Experimental study of sound generation by confined jets with application to human phonation
Abstract
Experiments were performed to investigate the fundamental aerodynamic sound generation mechanisms involved in human voice production. A full scale dynamic model of the larynx was used. The experimental facility allowed jet flows through orifices of different laryngeal-like geometries to be investigated, for various acoustic loads and working gas mixtures. The broadband sound generation by stationary jets was first investigated. Empirical non-dimensional relations for the amplitude and the spectral character of the sound radiated from confined jet flows were developed, utilizing an original spectral decomposition procedure. The results confirmed previous findings relative to the basic mechanisms involved, and provided improved models that could be used to predict the spectrum of the broadband noise generated at the glottis during phonation. Broadband noise generation in pulsating flows was also investigated. It was found that the quasi-steady approximation did not always yield accurate predictions for the broadband component of the radiated sound during the opening and closing stages of one glottal cycle. Otherwise, the periodic component of the radiated sound in pulsating flows, with and without a strong acoustic loading, was predicted well using the quasi-steady approximation within the accuracy limitations of the experimental facility. A species of jet tone was observed in the case of a stationary jet flow through an orifice with divergent walls. This was postulated to be caused by a dynamic stall phenomenon. The geometry, wall motion, and mechanical properties of the model did not replicate those of a human subject with great fidelity. However, many basic features were reproduced which allowed the verification of the quasi-steady approximation often used in voice production models to be verified over a range of flow conditions. The experimental results help clarify the role of monopole, dipole, and quadrupole sound sources involved in translaryngeal flows, and provide useful insight on basic flow-sound interactions within the human larynx.
Degree
Ph.D.
Advisors
Frankel, Purdue University.
Subject Area
Mechanical engineering
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.