Reed regeneration apparatus with controllable up- and downstream impedances
Peter L. Hoekje, A. H. Benade · The Journal of the Acoustical Society of America · 1983
Linear reed regeneration theory gives the oscillation condition as A⋅[(Zu + Zd)/Zr]⩾1, where A, Zr are the transconductance and impedance of the reed, and Zu and Zd are the input impedances of the air columns looking upstream and downstream from the reed. Extension to nonlinear regimes retains this relation between Zu, Zd and Zr. We have constructed a reed apparatus such that reeds of varying materials and thicknesses can be reproducibly set over continuous ranges of position and angle of the reed in the window in which it operates. Being end-for-end reversible and adjustable, the reed flow-controller can be operated in all four configurations (± E, ± I) of the Bouasse-Melde nomenclature, e.g., clarinet-type inward striking (+ E), and trumpet-type outward striking (+ I). Means are included to provide adjustment of peaks and dips of Zu, analogous to the accustomed control of the downstream air column Zd, while permitting DC flow at pressures above atmospheric. Provision is made for mircophones and probes placed symmetrically with respect to the reed. [Work supported by NSF.]