Dolby Laboratories Licensing Corporation

Sennheiser Electronic Gmbh & Co Kg

Thomson Licensing

Dolby International Ab

Alexander Krüger

Sven Kordon

Johannes Boehm

Johann-Markus Batke

Peter Jax

Alexander Nowak

Renato Pellegrini

Eugen Rasumow

Marios Athineos

Microphone arrays comprise several microphone capsules, the outputs of which being electronically combined for directional recording of sound. The directional and frequency properties of the microphone array depend on the number and positions of the microphone array. In order to obtain the smallest possible microphone array with only few microphone capsules, which, however, has an essentially uniform directional and frequency dependence over a speech frequency range, is scalable and robust against small incorrect positioning of the capsules, fifteen or twenty-one microphone capsules (K-K, K-K) are arranged on a carrier such that they lie on three similar branches, each with the same number of microphone capsules, which are rotated against each other by 120&#xb0;. Each of the microphone capsules lies on a corner of a triangle of a grid in a flat isometric coordinate system with three axes rotated by 120&#xb0; against each other and forming the grid of equilateral triangles.

Microphone array

For certain application cases, such as e.g., in a sports stadium, a microphone array having a particularly high directivity in the vertical direction and a high, yet in wide limits adjustable directivity in horizontal direction is provided. The microphone array has a plurality of microphones whose output signals are combined into at least one common output signal. The microphones are directional microphones with a preferred direction of high sensitivity and arranged substantially in one plane on a circle or segment of a circle, such that each microphone has a different direction of high directivity. For each of the microphones, the preferred direction of high sensitivity is substantially orthogonal to the circle or segment of the circle. A common output signal of the microphone array is obtained by beamforming. The microphone array has an adjustable preferred direction of high sensitivity, wherein the common output signal comprises the sound recorded from this adjustable direction.

In order for a microphone array to capture sound emanating from a moving object whose exact position is unknown at the time of arrival of the sound signal, a method for controlling the microphone array comprises steps of receiving position information that includes a position (p) and a velocity of the moving object from a tracking system, receiving a plurality of microphone signals that comprise sound of a sound event emanating from the moving object from a plurality of microphone capsules, calculating a directional characteristic from the plurality of microphone signals, wherein the directional characteristic is based on beamforming according to the position information and wherein an audio output signal is generated that includes the sound from a preferred direction of high sensitivity, and providing the audio output signal at an output. A beam width or opening angle (&#x3b1;) of the directional characteristic varies over time and depends on the velocity of the moving object, wherein a higher velocity of the moving object results in a larger beam width or larger opening angle respectively.

Method for controlling a microphone array and device for controlling a microphone array

A method and apparatus for decompressing a Higher Order Ambisonics (HOA) signal representation is disclosed. The apparatus includes an input interface that receives an encoded directional signal and an encoded ambient signal and an audio decoder that perceptually decodes the encoded directional signal and encoded ambient signal to produce a decoded directional signal and a decoded ambient signal, respectively. The apparatus further includes an extractor for obtaining side information related to the directional signal and an inverse transformer for converting the decoded ambient signal from a spatial domain to an HOA domain representation of the ambient signal. The apparatus also includes a synthesizer for recomposing a Higher Order Ambisonics (HOA) signal from the HOA domain representation of the ambient signal and the decoded directional signal. The side information includes a direction of the directional signal selected from a set of uniformly spaced directions.

Method and apparatus for compressing and decompressing a higher order ambisonics signal representation

A method for encoding multi-channel HOA audio signals for noise reduction comprises steps of decorrelating the channels using an inverse adaptive DSHT, the inverse adaptive DSHT comprising a rotation operation and an inverse DSHT, with the rotation operation rotating the spatial sampling grid of the iDSHT, perceptually encoding each of the decorrelated channels, encoding rotation information, the rotation information comprising parameters defining said rotation operation, and transmitting or storing the perceptually encoded audio channels and the encoded rotation information.

Methods and apparatus for encoding and decoding multi-channel HOA audio signals

Higher Order Ambisonics (HOA) represents a complete sound field in the vicinity of a sweet spot, independent of loudspeaker set-up. The high spatial resolution requires a high number of HOA coefficients. In the invention, dominant sound directions are estimated and the HOA signal representation is decomposed into dominant directional signals in time domain and related direction information, and an ambient component in HOA domain, followed by compression of the ambient component by reducing its order. The reduced-order ambient component is transformed to the spatial domain, and is perceptually coded together with the directional signals. At receiver side, the encoded directional signals and the order-reduced encoded ambient component are perceptually decompressed, the perceptually decompressed ambient signals are transformed to an HOA domain representation of reduced order, followed by order extension. The total HOA representation is recomposed from the directional signals, the corresponding direction information, and the original-order ambient HOA component.

In Higher Order Ambisonics, a problem is the tracking of time variant directions of dominant sound sources. The following processing is carried out: from a current time frame of HOA coefficients, estimating a directional power distribution of dominant sound sources, from said directional power distribution and from an a-priori probability function for dominant sound source directions, computing an a-posteriori probability function for said dominant sound source directions, depending on said a-posteriori probability function and on dominant sound source directions for the previous time frame, searching and assigning dominant sound source directions for said current time frame of said HOA coefficients.

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Hannover, Germany

Alexander Krüger