Innovative solution to enhance the Helmholtz resonator sound absorber in low-frequency noise by nature inspiration

Sound absorbing elements commonly used to make quieter spaces are very desirable for high-frequency noise control. It is more attractive if it is possible to produce sound absorbing structures that perform well for a wide frequency range, especially in low-frequencies. In this regard, Helmholtz resonator array is a well-known structure but the maximum performance of each resonator unit in an array panel can only be achieved at resonance frequency that is dependent on its size. Therefore, a resonator array panel with equal size units has insufficient performance in a wide frequency range. Hence, the consideration of suitable sizes for each resonator in an array panel consisting of unequal size units is a key point to widen the frequency range of sound absorption. On the other hand, it seems that engineering science can be developed by nature inspiration. In addition, Fibonacci sequence is a famous mathematical model which describes the shape/ratio of different phenomena which exist in nature. In this paper, Fibonacci sequence is utilized to investigate Helmholtz resonator arrangement to increase both the amount of sound absorption coefficient and frequency bandwidth of absorption without changing the total volume of resonator array with equal size units. Analytical solutions based on the modified equivalent electrical circuit theory is used to calculate the sound absorption coefficient of the proposed panel with numerical experiments in MAPLE and COMSOL Multiphysics softwares to validate the proposed overall approach. Results show that the Fibonacci sequence is an optimum candidate to design a resonator-based sound absorber in low-frequency noise.