Adaptive Audio Limited

Electronics and Telecommunications Research Institute

University of Southampton

Huawei Technologies Co., Limited

Rolls-royce Corporation

The Secretary of State for Trade and Industry in Her Britannic Majesty's

Adaptive Control Limited

Philip Arthur Nelson

Hareo Hamada

Takashi Takeuchi

Stephen J Elliott

Ole Kirkeby

Filippo Fazi

Ian McGregor Stothers

Felipe Orduna-Bustamante

Kyeongok Kang

Kyeong Ok Kang

Jeong Il Seo

Jeongil Seo

Jae Hyoun Yoo

Min Cheol Shin

Simone Fontana

Jean-Luc Rioual

Ferdinando Olivieri

Filippo Maria Fazi

Michael J Fisher

A signal processor for a sound reproduction system which is arranged to perform processing of a sound recording so as to provide input signals for an array of distributed loudspeakers, such that the sound field generated by the loudspeakers results in cross-talk cancellation in respect of multiple listener positions at substantially all frequencies reproduced by the loudspeakers, and wherein the sound field so generated is an approximation of a sound field produced by an Optimal Source Distribution, OSD.

Sound reproduction

The disclosure relates to an apparatus for generating a sound field on the basis of an input audio signal. The apparatus comprises a plurality of transducers, wherein each transducer is configured to be driven by a transducer driving signal qof the respective transducer; a plurality of filters configured to generate for each transducer the transducer driving signal qof the respective transducer; and a control unit configured to provide or receive a first transducer driving signal vector qof dimension L such that the gradient of J(q;&#x3c8;) with respect to q is zero in (q;&#x3c8;), the control unit is further configured to provide a second transducer driving signal vector {tilde over (q)} of dimension L such that the gradient of the cost function J(q;&#x3c8;) with respect to q is [approximately] zero in ({tilde over (q)}; {tilde over (&#x3c8;)}), the control unit is configured to provide the second transducer driving signal vector {tilde over (q)}.

Apparatus and method for generating a sound field

A sound reproduction system includes an electro-acoustic transducer and a transducer driver for driving the electro-acoustic transducer. The transducer drive includes a filter which is configured to reproduce at a listener's location an approximation to the local sound field that would be present at the listener's ears in recording space, taking into account the characteristics and intended position of the electro-acoustic transducer relative to the listener's ears. The electro-acoustic transducer includes a first sound emitter which provides an intermediate sound emission channel, and second and third sound emitters providing respective left and right sound emission channels. The first sound emitter is located intermediate of second and third sound emitters. Higher frequencies from at least one of the second and third sound emitters are transmitted closer to the first sound emitter while lower frequencies are transmitted away from the first sound emitter.

Sound reproduction systems

Method and, apparatus for implementing the method, the method comprising determining control signal data for an array of loudspeakers, the control signal data being such as to control the loudspeakers to produce a desired sound field associated with an audio signal, the method comprises determining control signal data for different frequency components of the desired sound field in respect of respective different positions in a listening volume of the loudspeaker array, wherein determination of the control signal data comprises sampling the desired sound field at the surface of a control volume (V).

Apparatus and method for reproducing a sound field with a loudspeaker array controlled via a control volume

Provided is a method and apparatus for reproducing a three-dimensional (3D) sound field. A method of reproducing a 3D sound field may determine a control region based on a wavelength of an excitation frequency, set, based on a loudspeaker array, at least one candidate control point in the control region, and determine a non-uniform control point corresponding to a non-uniform loudspeaker.

Method and apparatus for reproducing three-dimensional sound field

Sound recordings are played through a closely-spaced pair of loudspeakers with a predetermined listener position having an included angle of between 6&#xb0; and 20&#xb0;, and filter means being employed in creating said sound recordings, the filter means having characteristics such that when the sound recordings are played, the need to provide a virtual imaging filter means at the inputs to the loudspeakers to create virtual sound sources is avoided, the sound recording being such that when played through the loudspeakers a phase difference between vibrations of the two loudspeakers results where the phase difference varies with frequency from low frequencies where the vibrations are substantially out of phase to high frequencies where the vibrations are in phase, the lowest frequency at which the vibrations are in phase being determined approximately by a ringing frequency, f.

