Axial vibrations of brass wind instrument bells and their acoustical influence: Experiments

Authors

Thomas R. Moore, Department of Physics, Rollins CollegeFollow
Britta R. Gorman, Rollins College
Michelle Rokni, Rollins College
Wilfried Kausel, Institut fÄur Wiener Klangstil (Musikalische Akustik), UniversitÄat fÄur Musik und darstellende Kunst Wein , Austria
Vasileios Chatziioannou, UniversitÄat fÄur Musik und darstellende Kunst Wein, Austria

Document Type

Article

Publication Date

2015

Abstract

It has recently been proposed that the effects of structural vibrations on the radiated sound ofbrass wind instruments may be attributable to axial modes of vibration with mode shapes that contain no radial nodes [Kausel, Chatziioannou, Moore, Gorman, and Rokni, J. Acoust. Soc. Am.137, 3149–3162 (2015)]. Results of experiments are reported that support this theory. Mechanical measurements of a trumpet bell demonstrate that these axial modes do exist inbrass wind instruments. The quality factor of the mechanical resonances can be on the order of 10 or less, making them broad enough to encompass the frequency range of previously reported effects attributed to bell vibrations. Measurements of the input impedance show that damping bell vibrations can result in impedance changes of up to 5%, in agreement with theory.Measurements of the acoustic transfer function demonstrate that the axial vibrations couple to the internal sound field as proposed, resulting in changes in the transfer function of approximately 1 dB. In agreement with theory, a change in the sign of the effect is observed at the frequency of the structural resonance.

Comments

Copyright 2015 Acoustical Society of America. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the Acoustical Society of America.

This article appeared in Thomas R. Moore, Britta R. Gorman, Michelle Rokni, Wilfried Kausel and Vasileios Chatziioannou, “Axial vibrations of brass wind instrument bells and their acoustical influence: Experiments,” J. Acoust. Soc. Am. 138, 1233-1240 (2015). This article may be found at http://scitation.aip.org/content/asa/journal/jasa/138/2/10.1121/1.4928138?TRACK=RSS

Published In

Thomas R. Moore, Britta R. Gorman, Michelle Rokni, Wilfried Kausel and Vasileios Chatziioannou, “Axial vibrations of brass wind instrument bells and their acoustical influence: Experiments,” J. Acoust. Soc. Am. 138, 1233-1240 (2015).

Publication Title

Acoustical Society of America

DOI

10.1121/1.4928138