In the laboratory measurement of the sound transmission loss of platelike building elements, a specimen mounted between coupled rooms causes the so-called niche effect. Normally a specimen is mounted inside an aperture in a thick wall, whereas in a special case where a specimen is mounted flush with the wall, a projecting box frame is additionally installed outside the opening. Firstly, the measurements of a glass pane with the two types of niche are numerically modeled by vibro-acoustic simulation, and the niche effect is examined while changing the niche depth and specimen position. As a result, it is revealed that the effect of the projecting niche is generally smaller than that of the recessing niche. Secondly, regarding the cross-sectional shape of the recessing niche, the smaller effect of the staggered niche specified in ISO 10140 is validated by comparison with that of a flat niche. Additionally, the incidence angle dependence of the niche effect is clarified.
In order to predict the equivalent continuous A-weighted sound pressure level (LAeq) of road traffic noise in areas facing roads, knowledge of the insertion loss of buildings against road traffic noise is needed. The authors previously proposed formula F2012 for predicting the insertion loss of detached houses against road traffic noise using a point sound source model. F2012 is applicable to the evaluation of the Environmental Quality Standards for Noise in Japan (EQS). F2012 is composed of four factors: direct sound Edir, reflections Eref, first diffractions Edif,1, and others Edif,2. However, it is not easy to find the values of the parameters for Eref and Edif,1 in spite of their smaller sound energies than Edir and Edif,2. A simple calculation is essential for the evaluation of EQS. Therefore, a simplification of F2012 is examined and the simplified formula F2012* is proposed in this paper. In addition, a means of simplifying the computation of F2012* is examined.
An extended energy integral equation method has been developed for precise predictions of noise propagation in and around a multi-room building surrounded by other buildings. In this method, all energy flows between boundary elements of the calculation model are obtained by solving equations considering multiple reflections, multiple diffractions and sound transmission. In order to improve the precision of the method, the calculation of first reflections is separated from the calculation of multiple reflections, and the first reflections are calculated by the approximated method derived from the wave theory. This method is applied to the calculation of sounds transmitted through small openings. Predictions using these methods corresponded well with measurements from actual sound fields.
This paper presents the solution for the continuous space-time spectral element method (CSTSEM) based on Chebyshev polynomials for the acoustic wave equation. Acoustic wave propagation in various dimensions is simulated using quadrilateral, hexahedral, and tesseract elements. The convergence is studied for 1+1-dimensional wave propagation. The extended 2+1- and 3+1-dimensional wave equations are also numerically solved by CSTSEM and the dispersion characteristics are investigated. A fixed-ω (ω is the angular frequency) method is proposed for computing the dispersion of space-time coupled methods. CSTSEM is verified as a simple, practical isotropic algorithm with low dispersion and high accuracy.