Sound recording and reproduction systems

A sound reproduction system has pairs of sound emitters that subtend different angles &#x398;, the span angle, at the listener position. The pairs of sound emitters are arranged to be excited by different frequency bands of the signal output from an inverse filter means (H, H). The operational span-frequency range of the pairs of sound emitters is determined by an equation (I) where the transducer span &#x398; is the angle subtended at the listener by a pair of transducers, where O&#x3c;n&#x3c;2. c: is the speed of sound, and &#x394;r: is the equivalent distance between the ears. The sound emitters may be discrete speaker units, the different pairs of units being positioned at different span angles, or they be constituted by area portions of an extended transducer (FIG.). When discrete speaker units are employed a cross-over filter (FIG.) is used to provide drive signals in the different frequency bands to the different speaker pairs. When an extended transducer is employed, the vibration transmission characteristics of the transducer may be arranged to filter the vibrations transmitted along the transducer from an excitation means positioned at the higher frequency emitting end of the transducer.

Optimal source distribution

A method of recording sound for reproduction by a plurality of loudspeakers, or for processing sound for reproduction by a plurality of loudspeakers, is described in which some of the reproduced sound appears to a listener to emmanate from a virtual source which is spaced from the loudspeakers. A filter means (H) is used either in creating the recording, or in processing the recorded signals for supply to loudspeakers, the filter means (H) being created in a filter design step in which: a) a technique is employed to minimise error between the signals (w) reproduced at the intended position of a listener on playing the recording through the loudspeakers, and desired signals (d) at the intended position, wherein: b) said desired signals (d) to be produced at the listener are defined by signals (or an estimate of the signals) that would be produced at the ears of (or in the region of) the listener in said intended position by a source at the desired position of the virtual source. A least squares technique may be employed to minimise the time averaged error between signal reproduced at the intended position of a listener and the desired signal, or it may be applied to the frequency domain.

A sound reproduction system comprises a plurality of loudspeakers (S1, S2) spaced from a listener at a location (M1, M2), and a loudspeaker drive means (H) for driving the loudspeakers (S1, S2) in response to a plurality of channels of a sound recording (x) of the type being suitable for playing normally through a plurality of reference speakers that are optimally positioned at locations that are displaced from the actual positions of the loudspeakers (S1, S2). The loudspeaker drive includes a filter (H), having a filter characteristic selected by minimising the difference between a desired sound field that would be created by playing the unfiltered sound recording (x) through the reference speakers and sound field reproduced at the listener location (M1, M2) by playing the recording through the speakers (S1, S2). This results in creating a local sound field at the listener location (M1, M2) which is substantially equivalent to the local field that would result from playing the unfiltered sound recording (x) through the reference speakers.

Adaptive audio systems and sound reproduction systems

A stereophonic sound reproduction system is aimed at synthesizing at a multiplicity of points (L) in the listening space. An auditory effect obtaining at corresponding points (K) in the recording space, to compensate for crosstalk (C.sub.21, C.sub.12) between the loudspeakers, the acoustic response of the listening space, and imperfections in the frequency response of the speaker channels. Each speaker channel incorporates a digital filter (H) with the characteristics of which are adjusted in response to measurements of the reproduced field. The digital filters are provided by an inverse filter matrix (H) of which the matrix elements (H.sub.ij) are determined by a least squares technique, applied so as to minimize the sum of the squared errors resulting from the difference between the actual system impulse response and a desired impulse response. A full bandwidth signal is transmitted by a bypass route for combination with the output signal (9) from the filter, the bypass route including a delay means (F).

Sound Reproduction systems

Turbulence in the boundary layer of a flow of air across a surface is controlled by sucking air from the surface. A plurality of turbulence detectors are located in the surface downstream of apertures provided in the surface. The apertures are connected to a suction pump. Air is sucked through the apertures until the air flow of the most downstream of the detectors is non-turbulent.

Control of boundary layer flow

To reduce noise inside a motor car passenger compartment, two loudspeakers 37.sub.1, 37.sub.2 are driven by signals derived from a reference signal x(n) by adaptive filtering carried out by a programmed microprocessor and memory unit 36 which adapts the filtering in dependence on error signals e.sub.l (n) from four microphones 42.sub.1, 42.sub.2, 42.sub.3 and 42.sub.4 distributed in the passenger compartment. Reference filtering coefficients are initially determined by analysis of finite impulse responses when white noise is acoustically coupled from the loudspeakers 37 to the microphones 42, a white noise generator 48 being coupled to the unit 36. The reference signal x(n) is restricted to one or more selected harmonics or subharmonics of the fundamental noise frequency by a filter 34 which tracks the selected frequency. The selected frequency may be obtained from a coil 31 in the ignition circuit of the vehicle.

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Southampton, United Kingdom

Philip Arthur Nelson