Rigid-wall tube terminations fully reflect waves while open ends reflect with phase inversion.

Evidence

For a tube terminated in a rigid wall, the impedance of the termination Z2 >> Z1, the impedance of the tube, which implies from Equation (2.27) that R →1. When the termination is an open end, the impedance Z2 is very small (at low frequencies) and R →−1. — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 238

Categorization

• XREF: Underpins how organ pipes, flutes, and brass instruments form standing waves; connects to wind instrument acoustics.