On the acoustical design of the ears of flue organ pipes

Application of the ears to the flue organ pipe is one of the important voicing techniques. Ears are the projections on both sides of the pipe mouth. Organ builders say the ears make not only the sound lower and darker, but also the buildup of tone smoother and quicker. The aim of this research is to confirm their recognitions and make the causes clear. For that purpose, we made acoustical and flow measurements (measurement of the velocity profiles at the mouth) with model pipes. As a result, we could confirm the recognition of the organ builders. In addition, our experiments indicate a slight increase in the blowing pressure in the foot and an increase in the inharmonicity of the pipe eigenmodes. The ear reduces the maximum jet velocity but keeps the characteristic profiles. In some cases, the profiles move as a whole more inside of the pipe. Recent acoustic measurements (eigenmodes of the pipe resonator and of the mouth tone, attack transient and stationary spectrum) on real organ pipes with ears of different heights will be also reported at the meeting.