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Sound pressure of a plane wave with a frequency of 2 kHz traveling downward, synthesized by WFS and NFC-HOA with different orders M. The black dots indicate active loudspeakers, open circles inactive loudspeakers. The sound pressure is normalized at the center of the loudspeaker array, higher values are clipped.
Source publication
Sound field synthesis methods like Wave Field Synthesis (WFS) and Near-Field Compensated Higher Order Ambisonics synthesize a sound field in an extended area surrounded by loudspeakers. Because of the limited number of applicable loudspeakers the synthesized sound field includes artifacts. This paper investigates the influence of these artifacts on...
Context in source publication
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... demonstrate some of the properties of WFS and NFC-HOA, assume the synthesis of a mono-frequency plane wave with a frequency of 2 kHz using a circular loudspeaker array with a radius of 1.5 m, employing 56 loudspeakers with a distance of 17 cm between them. Figure 1 shows the resulting sound pressure using WFS, NFC-HOA with a high order, and spatial band-limited NFC-HOA with M chosen as half the number of loudspeakers. The synthesized sound field in the case of WFS and NFC-HOA with M ¼ 112 is nearly identical, only the number of active loudspeakers differ between the two setups. ...
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Citations
... However, it cannot be excluded that artifacts such as coloration occur above the aliasing frequency and become more pronounced with self-motion [4]. Recent studies on the physical and perceptual limitations of 2D multichannel rendering methods have found that localization accuracy improves with increasing Ambisonics order, and that loworder Ambisonics can lead to splitting of perceived localization [5,6]. Huisman et al. [7] found that the differences in localization accuracy between higher orders of Ambisonics are small. ...
Virtual reality with multichannel audio playback is increasingly used in hearing aid research. The purpose of this study is to compare horizontal (2D) and periphonic (3D) rendering methods in terms of localization, minimum audible angle, and perceptual ratings related to spatial quality. Higher Order Ambisonics, Vector-Base Amplitude Panning, and Nearest Speaker Selection were used, with playback through 16, 29 and 45 speakers. The results show that an improvement in vertical localization can be obtained by using periphonic rendering instead of horizontal rendering. The perceptual advantage of periphonic rendering depends on the spatial complexity of the scene; it disappears in complex acoustic environments. Scenes with low acoustic complexity, such as a single primary sound source in a room, benefit from Nearest Speaker Selection rendering. For more complex scenes with multiple sound sources, such as a symphony orchestra in a concert hall with many primary sources, or traffic on a road with moving sources, horizontal rendering methods such as 2D Higher Order Ambisonics will provide similar or better performance.
... The circular array is composed of 56 loudspeakers arranged on a circle of 1.5 m of radius, with a distance between loudspeakers of 17 cm. This layout has been extensively used in the past for WFS research [6,15]. ...
... However, these still describe specific and discrete points in the environment. Additionally, their presentation binaurally over headphones or via techniques such as stereophony and higher-order ambisonics (HoA) over loudspeakers confines the listener to a smaller sweet spot-the area where spatial sound is accurately reproduced (Wierstorf et al., 2017). These drawbacks make it difficult for groups to collectively "walk" through and explore auralizations together. ...
... This method allows for accurate sound reproduction across larger listening areas below a calculable spatial aliasing frequency. In this relatively larger region, listeners are able to localize recreated sound sources with greater accuracy than with HoA or stereophonic methods (Wierstorf et al., 2017). ...
This paper proposes an experiential method for learning acoustics and consequences of room design through the rapid creation of audio-visual congruent walkable auralizations. An efficient method produces auralizations of acoustical landmarks using a two-dimensional ray-tracing algorithm and publicly available floor plans for a 128-channel wave-field synthesis system. Late reverberation parameters are calculated using additional volumetric data. Congruent visuals are produced using a web-based interface accessible via personal devices, which automatically formats for and transmits to the immersive display. Massive user-contributed online databases are harnessed through application programming interfaces, such as those offered by the Google Maps Platform, to provide near-instant access to innumerable locations. The approach allows the rapid sonic recreation of historical concert venues with adequate sound sources. Listeners can walk through these recreations over an extended user area (12 m × 10 m).
