Aeroacoustics of the panpipes

Abstract

The generic term “flute-like instruments” includes a wide variety of instruments whose sound production is ensured by the coupling of an air jet with an acoustic resonator. Within the family, different kinds of resonator (for instance Helmholtz resonator, open-open, or open-closed tube), may be used with different kind of air supply systems such as the ones found in the recorder, the flue organ pipe, or the shakuhachi. It is common to extent the results obtained on one of the member of the family to the whole family. However, when an accurate description of the sound production mechanisms is required, small discrepancies may arise due to the wide variability in the geometries or in the air supply systems. Among other, a closed-end flute may have a different behavior than an open-open flute since the recirculation of air flow within the pipe may alter the hydrodynamics of the jet, and thus the auto-oscillation process. While most of the studies on flute-like instruments have focused on open pipes (organ pipes and recorder), the panpipes (a representative closed-end flute) has only received little attention. We present experimental data, including flow visualization and pressure signal measurement gathered on a closed pipe. A model of the flow in the pipe allows to interpret the data and compare the behavior of a closed pipe blown with a turbulent jet with that of an open pipe blown with a laminar jet.