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The acoustic performance of the ducted Helmholtz resonator (HR) system is analyzed theoretically and numerically. The periodic HR array could provide a wider noise attenuation band due to the coupling of the Bragg reflection and the HR’s resonance. However, the transmission loss achieved by a periodic HR array is mainly dependent on the number of HRs, which restricted by the available space in the longitudinal direction of the duct. The full distance along the longitudinal direction of the duct for HR’s installation is sometimes unavailable in practical applications. Only several pieces of the duct may be available for the installation. It is therefore that this paper concentrates on the acoustic performance of a HR array consisting of several periodic parts. The transfer matrix method and the Bragg theory are used to investigate wave propagation in the duct. The theoretical prediction results show good agreement with the Finite Element Method (FEM) simulation results. The present study provides a practical way in noise control application of ventilation ductwork system by utilizing the advantage of periodicity with the limitation of available completed installation length for HRs.

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The Helmholtz resonator (hereafter resonator) is qualified as a silencer with a narrow noise attenuation band at its designed resonance frequency. Combining several resonators in line is a possible way to produce a broader noise attenuation band. This paper focuses on improving the noise attenuation performance of a ductresonator system at low frequency. Two types of periodic duct-resonator system are analyzed theoretically and numerically: a duct-resonator system with identical resonators and a modified duct-resonator system with periodic two-resonator arrays. The planar wave theory and the transfer matrix method are used to investigate wave propagation in the duct-resonator system. The theoretical prediction results yield satisfactory agreement with the Finite Element Method simulation results. The results indicate that both the periodic duct-resonator system and the modified duct-resonator system can broaden the noise attenuation band. Furthermore, the proposed modified duct-resonator system in this paper contributes to a relatively broader noise attenuation band than the periodic duct-resonator system. The modified duct-resonator system provides a useful method for the design of such a system, in order to obtain a relatively broadband noise attenuation.

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Building Information Modelling (BIM) technology has been widely used in the construction industry in recent years. However, to date, it still cannot sufficiently meet the requirements of construction practitioners in terms of the layout design of floor tiles. Recently, the BIM-based Parametric Design (PD) platform has presented considerable potential in automatically generating and optimizing floor tile layout design. In this paper, we propose a workflow to generate and optimize the layout design of floor tiles globally. To develop the workflow, we first formalize the design algorithm of floor tiles according to the trade know-how cutting and planning rules. Then, we combine the design algorithm with an evolutionary algorithm (EA) to generate and optimize the layout design for floor tiles automatically while minimizing material wastage. A prototype system is established in the ArchiCAD (BIM) and Grasshopper (PD platform) software. An apartment room tiling layout is used to demonstrate the feasibility and effectiveness of the proposed approach. Compared with the existing design methods, the proposed approach (1) reduces the material waste rate by 14.58% and 11.46%; and (2) improves the calculation efficiency and reduces the required computation time by 17.3 s to 50.0 s. Moreover, this research improves the existing design algorithm, enabling the BIM- and PD-based approaches to be used reliably in optimizing floor tile planning with arc-shaped boundaries. The outcomes are summarized in order to provide valuable insights in terms of floor tile waste reduction for further sustainable construction practice.

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Helmholtz resonators (HR) are widely used in aero-engine systems for noise reduction. By connecting a pair of HRs in series (neck-cavity-neck-cavity), a dual HRs system is formed. This study investigated the influence of neck length, cavity volume and flow Mach number on the noise attenuation performance of a dual HRs system. A three-dimensional numerical simulation was performed to calculate the transmission loss results. The transmission loss (TL) results indicated that the second neck length can influence the second resonance frequency and TL max. Changing the cavity volume significantly influences the noise attenuation ability under lower flow rate conditions compared to higher flow rate conditions. The flow Mach number had a more significant impact on the first TL peak than on the second TL peak. This study shows the relationship between the geometric parameters, grazing flow and noise attenuation performance of a dual HRs system and could provide guidance in designing suitable dual HRs for aero-engine systems.