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... To the best of my knowledge, there are perceptual studies of first-order and higher-order ambisonics at central and off-center listening positions, but no systematic perceptual study at dynamic listening positions. For a 5th-order HOA, the best-achieved localization accuracy for a central listening position is 3 degrees using 12 loudspeakers with a circumradius of 3.86 m [30]. A lower-localization accuracy is expected in the case study, since only the 3rdorder HOA is used in the octophonic setup, with a circumradius of 5.94 m. ...
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... Plausible reproduction requires knowledge on how to create and design perceptually convincing representations of real or artificial spatial sound phenomena within the sweet area, cf. [13,[22][23][24][25][26][27][28]. Perceptual quality assessments on different reproduction methods on different array types are typically approached for simple virtual source types and audio scenes, often searching for correlations of technical quality measures with perceptual ones. ...
... For frequencies above the aliasing frequency HOA error is low in a central region that shrinks with frequency, whereas for WFS the error is usually significant everywhere (Using focused sources it is possible, however, to achieve a low error with WFS in this case 20 ). If the spacing is greater than head width, typically 0.17m, so that the alias frequency is less than the top of the ITD range, then the localisation performance of WFS is generally better than NFC-HOA outside the central region 19 . This is unsurprising considering that for each image source WFS driving energy is more localised on the array, and so produces less error outside the central region. ...
Sound fields can be encoded with a fixed number of signals, using microphones or panning functions. The sound field may later be reproduced approximately by decoding the signals to a loudspeaker array. The Stereo and Ambisonic systems provide examples. A framework is presented for addressing general questions about such encodings. The first problem considered is the conversion between encodings. The solution is applied to the decoding of scene encodings to a loudspeaker array. This is generalised to the decoding of $sub-scenes$ where the resolution is focused in an angular window. Within an object based audio framework such sub-scenes are useful for representing complex objects without using all the channels required for a full scene. The second problem considered is the compression of a scene encoding to a smaller encoding, from which the original can be reconstructed. The spatial distribution of compression error can be controlled.
Up to now, little attention is paid to the location where a sound is perceived as coming from. This is done because that part of the perceptual system that estimates the location of a sound source, and that which determines what is heard, work to a large extent independently of each other up to high levels of the auditory system. This chapter discusses what auditory information is used in human sound localization. It is shown that more than a dozen sources of information are used varying from the time and intensity differences with which a sound reaches both ears, to the Doppler effect and moving around. It turns out than none of these sources of information on its own is enough to accurately localize a sound in less than two dimensions. This implies that accurate localization can only be realized for sounds rich in information and by combining the information from various of these sources of information. A description is presented of how various sources of information are used to estimate the distance of the sound source from the listener and the direction where the sound comes from, i.e., the azimuth and the elevation. The role played by moving around is underscored. This chapter ends by showing that auditory localization is a very plastic system continuously adapting to changing situations.
Ansätze zur Schallfeldsynthese zielen darauf ab, ein gewünschtes Schallfeld zu erzeugen. Konventionell sind diese Ansätze physikalisch motiviert. Akustische Eigenschaften definieren das gewünschte Schallfeld. Auf die technische Umsetzung folgt eine wahrnehmungsbezogene Bewertung des Hörerlebnisses. Die psychoakustische Schallfeldsynthese, wie sie in diesem Kapitel vorgestellt wird, verfolgt ein anderes Paradigma. Hier bestimmen die psychoakustischen Eigenschaften das gewünschte Schallfeld. Dieses Paradigma erlaubt die Implementierung von Hörschwellen und Integrationszeiten des Gehörs in die Herleitung des Schallfeldsynthesekerns. Dies ermöglicht eine unhörbare Reduzierung der zeitlichen, räumlichen und spektralen Auflösung. Das Ergebnis ist ein natürliches, räumliches Hörerlebnis und eine präzise Schallquellenlokalisation für mehrere Hörer bei vergleichsweise geringem Rechenaufwand und unhörbaren Synthesefehlern.
