摘要 :
Microphone arrays are commonly used to record spatial sound information. Several techniques, collectively known as harmonic beamforming, can be used to pick up sounds arriving from specific directions. This serves as a starting po...
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Microphone arrays are commonly used to record spatial sound information. Several techniques, collectively known as harmonic beamforming, can be used to pick up sounds arriving from specific directions. This serves as a starting point for spatial analysis and encoding methods, such as high-order Ambisonics. This research compares the effects that microphone positioning and calibration errors have in the performance of harmonic beamformers using spherical and cylindrical microphone arrays. The results show a comparable performance for both geometries, with cylindrical arrays being slightly more robust to imprecise microphone positioning and calibration.
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Although auditorium acoustics has been extensively studied from an audience perspective, studies of musicians' preferences on stage are far more limited. The present work tests and extends the hypothesis, suggested in recent studi...
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Although auditorium acoustics has been extensively studied from an audience perspective, studies of musicians' preferences on stage are far more limited. The present work tests and extends the hypothesis, suggested in recent studies by others, that the directional distribution of early reflected energy on stage is subjectively important to musicians. The paper presents results of subjective surveys completed by musicians of the Australian Chamber Orchestra immediately after performing in eight Australian purpose-built concert halls and compares these with complementary on-stage acoustic measurements undertaken in the same eight auditoria using a 32-channel spherical microphone array (Eigenmike). Spatial acoustic parameters are investigated together with the traditional omnidirectional parameters defined in the international standard for auditorium acoustics measurements, and a parameter is proposed that compares early energy arriving on stage from above relative to the sides. The parameter is shown to correlate well with musicians' subjective ratings, with generally lower values preferred. By contrast, standard omnidirectional parameters provided only limited insights into musician preferences for the eight auditorium stages surveyed.
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Sound field reproduction systems using loudspeaker arrays promise to convey three-dimensional sound information with very high accuracy. However, their formulation assumes free-field conditions which are not met when a listener is...
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Sound field reproduction systems using loudspeaker arrays promise to convey three-dimensional sound information with very high accuracy. However, their formulation assumes free-field conditions which are not met when a listener is present. Furthermore, evaluation of the physical accuracy in the results tells little about actual human perception. This research seeks to evaluate simple but important perception cues in an actual sound field reproduction system by taking dummy-head measurements inside a loudspeaker array.
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In this paper, we propose a design method for 3-D higher order ambisonics (3-D HOA) encoding matrices which offers the possibility to impose spatial stop-bands in the directivity patterns of all the spherical-harmonic audio channe...
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In this paper, we propose a design method for 3-D higher order ambisonics (3-D HOA) encoding matrices which offers the possibility to impose spatial stop-bands in the directivity patterns of all the spherical-harmonic audio channels while keeping the transformed audio channels still compatible with the 3-D HOA reproduction sound format. This might be useful as an encoding technique which suppresses interfering signals from specific directions in a 3-D HOA recording, or in other situations where certain spatial areas should be suppressed. The design method is adapted from recent work on the optimization of spherical microphone array beamforming. Using the proposed optimization method and the spherical harmonics mathematics framework, the relationship between several design factors, e.g., distortions in the desired response, the dynamic range of matrix coefficients, can be analyzed and illustrated as function of frequency. Based on the proposed optimization formulation, additional constraints can also be easily included and solved. In some of the formulations, the processing can be applied as a matrix multiplication to recorded spherical harmonics coefficients, that is, already encoded 3-D HOA format signals. The modified signals can be of the same or a lower spherical harmonics order. For a full optimization that gives a globally optimal solution, on the other hand, the processing must be applied to the microphone signals themselves. Numerical and experimental results validate the proposed method.
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摘要 :
Ambisonics is a technique for sound field synthesis and reproduction that has shown promising results for the presentation of three dimensional sound spaces. Sound fields are naturally represented by their expansions in terms of s...
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Ambisonics is a technique for sound field synthesis and reproduction that has shown promising results for the presentation of three dimensional sound spaces. Sound fields are naturally represented by their expansions in terms of spherical harmonic functions; such descriptions are known as Ambisonic encodings. Precise regeneration of the sound field from a set of spherical harmonic expansion coefficients requires a sufficient number of loudspeakers arranged in a regular layout. Decoding of Ambisonic recordings for their reproduction using a spherical, uniform loudspeaker array is not difficult. Nevertheless, evenly distributing a large number of loudspeakers is unfeasible in most scenarios. Irregular configurations are known to lead to ill-conditioned and singular re-encoding matrices. We propose a method to decompose high order Ambisonic recordings, based on the geometry of the target array, for accurate reproduction over irregular loudspeaker arrays.
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摘要 :
Ambisonics is a technique for sound field synthesis and reproduction that has shown promising results for the presentation of three dimensional sound spaces. Sound fields are naturally represented by their expansions in terms of s...
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Ambisonics is a technique for sound field synthesis and reproduction that has shown promising results for the presentation of three dimensional sound spaces. Sound fields are naturally represented by their expansions in terms of spherical harmonic functions; such descriptions are known as Ambisonic encodings. Precise regeneration of the sound field from a set of spherical harmonic expansion coefficients requires a sufficient number of loudspeakers arranged in a regular layout. Decoding of Ambisonic recordings for their reproduction using a spherical, uniform loudspeaker array is not difficult. Nevertheless, evenly distributing a large number of loudspeakers is unfeasible in most scenarios. Irregular configurations are known to lead to ill-conditioned and singular re-encoding matrices. We propose a method to decompose high order Ambisonic re cordings, based on the geometry of the target array, for accurate reproduction over irregular loudspeaker arrays.
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摘要 :
The science and art of Spatial Audio is concerned with the capture, production, transmission, and reproduction of an immersive sound experience. Recently, a new generation of spatial audio technology has been introduced that emplo...
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The science and art of Spatial Audio is concerned with the capture, production, transmission, and reproduction of an immersive sound experience. Recently, a new generation of spatial audio technology has been introduced that employs elevated and lowered loudspeakers and thus surpasses previous ‘surround sound’ technology without such speakers in terms of listener immersion and potential for spatial realism. In this context, the ISO/MPEG standardization group has started the MPEG-H 3D Audio development effort to facilitate high-quality bitrate-efficient production, transmission and reproduction of such immersive audio material. The underlying format is designed to provide universal means for carriage of channel-based, object-based and Higher Order Ambisonics based input. High quality reproduction is provided for many output formats from 22.2 and beyond down to 5.1, stereo and binaural reproduction—independently of the original encoding format, thus overcoming the incompatibility between various 3D formats. This paper provides an overview of the MPEG-H 3D Audio project and technology and an assessment of the system capabilities and performance.
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This paper reviews the current state of loudspeaker-based spatial sound reproduction methods from technical perspective as well as perceptual perspective. A nomenclature is developed that allows for a strict separation between the...
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This paper reviews the current state of loudspeaker-based spatial sound reproduction methods from technical perspective as well as perceptual perspective. A nomenclature is developed that allows for a strict separation between these two perspectives. The physical fundamentals, practical realization, and results from perceptual studies are discussed for a number of well-established and emerging reproduction techniques. Further, the paper outlines novel approaches to spatial sound evaluation in terms of perceived quality and provides a comparison of current approaches.
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