Experimental and numerical studies on the design of a sonic crystal window
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2017-05-15 |
| Journal | Journal of Vibroengineering |
| Authors | Hsiao Mun Lee, Kian Meng Lim, Heow Pueh Lee |
| Institutions | National University of Singapore, Université Bourgogne Franche-Comté |
| Citations | 2 |
| Analysis | Full AI Review Included |
Sonic Crystal Window Design for Traffic Noise Mitigation
Section titled âSonic Crystal Window Design for Traffic Noise MitigationâExecutive Summary
Section titled âExecutive SummaryâThis study details the numerical and experimental optimization of a Sonic Crystal (SC) window, incorporating Helmholtz Resonators (HRs), designed to mitigate external traffic noise effectively. The findings provide critical guidance for structural acoustic engineers seeking high-performance noise barriers that maintain ventilation.
- Acoustic Mitigation Goal: Successful design and validation of an SC window prototype targeting the reduction of typical road traffic noise (peak around 1000 Hz).
- Optimal Geometry: Rectangular scatterer shapes consistently demonstrated the highest Transmission Loss (TL) across the full frequency range (300 Hz to 3000 Hz) compared to diamond and semi-circle configurations.
- Array Configuration: The fully staggered pattern proved superior for noise mitigation below 1700 Hz, achieving up to 41 dB TL at 1600 Hz (numerical).
- Low-Frequency Enhancement: Helmholtz Resonators were essential for addressing low-frequency noise, achieving a numerical peak TL of 53 dB at 500 Hz, a frequency range where conventional solid SCs perform poorly.
- Validated Performance: The final prototype, tested experimentally, achieved a maximum TL of 18 dB at 900 Hz and maintained robust attenuation of greater than 10 dB across the critical traffic frequency band (900 Hz to 1400 Hz).
- Methodology: Analysis relied on 3D time-harmonic simulations (Comsol) validated by corridor testing using a Bruel & Kjaer sound system.
Technical Specifications
Section titled âTechnical SpecificationsâExtracted quantitative parameters defining the acoustic performance and physical geometry of the Sonic Crystal elements and window prototype.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Max TL (Numerical, with HRs) | 53 | dB | Maximum simulated Transmission Loss (TL) observed at 500 Hz. |
| Max TL (Experimental) | 18 | dB | Maximum measured TL observed at 900 Hz for the final prototype. |
| Broadband TL Efficacy | > 10 | dB | Sustained noise mitigation observed between 900 Hz and 1400 Hz. |
| Design Center Frequency (fc) | 1000 | Hz | Targeted acoustic band gap center frequency (using n=1, $\theta$=90°). |
| Lattice Constant (a) | 0.1715 | m | Distance between adjacent SC scatterers. |
| Typical Traffic Noise Peak | ~1000 | Hz | Frequency commonly cited for road traffic noise. |
| SC Element Dimensions | 0.05 x 0.1 | m | Width x Height of basic rectangular SC element. |
| SC Wall Thickness | 3 | mm | Wall thickness of hollow rectangular tubes. |
| Resonator Slit Size 1 (fr ~ 930 Hz) | 0.003 | m | Slit size used to tune Helmholtz Resonator. |
| Resonator Slit Size 2 (fr ~ 1251 Hz) | 0.02 | m | Slit size used to tune Helmholtz Resonator. |
| Resonator Slit Size 3 (fr ~ 1270 Hz) | 0.025 | m | Slit size used to tune Helmholtz Resonator. |
| Array Configuration (Final) | 3 rows x 11 columns | N/A | Total scatterers in the final SC window design. |
Key Methodologies
Section titled âKey MethodologiesâThe following is an ordered summary of the design and validation steps utilized in the research:
- 3D Numerical Modeling: All acoustic performance simulations were executed using 3D models with time-harmonic analysis in Comsol software.
- Geometry Optimization: Initial studies evaluated four scatterer shapes (Rectangular, Diamond, Semi-Circle) to determine optimal geometric band gap formation, confirming rectangular shapes offer the highest TL.
- Array Pattern Refinement: Simulations tested three staggering patterns (Non-staggered, 50% Staggered, Fully Staggered). The fully staggered pattern was selected due to its superior performance in shifting maximum TL to the lower frequency range (< 1700 Hz).
- Low-Frequency Mitigation Integration: Rectangular SCs were modified to integrate Helmholtz Resonators (HRs). HR performance was tuned using specific slit sizes (ranging from 0.003 m to 0.025 m) to target resonance frequencies (fr) around 1000 Hz.
