blog post/research

This is really interesting

Fascinating! Did not know this until now.

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


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

Reminds me of


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.


"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


This is linked from the above article: https://en.wikipedia.org/wiki/Microwave_auditory_effect

Which further links to: 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.

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...

Laser headphones would sell well to audiophiles.

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

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

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