1,721,002 research outputs found
Acoustic Source Localization with Distributed Asynchronous Microphone Networks
No full textWe propose a method for localizing an acoustic source with distributed microphone networks. Time Differences of Arrival (TDOAs) of signals pertaining the same sensor are estimated through Generalized Cross-Correlation. After a TDOA filtering stage that discards measurements that are potentially unreliable, source localization is performed by minimizing a fourth-order polynomial that combines hyperbolic constraints from multiple sensors. The algorithm turns to exhibit a significantly lower computational cost compared with state-of-the-art techniques, while retaining an excellent localization accuracy in fairly reverberant conditions
Exact Localization of Planar Acoustic Reflectors in Three-Dimensional Geometries
No full textIn this paper we propose a methodology for localizing acoustic planar reflectors in a 3D geometry, using acoustic measurements acquired by a set of microphones. An acoustic source emitting a known signal is placed close to the wall to be identified, and is used for estimating the source-to-microphone impulse responses. In a preliminary step, such estimates are employed for localizing the source. After that, the Times Of Arrival (TOAs) associated to the first order reflective paths are extracted from the impulse responses and converted into quadratic constraints (ellipsoids) acting on the reflective plane. The constraints are then collected into a cost function, whose exact minimization leads to the searched plane. A theoretical analysis is performed for predicting the impact of measurement errors on the estimation. Moreover, experimental results in a real meeting room prove the effectiveness of the method
Estimation of the radiation pattern of a violin during the performance using plenacoustic methods
No full textA Psychoacoustic-Based Analysis of the Impact of Pre-Echoes and Post-Echoes in Soundfield Rendering Applications
No full textIn this paper we propose two metrics for the evaluation of the impact of pre-echoes and post-echoes on theperceived quality in soundfield rendering applications. These metrics are derived from psychoacoustic-basedconsiderations, in particular the masking effect, well known in the literature of perceptual coding. Themeasurement is accomplished through a virtual microphone array that samples the soundfield on acircumference. The soundfield within the circle is estimated by means of the circular harmonic decomposition. As a result, space-time impulse responses of the rendering system are obtained, which are then analyzed through the masking curve to extract the pre- and post-echoes metrics. A comparison between experimentaland simulative results, conducted using the same setup, allows to discriminate the impact of the adopted rendering engine and of the non-idealities of the real system (environment and loudspeakers) on pre- andpost-echoes
A room-compensated virtual surround system exploiting early reflections in a reverberant room
Full text linkIn this paper we propose a novel methodology for rendering a surround sound in a prescribed area using a loudspeaker array, which exploits the early reflections on the walls of the room. With respect to the state of the art, the proposed technique is able to take advantage of the knowledge of the acoustic scene (i.e. room geometry and reflective properties of the walls) in order to reduce undesired wall reflections. Simulative results show that the use of room compensation enables an improved accuracy of the virtual surround
Wave-based and Geometric Representations of Sound Fields
No full textThe two main approaches for the description of sound
fields are methods derived from solutions of the wave
equation and geometric methods based on analogies to ray
optics. Their mathematical representations are reviewed
and it is shown that representations by projective geometry
and descriptions by Fourier acoustics lead to similar parametric representations of sound fields
Distributed 3D source localization from 2D DOA measurements using multiple linear arrays
Full text linkThis manuscript addresses the problem of 3D source localization from direction of arrivals (DOAs) in wireless acoustic sensor networks. In this context, multiple sensors measure the DOA of the source, and a central node combines the measurements to yield the source location estimate. Traditional approaches require 3D DOA measurements; that is, each sensor estimates the azimuth and elevation of the source by means of a microphone array, typically in a planar or spherical configuration. The proposed methodology aims at reducing the hardware and computational costs by combining measurements related to 2D DOAs estimated from linear arrays arbitrarily displaced in the 3D space. Each sensor measures the DOA in the plane containing the array and the source. Measurements are then translated into an equivalent planar geometry, in which a set of coplanar equivalent arrays observe the source preserving the original DOAs. This formulation is exploited to define a cost function, whose minimization leads to the source location estimation. An extensive simulation campaign validates the proposed approach and compares its accuracy with state-of-the-art methodologies
Dictionary-based Equivalent Source Method for Near-Field Acoustic Holography
Full text linkIn this paper, we propose a modification of the standard Equivalent Source Method (ESM) for Near-Field Acoustic Holography (NAH). As in EMS, we aim at modeling the acoustic pressure radiated from a vibrating object, and its surface velocity, as the joint effect of a set of equivalent sources located within or close to the object itself. The estimation of the equivalent source strengths (weigths) comes from the solution of a highly ill-conditioned problem. Rather than solving this problem in the least-squares sense, we exploit the 3D model of the vibrating object, along with a rough estimate of its physical parameters, to restrict the space of the solutions. More specifically, we make use of Finite Element Analysis for populating a compressed dictionary of possible equivalent source weights. NAH is then approached by seeking a sparse linear combination of the entries of the dictionary. Experiments carried on a public database prove the effectiveness of the proposed technique, especially when the number of available microphones is limited, and in the presence of a significant level of measurement noise
Localization of virtual acoustic sources based on the Hough transform for sound field rendering applications
No full textVisibility-Based Beam Tracing for Soundfield Rendering
No full textIn this paper we present a visibility-based beam tracing solution for the simulation of the acoustics of environment that makes use of a projective geometry representation. More specifically, projective geometry turns out to be useful for the precomputation of the visibility among all the reflectors in the environment. The simulation engine has a straightforward application in the rendering of the acoustics of virtual environments using loudspeaker arrays. More specifically, the acoustic wavefield is conceived as a superposition of acoustic beams, whose parameters (i.e. origin, orientation and aperture) are computed using the fast beam tracing methodology presented here. This information is processed by the rendering engine to compute spatial filters to be applied to the loudspeakers within the array. Simulative results show that an accurate simulation of the acoustic wavefield can be obtained using this approach
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