Comparing steady-state and transient phenomena in brass instruments

Abstract

Input impedance and radiation patterns are well-known examples of important brass instrument characteristics measured under steady state conditions. Transient phenomena are less studied, but potentially as important to the player and listener. For example, the heights and harmonicity of the peaks of the instrument's input impedance affect its steady-state playing response, which the player might describe on a range from “stuffy” to “open” or “free-blowing.” However, the player also wants an instrument that will facilitate clean and reliable attacks. The development of the instrument's pressure spectrum during the onset transient can serve as an additional diagnostic tool to reveal information about the instrument response under playing conditions. The contribution of the instrument body vibrations to the radiated sound field is small and generally imperceptible under steady-state conditions. However, the bandwidths of the body vibration resonances are generally much narrower than those of the air column resonances and accordingly their transient responses are much longer. This leads to a time signature that enhances their detection by the listener. A complete picture requires consideration of both the steady-state and transient phenomena.