Material Influence on the Sound of Brasses

Musical acoustics is a rapidly developing field of research which still contains some major research questions. An important and controversial issue, requiring further serious study, is the influence of the used materials on the vibrational behavior of brass wind instruments and the resulting acoustical effects.

This project emphasis on how materials and processing techniques used to build modern and period brass wind instruments affect and change structural vibrations and subsequently the radiated sound. A better understanding of the factors related to sound quality and playability of brass wind instruments and early brasswind instruments in particularly, is the overall goal of the project. Studying structural vibrations of brasswind instruments and relating those to acoustical characteristics like input impedance and sound pressure transmission will allow further validating existing theoretical models and deriving from those basic physical parameters of the used wall material.

Archival research will be conducted upon historical manuscripts that contain additional information on historical brass making techniques and used materials and of acoustical analysis of surviving historical instruments in order to define sound quality targets for remanufacturing them. Primary source study might extend the knowledge about the raw material used and how this material has been processed. Subsequently a full documentation of acoustical relevant properties of all surviving 16th century trombones will be made. Based on the findings an accurate reconstruction will be made of one instrument, in order to use as test instrument for further acoustical analysis.

• State of the art geometrical measuring techniques will be used to accurately reconstruct the shape of the preserved renaissance trombones, including their wall-thickness.
• Physical modeling and computer optimization will be used to validate and refine the obtained bore profiles.
• Non-destructive material testing methods like X-ray spectroscopy will be applied to identify alloys.
• Optical methods like time-averaged and time-resolved Electronic Speckle Pattern Interferometry together with vibro-acoustical methods like accelerometer array recordings and pulse hammer operated modal analysis will reveal all the important details of structural vibrations.
• FEM (Finite Element Methods) simulations will be used to validate and refine material and geometric parameters of a structural model.
• Finally purely acoustical methods like microphone array recordings, input impedance and pressure transmission measurements with speaker generated sine wave sweep will be used to identify timbre, intonation and playability differences caused by the wall material.