resonating pitch

i was looking for this geocache last month and it's located near the boys club road culverts




View Larger Map

and i've always been interested in the resonating frequencies of things, and these culverts are corrugated tubes more or less round passing under the interstate.

so while i was ostensibly there to find the geocache, i spent most of my time on location tromping up and down inside the culverts, because everything has a resonating pitch, but tubes and strings make this especially obvious.

as you walk through one of these things if you listen carefully to the echoes of even just your footsteps, you can hear some of the overtones the tube makes. because it's not perfectly round and not smooth on the inside, the harmonics you hear are maybe not just the plain series, and maybe not just a sin waveform, but if you make a noise that shares a resonating frequency, you can get a better echo.

if you can find a pitch closely related to the fundamental, you can make that thing ring.

so i played with that some.

little things amuse me.