The original plan was to build a 50ft by 60ft by 55ft chamber, with about half of it being underground. Given the exterior noise level of around 20 dBA (the plant is located in the wilderness), the thick concrete walls of the facility, and some additional noise and structural isolation he might very well beat Orfield's record with a much larger chamber (meaning it will be anechoic down to a lower frequency). If he can get the funding.

If you're ever in the area, Ron is a friendly guy and he'll be happy to give you a tour (he's on LinkedIn).

There was a safety microphone wired to the door switch for this reason (which also meant it wasn't QUITE such a good idea to say rude things about people in there :-)

Look carefully at the picture, he's not standing on a solid floor, he's standing on a wire frame over more absorbers. Their website has a better pic: http://www.orfieldlabs.com/Researchtour4.html

IOW, their chamber is (fully) anechoic, not just hemi-anechoic.

Looks like their wire floor is a bit more permanent than the design I was using; my microphone was on a rotating boom that could be swept 360 degrees from outside, and my sample mounting was a pole down to the real floor, so we could have the absolute minimum of interference from the mountings.

> Cage entered the chamber expecting to hear silence, but as he wrote later, he "heard two sounds, one high and one low. When I described them to the engineer in charge, he informed me that the high one was my nervous system in operation, the low one my blood in circulation."

For all of us that don't have access to such facilities, this kind of before/after diary might be very interesting.

Send me an email since you don't have one listed in your profile! [email protected]

It's not just a break from humanity, it's a break from everything (including nature, which typically fills the void when humanity is absent).

If you haven't been in a very quiet space, it becomes disorienting very quickly. The quietest space I've been in has been <12 dBA (my measurement equipment only went that low so I couldn't get the true Lmin). At that level, I could hear the blood rushing through my ear. I have a minor case of tinnitus which is typically inaudible, but in that space it was like an alarm clock screaming into one ear. The other ear seemed to desperately find something to "lock" onto, so it was amplifying every little thing it could.

After about 15 minutes I wound up opening a window to let a little wind noise into the room. That raised noise levels up to about 19 dBA and was much more comfortable.

Ah, I was wondering about that. (Now scrolls up to delete question asked elsewhere.)

The absolute silence exacerbates the issue but it's not the only factor at play.

The most interesting thing is the measured extent of what they've produced.

While they are both considered waves, it is not frequency regimes that differentiate acoustic pressure waves and RF waves -- RF waves can be anywhere within the "audio" spectrum and beyond, and audio waves can be well into the ultrasonic range and into the UHF regime.

The idea of the anechoic chamber is the same (blocking all reflections), but it is not just as simple as tuning to different frequencies. They do however need to be designed for a specific frequency range.

I am not an expert on anechoic chamber design (or acoustic wave propagation for that matter), but an RF anechoic chamber is not the same as an acoustic anechoic chamber, although it will show some functionality as one. Does that make sense, or am I just confusing the conversation? It did when I started writing all this. :/

Neither of the RF chambers I used had the foam cones on the floor; just carbon tiles.

Theoretically, at sea level on earth, the mean free path of air molecules allows for 3.4 GHz. But attenuation is proportional to f^2 which results in an upper limit of 100MHz. You need a medium denser than air at sea level for higher frequencies.

EM waves vs pressure waves, they're not the same thing (although the math is basically the same, just with different constants). Something that affects an EM wave won't necessarily affect a pressure wave - a Faraday cage for example will block EM waves but won't do anything to block sound waves.

There are some mathematical differences between transverse and longitudinal waves, so it's not just the same math with a different medium.

That's why an RF anechoic chamber looks a lot like an acoustical anechoic chamber, and often sounds like one too.

An acoustic wavelength at STP is around 1ft/30cm, not 3m (which is closer to 100 Hz).

Point stands, though.

Relevant: I do wonder though if the disorientation would be less for someone with complete deafness in one ear. I would think that they are already somewhat used to the balance/orientation issues.

