Efficient binaural rendering of spherical microphone array data by linear filtering

AbstractHigh-quality rendering of spatial sound fields in real-time is becoming increasingly important with the steadily growing interest in virtual and augmented reality technologies. Typically, a spherical microphone array (SMA) is used to capture a spatial sound field. The captured sound field can be reproduced over headphones in real-time using binaural rendering, virtually placing a single listener in the sound field. Common methods for binaural rendering first spatially encode the sound field by transforming it to the spherical harmonics domain and then decode the sound field binaurally by combining it with head-related transfer functions (HRTFs). However, these rendering methods are computationally demanding, especially for high-order SMAs, and require implementing quite sophisticated real-time signal processing. This paper presents a computationally more efficient method for real-time binaural rendering of SMA signals by linear filtering. The proposed method allows representing any common rendering chain as a set of precomputed finite impulse response filters, which are then applied to the SMA signals in real-time using fast convolution to produce the binaural signals. Results of the technical evaluation show that the presented approach is equivalent to conventional rendering methods while being computationally less demanding and easier to implement using any real-time convolution system. However, the lower computational complexity goes along with lower flexibility. On the one hand, encoding and decoding are no longer decoupled, and on the other hand, sound field transformations in the SH domain can no longer be performed. Consequently, in the proposed method, a filter set must be precomputed and stored for each possible head orientation of the listener, leading to higher memory requirements than the conventional methods. As such, the approach is particularly well suited for efficient real-time binaural rendering of SMA signals in a fixed setup where usually a limited range of head orientations is sufficient, such as live concert streaming or VR teleconferencing.

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SCaLAr – A surrounding spherical cap loudspeaker array for flexible generation and evaluation of virtual acoustic environments

Acta Acustica ◽

10.1051/aacus/2020014 ◽

2020 ◽

Vol 4 (5) ◽

pp. 19

Author(s):

Florian Pausch ◽

Gottfried Behler ◽

Janina Fels

Keyword(s):

Performance Metrics ◽

Transfer Functions ◽

Finite Impulse Response ◽

Signal To Noise Ratio ◽

Signal Transmission ◽

Sound Field ◽

Low Noise ◽

High Signal ◽

Spherical Cap ◽

Channel Separation

Introduction: Surrounding spherical loudspeaker arrays facilitate the application of various spatial audio reproduction methods and can be used for a broad range of acoustic measurements and perceptual evaluations. Methods: Installed in an anechoic chamber, the design and implementation of such an array of 68 coaxial loudspeakers, sampling a spherical cap with a radius of 1.35 m on an equal-area grid, is presented. A network-based audio backbone enables low-latency signal transmission with low-noise amplifiers providing a high signal-to-noise ratio. To address batch-to-batch variations, the loudspeaker transfer functions were equalised by individually designed 512-taps finite impulse response filters. Time delays and corresponding level adjustments further helped to minimise radial mounting imperfections. Results: The equalised loudspeaker transfer functions measured under ideal conditions and when mounted, their directivity patterns, and in-situ background noise levels satisfy key criteria towards applicability. Advantages and shortcomings of the selected decoders for panning-based techniques, as well as the influence of loudspeaker positioning errors, are analysed in terms of simulated performance metrics. An evaluation of the achievable channel separation allows deriving recommendations of feasible subset layouts for loudspeaker-based binaural reproduction. Conclusion: The combination of electroacoustic properties, simulated sound field synthesis performance and measured channel separation classifies the system as suitable for its target applications.

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Interactive real-time auralization of airborne sound insulation in buildings

Acta Acustica ◽

10.1051/aacus/2021013 ◽

2021 ◽

Vol 5 ◽

pp. 19

Author(s):

Imran Muhammad ◽

Anne Heimes ◽

Michael Vorländer

Keyword(s):

Real Time ◽

Transfer Functions ◽

Traffic Noise ◽

General Scheme ◽

Sound Field ◽

Human Perception ◽

Mean Free Path ◽

Sound Insulation ◽

Noise Effects ◽

Building Elements

Sound insulation auralization can be used as valuable tool to study the perceptual aspects of sound transmission in built environments for assessment of noise effects on people. It may help to further develop guidelines for building constructions. One advanced goal of real-time sound insulation auralization is to appropriately reproduce the condition of noise effects on the human perception and cognitive performance in dynamic and interactive situations. These effects depend on the kind of noise signal (i.e. speech, music, traffic noise, etc.) and on the context. This paper introduces a sound insulation auralization model. The sound insulation filters are constructed for virtual buildings with respect to complex sound propagation effects for indoor and outdoor sound sources. The approach considers the source room sound field with direct and diffuse components along with source directivity and position. The transfer functions are subdivided into patches from the source room to the receiver room, which also covers composite building elements, thus providing more detail to the actual building situations. Furthermore, the receiving room acoustics includes the reverberation of the room based on its mean free path, absorption and binaural transfer functions between its radiating walls elements and the listener. This more exact approach of sound insulation model agrees reasonably well with the ISO standard (i.e. diffuse field theory) under standard settings. It is also shown that the sound field significantly influences the transmitted energies via building elements depending on the directivity and position of the source. The proposed method is validated as a general scheme and includes more details for real-time auralization in specific situations especially in the cases where the simplified diffuse sound field approach fails. It is capable to be used in interactive Virtual Reality (VR) systems, which opens new opportunities for psychoacoustics research in noise effects on human.

