T. Bravo and C. Maury
Forum Acusticum 2023
Del 11 al 15 de septiembre de 2023, Torino, Italy.
Improvement of acoustic absorption and transmission in the low frequency range when facing constraints on total volume and weight constitutes a constant challenge in the field of noise control. Emergence of acoustic metamaterials has allowed the development of compact sub-wavelength absorbers that can provide solutions in terms of the required wideband low-frequency sound dissipation. In a lined waveguide, the effective velocity of the incoming sound can be progressively reduced to zero leading to the Acoustic Black Hole (ABH) effect. In this work, this concept of sound trapping has been mostly explored for widely-opened ABH silencer for the reduction of the transmission properties without obstructing flow circulation. Attention has been paid to the attenuation of the acoustic backreflections that can be of interest for improving engine combustion efficiency for instance. Parametric studies are carried out to study the influence of the physical ABH factors on the acoustic performance. We have also performed a causality-constrained optimization to determine the minimum bandwidth-to-length ratio required for a fixed dissipation requirement. Results have been validated with experimental results.
