Open planar acoustic notch filter using a film-integrated Helmholtz resonator array

Abstract

Acoustic filters are used to transmit or attenuate noise in a specific frequency band. However, previous acoustic filters consisting of rigid structures generally required a large housing of a size equivalent to the wavelength, limiting their downsizing. This study presents an open planar acoustic notch filter using a film-integrated Helmholtz resonator (HR) array. A film divides the HR chamber and resonates with the HR. The film-integrated HR array filter achieved smaller housing dimensions than a no-film HR array filter with the same notch frequency. The transmittance of the film-integrated HR array was theoretically calculated using the transfer-matrix method. The calculated spectra were very similar to the simulation results. The notch frequency of the film-integrated HR array filter was 4.04 kHz, 0.74 kHz lower than a no-film HR array filter. The design and analysis of the acoustic filter presented should motivate further development of advanced acoustic filters.

A study of acoustic focusing based on the taboo genetic algorithm

“…In order to achieve the filtering, 40) the subsequent optimization goal is to make the sound waves of all three frequencies achieve a better focusing effect when the sound waves with frequencies of f 0.5 , 0 f 0 and f 2 0 are incident. If the incident wave is a mixture of the three frequencies, the sound waves can be separated by the focal point position.…”

“…In this paper, we not only design a metasurface that can realize both transmission focusing and reflection focusing, but also a metasurface that utilizes acoustic focusing for filtering. 40) The acoustic metasurface consists of three structures that modulate acoustic waves with frequencies of f 0.5 , 0 f 0 and f 2 0 respectively. However, since the different structures interact with each other, when the three structures are arranged in a certain order, the actual focus positions obtained will be different from the focus coordinates given by using the generalized Snell's law.…”