Flue organ pipe operating regimes and voicing practices

Dirk Steenbrugge

A combination of certain pipe voicing parameters, including wind pressure, sets up a specific feedback cycle operating regime when the pipe is blown. It is the most important voicing adjustment. In most blowing conditions maximum energy is expected to be transferred to the acoustic field inside the pipe when the jet injects air in phase with the acoustic pressure, the phase delay on the jet then being about half a period and the pipe sounding at its fundamental passive resonance frequency. In this study the relationship between this optimum concept and voicing practices is investigated. A procedure to determine the operating regime of pipes from various registers and organs using data from in situ acoustic and flow measurements was developed. Correlations were sought with pipe scaling, pitch range and tonal architecture. Principal pipes turn out to usually operate at pressures above this theoretical optimum, and acoustic power is traded for spectral richness, leading to different voicing styles. As a general rule, voicers appear to intuitively attempt to put forth the distinctive acoustic features of the resonators. Erratic variations in operating points throughout pipe ranks were also observed, the resulting differences being more or less successfully compensated by other voicing parameters.

Mots clés: pipe organs; flue organ pipes; voicing; aeroacoustic feedback

Domaines: Acoustique [physics.class-ph]

Dirk Steenbrugge. Flue organ pipe operating regimes and voicing practices. Acoustics 2012, Apr 2012, Nantes, France. ⟨hal-00811336⟩