Multizone Soundfield Research Articles

Vehicle Interior Multi-Zone Sound Field Reproduction with Uncertain Disturbance of Acoustic Transfer Function

Vehicle Interior Multi-Zone Sound Field Reproduction with Uncertain Disturbance of Acoustic Transfer Function

Multizone sound field reproduction using pressure matching with sparse equivalent source

Multizone sound field reproduction aims to create different acoustic environments in multiple spatial zones, allowing listeners to enjoy their individual sounds without being disturbed by sound from other zones. The conventional pressure matching method is used in practice to reproduce the desired sound field by minimizing the sound field error with a limited number of control points, whose reproduction performance decreases above the cutoff frequency. In this paper, a multizone sound field reproduction method based on a sparse equivalent source method is proposed to reproduce the sound field in the whole target region. The acoustic transfer function of each loudspeaker and the desired sound field are represented by the sparse equivalent sources. The whole target region is controlled by interpolating fine virtual control points within the region of the uncontrolled points, and the acoustic transfer functions between the virtual control points and the loudspeaker array are interpolated by the sparse equivalent sources. An optimization reproduction model with the objective of reproducing a desired sound field in the bright zone and constraining the acoustic energy in the dark zone is formulated to find the sparse loudspeaker weights. The simulation results and experimental results show that the proposed method achieves better performance than the conventional pressure matching method in free field and reverberant environments.

Stepwise-based optimizing approaches for arrangements of loudspeaker in multi-zone sound field reproduction

Stepwise-based optimizing approaches for arrangements of loudspeaker in multi-zone sound field reproduction

Multizone sound field reproduction based on equivalent source decomposition

Multizone sound field reproduction attempts to recreate a desired sound field on the bright zone and reduce sound field energy on the dark zone. Conventional pressure-matching based multizone reproduction method is only able to control sound pressures at limited number of measurement points on the bright zones which are equal to target sound field recording points number. The reproduction performance is strongly affected by the number of recording points. In this paper, a reproduction method based on the sparse plane wave decomposition method is proposed to improve the reproduction performance when the target sound field is generated by one or a small number of sources. The recorded target sound field is decomposed into a group of plane waves. Loudspeaker weights are calculated as a summation precalculated corresponding plane waves weights. A simulation is conducted in a room to verify the performance of the proposed method. Compared with the conventional method, the proposed method achieves better sound field reproduction accuracy on the bright zone and similar acoustic contrast performance.

Enhancing acoustic contrast in multi-zone sound field reproduction through optimization of loudspeaker arrangements

In this study, we propose a stepwise-based approach, predefined in descending order of source power, to optimize loudspeaker placement in multi-zone sound field reproduction systems. The aim is to enhance the acoustic contrast (AC) between acoustically bright and dark zones. The proposed method is benchmarked against two previously studied approaches: the Genetic Algorithm (GA) and the Greedy-based approach. Numerical simulations are conducted to evaluate and compare the performance of each method. Results demonstrate that the proposed method surpasses the Greedy-based approach in terms of AC, while offering performance comparable to the GA-based approach. Importantly, the proposed method exhibits lower computational complexity than the GA, suggesting a more practical solution for real-world applications.

A multizone sound field reproduction method based on modal domain analysis

Multizone sound field reproduction for synthesizing desired sound fields over multiple spatial zones has been widely studied. In the traditional multizone sound field reproduction modal domain method, the final loudspeaker weights required to reproduce the desired sound field are obtained by translating the optimal equivalent global modal domain coefficients, which is susceptible to the characteristics and location of the loudspeakers and reduces the reproduction performance. This paper investigates a multizone sound field reproduction in modal domain for directly obtaining the reproducing loudspeaker weights. The optimization model is formulated to the objective of reproducing a desired sound field within the bright zone and with constraints on acoustic energy in the dark zone. The loudspeaker weights for reproducing the desired sound field are solved by the CVX toolbox. The numerical simulation results indicate that the proposed method is superior to the acoustic contrast control method and the mode matching method in terms of the accuracy of the reproduction desired sound field in the bright zone and the acoustic contrast between the bright and dark zones.

Amplitude Matching for Multizone Sound Field Control

A multizone sound field control method, called amplitude matching, is proposed. The objective of amplitude matching is to synthesize a desired amplitude (or magnitude) distribution over a target region with multiple loudspeakers, whereas the phase distribution is arbitrary. Most of the current multizone sound field control methods are intended to synthesize a specific sound field including phase or to control acoustic potential energy inside the target region. In amplitude matching, a specific desired amplitude distribution can be set, ignoring sound propagation directions. Although the optimization problem of amplitude matching does not have a closed-form solution, our proposed algorithm based on the alternating direction method of multipliers (ADMM) allows us to accurately and efficiently synthesize the desired amplitude distribution. We also introduce the differential-norm penalty for a time-domain filter design with a small filter length. The experimental results indicated that the proposed method outperforms current multizone sound field control methods in terms of accuracy of the synthesized amplitude distribution.

A room impulse response database for multizone sound field reproduction (L).

