Development of stackable subwavelength sound absorber based on coiled-up system

• Published in: Applied acoustics 2022-06, Vol.195, p.108842, Article 108842
• Main Authors: Prasetiyo, Iwan, Anwar, Khoerul, Brahmana, Ferio, Sakagami, Kimihiro
• Format: Article
• Language: English
• Subjects: Broadband sound absorption; Coiled up structure; Sub-wavelength sound absorber; Tunable sound absorber
• ISSN: 0003-682X; 1872-910X
• DOI: 10.1016/j.apacoust.2022.108842

•Narrowband and broadband absorbers have been developed based on coplanar coiled up resonator units that are permitted to be stackable.•Sub-wavelength absorbers with a great tunability and configurable are offered by the proposed system.•The effect of abrupt change in cross-section is considered to account for discontinuity between adjacent resonator units; this improves the calculation results. A subwavelength structure absorber is developed and demonstrated. Unlike other subwavelength systems, we use several coiled-up resonator systems combined in a stack way. Such a system is proposed to cover acceptable absorption coefficient as well as obtain relatively wider absorption bandwidth. Moreover, it is expected that such a system offers a great tunability and configurable system in absorption to meet targeted frequency and bandwidth. The theoretical prediction is derived for such a system, while experimental works are provided to validate the concept. It is found that the proposed approach can offer a resonance absorption tuning framework in which the total length of the resonator channel is adjusted by adding or reducing the number of resonator units while the cross-section is kept the same for all elements involved. Meanwhile, absorption bandwidth extension can be obtained by combining two or more resonator units with different cross-sections and channel lengths. All these features have been confirmed by the experimental results. Compared to the conventional resonance-based absorbers, the proposed structure can be 94 % thinner for single absorption peak and 66 % thinner for the case of three absorption peaks that forms a broadband absorption characteristic.