Superdirective spherical radiator

Butler, John L.; Ehrlich, Stanley L.

doi:10.1121/1.381457

Cited by 30 publications

(7 citation statements)

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“…[4][5][6][7]. More recently, spherical arrays with independently controlled transducers were used as sources featuring adjustable directivity [8][9][10][11][12]. Spatial computer music applied such sources to produce focused beams of sound, e.g.…”

Section: Introductionmentioning

confidence: 99%

Investigation of Auditory Objects Caused by Directional Sound Sources in Rooms

Zotter

Frank

2015

Acta Phys. Pol. A

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The auditory impression of sound sources is strongly influenced by the room, which, e.g., determines the apparent source width. What is more, typical sources are not omnidirectional, which also makes their orientation a strong influence. This influence, however, has only been investigated a little, although it can even change the perceived location of the source. To provide more insight, we performed extensive listening experiments inside our anechoic laboratory that is equipped with a 24-channel loudspeaker playback to simulate both the directional source and the room. The directional source is described by two frequency-independent 3rd order directivity designs in 36 different orientations, and the room is simulated by the two-dimensional 1st and 2nd order image source method. Results of the experiment indicate that, in most cases, the auditory location can be determined by the loudest unmasked acoustic reflection path. This allows to explain the primary direction perceived with an astonishingly simple model including precedence effects.

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Section: Introductionmentioning

confidence: 99%

Investigation of Auditory Objects Caused by Directional Sound Sources in Rooms

Zotter

Frank

2015

Acta Phys. Pol. A

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“…Denoting the different loading factors by γ m M−1 m=0 and using the original eigenvalues λ m instead of the sorted onesλ m for convenience, we can modify (21) as…”

Section: The Lvf Methodsmentioning

confidence: 99%

“…In [19] and [20], it was proved that the maximum directivity factor (DF) of an M-sensor linear array can reach M 2 at its endfire direction. It was also proved that the maximum DF of a spherical array is N 2 with N being the mode number [21].…”

Section: Introductionmentioning

confidence: 98%

Design of robust high-order superdirectivity for circular arrays with sensor gain and phase errors

Wang

Yang

et al. 2017

EURASIP J. Adv. Signal Process.

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Though the high-order superdirectivity theory proposed in recent years is attractive, it is hard to implement in practice due to its poor robustness to small random array errors. Hence, in this paper, we present two robust designs of high-order superdirectivity for circular arrays with gain and phase errors. Firstly, we study on the sensitivity function of the high-order superdirectivity and give an alternative solution for a robust superdirective beamformer based on sensitivity function constraint. This method could achieve an arbitrary compromise between directivity and robustness, so it is more flexible and applicable than the existing higher-order truncation method. Although it does not improve on computational complexity or performance with respect to the second-order cone programming obviously, it could lay the foundation for the following robust design method. Then, considering the fact that different eigenbeams correspond to different eigenvalues, we study the method of diagonal loading with variable factors in detail, and further improve the performance of the former sensitivity function constrained method by loading variable factors to different eigenbeams, which results in better performance and greater flexibility in making a compromise. We also show that this proposed loading variable factors method can achieve an equivalent result to the higher-order truncation method by setting proper factors. Simulation results demonstrate the robustness and effectiveness of the above two methods, especially the performance improvement of the loading variable factors method.

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“…In addition to this, an array synthesis technique has been given by Thompson. 3 An alternative approach, which depends on the superposition of radiation modes, was presented by Butler and Ehrlich 4 for the case of a spherical array. Although these approaches can provide a high directivity index 5 (DI) and very narrow beam from a small source or array, the reproduction and efficiency of the device can suffer from large phase variations over the array or the higher order modes of the spherical radiator.…”

Section: Introductionmentioning

confidence: 99%

The modal projector

Butler

Butler²,

Butler³

2011

The Journal of the Acoustical Society of America

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The superposition of acoustical modes radiated from a transducer can provide directionality from a compact projector. This paper presents the foundation, as well as examples, of piezoelectric ceramic, piezoelectric single crystal, and magnetostrictive versions of this "modal projector." Measured and analytical, as well as finite element analysis modeled, results show good agreement and establish this transducer as a viable source of intensity with the advantages of an improved directivity index, reducing the power needed from a compact source.

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Superdirective spherical radiator

Cited by 30 publications

References 0 publications

Investigation of Auditory Objects Caused by Directional Sound Sources in Rooms

Investigation of Auditory Objects Caused by Directional Sound Sources in Rooms

Design of robust high-order superdirectivity for circular arrays with sensor gain and phase errors

The modal projector

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