Analysis of flow and acoustic radiation in reed instruments by compressible flow simulation

Abstract

Direct aeroacoustic simulations of flow and sound around an instrument with an oscillating reed were performed on the basis of compressible Navier-Stokes equations along with experiments with an artificial blowing device. The measured reed displacement was utilized as forced vibration in the computations. The predicted sound pressure spectrum shows that the level of the fundamental tone almost agrees with the measured result. The numerical results showed that the lowest acoustic mode of clarinet-type reed instruments (one-quarter wavelength mode) was reproduced. Moreover, the sound generation mechanism was discussed in detail using the predicted gradient of mass flow rate in the instrument. It was found that compression and expansion occur inside the mouthpiece, where the flow separation occurs after the spreading of the air jet from the reed channel exit along the inner wall of the mouthpiece. In addition, vortex ring shedding attributable to the acoustic particle velocity around the open end of the instrument was found to occur, causing an expansion wave from the instrument.

Effects of the Bore Diameter on Oscillation Threshold Pressure and Tone Quality of Clarinet Mouthpieces

“…The pressure chamber was relatively large compared to the actual human mouth volume, however, the jet flow from the air tube does not interfere with the reed oscillation, and stable reed oscillation can be achieved. Details are reported in [11][12].…”