Abstract

This thesis investigates how musical instruments radiate sound, with a focus on directional behavior under realistic performance conditions. High-resolution measurements using a rotating microphone array were used to study percussion and woodwind instruments, providing new insight into how design, excitation, and frequency content shape acoustic output. The first set of experiments analyzed the directivity of the bass drum, triangle, and open snare. Each instrument exhibited unique radiation patterns reflecting its structure and playing method. The bass drum showed dipole-like behavior at low frequencies, transitioning to omnidirectional spreading at mid frequencies, and increasingly irregular patterns at higher frequencies. The triangle, due to its rigid and open-frame design, produced sharp directional lobes, especially at high frequencies. The open snare demonstrated complex frequency-dependent behavior influenced by interactions between its shell, heads, and cavity. Together, these results highlight how percussion instrument radiation depends on both structural geometry and striking technique. The next experiment focused on the glockenspiel, comparing the radiated sound from a fully mounted instrument to that of an individual bar under different boundary conditions. At low frequencies, the full instrument's behavior matched that of a bar mounted on a rigid baffle, suggesting strong influence from the supporting frame. At higher frequencies, the directivity more closely resembled that of an unbaffled bar, indicating that bar-specific modal behavior becomes dominant. Scanning laser Doppler vibrometry confirmed these observations by visualizing both bending and torsional modes of vibration. The final investigation explored the alto saxophone by analyzing the radiated sound from the same B flat pitch played in three registers. The results showed that while the low B flat radiated primarily from the bell, the middle and high B flats exhibited similar patterns resembling distributed sources along the instrument's body, consistent with a phased line array. Spectral analysis revealed stable harmonic spacing but register-dependent changes in energy distribution and directionality. Overall, this work provides new high-resolution data on instrument directivity and demonstrates how structural features, mounting, and register impact radiated sound. These findings offer practical value for acoustic modeling, microphone placement, and the design of musical performance and recording spaces.

Degree

MS

College and Department

Computational, Mathematical, and Physical Sciences; Physics and Astronomy

Rights

https://lib.byu.edu/about/copyright/

Date Submitted

2025-06-26

Document Type

Thesis

Keywords

musical instruments, directivity, percussion instruments, wind instruments, sound radiation

Language

english

Download

Share

COinS