Low frequency sound resonator pipe @ 18.5 Hz, what length and diameter should the pipe be?

Question

If I was to use a 12" subwoofer inside of a resonant pipe, what should the dimensions be

Like the infrasound pipe on church organs, would a whistle, blower or subwoofer be a good sound source so the pipe can amplify the infrasound

What material of pipe also?

Answer 1

The speed of sound in air at 72°F is about 1,131.7 ft/s.

A resonant pipe open at both ends would need to be

(1,131.7 ft/s) / (18.5 Hz) ≈ 61.175 ft. ≈ 61 ft. 2 in.

If the pipe is open at only one end it needs to be

30.588 ft. ≈ 30 ft. 7 in.

The material can be steel, brass, aluminum, PVC, or even wood made into a box shape.