Removing a trumpet bell empirically strengthens the high partials above 1500Hz

Evidence

The author’s trumpet provided another test. A piece of 1.9-cm-diameter, thin-walled brass tubing thrust into the beginning of the flare took the bell out of action; the tube extended just beyond the bell. The open B3b was played normally. When the extra tubing was inserted, a rather unstable note of nearly the same pitch could be achieved, but not nearly as pleasing a sound. Crucially, the bell-less tone had stronger partials above 1500Hz than the tone with the bell, after equalizing the total power in the two samples. — Eric J. Heller, Why You Hear What You Hear- An…, 1530

Categorization

• XREF: connects to: The bell reflects low frequencies deep inside and high ones near its rim — David Howard, Jamie Angus, coustics and Psychoacoustics, 1272