Input impedance of brass musical instruments—Comparison between experiment and numerical models

We present a sequence of measured and calculated input impedance curves for tubes of increasing complexity, culminating in curves for a trombone and for a tuba. Measurements were made by the indirect method in a manner which afforded unprecedented accuracy. Calculations were done with a one-dimensional model, including visco-thermal losses, by a method of discretization, employing truncated cones. The correspondence between theory and experiment is sufficiently good that one can use model calculations to predict with some confidence the changes in input impedance caused by modifications to real instruments.