The room acoustic theory was established based on Sabine's reverberation theory. However, in Sabine's theory, the reverberation time does not reach zero, even if the absolute absorption condition is satisfied. This is a contradiction of Sabine's theory, and Eyring revised the reverberation theory to resolve this contradiction. In this paper, a theoretical framework for the consistent reverberation theory is presented. Using this framework, it was demonstrated that Eyring's theory has a contradiction between the sound energy density in the steady state and energy decay from the steady state, which is absent in Sabine's theory. Based on the proposed theoretical framework, Sabine's reverberation theory was revised using an approach that is different from that of Eyring. The reverberation time obtained using the revised theory was shorter than that obtained using Sabine's theory and longer than that obtained using Eyring's theory. Results of sound ray tracing simulations were in better agreement with the values calculated using the revised theory rather than those calculated using Sabine's and Eyring's theories.

The specific signal such as road traffic noise is measured in decibel scale and often contains the fuzziness due to several causes. Furthermore, there exists usually a background noise in addition to the specific signal. In this study, a Bayesian filter for estimating the specific signal, based on the observed data containing the fuzziness and the effects of a background noise with non-Gaussian type, is proposed. More specifically, the energy variables satisfying the additive property of the specific signal and background noise are first considered. Next, after introducing an expansion expression of the probability density function based on a log-normal distribution and a new type of membership function, which are suitable for the nonlinear relationship between the energy variable and the measurement in decibel scale, by applying probability measure of fuzzy events, a state estimation method is theoretically derived. The proposed theory is applied to the actual observation data of road traffic noise, and its usefulness is experimentally confirmed.

This study investigates acoustic differences between laughter and screaming in spontaneous dialog. First, three classification experiments, i.e., speaker-closed, speaker-open, and corpus-open experiments, demonstrate the acoustic discriminability of spontaneous laughter and screaming. The results of the speaker-closed experiment reveal that laughter and screams can be acoustically classified with high F-measures of 91.80% and 82.39%, respectively. The results of the speaker-open experiment reveal that the model exhibites 2.27% (laughter) and 2.45% (screams) lower F-measures than the speaker-closed experiment. In the corpus-open experiment, the model correctly classified laughter and screams with F-measures of 85.50% and 73.33%, respectively. Next, logistic regression analysis using feature selection is conducted to identify effective acoustic features for discriminating between laughter and screaming. The results reveal that although the acoustic features that effectively discriminate laughter from screams vary across corpora, the harmonics-to-noise ratio (HNR) can be used to discriminate them in both tested corpora. This applicability of the HNR suggests that the presence of an unvoiced vocal segment in laughter might influence discrimination between laughter and screaming.

This paper presents a proposal of sub-wavelength acoustic metasurface (AMS) sound absorbers, designated as MeAMS absorbers, with coupled-microslit resonators of gradually decreasing sizes in the respective component resonators. A MeAMS absorber can provide bandpass filter-shaped near-perfect absorption. The prediction theory of the present AMS absorbers is also proposed with two design methods to ascertain the dimensions of respective component resonators. The theory for AMS absorbers composed of single-microslit resonators is first verified with finite element method (FEM) simulation using thermoviscous boundary layer impedance boundary conditions. It is validated further for two 3D printed samples by an impedance tube measurement. Then, the theoretical predictability of absorption characteristics of MeAMS absorbers is discussed via FEM simulations and the impedance tube measurement for three 3D printed samples, revealing that the present theory provides a reasonable approximation of the absorption characteristics of MeAMS absorbers. Two one-third octave band near-perfect absorbers are also presented for practical applications.