❜ ❜Za/2 Za/2

Woodwind toneholes not only provide a means for bore length variation but also control sound radiation behavior according to their radius, height, and if present, keypad location. The influence of open and closed toneholes on wave propagation within a musical instrument bore greatly complicates the ideal behaviors previously discussed. 1.1 A Two-Port Tonehole Model • The fundamental acoustic properties of toneholes have been extensively studied and reported by Keefe [1981, 1990a], Dubos et al. [1999], Dalmont et al. [2002], Nederveen et al. [1998], Lefebvre and Scavone [2012]. • The model described by Keefe [1990a] is an accurate representation for a tonehole unit, assuming adjacent tonehole interactions are negligible. • In this description, acoustic variables at the tonehole junction are related by a transfer matrix of series and shunt impedance parameters. • Keefe’s original derivation of the tonehole parameters was based on a symmetric T section, as shown in Fig. 1 [Keefe, 1981]