Tunable acoustic absorber using a micro acoustic hole array

Abstract

We propose a tunable acoustic absorbing device using a Helmholtz resonator. Timing the resolution frequency of the device to a desired frequency makes it possible to absorb variable sounds. The designed device forms an array of the Helmholtz resonator with a tunable compliance. The experimental results on controlling the resonant frequency of the device will be described. A deep hole array formed by X‐ray lithography is fabricated into the front plate of the device in order to absorb low‐frequency noise. © 1999 Scripta Technica, Electron Comm Jpn Pt 2, 83(1): 1–6, 2000

An experimental study on the optimization of the production and efficiency of tunable Helmholtz absorbers for the modal control of small rooms

“…18 Another alternative to optimize Helmholtz absorbers is the development of tunable solutions. [19][20][21] Instead of providing performance within broad bands, this type of absorber is designed to allow adjustments in the respective resonant frequency depending on the acoustic field to be conditioned. The tuning process depends on geometrical modifications allowed by and performed on the system, which can be achieved without impairing the simplicity of the Helmholtz absorber.…”

“…The tuning process depends on geometrical modifications allowed by and performed on the system, which can be achieved without impairing the simplicity of the Helmholtz absorber. The studies conducted by Konishi et al 19 and Wu et al 20 do not view modal control as the final application of the solutions, which stand out exclusively by their tuning capacity. Souza and Patraquim, 21 on the contrary, used theoretical models to evaluate the performance of the proposed solution to the modal problems commonly found in small rooms (volumes up to 60 m 3 ), thus considering the first frequencies of the audible spectrum.…”

Smart window for tuning transparency and noise absorption

“…Similarly, a stepper motor [175,221] was previously used to change the back-cavity volume of the MPP absorber, moving the back-cavity plate from 6mm to 12mm. These cavity tuning methods are however impractical and costly for large-area MPP.…”

“…This is achieved by voltage activation that reduces the membrane tension and thus hole size. Such a membrane tuning method does not require discrete mechanical parts as for the reported cavity tuning method [158,175,221].…”

“…Such Helmholtz resonators were installed in the Royal Festival Hall in London to cover the frequency range from 60Hz to 700Hz[158]. In a similar design by S. Konishi et al[174][175][176], a stepping motor was used to change the back-cavity depth (D) of an MPP absorber (see). The MPP consisted of a plate of 40mm diameter and 1mm thickness with 400 holes of 100μm…”