Acoustic Response of a Thin Poroelastic Plate

Abstract: The Helmholtz integral equation formulation is used to produce the solution for the sound field reflected from an infinite, thin, porous, elastic plate. The effect of an air cavity behind the plate is considered. A parametric study is performed to predict the effect of variations in microscopic and structural parameters of the poroelastic plate

A frequency domain finite element solver for acoustic simulations of 3D rooms with microperforated panel absorbers

Microperforated panel (MPP) absorbers, which provide broadband sound absorption without the use of fibrous materials, have favorable material properties that support recyclability, flexibility of design, hygiene demands, and cleaning. Many earlier studies have specifically examined the development of absorbers themselves. However, to use the absorption performance of MPP absorbers sufficiently in room acoustic applications, it is beneficial to develop accurate prediction methods of sound fields in rooms with MPP absorbers. Such methods are expected to be useful for room acoustics design and absorber design tools. This study constructs a frequency domain finite element (FE) solver for acoustic simulations of a practical sized room with MPP absorbers. Then the accuracy and effectiveness are evaluated. In the FE solver, spatial domains are discretized by fourth-order accurate FEs in terms of dispersion error, and MPP absorbers are modeled using first-order hexahedral limp MPP elements that can deal with sound propagation in the backing structure of absorbers. First, the accuracy of present FE solver is demonstrated using impedance tube problems in comparison with conventional second-order accurate FEs. Results show higher convergence of solutions for the present FE solver. Then, exploration of an iterative solver for efficient multi-frequency analyses reveals that the recently developed CSQMOR is a faster and more stable solver. Finally, comparison with a conventional surface impedance model based on a locally reacting assumption confirms the effectiveness of present FE solver by presenting the importance of dealing with the incident angle dependence of reactance of a rigid-backed air cavity in the modeling of single-leaf MPP absorbers

A note on the acoustic environment in a usually quiet residential area after the ‘state of emergency’ declaration due to COVID-19 pandemic in Japan was lifted: supplementary survey results in post-emergency situations

In a preceding report (UCL Open: Environment, 2020;1;6), an example of results on changes in the acoustic environment from a local-scale survey in a quiet residential area during and after the ‘state of emergency’ due to COVID-19 pandemic in Japan is presented: the noise level was 1–2 dBA lower during the state of emergency, which is smaller than reported from large cities. This note presents the results of a follow-up survey in the same area to provide some more examples to gain an insight into the acoustic environment in this area. In this note, the measurement results of noise levels in June 2020, a few weeks after the cancellation of the state of emergency, are mainly reported. As the results are almost the same as those from during the state of emergency, we can infer that either the noise level was reduced in June to a level that was almost the same as that during the state of emergency, or the noise level after its cancellation in May was possibly higher than usual. In either case, the change in noise level was small, and it was difficult to conclude which case was true