It is an interesting experience even thoughthe reverberation room is not designed for beautiful acoustics but to be able to meausure transmission loss of building elements (absorbtion of different materials). It is situated in the Technical University of Denmark, in Lyngby, north of Copenhagen. The surfaces are hard (concrete), and the cones on the floor and walls work as difusers which spread the sound waves and allow an experience of a room much bigger than it actually is.

My friend Flemming and I were kindly allowed to do recordings, videos, and photos for an article and along the way we caught the moment to do a few vocal improvisations.
We are not throat singers, so you may ask what tempted us to do basso profundo/vocal fry/strohbass.
One of the factors is obviously the dimensions of the room. We didn't bring a measure tape but knew that its volume is 240 cubic meters, meaning that each side and the height is between 5 and 8 meters.
Using the wave formula this allows us to find some of the prominent resonances.
f x λ = v , where f is the frequency, lambda is the wave length, and the constant v is the speed of sound in air:

f(8 m) = 343 m/s : 8 m = 42,875 Hz (s^-1)
f(5 m) = 343 m/s : 5 m = 68,6 Hz

This roughly corresponds to the interval G1:C2 ('scientific pitch notation').
... and it is the tonal depths that Flemming and I for some reason where inspired to delve into.