Research

Current project: Intensifying the tone by manipulation of the wall thickness of voiced pipes
Method: The pitch of the pipe wall, produced by mechanical excitation (tapping) is detected in various regions. Those regions sounding higher will be thinned out until the sound becomes uniform to the deeper sounding regions. More systematic researches are planned, 


Analysis of the changes:
1. Wall vibration measurement using the Polytec laser vibrometer
A pipe is excited by the air column (blowing) and the wall vibration amplitudes were measured along the whole surface. The data is presented as a plane vibration field, corresponding to the pipe body cut up along the soldering and rolled out in a plane. The vibration amplitude is coded by colours. The same voiced pipe was measured and compared before and after the wall manipulation.
The thinned-out pipe exhibits somewhat larger amplitudes and the wave peaks on both sides of the mouth become more symmetric. The transition to the pipe end which oscillates in the opposite phase is smoother (Figures 1 and 2).
Comparing the vibration spectra there are particular strong changes in the third and the fourth partial tones (Figures 3 and 4).


Figure 3                                                                                      Figure 4
2. Acoustical measurements in the anechoic room of the Fraunhofer-Institue for Building Physics in Stuttgart
The measurements show that higher partials can be amplified or weakened (higher than eights ) and that non harmonic peaks can be modified or shifted by thinning out the walls (Figures 5 and 6).


Figure 5                                                                                      Figure  6
3. By thinning out the walls the timbre is be percieved warmer, more intensive but also more quiet. The ability of sound-mixing between the pipes improves, the voicing becomes more stable and the attack more vocal.
Summary: Points 1. and 2. indicate that by removing only a few chips of metal, the vibration pattern of the pipe wall is changed and the acoustic behaviour of the sounding pipe is influenced, without applying any of the classical voicing steps. 
This method of wall manipulation is a new technique which is absolutely essential for me when voicing new pipes, in spite of the extraordinary effort needed.
Acknowledgements: I would like to express my sincere gratitude towards Prof. Zipser and Dr. Franke at the University of Applied Sciences in Dresden as well as Dr. Angster and Prof. Miklós at the Fraunhofer Institute for Building Physics in Stuttgart for carrying out the measurements. Special thanks to Dr. György Paál, who performed several experiments for over the years and gave me scientific support.
P.S.: Because of the lack of space only a small part of the research results are presented here. I am planning to publish the results in an organ journal in the near future.