Demonstration of effective acoustic properties of different configurations of Helmholtz resonators

Abstract Acoustic metamaterial attains uncommon material properties over natural material such as negative effective mass density or negative effective bulk modulus or both. The effective bulk modulus of a classical acoustic reactive filter such as Helmholtz resonator has been observed negative, using lumped element model, at resonance point, which desires further investigations. Present research demonstrates and establishes robust method to estimate and measure acoustic metamaterial properties of a Helmholtz resonator analytically, numerically and experimentally in detail. The proposed numerical technique simulates ASTM-2611 standard of measurement to extract corresponding reflection and transmission coefficients to evaluate the effective acoustic metamaterial properties. The subsequent investigations have been carried out by taking eight different configurations of Helmholtz resonators such as parallel and series using similar and dissimilar resonators. Performance of each configuration has been investigated analytically, numerically and validated experimentally. At last, a finite array of Helmholtz resonators has been investigated. From investigations, it has been observed that five configurations of Helmholtz resonators and finite array have negative effective mass density and effective bulk modulus. Summarizing, the present research endeavors analytical, numerical and experimental investigations of different configurations of Helmholtz resonators in detail, which is first in its own kind.