Spatial Acoustic Vector Based Sound Field Reproduction

Spatial sound field reproduction aims to recreate an immersive sound field over a spatial region. The existing sound pressure based approaches to spatial sound field reproduction focus on the accurate approximation of original sound pressure over space, which ignores the perceptual accuracy of the reproduced sound field. The acoustic vectors of particle velocity and sound intensity appear to be closely linked with human perception of sound localization in literature. Therefore, in this thesis, we explore the spatial distributions of the acoustic vectors, and seek to develop algorithms to perceptually reproduce the original sound field over a continuous spatial region based on the vectors. A theory of spatial acoustic vectors is first developed, where the spatial distributions of particle velocity and sound intensity are derived from sound pressure. To extract the desired sound pressure from a mixed sound field environment, a 3D sound field separation technique is also formulated. Based on this theory, a series of reproduction techniques are proposed to improve the perceptual performance. The outcomes resulting from this theory are: (i) derivation of a particle velocity assisted 3D sound field reproduction technique which allows for non-uniform loudspeaker geometry with a limited number of loudspeakers, (ii) design of particle velocity based mixed-source sound field translation technique for binaural reproduction that can provide sound field translation with good perceptual experience over a large space, (iii) derivation of an intensity matching technique that can reproduce the desired sound field in a spherical region by controlling the sound intensity on the surface of the region, and (iv) two intensity based multizone sound field reproduction algorithms that can reproduce the desired sound field over multiple spatial zones. Finally, these techniques are evaluated by comparing to the conventional approaches through numerical simulations and real-world experiments

Spatial sound intensity vectors in spherical harmonic domain

Sound intensity is a fundamental quantity describing acoustic wave fields and it contains both energy and directivity information. It is used in a variety of applications such as source localization, reproduction, and power measurement. Until now, intensity is defined at a point in space, however given sound propagates over space, knowing its spatial distribution could be more powerful. This paper formulates spatial sound intensity vectors in spherical harmonic domain such that the vectors contain energy and directivity information over continuous spatial regions. These representations are derived with finite sets of closed form coefficients enabling ease of implementation

3D Multizone Soundfield Reproduction in a Reverberant Environment Using Intensity Matching Method

Sound intensity is a good predictor of human perception of sound location, which can be controlled to provide impressive direction perception to humans in soundfield reproduction systems, especially when the loudspeakers are non-uniformly distributed. However, the previous works in this field are all constrained to a single sweet spot/spatial zone. We address this challenge and propose a multizone reproduction method for 3D soundfield in a reverberant room based on intensity matching. We develop spatial sound intensity expressions in a reververant room using spherical harmonic decomposition, and build a cost function to optimize sound intensity within multiple spatial zones. Finally, simulation results showing the performance are presented.This work is supported by ARC Linkage Grant No. LP160100379 and the China Scholarship Council with the Australian National Universit

Intensity Based Soundfield Reproduction over Multiple Sweet Spots Using an Irregular Loudspeaker Array

Intensity based soundfield reproduction methods are shown to provide impressive human perception of sound localization. However, most of the previous works in this domain either focus on a single sweet spot for the listener, or are constrained to a regular loudspeaker geometry, which is difficult to implement in real-world applications. This paper addresses both of the above challenges. We propose an intensity matching technique to optimally reproduce sound intensity at multiple sweet spots using an irregular loudspeaker array. The performance of the proposed method is evaluated by comparing it with the pressure and velocity matching method through numerical simulations and perceptual experiments. The results show that the proposed method has an improved performance.This work is supported by ARC Linkage Grant No. LP160100379 and the China Scholarship Council with the Australian National University

Exterior-interior 3D sound field separation using a planar array of differential microphones

Sound field separation using spherical microphone arrays was recently introduced and has many applications, however, it is inconvenient to implement in realistic environment. In this paper, we propose a solution to separate 3D interior and exterior sound field by using a planar array of differential microphones. The even coefficients and odd coefficients of sound fields are separated in two different ways due to the properties of associated Legendre functions. Simulation shows this practical geometry has a good performance on interior and exterior sound field separation in both noiseless and noisy environments. We also evaluate the reconstruction accuracy of separated sound fields on different spherical surfaces.This work is supported by Australian Research Council Discovery Grant DP180102375 and the China Scholarship Council with the Australian National Universit

Particle Velocity Assisted Three Dimensional Sound Field Reproduction Using a Modal-Domain Approach

