The bell reflects low frequencies deep inside and high ones near its rim

Evidence

The bell modifies as a function of frequency the manner in which the open end of the pipe acts as a reflector of sound waves arriving there from within the pipe. A detailed discussion is provided by Benade (1976) from which a summary is given here. Lower-frequency components are reflected back into the instrument from the narrower part of the bell while higherfrequency components are reflected from the wider regions of the bell. Frequencies higher than a cut-off frequency determined by the diameter of the outer edge of the bell (approximately 1500 Hz for a trumpet) are not reflected appreciably by the bell. … Adding a bell to the main bore of the instrument has the effect of making the effective pipe length longer with increasing frequency. — David Howard, Jamie Angus, coustics and Psychoacoustics, 1272

Categorization

• XREF: The frequency-dependent reflection point in a bell parallels how psychoacoustic attention/reflection is selective across frequency — relevant to the reader’s project of interpreting life acoustically. — connects to: A brass bell reflects sounds selectively by frequency; A bell lowers a tube’s cutoff frequency, easing high-frequency escape — Eric J. Heller, Why You Hear What You Hear- An…, 1506; Brass instrument bells reflect low frequencies early and pass high ones. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1246 (+3 more)

Broader Connections

• Brass instrument bells reflect low frequencies early and pass high ones. #corroborates (0.85) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1246
• A brass bell reflects sounds selectively by frequency #expands (0.80)
• The bell acts as a frequency-dependent reflector that shifts brass mode frequencies. #expands (0.80)
• A bell lowers a tube’s cutoff frequency, easing high-frequency escape #contradicts (0.75) — Eric J. Heller, Why You Hear What You Hear- An…, 1506
• Removing a trumpet bell empirically strengthens the high partials above 1500Hz #contradicts (0.75) — Eric J. Heller, Why You Hear What You Hear- An…, 1530