A Beamformer to Play with Wall Reflections: The Icosahedral Loudspeaker

Zotter, Franz; Zaunschirm, Markus; Frank, Matthias; Kronlachner, Matthias

doi:10.1162/comj_a_00429

Cited by 17 publications

(20 citation statements)

References 18 publications

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“…Firstly, auralized signals were encoded using the ambiX encoder, then converted using ambiX converter, and lastly filtered according to [10] using mcfx convolver. This yields twenty-channel audio files used as conditions for the experiment.…”

Section: Methodsmentioning

confidence: 99%

“…In addition to Laitinen's work, our paper establishes models of the hereby achieved auditory distance using simple acoustical measures. In extension to our previous study presented at DAFx [9], this article also includes the results of a second experiment using (v) the icosahedral loudspeaker (IKO), with a more elaborate third-order beampattern control [10] to synthesize the various beampatterns in a room.…”

Section: Introductionmentioning

confidence: 99%

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Auditory Distance Control Using a Variable-Directivity Loudspeaker

et al. 2017

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Abstract:The directivity of a sound source in a room influences the D/R ratio and thus the auditory distance. This study proposes various third-order beampattern pattern designs for a precise control of the D/R ratio. A comprehensive experimental study is conducted to investigate the hereby achieved effect on the auditory distance. Our first experiment auralizes the directivity variations using a virtual directional sound source in a virtual room using playback by a 24-channel loudspeaker ring. The experiment moreover shows the influence of room, source-listener distance, signal, and additional single-channel reverberation on the auditory distance. We verify the practical applicability of all the proposed beampattern pattern designs in a second experiment using a variable-directivity sound source in a real room. Predictions of experimental results are made with high accuracy, using room acoustical measures that typically predict the apparent source width.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Auditory Distance Control Using a Variable-Directivity Loudspeaker

et al. 2017

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“…If this is accomplished, the acoustic radiation can be modeled and equalized by the spherical cap model, cf. [6,15,25,26]. Cap model.…”

Section: Higher-order Compact Spherical Loudspeaker Arrays and Ikomentioning

confidence: 99%

“…6.6) qualitatively differs by a factor k. Practical implementation of radiation control filters and their regularization is therefore quite similar to radial filters of spherical microphone arrays. There are three main differences, as explained in [15]:…”

Section: Directivity Controlmentioning

confidence: 99%

Compact Spherical Loudspeaker Arrays

Zotter

Frank

2019

Ambisonics

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This chapter introduces auditory objects that can be created by adjustabledirectivity sources in rooms. After showing basic positioning properties in distance and direction, we describe physical first-and higher-order spherical loudspeaker arrays and their control, such as the loudspeaker cubes or the icosahedral loudspeaker (IKO). Not only static auditory objects, but such traversing space by their timevarying beam forming are considered here. Signal dependency and different practical setups are discussed and briefly analyzed. This young Ambisonic technology brings new means of expression to sound reinforcement, electroacoustic or computer music. While surrounding Ambisonic loudspeaker arrays play sound from outside the listening area into the audience, compact spherical loudspeaker arrays play sound into the room from a single position. Directivity adjustable in orientation and shape can be used to steer sound beams in order to excite wall reflections in the given, acoustic environment. The directional shapes and orientations of such beams are all controlled by-guess what-Ambisonic signals. Despite the huge practical difference, both applications do not only share the spherical harmonics that lend their shapes to Ambisonic signals: The control of radiating sound beams employs nearly the same model-or measurement-based radial steering filters as those of compact higher-order Ambisonic microphones. The works of Warusfel [3], Kassakian [4], Avizienis [5], Zotter [6, 7], Pomberger [8], Pollow [9], Mattioli Pasqual [10] established the electroacoustic background technology required to describe compact spherical loudspeaker arrays built with electrodynamic transducers. The early works on auditory objects were written by Schmeder [11], Sharma, Frank, and Zotter [2, 12, 13]. And some contemporary results were found in the project "Orchestrating the Space by Icosahedral Loudspeaker" (OSIL) between 2015 and 2018 [14-19].

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“…Moreover, Ambisonic signals of different orders are differently loud, so also diffuse-field equalization of the E measure is desirable in every band. To fulfill the above constraints, we propose to use the following set of FIR filter responses as given in [26,27], that are modified by a filter bank employing diffuse-field normalized max-r E -weights in separate frequency bands b = 0, . .…”

Section: Loudness-normalized Sub-band Side-lobe Suppressionmentioning

confidence: 99%

Higher-Order Ambisonic Microphones and the Wave Equation (Linear, Lossless)

Zotter

Frank

2019

Ambisonics

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… a turning point has been the design of HOA microphones, opening an exciting experimental field in terms of real 3D sound field recording … Jérôme Daniel [1] at Ambisonics Symposium 2009.Abstract Unlike pressure-gradient transducers, single-transducer microphones with higher-order directivity apparently turned out to be difficult to manufacture at reasonable audio quality. Therefore nowadays, higher-order Ambisonic recording with compact devices is based on compact spherical arrays of pressure transducers. To prepare for higher-order Ambisonic recording based on arrays, we first need a model of the sound pressure that the individual transducers of such an array would receive in an arbitrary surrounding sound field. The lossless, linear wave equation is the most suitable model to describe how sound propagates when the sound field is composed of surrounding sound sources. Fundamentally, the wave equation models sound propagation by how small packages of air react (i) when being expanded or compressed by a change of the internal pressure, and to (ii) directional differences in the outside pressure by starting to move. Based there upon, the inhomogeneous solutions of the wave equation describe how an entire free sound field builds up if being excited by an omnidirectional sound source, as a simplified model of an arbitrary physical source, such as a loudspeaker, human talker, or musical instrument. After adressing these basics, the chapter shows a way to get Ambisonic signals of high spatial and timbral quality from the array signals, considering the necessary diffusefield equalization, side-lobe suppression, and trade off between spatial resolution and low-frequeny noise boost. The chapter concludes with application examples.Gary Elko and Jens Meyer are the well-known inventors of the first commercially available compact spherical microphone array that is able to record higher-order Ambisonics [2], the Eigenmike. There are several inspiring scientific works with

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A Beamformer to Play with Wall Reflections: The Icosahedral Loudspeaker

Cited by 17 publications

References 18 publications

Auditory Distance Control Using a Variable-Directivity Loudspeaker

Auditory Distance Control Using a Variable-Directivity Loudspeaker

Compact Spherical Loudspeaker Arrays

Higher-Order Ambisonic Microphones and the Wave Equation (Linear, Lossless)

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