Kopytko Y.S. Acoustic resonators of complex shape. – Qualifying scientific work on the rights of the manuscript.
Thesis for the degree of Philosophy Doctor, in specialty 171 “Electronics”. - National Technical University of Ukraine "Igor Sikorsky Kyiv Polytechnic Institute", Kyiv, 2020.
The following scientific results were obtained in the dissertation for the first time:
1. For the first time, the method for calculating of the additional resonances based on the separate calculations of the values of the resonant frequencies of the throat part and of the Helmholtz resonator cavity and the subsequent harmonization of these values is proposed.
2. For the first time, a model of a complex-shaped resonator as a system with lumped parameters is investigated for finding resonant frequencies.
3. For the first time, the values of elastic bonds between the masses of air in the flask, throat and the attached mass above the throat are estimated.
4. For the first time, a model of a resonator of a complex shape, as a system with distributed parameters, was investigated, and the sound fields inside such a system were investigated.
5. For the first time, the resonant frequencies and amplitudes of oscillations of the throat part of the Helmholtz resonator were calculated and the results were used to calculate the resonant frequencies of the resonator according to the equations obtained for the mechanical model.
6. The accuracy of the calculated formulas of the self-resonant frequency formulas of the Helmholtz resonator is investigated, taking into account and without taking into account the added neck length.
7. The effect of acoustic performance on the resonant frequencies of the Helmholtz resonator is investigated.
The dissertation is devoted to research of the oscillation processes in the Helmholtz resonators at frequencies close to resonance; to develop the methods of the research and calculation of the additional resonances; to research influence of the acoustic design on the resonant frequencies of the Helmholtz resonator and influence of the resonator parameters on the value of the attached length of its throat part.
The practical significance of the results obtained in the dissertation is that the research results can be used to solve acoustic problems requiring the accuracy of calculating the natural resonance frequency of the Helmholtz resonator with an error of no more than 1% in cases where standard formulas give an error of about 3% (simpler formulas that take into account the attached length) and up to 75% for calculations using the Helmholtz formula.
Possession of information about the presence and values of additional resonances can be used to refine broadband acoustic systems. Taking into account the influence of the presence of an acoustic performance on the natural resonant frequency of the Helmholtz resonator will improve the results of the development of metamaterials to obtain a value of the working frequency of the metamaterial that is closer to the planned one.
The results of the work are introduced into the educational process of the Department of Acoustic and Multimedia Electronic Systems of the National Technical University of Ukraine "Igor Sikorsky Kyiv Polytechnic Institute" when giving lectures and conducting laboratory works in the following disciplines: "Physical acoustics", "Modern trends in electroacoustic technologies", "Noises and vibrations".
Keywords: resonators of complex shape, Helmholtz resonator, the resonance frequency of the resonator, frequency equations, resonant frequencies of Helmholtz resonator, acoustic resonator, additional resonances, natural resonance, additional resonant frequencies of the resonator, acoustic performance of the resonator, the attached length of the resonator neck, cubic resonator.
