Design of flat broadband sound insulation metamaterials by combining Helmholtz resonator and fractal structure

Abstract

A new sound insulation metamaterial (SIM) is designed by combining a Helmholtz resonator and a fractal structure for sound insulation in the frequency range of 600 to 1700 Hz. Using a fractal-based internal structure, the designed hybrid SIM shows a relatively constant value of sound transmission loss (STL) over the target frequency range. The basic concept of this work is to develop two functional parts working in each effective frequency range. One is a Helmholtz resonance structure that operates with a high value of STL from 600 to 1000 Hz, and the other is an internal fractal structure that shows a high STL at higher frequencies in the 1000 to 1700 Hz range. In this work, the proposed metamaterial has a mean of 16.34 dB with a standard deviation of 1.73 dB within the wide target range of 600 to 1700 Hz. Additionally, the proposed SIM is approximately 40 % smaller in size than the previous resonator and has a higher mean STL with a small ∆STL of 1.7 dB between highest and lowest values.

Design of sound absorptive metamaterials with shared waveguides by means of numerical analysis and analytical modeling

“…This quality can also make them spaceefficient, making them particularly suitable for application in buildings. This category can also include designs where the HR necks have a shared opening or waveguide [8]. If the waveguide is only opened to a source room, the resulting HR array can be considered an absorptive panel.…”

“…The use of acoustic metamaterials is a promising approach to address the low-frequency noise problem more effectively. Research has demonstrated that resonant absorbers, which incorporate arrays of Helmholtz resonators (HRs) with varying resonant frequencies, can provide effective sound absorption in increasingly broader fre-quency spectra [5][6][7][8]. Additionally, HR arrays can be designed to serve as sound barriers capable of achieving good transmission losses while maintaining open cavities for airflow [9][10][11].…”

Sound-absorption performance of a coupled square-neck embedded Helmholtz resonator

“…Acoustic metamaterials [2][3][4][5][6] and acoustic metasurfaces [7][8][9][10] are typical subwavelength structures. Common structure types are Helmholtz resonators, [11][12][13] membrane resonators, 14,15) Fabry-Pérot (FP) cavities, [16][17][18][19][20][21][22] and fractal structures. 23,24) Seoung-HoBaek et al 12) combined a Helmholtz resonator with a fractal structure 23) and designed a sound-insulation metamaterial to reach an average sound-transmission loss of 16.34 dB in the frequency range of 600-1700 Hz.…”

“…Common structure types are Helmholtz resonators, [11][12][13] membrane resonators, 14,15) Fabry-Pérot (FP) cavities, [16][17][18][19][20][21][22] and fractal structures. 23,24) Seoung-HoBaek et al 12) combined a Helmholtz resonator with a fractal structure 23) and designed a sound-insulation metamaterial to reach an average sound-transmission loss of 16.34 dB in the frequency range of 600-1700 Hz. Similarly, Wu et al 16) designed the coupling structure of microperforated and Fabry-Pérot (FP) folding channels and effectively absorbed sound waves below 500 Hz.…”