A sound pulse passes an open pipe end unreflected when matching pressure exists outside

Evidence

As an interesting test of our understanding, suppose we send a pulse through a tube heading toward an open end, but this time the pulse exists outside the pipe as well. What will happen when the pulse reaches the end of the tube? The air inside the pipe has no idea that the pressure pulse exists outside until it reaches the end; as the pressure exits the pipe, instead of finding lower pressure laterally as it did before, it now finds matched higher pressure outside. There is no sudden pressure release laterally, no impedance change. The entire pulse proceeds as if nothing happened; there is no back reflection inside the pipe at all. — Eric J. Heller, Why You Hear What You Hear- An…, 117

Categorization

• QUESTION: A striking result — reflection depends not on the geometry but on the impedance match the pulse actually encounters. What real-world configurations emulate this?
• XREF: connects to: Air reed oscillation is driven by pressure pulse reflections at the pipe mouth — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1159