This letter introduces a database of Room Impulse Responses (RIRs) measured in seven different rooms for multizone sound field reproduction research in various acoustic environments. A circular array of 60 loudspeakers was installed in each room, with two microphone arrays placed sequentially in five different zones inside the loudspeaker array. A total of 260 400 RIRs were measured to establish the database. As a demonstration application of the database for multizone sound field reproduction, simulations were performed on the pressure matching and acoustic contrast control methods to investigate how a system optimized with the RIRs measured in one room would perform in other rooms.

Evolutionary array optimization for multizone sound field reproduction.

Multizone sound field reproduction aims to generate personal sound zones in a shared space with multiple loudspeakers. Traditional multizone sound field reproduction methods have focused on optimizing the source strengths given a preset array configuration. Recently, however, various methods have explored optimization of the loudspeaker locations. These can be categorized into sparse regularization and iterative methods with existing studies based on numerical simulations and mostly aiming at single-zone sound field reproduction. In this paper, unique experiments compare the state-of-the-art loudspeaker placement optimization methods by selecting a smaller number of loudspeakers from the candidates uniformly placed along a circle. An evolutionary array optimization scheme is proposed and shown to outperform the best existing methods in terms of mean square error in the bright zone and acoustic contrast between the bright and dark zones at frequencies below 1 kHz. The proposed evolutionary optimization scheme is simple, flexible, and can be extended to broadband optimization and other cost functions.

A two-zone sound field reproduction based on the region energy control

Multizone sound field reproduction aims to create different acoustical environments in regions without physical isolation. For a real reproduction system, it is always expected to improve system performance and reduce measurement effort. In this paper, a two-zone sound field reproduction is investigated with a proposed region control method. Conventional multipoint method only controls sound field at limited number of measurement points. However, the proposed method tries to control the sound field energy over the whole region. Considering the system's diverse work environment, different interpolation methods are applied in the proposed method. Simulations are conducted under free field and reverberation condition in order to deeply compare with conventional method and another harmonic domain method. Simulation results show that the proposed method achieves better performance than the conventional multipoint method in free field and reverberant environment. On the other hand, the region control method proposed in this paper is free from microphone array geometry requirement, which means the method is more convenient for the practical application.

Comparative study of loudspeaker position optimization techniques for multizone sound field reproduction

Mutlizone sound field reproduction aims to generate personal sound zones in a shared space with multiple loudspeakers. Conventionally, loudspeakers are placed to form a regular pattern such as circular, arc or linear array, which are empirical rather than optimal mainly for the convenience of physical placement. Recently, several algorithms have been proposed to select a fixed number of loudspeaker locations from a large set of candidate positions, such as the sparse regularization (i.e. Lasso and Elastic Net) methods, the Constrained Match Pursuit (CMP) method, the Gram-Schmidt Orthogonalization (GSO) method etc. Most of these methods were investigated for single-zone rather than mulit-zone sound field reproduction based on the pressure matching techniques. This paper compares the performance of the state-of-the-art techniques for loudspeaker position optimization in a multizone sound field reproduction system in terms of reproduction error, acoustic contrast and array effort. Simulation results demonstrate that the CMP-LS method shows the best performance in terms of lower MSE and higher AC while the Lasso method needs the lowest AE.

An iterative approach to optimize loudspeaker placement for multi-zone sound field reproduction

Various array patterns, such as circular, linear, and arc-shaped arrays, have been used in multi-zone sound field reproduction, but most of them are based on empirical rather than judicious selection. This article proposes an iterative optimization method to select the loudspeaker positions from a large set of candidate locations. Both the number and locations of the loudspeakers can be designed with superior performance. Both single-frequency and broadband simulations based on the acoustic contrast control method are performed to validate the proposed scheme, and the performance of the optimized array is compared with that of an arc-shaped array and that of an array optimized with an existing method.

Multizone Sound Field Reproduction Based on Equivalent Source Method

In this paper, the two-zone sound field reproduction problem is investigated with a newly proposed method. The aim of the two-zone reproduction problem is to achieve sound field reproduction in the bright zone while keeping the sound field energy in the dark zone as low as possible. The main difference between the proposed method and the conventional method is that the sound field control in the dark zone is not limited to a small number of measurement points on the region boundary but to measurement points throughout the whole dark zone. For practical reasons, the whole region is discretized into a grid, and the grid selection method is also provided in this paper. Simulations are performed to compare the performances of the proposed and conventional methods with different virtual source directions, and a comparison of the robustness to the regularization parameter shows that the proposed method is less sensitive to the selection of the regularization parameter. Finally, an experiment is performed with a circular loudspeaker array in a real listening room. A quieter dark zone is achieved by the proposed method while keeping the reproduction error in the bright zone close to that of the conventional method, similar to the simulation results. These outcomes verify that the proposed method performs well in both free-field and reverberation environments.

Three-dimensional wave-domain acoustic contrast control using a circular loudspeaker array.