In literature, particle velocity has been introduced to improve performance of spatial sound field reproduction systems. However, all existing work requires to have accurate particle velocity measurements at all of the discrete control points, which is difficult to obtain in real-world applications. In this work, we formulate continuous particle velocity expressions over space as a function of pressure coefficients in the modal domain that can be easily extracted by using a higher order microphone. The sound field within a target region is controlled by a weighted cost function we built to optimize the continuous particle velocity, as well as sound pressure, on the boundary of the region. In contrast to the conventional spatial sound field reproduction methods in the modal domain, the proposed method allows for non-uniform loudspeaker geometry with a limited number of loudspeakers, thus providing a flexible array arrangement. The performance of the proposed method is evaluated through numerical simulations in both a free field and a reverberant room. Finally, we prove the proposed method in an objective experiment with real-world measurements of room impulse response.This work is supported by ARC Discovery Grant No. DP180102375 and the China Scholarship Council with the Australian National University

Intensity Based Spatial Soundfield Reproduction Using an Irregular Loudspeaker Array

Sound intensity is an acoustic quantity closely linked with human perception of sound location, and it can be controlled to create a high level of realism to humans in soundfield reproduction systems. In this paper, we present an intensity matching technique to optimally reproduce sound intensity over a continuous spatial region using an irregular loudspeaker array. This avoids several known limitations in the previous works on intensity based soundfield reproduction, such as a single sweet spot for the listener and a regular loudspeaker geometry that is difficult to implement in real-world applications. In contrast to the previous works, the new technique uses a cost function we built to optimize sound intensity over space by exploiting spatial sound intensity distributions. The spatial sound intensity distribution is represented by spherical harmonic coefficients of sound pressure, which are widely used to describe a spatial soundfield. Compared to the conventional spatial soundfield reproduction method of pressure matching in the spherical harmonic domain and the HOA $max$-$r_E$ decoding method optimizing sound intensity at a single position, we show that the intensity matching technique has better overall performance with two different irregular loudspeaker layouts through simulations. The impact of microphone noise on reproduction performance is also assessed. Finally, we carry out perceptual localization experiments to validate the proposed method.This work is supported by ARC Discovery Grant No. DP180102375 and the China Scholarship Council with the Australian National University

Bio-Inspired PHM Model for Diagnostics of Faults in Power Transformers Using Dissolved Gas-in-Oil Data

Prognostics and Health Management (PHM) is an emerging technique which can improve the availability and efficiency of equipment. A series of related optimization of the PHM system has been achieved due to the growing need for lowering the cost of maintenance. The PHM system highly relies on data collected from its components. Based on the theory of machine learning, this paper proposes a bio-inspired PHM model based on a dissolved gas-in-oil dataset (DGA) to diagnose faults of transformes in power grids. Specifically, this model applies Bat algorithm (BA), a metaheuristic population-based algorithm, to optimize the structure of the Back-propagation neural network (BPNN). Furthermore, this paper proposes a modified Bat algorithm (MBA); here the chaos strategy is utilized to improve the random initialization process of BA in order to avoid falling into local optima. To prove that the proposed PHM model has better fault diagnostic performance than others, fitness and mean squared error (MSE) of Bat-BPNN are set as reference amounts to compare with other power grid PHM approaches including BPNN, Particle swarm optimization (PSO)-BPNN, as well as Genetic algorithm (GA)-BPNN. The experimental results show that the BA-BPNN model has increased the fault diagnosis accuracy from 77.14% to 97.14%, which is higher than other power transformer PHM models

Considering life-cycle environmental impacts and society's willingness for optimizing construction and demolition waste management fee : an empirical study of China

A large amount of construction waste is generated every year over the world. Many studies indicated that waste management fee is an effective approach that could minimize the generation of waste and maximize the diversion rate of landfills. However, there are limited number of studies conducted on determining the waste management fee for construction waste. This study proposes a method to optimize the construction waste management fee by considering life-cycle environmental impacts of construction waste and society's willingness to improving the management of construction waste. This contributes to the knowledge body of construction waste management by expand the current models from these aspects. The environmental impacts taxes are selected as the evaluation basis that avoided subjective consequences in previous models. This study provides a series of suggestions for construction waste management sector in China to determining construction waste management fee, based on the findings. It is suggested that the waste management fee for 1 ton of metal waste could be 60.42 yuan (about US$9.30), followed by wood waste 38.47 yuan (about US$5.92) and masonry waste 27.65 yuan (about US$4.25). The average waste management fee for unit comprehensive construction waste of all types of buildings could be 23.61 yuan/ton (about US$3.63/ton). The average waste management fee for unit construction area (1 m2) of all types of buildings is 0.81 yuan/m2 (about US$0.12 m2). The proposed method and suggestions could be helpful for waste policy makers as well as researchers for developing construction waste management fee schemes. It worth to mention that these proposed waste management fee would vary over time and regions, as any change of factors in the calculation models would result in a change of the final result. As the application of waste management fee would affect the attitudes and behaviors of stakeholders including the government departments, owners of landfills, collection and transportation parties, waste recycling parties, landfills parties and so on. The determination of waste management fee is a very complex issue and need to be solved via systematic approaches from different perspectives