Sound zone control is posed as an optimization problem where finite impulse response control filters are jointly optimized for low transmit power, while maintaining a sufficiently high ...signal-to-interference-plus-noise ratio (SINR) in all zones. This problem statement in particular allows the consideration of sound zone control under the additional influence of external noise, which is rarely taken into account and indeed necessitates an alternative problem statement. In addition, the spectral characteristics of the audio signals are taken into account, both for the transmit power minimization and computing the SINR. The optimization problem is shown to be solved optimally by semidefinite relaxation, but the computational cost is high. An alternate method is proposed, inspired by a duality between transmit and receive beamforming commonly exploited in digital communications. A virtual receive optimization problem for sound zone control is derived, and it is shown to have the same optimal solution as the original transmit optimization problem. The receive optimization problem is solved efficiently through a fixed point iteration algorithm. The two proposed methods are compared against acoustic contrast control in a simulated reverberant environment, where it is shown that the proposed methods require less transmit power to produce similar SINRs.
Time-domain spatial active noise control (ANC) algorithms based on kernel interpolation of a sound field are proposed. Spatial ANC aims to suppress a primary noise field in a region by synthesizing ...an anti-noise field using secondary loudspeakers. In contrast to the multipoint pressure control by conventional ANC methods, it is necessary to estimate a sound field from microphone measurements at discrete positions. A promising approach is the kernel-interpolation-based spatial ANC method, which allows for flexible array configurations. However, most of the current methods are formulated only in the frequency domain, which cannot handle broadband noise with straightforward implementation. We formulate two time-domain spatial ANC algorithms based on kernel interpolation using a spatial interpolation filter defined by the kernel function. Numerical simulation results indicate that our filtered-x least-mean-square-based algorithms are effective for reducing nonstationary broadband noise in a region, as compared with multipoint pressure control.
An active noise control (ANC) method to reduce noise over a region in space based on kernel interpolation of sound field is proposed. Current methods of spatial ANC are largely based on spherical or ...circular harmonic expansion of the sound field, where the geometry of the error microphone array is restricted to a simple one such as a sphere or circle. We instead apply the kernel interpolation method, which allows for the estimation of a sound field in a continuous region with flexible array configurations. The interpolation scheme is used to derive adaptive filtering algorithms for minimizing the acoustic potential energy inside a target region. A practical time-domain algorithm is also developed together with its computationally efficient block-based equivalent. We conduct experiments to investigate the achievable level of noise reduction in a two-dimensional free space, as well as adaptive broadband noise control in a three-dimensional reverberant space. The experimental results indicated that the proposed method outperforms the multipoint-pressure-control-based method in terms of regional noise reduction.
A sound zone control method is proposed, based on the frequency domain variable span trade-off filter (VAST). Existing VAST methods optimizes the sound field at a set of discrete points, while the ...proposed method uses kernel interpolation to instead optimize the sound field over a continuous region. When the loudspeaker positions are known, the performance can be improved further by applying a directional weighting to the interpolation procedure. The proposed method is evaluated by simulating broadband sound in a reverberant environment, focusing on the case when microphone placement is restricted. The proposed method with directional weighting outperforms the pointwise VAST over the full bandwidth of the signal, and the proposed method without directional weighting outperforms the pointwise VAST at low frequencies.
The canonical algorithm for active noise control is the filtered-x least mean squares (FxLMS) algorithm. In the multichannel case, as the number of loudspeakers and microphones increases, the ...algorithm becomes very computationally costly. The dominant computational cost stems from a large number of linear convolutions with long impulse responses. In this paper a multichannel FxLMS algorithm is derived which makes use of and adaptively identifies a low-rank decomposition of the desired impulse responses. The low-rank decomposition can be used to implement a low-cost convolution, leading to an overall reduction in computational cost. This method does not add any latency, unlike frequency-domain approaches, which is important for broadband noise reduction. It is demonstrated through simulations that the proposed algorithm also provides similar or better noise reduction performance compared to the conventional FxLMS.
A new impulse response (IR) dataset called "MeshRIR" is introduced. Currently available datasets usually include IRs at an array of microphones from several source positions under various room ...conditions, which are basically designed for evaluating speech enhancement and distant speech recognition methods. On the other hand, methods of estimating or controlling spatial sound fields have been extensively investigated in recent years; however, the current IR datasets are not applicable to validating and comparing these methods because of the low spatial resolution of measurement points. MeshRIR consists of IRs measured at positions obtained by finely discretizing a spatial region. Two subdatasets are currently available: one consists of IRs in a three-dimensional cuboidal region from a single source, and the other consists of IRs in a two-dimensional square region from an array of 32 sources. Therefore, MeshRIR is suitable for evaluating sound field analysis and synthesis methods. This dataset is freely available at https://sh01k.github.io/MeshRIR/ with some codes of sample applications.
