Abstract
The application of acoustic ring resonator structures for the manipulation of audio frequency acoustic waves is demonstrated experimentally and via numerical simulation. Three ring resonator systems are demonstrated: a simple single ring structure that acts as a comb/notch filter, a single ring between two parallel waveguides that acts as an add-drop filter, and a sequential array of equally spaced rings that creates acoustic bandgaps. The experiments are conducted in linear waveguides using an impulse response method. The ring resonators were created via 3D printing. Finite element numerical simulations were conducted using COMSOL.
Highlights
Three ring resonator systems are demonstrated: a simple single ring structure that acts as a comb/notch filter, a single ring between two parallel waveguides that acts as an add-drop filter, and a sequential array of spaced rings that creates acoustic bandgaps
This study explores the use of acoustic ring waveguides as resonant elements in comb/notch filters, add-drop filters, and acoustic bandgap arrays
The 3D printed ring resonators are sized such that the frequency test range begins below the lowest resonant frequency of the ring, a regime that cannot be explored in optical ring resonator systems
Summary
This study explores the use of acoustic ring waveguides as resonant elements in comb/notch filters, add-drop filters, and acoustic bandgap arrays. The main results of the latter studies concerned the so-called parallel loop systems, which have rectangular loops with one arm of the rectangle being part of the waveguide itself. This change alters the behavior of the filter properties compared to the tangential loops because there are many different destructive interference paths due to the shared arm. These interference avenues lead to both broad notch-type filters and sharp, narrow transmission minima. The sharp minima had anomalous phase profiles that enabled the demonstration of negative group delays of suitably tuned pulses. The investigation of novel acoustic elements, such as the ring resonator structures described here, can find application in architectural acoustics for the frequency-selective attenuation of sound in ducts and conduits or in the suppression of vibration wave buildup in flowing gas pipelines
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