Chirping Fence

So I take a walk outside to bring the cat in, like I do every night, and the little critter is hiding out by the fence. It’s just one of those chicken wire fences with the wooden slats. So I’m crouched down calling the cat and snapping my fingers.

Then I hear: Chirp. Chirp. Chirp.

It’s night time. There are no little birdies flying around. And every time I snap my fingers, I hear this chirp.

Then I clap my hands, and get the mother of all chirps: NEEYOWMP.

Finally I figured out what was going on. The regular spacing of the slats was diffracting the sound, splitting it into its component frequencies. Since low frequencies are diffracted more, they took longer to echo off the fence, and the result was a reverse crescendo.

I should like to amend the following to the conclusions in the OP:

The fence was acting as a diffraction grating. Diffraction gratings are used professionally to split light into its component wavelengths (colors) to analyze spectra. In a grating, the waves of light or sound interfere, creating the spectrum pattern.

Crystals are natural difraction gratings which, because of their extremely small interatomic spacing, diffract X-rays. X-ray crystallography, which involves directng a beam of X-rays through a crystal and recording the diffraction pattern on film, is used to deduce the crystalline structure.

I hope this clarifies any uncertainty with regards to the conclusions expressed in my OP.

My horse plays gate harp.

In his stall, he can reach a metal pipe gate closing off the end of the barn aisle. It amuses him to slide his nose back and forth along the top bar, producing a weird, moaning-groan hum.