Information Services banner Edinburgh Research Archive The University of Edinburgh crest

Edinburgh Research Archive >
Edinburgh College of Art >
Edinburgh College of Art thesis and dissertation collection >

Please use this identifier to cite or link to this item: http://hdl.handle.net/1842/4378

This item has been viewed 64 times in the last year. View Statistics

Files in This Item:

File Description SizeFormat
MacDThesisImages.zip28.25 MBPostscriptView/Open
MacDonald.pdf32.76 MBAdobe PDFView/Open
Title: Study of the undercutting of woodwind toneholes using particle image velocimetry
Authors: MacDonald, Robert
Supervisor(s): Campbell, Murray
Issue Date: 2009
Publisher: The University of Edinburgh
Abstract: The undercutting of toneholes has been practised for centuries with the aim of improving the tuning and playability of woodwind instruments. The influence of undercutting on tuning can be understood in terms of linear acoustic theory. Its effect on other playing characteristics is thought to lie in its reduction of local non-linear flow phenomena (boundary layer separation and the formation of jets and vortices) at the tonehole. Particle Image Velocimetry (PIV) is used to examine the oscillating airflow around a model woodwind tonehole. Velocity and vorticity information is obtained and compared for a square-edged tonehole and an undercut tonehole at a variety of sound levels. The upstream, internal edge of the tonehole is found to be the location of the most significant local non-linear flow behaviour. Undercutting is found to reduce the strength of local non-linear flow phenomena at a given sound level. Microphone measurements carried out in a reverberation chamber show that undercutting the tonehole also reduces the harmonic distortion introduced to the radiated pressure signal by the non-linear flow. Proper Orthogonal Decomposition (POD) is then applied to PIV data of oscillating flow at the end of a tube. It is used to approximately separate the acoustic field from the induced local non-linear flow phenomena. The POD results are then used to approximate the percentage of kinetic energy present in the non-linear flow. POD analysis is applied to the case of flow around the two toneholes. It shows a smaller transfer of kinetic energy to non-linear flow effects around the undercut tonehole at a given sound level. The dependence of the local non-linear flow kinetic energy on Strouhal number is considered.
Sponsor(s): Engineering and Physical Sciences Research Council (EPSRC)
Keywords: toneholes
undercutting
linear acoustic theory
tuning
oscillating airflow
Particle Image Velocimetry
Proper Orthogonal Decomposition
URI: http://hdl.handle.net/1842/4378
Appears in Collections:Edinburgh College of Art thesis and dissertation collection

Items in ERA are protected by copyright, with all rights reserved, unless otherwise indicated.

 

Valid XHTML 1.0! Unless explicitly stated otherwise, all material is copyright © The University of Edinburgh 2013, and/or the original authors. Privacy and Cookies Policy