Existing sound zone control methods can in principle be used for spatial audio, but faithful reproduction of a spatial sound scene is difficult, and current sound zone control methods do not allow ...for easy combination with state-of-the-art sound field reproduction methods. An alternative sound zone control problem statement is considered, where sound field reproduction is considered a separate process which generates loudspeaker signals representing the desired signal. The task is then to modify those signals such that the sound field in the dark zones is suppressed while the bright zone is preserved. A general problem statement is constructed, and solved using common assumptions of linearity and a cost function based on expected square Euclidian distance. The result is a simple algorithm that decouples the sound zone control and sound field reproduction steps. Under certain conditions the proposed method is equiv-alent to the conventional sound zone control method pressure matching. However, the proposed method can be easily applied in a wider range of situations, for example when the sound field reproduction is considerably complex, or when the desired sound field is unknown. The effectiveness of the method is demonstrated in a simulated reverberant environment applied to channel-based surround sound.
A new impulse response (IR) dataset called "MeshRIR" is introduced. Currently available datasets usually include IRs at an array of microphones from several source positions under various room ...conditions, which are basically designed for evaluating speech enhancement and distant speech recognition methods. On the other hand, methods of estimating or controlling spatial sound fields have been extensively investigated in recent years; however, the current IR datasets are not applicable to validating and comparing these methods because of the low spatial resolution of measurement points. MeshRIR consists of IRs measured at positions obtained by finely discretizing a spatial region. Two subdatasets are currently available: one consists of IRs in a three-dimensional cuboidal region from a single source, and the other consists of IRs in a two-dimensional square region from an array of 32 sources. Therefore, MeshRIR is suitable for evaluating sound field analysis and synthesis methods. This dataset is freely available at https://sh01k.github.io/MeshRIR/ with some codes of sample applications.
In this work we explore online secondary path modelling (SPM) in the context of spatial active noise control (ANC). Specifically, we are interested in the reduction of broadband noise over a ...three-dimensional region, without restrictions on microphone and loudspeaker array placement. As spatial ANC generally requires many channels, both ANC and SPM methods must have low computational cost. The SPM methods are intended to be used with a specific spatial ANC algorithm based on kernel interpolation. By incorporating SPM, the spatial ANC method is enabled to operate under timevarying secondary paths. Four SPM methods are considered in detail, of which three are based on the auxiliary noise technique. Descriptions of the algorithms are presented for the multichannel case, in addition to block-based implementations taking advantage of the fast Fourier transform to drastically reduce computational cost. Impulse responses to simulate a soundfield are recorded using a programmable robot arm. The algorithms are evaluated through simulations to show their respective strengths and weaknesses. It is found that the auxiliary noise based SPM methods have good convergence properties for both control filter and secondary path estimate, although the auxiliary noise’s degrading effect on the residual noise leads to a similar total noise reduction as the auxiliary noise free method. For all algorithms, the noise control performance worsens, and the convergence time increases by more than an order of magnitude, compared to when the secondary paths are known. It is verified that the kernel interpolation based spatial ANC method successfully reduces noise over a region even when used with online SPM.
I detta projekt undersöks sekundärvägsmodellering för spatial aktiv brusreducering. Fokus ligger på minskning av brus över en tredimensionell region, för metoder utan några restriktioner när det gäller mikrofon- och högtalarplacering. Efterssom spatial brusreducering generellt kräver många kanaler, behöver både sekundärvägsmodellering samt brusreducering ha mycket låg beräkningskostnad. Metoderna för sekundärvägsmodellering är menade att användas tillsammans med en specifik spatial brusreduceringsalgoritm baserad på kärninterpolation. Genom att inkludera sekundärvägsmodellering kan den spatiala brusreduceringsmetoden operera även då sekundärvägarna är tidsvarierande. Fyra metoder för sekundärvägsmodellering är undersökta i detalj, tre av vilka är baserade på auxiliärbrusprincipen. Dessa algoritmer är beskrivna för multikanalsfallet, tillsammans med blockbaserade implementationer som utnyttjar den snabba Fouriertransformen för att drastiskt minska sina beräkningskostader. Impulssvar som kan användas för att simulera ett ljudfält är inspelade med hjälp av en programmerbar robotarm. Algoritmerna är utvärderade genom simuleringar för att visa deras respektive styrkor och svagheter. Experimenten visade att de algoritmer som använder sig av auxiliärbrus har bra konvergenskaraktäristik för både kontrollfilter och sekundärvägsestimat. Däremot, på grund av auxiliärbrusets negativa inverkan på residualbruset i rummet, är den totala brusreduceringen snarlik det den auxiliärbrusfria metoden ger. För alla algoritmer blir brusreduceringen försämrad och konvergenstiden ökad med mer än en storleksordning när sekundärvägsmodellering används, jämfört med när sekundärvägarna är kända. Det verifierades också att den spatiala brusreduceringsmetoden baserad på kärninterpolation kan reducera brus över en region även när den används tillsammans med sekundärvägsmodellering.
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