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Abstract

A high level of noise, combined with pure tones, is often encountered in ship's cabins, leading to severe psychological and physiological issues for the crew. To address this problem, an indoor noise abatement solution becomes necessary that utilizes efficient acoustic boards integrated with resonators, positioned along the inner walls of the cabin. However, the thickness of the acoustic boards must be strictly limited due to maintenance and operational considerations. This limitation results in insufficient sound absorption capabilities and a restricted range of tuned frequencies, as the resonating frequency of a standard Helmholtz resonator is closely tied to its cavity. A modified Helmholtz resonator with an internally extended resonating tube is adopted to overcome this drawback. This modification saves space while maintaining the same tuning effect. Two types of acoustic boards are proposed in this study: acoustic board A, which consists of a one-layered acoustical board and an extended Helmholtz type resonator, and acoustic board B, which includes a two-layered acoustical board and an extended Helmholtz type resonator. An accuracy check of the modified Helmholtz resonator is conducted using experimental data before proceeding with the optimization of the acoustic boards. Additionally, a sensitivity analysis is performed to evaluate the impact of the geometric parameters of the acoustic boards. Two bionic algorithms, namely APSO (Accelerated Particle Swarm Optimization) and SA (Simulated Annealing), are employed to achieve an optimal design. The results of optimization demonstrate that the APSO algorithm slightly outperforms the SA algorithm. Furthermore, acoustic board B exhibits a wider spectrum of acoustical attenuation compared to acoustic board A. Consequently, this study showcases the effective reduction of noise in an enclosed machine cabin using APSO and SA, while taking into account the constraint of limited thickness.

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