# Demonstrating microwave hearing?

Discussion in 'General Technical Questions and Answers' started by RRAB, Jun 13, 2021.

1. ### RRABQRZ Member

This video shows a professor with what looks like a microwave waveguide horn aimed at his cranium, who then describes hearing a "click" or "chirp" with a "tonal quality" to the noise.
How might a HAM recreate/demonstrate this microwave auditory effect?

From a hackaday article, emphasis mine:
"As an example – the weakest transmitter Frey used was able to output a power density of 4 w/m² at 1310 Mhz. The peak power was 2670 w/m². The US guideline for human exposure at that frequency is 6.55 w/m². A different transmitter Frey used measured 71 w/m² at 425 MHz, with peaks at 2540 w/m². Compare this to the FCC guideline of 2 w/m² at that frequency."

From a paper first published in 1975, emphasis mine:
"a microwave pulse with a slow rise time is ineffective in producing an auditory response; only if the rise time is short, resulting in effect in a square wave with respect to the leading edge of the envelope of radiated radio-frequency energy, does the auditory response occur. Thus, the rate of change (the first derivative) of the wave form of the pulse is a critical factor in perception."

It's understood that doing this requires possibly unsafe power levels being aimed at the cranium. Will a HAM technicians license at 200w max accomplish this with a directional antenna, or will this require a general class to cover the peak power output? Would this require a Faraday cage to test responsibly? Is there a way to test such a setup responsibly? If that professor can demonstrate the effect safely enough to aim it at his own head, can this also be accomplished by amateurs? Is this better left up to the PhD holding professionals?
What might a shopping list look like to demonstrate what was achieved in the video?

2. ### N0TZUPlatinum SubscriberPlatinum SubscriberQRZ Page

AE8W and KO4LZ like this.

HAM

K3XR and N0TZU like this.

Oh boy.
Mike N3PM

5. ### K3XRHam MemberQRZ Page

This is your brain on...well, you get the idea.

WA9SVD likes this.
6. ### KO4LZXML SubscriberQRZ Page

It's very possible that the perceived sound is due to rapid heating within some part of the auditory system (e.g. the basilar membrane).

I tell people that my job involves something that can't normally be sensed by human beings, but if you *do* start sensing RF with your body, you need to stop what you're doing and/or leave the area. [This has happened to me on several occasions]

In my opinion (as an RF engineer, not a biologist, doctor, etc.), there is no reason why an amateur ... or perhaps anyone ... should be trying to reproduce this experiment. Seriously.

WA9SVD, AE8W and KI4ZUQ like this.
7. ### WA9SVDHam MemberQRZ Page

It sounds like a BAD (or worse) idea to try to duplicate, but what does having/needing a General license have to do with it? Techs and Generals both have the SAME power limits on frequencies of 50 MHz and higher.

8. ### KA0HCPXML SubscriberQRZ Page

I think that this phenomenon is dangerous to explore. It is reasonable to accept the word of experts on what causes it.

9. ### AF7TSHam MemberQRZ Page

IMHO exploring this at high power densities as an amateur is simply a stupid idea.

I don't think one needs to be a PhD holder to investigate such, but the sort of research done properly would require lots of library time figuring out proper safety protocols, research into proper mechanisms, etc. In other words exactly the sort of stuff that might earn one a PhD.

On the other side of the coin, this might be fun to explore at _low_ power levels. If you find a way to discern audible effects at power densities well below what is considered safe, that would IMHO be very interesting _and_ be useful data, possibly suggesting pathways in which what is currently considered safe really isn't...or fun new ways of using RF at levels that are safe.

I suspect that doing so would involve resonance, likely AM modulating low power microwave radiation with audio that is resonant with something in your skull.

With a high gain antenna one could certainly exceed safety power density limits; RF safety is one of the things that all amateurs should know, and I encourage the OP to refresh on this subject.

-Jon