This paper proposes a three-dimensional wave-domain acoustic contrast control method to reproduce a multizone sound field using a circular loudspeaker array. In this method, sound field analysis is based on spherical harmonic decomposition, and the loudspeaker weights are obtained by maximizing the acoustic energy contrast between the predefined bright zone and dark zone. Simulation results show that the proposed method provides good multizone separation performance over a large spatial region and requires lower-order spherical harmonics, resulting in a much lower number of microphones required to measure the acoustic transfer functions.

Two-dimensional multizone sound field reproduction using a wave-domain method.

This paper addresses a two-dimensional multizone sound field reproduction approach using a wave-domain method. The desired sound fields in the bright and dark zones are described as orthogonal expansions of basis functions over the regions. The loudspeaker weights are obtained by maximizing the contrast among multiple zones in the wave domain. Simulation results demonstrate that compared with the conventional acoustic contrast control approach, the proposed method improves the level of acoustic contrast and array gain over the entire control region and is less sensitive to the selection of the regularization parameter.

Multizone Soundfield Reproduction With Privacy- and Quality-Based Speech Masking Filters

Reproducing zones of personal sound is a challenging signal processing problem that has garnered considerable research interest in recent years. We introduce in this work an extended method to multizone soundfield reproduction that overcomes issues with speech privacy and quality. Measures of speech intelligibility contrast (SIC) and speech quality are used as cost functions in an optimization of speech privacy and quality. Novel spatial and (temporal) frequency domain speech masker filter designs are proposed to accompany the optimization process. Spatial masking filters are designed using multizone soundfield algorithms that are dependent on the target speech multizone reproduction. Combinations of estimates of acoustic contrast and long term average speech spectra are proposed to provide equal masking influence on speech privacy and quality. Spatial aliasing specific to multizone soundfield reproduction geometry is further considered in analytically derived low-pass filters. Simulated and real-world experiments are conducted to verify the performance of the proposed method using semi-circular and linear loudspeaker arrays. Simulated implementations of the proposed method show that significant SIC and speech quality is achievable between zones. A range of perceptual evaluation of speech quality mean opinion scores that indicate good quality are obtained while at the same time providing confidential privacy as indicated by SIC. The simulations also show that the method is robust to variations in the speech, virtual source location, array geometry, and number of loudspeakers. Real-world experiments confirm the practicality of the proposed methods by showing that good quality and confidential privacy are achievable.

Analysis and control of multi-zone sound field reproduction using modal-domain approach.

Multi-zone sound control aims to reproduce multiple sound fields independently and simultaneously over different spatial regions within the same space. This paper investigates the multi-zone sound control problem formulated in the modal domain using the Lagrange cost function and provides a modal-domain analysis of the problem. The Lagrange cost function is formulated to represent a quadratic objective of reproducing a desired sound field within the bright zone and with constraints on sound energy in the dark zone and global region. A fundamental problem in multi-zone reproduction is interzone sound interference, where based on the geometry of the sound zones and the desired sound field within the bright zone the achievable reproduction performance is limited. The modal-domain Lagrangian solution demonstrates the intrinsic ill-posedness of the problem, based on which a parameter, the coefficient of realisability, is developed to evaluate the reproduction limitation. The proposed reproduction method is based on controlling the interference between sound zones and sound leakage outside the sound zones, resulting in a suitable compromise between good bright zone performance and satisfactory dark zone performance. The performance of the proposed design is demonstrated through numerical simulations of two-zone reproduction in free-field and in reverberant environments.

Theory and Design of Multizone Soundfield Reproduction Using Sparse Methods

Multizone soundfield reproduction over an extended spatial region is a challenging problem in acoustic signal processing. We introduce a method of reproducing a multizone soundfield within a desired region in reverberant environments. It is based on the identification of the acoustic transfer function (ATF) from the loudspeaker over the desired reproduction region using a limited number of microphone measurements. We assume that the soundfield is sparse in the domain of planewave decomposition and identify the ATF using sparse methods. The estimates of the ATFs are then used to derive the optimal least-squares solution for the loudspeaker filters that minimize the reproduction error over the entire reproduction region. Simulations confirm that the method leads to a significantly reduced number of required microphones for accurate multizone sound reproduction, while it also facilitates the reproduction over a wide frequency range. Practical experiments are used to verify the sparse planewave representation of the reverberant soundfield in a real-world listening environment.

Multi-zone Sound Field Control by the Inverse Approach in a Vehicle Interior

Multi-zone Sound Field Control by the Inverse Approach in a Vehicle Interior

112 自動車車室内におけるスマートサウンドスペースの適用とその効果(振動・騒音と人間)

The optimized individual sound environment is necessary to more than one people in the Smart Sound Space having the ability to support the activities of the people. In this research, multi-zone sound field control using multi-speaker in interior space of the car is researched. For the purpose of the evaluation for the multi-zone, the physiological reaction is evaluated using oxy-Hb by the optical topography (NIRS) and LF/HF based on RRJ of the electrocardiogram in order to achieve the separation of the space based on objective assessment. The effect for the SPL change of the music and car-navigation voice under the cruise noise is observed by the 12 subjects.