Nonlinear behaviour of lossy acoustic black holes

Umnova, O.; Brooke, D.; Leclaire, P.; Dupont, T.

Abstract

Sound absorption properties of acoustic black holes are studied for high pressure amplitudes. The absorbers consist of thin circular plates, each with a central perforation, separated by annular air cavities. Radius of the perforation of each plate depends on its position thus forming a central channel with a gradually decreasing radius. In our previous work, a linear equivalent fluid model accounting for the variations of the effective properties of air inside this channel was developed. However, the FEM simulations show that flow resistivity of the structure increases with the flow rate according to Forchheimer’s law. This indicates that an extension of the model is necessary for the incident waves of high amplitude. In the current work, the measurements are performed for continuous high amplitude sound. A specially designed impedance tube is used for the experiments. The measurements and modelling show that the nonlinearity of acoustic black holes affects mostly the low frequencies. At higher frequencies, the absorption performance is weakly affected by the nonlinearity. This opens a possibility of using these structures as effective broadband absorbers of high amplitude sound.

• Presentation Conference Type: Conference Paper (published)
• Conference Name: 10th Convention of the European Acoustics Association Forum Acusticum 2023
• Acceptance Date: Aug 7, 2023
• Online Publication Date: Jan 17, 2024
• Deposit Date: Feb 21, 2024
• Publicly Available Date: Feb 21, 2024
• Journal: Proceedings of the 10th Convention of the European Acoustics Association Forum Acusticum 2023
• Peer Reviewed: Peer Reviewed
• DOI: https://doi.org/10.61782/fa.2023.0652