It is like a super-bass flute- which may describe the NASA-Ames wind tunnel mentioned above.
Interesting thought. One could compute the length of a pipe organ to give this frequency and compare it to the NASA photo in Wikipedia or Google for scale.
Could be 1/4 or 1/2 wave also. Depending on air pressure inside the speed of sound in the wind tunnel could be altered a bit too.
Still, you should be within the right magnitude.
Using 343m/s at TPS as the speed of sound, 2.7 Hz gives me 127m wavelength. (1/2= 63.5 and 1/4=31.7m ). Any pipes, tunnels, elevator shaft or chimneys of that size around that could get exited by wind in the right direction and the right speed?
Would also be nice if you had something like a Geophone (seismometer, it can be tuned to go lower than specs for 2. to 4.5 Hz with some mods) and see if there is a corresponding signal from the ground. I am thinking of the famous Windsor (Canada) hum here, possibly coming from a plant on the US side.