Comparison of Estimation Methods of Room Impulse Responses in Local Region Using Small Number of Microphones

Measurements of Room Impulse Responses (RIRs) at multiple points have been used in various acoustic techniques using the room acoustic characteristics. To obtain multi-point RIRs more efficiently, spatial interpolation of RIRs using plane wave decomposition method (PWDM) and equivalent source method (ESM) has been proposed. Recently, the estimation of RIRs from a small number of microphones using spatial and temporal sparsity has been studied. In this study, by using the measured RIRs, we compare the estimation accuracies of RIRs interpolation methods with a small number of fixed microphones. In particular, we consider the early and late reflections separately. The direct sound and early reflection components are represented using sparse ESM, and the late reflection component is represented using ESM or PWDM. And then, we solve the two types of optimization problems: individual optimization problems for early and late reflections decomposed by the arrival time and a single optimization problem for direct sound and all reflections. In the evaluation experiment, we measured the multiple RIRs by moving the linear microphone array and compare the measured and estimated RIRs.

PERFORMANCE ANALYSIS OF UWOC-4QAMOFDM SYSTEM WITH MIMO

The Underwater wireless optical communication (UWOC) may be a communication system that transmits data in an underwater environment using light. UWOC provides variety of advantages over the underwater radio frequency and acoustic techniques, including a broad unlicensed spectrum with high information bandwidth and low power requirements. A major purpose of this study is intended to grasp the simplest system architecture, practicality, and constancy of high-speed underwater optical communications thanks to various phenomena of propagation that affect the system's performance, like characterization of the channel, modulation techniques, and various noise sources caused by reflection, diffusing, and absorption. The Orthogonal Frequency Division Multiplexing (OFDM) accompanying Quadrature Amplitude Modulation (QAM) by employing Multi-Input-Multi-Output (MIMO) aims to boost data rate and range, which will benefit in the subsequent development of underwater optical communication. The system's performance was assessed in a high turbulent underwater channel and analyzed by changing the link range and the results are presented as comparisons between various data rates.

Probing syllable structure through acoustic measurements: case studies on American English and Jazani Arabic

Previous research has found that different syllabic (particularly simplex vs. complex onset) organisations have different temporal stability signatures in articulations – this observation is based entirely on articulatory measurements. In this article, we present the results of three production experiments which show that similar correlations between onset organisation and temporal stability metrics are observable in an analysis of acoustic measurements in American English and Jazani Arabic. The results that we present show stability across speakers and test items for both language groups, and highlight the possibility of using acoustic techniques to help to investigate the organisation of onsets in other languages.

Concentration and velocity measurements in experimental turbidity currents

<p>Turbidity currents are in the range of highly sediment concentrated flows, challenging traditional (i.e. optical and acoustic) techniques that aim to measure concentration and velocity quantities. In typical laboratory conditions, difficulties increase in the presence of highly non-uniform and unsteady flows. However, the measurement of those quantities along with a longitudinal profile is necessary to quantify and depict key mechanisms of mass and momentum transport, related to the mean and turbulent flow fields. The possible solutions often require prohibitive costs or resources. In this work, visual, acoustic, electrical, and statistical tools are tested. The aim of these tests is to find appropriate techniques and strategies for measuring concentration and velocity quantities in the broader research scope involving turbidity currents triggered by a 2D water jet. The outcomes will be applied in the quantification of turbidity currents with various boundary and initial conditions in a flume 4 m long, 2 m deep, and 22 cm wide. Additionally, the findings can potentially be transferred to other laboratory applications involving turbidity currents or other types of sediment-laden flows.</p><p>Acknowledgements: CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, a Foundation within the Ministry of Education in Brazil), grant number 88881.174820/2018-01.</p>