The most interesting thing would be whether or not my tinnitus is going to drive me insane or not :P

Steve's a great guy. He'll give you a little tour of everything going on at Orfield labs, but the price of admission is a $20 check to a local food-bank.

He told my friends and I a lot of interesting things. Like how corporate offices use subtle noise from the air-ducts to drown out coworkers' conversations; or how casinos use echoing plates to project the sound of a jackpot across the entire gaming floor.

I definitely recommend paying it a visit if you ever find yourself in Minneapolis.

> ...a reverberation chamber with bowed aluminum panels in which he sounds the same from 300 feet away as 3 feet away.

Anyway, I didn't know that before today :)

Any acoustically well-designed movie theater (THX or HPS-4000 certified among others), performance space, concert hall or auditorium will be decently diffuse, at least at higher frequencies.

Give me a good book and I'll spend 45 hours in one.

I understand that you begin to hear your heartbeat and so on, but surely anyone who is even slightly deaf (e.g. even from just prolonged listening to loud music) wouldn't hear these very low-decibel sounds?

So it can't be the lack of sound, as a slightly hard of hearing person hears the noise floor drop out quite frequently. (Correct me if I'm wrong here; it's just my assumption). Is it that these sounds become so annoying, such a nuisance?

If someone had a noise-free keyboard (maybe touch) and were coding in there, would anything be a distraction? Would anything limit your stay?

I find sitting into a dead-silent room with a laptop (e.g. somewhere where you can't even hear a clock tick, nor any street sounds, nothing) to be completely maddening initially...but then after about 2-3 minutes you can immerse yourself and do something with extreme concentration.

Top it off with the fact that usually such rooms are entirely sealed off and that you're standing or sitting on a big mesh trampoline floating in the center of the room, and it all comes to one seriously creepy experience after about ten minutes.

Even though some of the sound travels through the facial bone structure (like when you hear your own voice) I guess most sounds come from outside

Also, earplugs add pressure to the ear canal so I guess this muffles somethings

You got to try an anechoic chamber to believe it. BTW: many universities have one. The one I worked at (BYU, long ago) has this one:

http://www.physics.byu.edu/research/acoustics/facilities.asp...

http://vimeo.com/15855229 (a corny advertisement, but shows the room well)

http://www.youtube.com/watch?v=0PGF_cGS8ts

It's a very good facility. Interestingly, I believe the main anechoic chamber used to be an echo chamber!

An anechoic chamber is used to test acoustics in an environment with absolutely no reflection (reverb, echo, etc.).

I'm wondering what it is they 'can't stand.' The article text is pretty vague. '“Your eyes don’t feel as comfortable in this room,” Orfield pointed out, adding that some visitors have had hallucinations during or after a spell in there. “You lose your touchstones.” Small wonder, then, that even Orfield spends no more than a half-hour at a time in the 99.99 percent soundproof anechoic chamber, and no one has lasted in there for more than 45 minutes.'

It doesn't match either my experience or my expectation, which is why I asked about it above. If someone had a silent computer to code on in there, could they crank out code for a couple of hours without nuisance, or would something bother them? If the latter, then what exactly would bother them?

First of all, I'm seriously disappointed I can't test this because no computer is quiet enough. Second of all, I can't stand working in sound-proofed rooms. I much prefer working in an environment with (non-distracting) ambient sounds.

But I have no doubt that, properly motivated, you could easily spend an hour in there. Hell, if I had access to one I'd go do it right now just for dumb internet bragging rights.

Not all anechoic chambers are equal, and not all anechoic chambers are necessarily quiet - they're only as quiet as they need to be for whatever it's designed to test (an anechoic chamber designed to test ICE equipment might have background noise levels in the 40-50 dBA range), so be careful about extrapolating your experience to the quietest anechoic chamber in the world.

Have they had open competitions? I feel relatively certain that people would endure in there effectively indefinitely: People can tolerate remarkable things.