Input impedance curves for the brass instruments

Abstract

Apparatus previously described [J. Acoust. Soc. Am. 56, 1266–1279 (1974)] to obtain input impedance curves for the woodwind instruments has been applied to the brass instruments. These curves show, for example, the importance of the bell and the mouthpiece in putting the resonance frequencies in their musically necessary places. The mouthpiece also has the important effect of increasing the input impedance presented to the player. The trumpet has input impedances at the various resonance frequencies ranging up to 1000 cgs acoustic ohms; trombones and French horns have about one-third as much. Trumpet mutes were investigated and found to behave as bandpass or high-pass filters which change the instrument’s radiated tone quality. The long-argued question about hand-stopping of horns was investigated; it was concluded that the effect of hand stopping is to lower the frequencies of all the modes. Subject Classification: [43]75.40.