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Dynamic Binaural Rendering: The Advantage of Virtual Artificial Heads over Conventional Ones for Localization with Speech Signals

Applied Sciences ◽

10.3390/app11156793 ◽

2021 ◽

Vol 11 (15) ◽

pp. 6793

Author(s):

Mina Fallahi ◽

Martin Hansen ◽

Simon Doclo ◽

Steven van de Par ◽

Dirk Püschel ◽

...

Keyword(s):

Transfer Functions ◽

Microphone Array ◽

Head Tracking ◽

Impulse Responses ◽

Sound Fields ◽

Listening Tests ◽

Spatial Sound ◽

Localization Performance ◽

Complex Valued ◽

Positive Effect

As an alternative to conventional artificial heads, a virtual artificial head (VAH), i.e., a microphone array-based filter-and-sum beamformer, can be used to create binaural renderings of spatial sound fields. In contrast to conventional artificial heads, a VAH enables one to individualize the binaural renderings and to incorporate head tracking. This can be achieved by applying complex-valued spectral weights—calculated using individual head related transfer functions (HRTFs) for each listener and for different head orientations—to the microphone signals of the VAH. In this study, these spectral weights were applied to measured room impulse responses in an anechoic room to synthesize individual binaural room impulse responses (BRIRs). In the first part of the paper, the results of localizing virtual sources generated with individually synthesized BRIRs and measured BRIRs using a conventional artificial head, for different head orientations, were assessed in comparison with real sources. Convincing localization performances could be achieved for virtual sources generated with both individually synthesized and measured non-individual BRIRs with respect to azimuth and externalization. In the second part of the paper, the results of localizing virtual sources were compared in two listening tests, with and without head tracking. The positive effect of head tracking on the virtual source localization performance confirmed a major advantage of the VAH over conventional artificial heads.

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Sound Field Projection System using Optical See-Through Head Mounted Display

INTER-NOISE and NOISE-CON Congress and Conference Proceedings ◽

10.3397/in-2021-1797 ◽

2021 ◽

Vol 263 (5) ◽

pp. 1267-1274

Author(s):

Atsuto Inoue ◽

Wataru Teraoka ◽

Yasuhiro Oikawa ◽

Takahiro Satou ◽

Yasuyuki Iwane ◽

...

Keyword(s):

Real Time ◽

Virtual Worlds ◽

Transmission Control Protocol ◽

Microphone Array ◽

Sound Field ◽

Optical Methods ◽

Beam Forming ◽

Projection System ◽

Visualization System ◽

Head Mounted Display

There are various ways to grasp the spatial and temporal structures of sound field. Sound field visualization is an effective technique to understand spatial sound information. For example, acoustical holography, optical methods, and beam-forming have been proposed and studied. In recent years, augmented reality (AR) technology has rapidly developed and is now more familiar. Many sensors, display devices, and ICT technologies have been implemented in AR equipment, which enable interaction between real and virtual worlds. In this paper, we propose an AR display system, which displays the results obtained by the beam-forming method. The system consists of 16ch microphone array, real-time sound field visualization system and optical see-through head mounted display (OST-HMD). Real-time sound field visualization system analyses sound signals recorded by 16ch microphone array by beam-forming method. Processed sound pressures data are sent to OST-HMD by using transmission control protocol (TCP), and colormap is projected on real world. Settings property of real-time sound field visualization system can be changed by using virtual user interface (UI) and TCP. In addition, multi-users can experience the system by sharing sound pressures and settings property data. Using this system, users wearing OST-HMD can observe sound field information intuitively.

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Analysis of effects of spherical microphone array physical parameters using simulations

Facta universitatis - series Electronics and Energetics ◽

10.2298/fuee1302107c ◽

2013 ◽

Vol 26 (2) ◽

pp. 107-119

Author(s):

Dejan Ciric ◽

Ana Djordjevic ◽

Marko Licanin

Keyword(s):

Sound Source ◽

Microphone Array ◽

Sound Field ◽

Embedded Software ◽

Microphone Arrays ◽

Field Analysis ◽

Physical Parameters ◽

Spatial Sound ◽

Spherical Microphone Arrays

Spherical microphone arrays are used for spatial sound field analysis. Although there are commercially available products, they are not the most suitable for research due to their price and working limits of the embedded software. In those cases it is more convenient to build an own prototype in a lab. In this paper, the analysis of the effects of the physical parameters of a spherical microphone array is presented. The observed parameters are radius of the sphere, distance from the sound source and distribution of the microphone elements points over the sphere. The obtained results provide useful inputs for building a spherical microphone array for the desired applications.

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Electrical Probing and Surface Imaging of Deep Sub-Micron Integrated Circuits

ISTFA 1999: Conference Proceedings from the 25th International Symposium for Testing and Failure Analysis ◽

10.31399/asm.cp.istfa1999p0039 ◽

1999 ◽

Author(s):

Kenneth Krieg ◽

Richard Qi ◽

Douglas Thomson ◽

Greg Bridges

Keyword(s):

High Resolution ◽

Integrated Circuits ◽

Real Time ◽

High Speed ◽

Time Signal ◽

Surface Imaging ◽

Atomic Force ◽

Submicron Structures ◽

High Resolution Images ◽

Capacitive Loading

Abstract A contact probing system for surface imaging and real-time signal measurement of deep sub-micron integrated circuits is discussed. The probe fits on a standard probe-station and utilizes a conductive atomic force microscope tip to rapidly measure the surface topography and acquire real-time highfrequency signals from features as small as 0.18 micron. The micromachined probe structure minimizes parasitic coupling and the probe achieves a bandwidth greater than 3 GHz, with a capacitive loading of less than 120 fF. High-resolution images of submicron structures and waveforms acquired from high-speed devices are presented.

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