A study of impedance of brass instruments and mouthpieces—Comparison of models and measurements

Abstract

The impedance of a brass instrument has an important influence on the frequencies of the notes that can be played and on the timbre of the sound. The shape of the mouthpiece has various features, such as the cup volume and shape, opening diameter, and length, that determine the characteristics of the overall impedance of the instrument-mouthpiece combination. Brass instruments, and especially mouthpieces, are designed for specific purposes, and many brass players own several different horns or mouthpieces, and choose which to use depending on their particular musical requirements at the time. In order to investigate the relationship between the physical parameters of instruments and mouthpieces and the resulting impedance, brass instruments and mouthpieces have been modeled with transfer matrix techniques, and the results are compared with impedance measurements of the instruments alone, the mouthpieces alone, and combination of instruments and mouthpieces. Trumpets, flugelhorns, horns, trombones, and the corresponding mouthpieces have been used for this study. The mouthpiece-instrument combination has been investigated in terms of intonation, playability, and timbre. The question of whether (and why) some mouthpieces are more suited to certain instruments and certain playing styles is investigated as well as the effect of varying the physical parameters of mouthpieces and instruments.