- Array Size Scaling: The final design maximized Transmission Loss by increasing the number of SC elements in the direction perpendicular to sound propagation (x-direction), culminating in a 3 rows x 11 columns configuration.
- Experimental Validation Setup: A full-scale prototype (1.4 m wide) was fabricated and tested in a corridor environment. White noise was generated using a Bruel & Kjaer (B&K) Omni-source loudspeaker, and Sound Pressure Levels (SPLs) were recorded to determine the final Transmission Loss (TL).
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD provides the high-performance material science and engineering support necessary to replicate, scale, and dramatically enhance Sonic Crystal and acoustic barrier research, particularly where conventional materials limit performance, size, or integration capabilities.
Applicable Materials for Advanced Sonic Crystals
Section titled âApplicable Materials for Advanced Sonic CrystalsâTo achieve or exceed the acoustic performance documented in this study, especially for high-power, high-frequency, or active/integrated SC designs, high-performance MPCVD diamond is required.
| 6CCVD Material Recommendation | Required Property/Function | Technical Advantage Over Conventional Materials |
|---|---|---|
| High-Purity Polycrystalline Diamond (PCD) | Extreme Acoustic Stiffness (Sound Hardness) | Diamond has the highest Youngâs modulus (> 1000 GPa). This ensures the SC elements act as perfectly rigid, âsound hardâ boundaries, maximizing Bragg interference and band gap efficacy over a wide range of incident angles. |
| Optical Grade Single Crystal Diamond (SCD) | Precision Structure & Ultra-Low Surface Roughness | SCD wafers (Ra < 1 nm) minimize parasitic scattering losses at high frequencies, which is crucial for maximizing TL bandwidth. SCD offers unparalleled geometric uniformity. |
| Boron-Doped Diamond (BDD) Substrates | Integrated Active Acoustic Control | BDD allows for semiconductor behavior. It can be patterned to integrate micro-sensors, transducers, or heating elements (Ti/Pt/Au metalization) directly onto the SC surface for active, tunable resonance control in the Helmholtz elements. |
Customization Potential
Section titled âCustomization PotentialâThe optimization of SCs is highly dependent on precise geometry, lattice constant ($a$), and boundary conditions. 6CCVDâs capabilities directly address these stringent requirements:
- Custom Dimensions: While the paper used a 1.4 m window, SC elements are small (0.05 m wide). 6CCVD offers custom PCD plates up to 125 mm in diameter and substrates up to 10 mm thick. For specific SC shapes (rectangular, diamond), we utilize precision laser cutting services to dice complex geometries with micron-level accuracy.
- Thickness Control: 6CCVD guarantees extremely tight tolerance on diamond thickness, providing SCD and PCD material from 0.1 ”m up to 500 ”m for resonators or plates requiring ultra-precise acoustical mass density and resonance characteristics.
- Integrated Functionality: For next-generation SC windows requiring active tuning or sensing capabilities, 6CCVD provides full in-house metalization using stacks of Au, Pt, Ti, and W. This enables the integration of heating films or piezoelectric components necessary for active phononic crystal applications.
- Global Logistics: We ensure reliable delivery of custom diamond materials worldwide, with DDU as the default shipping method and DDP available upon request, supporting international research teams.
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house PhD material science team specializes in connecting fundamental acoustic and phononic requirements with optimal diamond properties. We can assist researchers and technical engineers with material selection, geometry analysis, and processing parameters for projects requiring high-performance passive or active acoustic mitigation or resonant structure design.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Four sets of numerical models were created to study the eïŹects of shapes, staggering patterns, Helmholtz resonators and array conïŹgurations on the acoustical performance of sonic crystals (SCs) in order to design an eïŹcient SC window to mitigate the traïŹc noise level at a room in a student hostel of NUS. Rectangular SCs consistently obtained highest transmission loss for frequencies ranging from 300 Hz to 3000 Hz compared to diamond and semi-circle SCs. Fully staggered pattern performed better than non-staggered and 50 % staggered patterns for frequencies below 1700 Hz. Helmholtz resonators were useful for enhancing low frequency noise mitigation. The prototype of the ïŹnal designed SC window was fabricated and tested in order to validate the simulation result. Generally, numerical and experimental results were in similar trends. Maximum transmission loss of the SC window was found to be occurred at 900 Hz which was about 18 dB.