Wind instruments resonantly amplify only frequencies that reflect back at the drive period

Evidence

Now, suppose this drive is connected to the tank, as shown in figure 16.24. Waves reflect at the open end, especially the longer wavelengths, as with a pipe in air. Crests reflect as troughs, but on their second try they come back as crests. If the crests return at the period of the valve and float, the valve will open as crests return—resonantly adding to their amplitude. This happens periodically, causing the wave amplitude to build up considerably, until the radiated (not reflected) waves are dumping as much power out as the valve is putting in. The drive, as well as the wave inside, has many harmonics, but the lower frequencies are emphasized, since they are largely reflected at the open end, while the shorter wavelengths get out and are not resonantly enhanced. — Eric J. Heller, Why You Hear What You Hear- An…, 1548

Categorization

• DEFINE: Explains why open-end pipes emphasize low frequencies: longer wavelengths reflect strongly while short ones radiate away.
• XREF: connects to: Tree branches, not leaves or twigs, resonate as forced acoustic oscillators near 275-450 cps. — T. F. W. Embleton, Sound Propagation in Homogeneous…, 49