Reed pipes behave as stopped-end resonators, unlike open-ended flue pipes

Evidence

All reed pipes have resonators. The effect of a resonator has already been described and illustrated in Figure 4.16 in connection with air reeds. The same principles apply to reed pipes, but there is a major difference in that the shallot end of the resonator acts as a stopped end (as opposed to an open end as in the case of a flue). This is because during reed vibration, the pipe is either closed completely at the shallot end (when the reed is in contact with the shallot) or open with a very small aperture compared with the pipe diameter. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1205

The action of a vibrating reed at the end of a pipe is controlled as a function of the relative air pressure on either side of it in terms of when it opens and closes. It is therefore usually described as a pressure-controlled valve, and the reed end of the pipe acts as a stopped end (pressure antinode and velocity node—see Figure 4.18). Note that although the reed opens and closes such that airflow is not always zero, the reed opening is very much smaller than the pipe diameter elsewhere, making a stopped end reasonable. This is in direct contrast to the air reed in woodwind flue instruments such as the flute and recorder (see earlier), which, as a flow-controlled valve, provides a velocity antinode and a pressure node, and where the flue end of the pipe acts as an open end (see Figure 4.18). — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1209

Categorization

• DEFINE: Explains the stopped/closed end condition that distinguishes reed-pipe resonator behavior from flue-pipe (open end) behavior.
• corroborated: 5 independent passages support this claim — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1205; David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1209
• XREF: connects to: A closed pipe end reflects a pulse with no energy loss without moving; Reflected pulses at the flue end flip the air reed’s oscillation direction — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1159; Hard reeds fix pitch, freeing resonators to shape only harmonics (+6 more)

Broader Connections

• Reed instruments can use fractional-length resonators because reeds fix the fundamental frequency #expands (0.90)
• Hard reeds fix pitch, freeing resonators to shape only harmonics #expands (0.75)
• Open and stopped organ pipes audibly start on different overblown harmonics #complicates (0.70) — David Howard, Jamie Angus, coustics and Psychoacoustics, 1471