Audio signal processing apparatus and a sound emission apparatus

• US 10,405,089 B2
• Filed: 02/12/2018
• Issued: 09/03/2019
• Est. Priority Date: 08/13/2015
• Status: Active Grant

• Current Assignee: Huawei Technologies Co., Ltd. (Huawei Investment & Holding Co., Ltd.), University of Southampton
• Original Assignee: Huawei Technologies Co., Ltd. (Huawei Investment & Holding Co., Ltd.)
• Inventors: Fontana, Simone, Lang, Yue, Fazi, Filippo, Shin, Mincheol, Oliveri, Ferdinando
• Primary Examiner(s): Jamal, Alexander
• Application Number:
  US15/894,485
• Publication Number:
  US 20180184199A1
• Time in Patent Office: 568 Days
• Field of Search: 381335, 381336, 381425, 381430, 381300, 381308, 381395
• CPC Class Codes: H04R 1/403 loud-speakers
• CPC Class Codes: H04R 2201/021 Transducers or their casings adapted for mounting in or to a wall or ceiling
• CPC Class Codes: H04R 2201/401 2D or 3D arrays of transducers
• CPC Class Codes: H04R 2203/12 Beamforming aspects for stereophonic sound reproduction with loudspeaker arrays
• CPC Class Codes: H04R 2205/024 Positioning of loudspeaker enclosures for spatial sound reproduction
• CPC Class Codes: H04R 3/12 for distributing signals to two or more loudspeakers specially adapted for hearing aids H04R25/407
• CPC Class Codes: H04R 5/02 Spatial or constructional arrangements of loudspeakers

Abstract

An audio signal processing apparatus for processing an input audio signal is provided, the apparatus comprising a plurality of filters, each filter configured to filter the input audio signal to obtain a plurality of filtered audio signals, each filter designed according to an extended mode matching beamforming applied to a surface of a half revolution, the surface partially characterizing a loudspeaker enclosure shape, a plurality of scaling units, each scaling unit configured to scale the plurality of filtered audio signals using a plurality of gain coefficients to obtain a plurality of scaled filtered audio signals, and a plurality of adders, each adder configured to combine the plurality of scaled filtered audio signals, thereby providing an output audio signal for producing a sound field having a beam directivity pattern defined by the plurality of gain coefficients.

Claims

1. An audio signal processing apparatus for processing an input audio signal, the audio signal processing apparatus comprising:

a plurality of filters, each filter configured to filter the input audio signal to obtain a plurality of filtered audio signals, each filter designed according to an extended mode matching beamforming applied to a surface of a half revolution, the surface partially characterizing a loudspeaker enclosure shape;

a plurality of scaling components, each scaling component configured to scale the plurality of filtered audio signals using a plurality of gain coefficients to obtain a plurality of scaled filtered audio signals; and

a plurality of adders, each adder configured to combine the plurality of scaled filtered audio signals, so as to provide an output audio signal for producing a sound field having a beam directivity pattern defined by the plurality of gain coefficients, where the filters use a function describing a radiation polar pattern of a transducer array conforming to the surface of a full revolution comprising the surface of a half revolution.

2. The audio signal processing apparatus of claim 1,

wherein the impulse response of an n-th filter of the plurality of filters is obtained through the following:

3. The audio signal processing apparatus of claim 2, wherein the impulse response of the n-th filter is obtained through the following:

4. The audio signal processing apparatus of claim 2, wherein Γ

_n is obtained through the following;

Γ

_n=2i<sup>−

n</sup>b_n(kR),

wherein the function b_n(kR) is obtained through the following;

5. The audio signal processing apparatus of claim 2, wherein the output audio signal for the l-th transducer of the transducer array is obtained through the following:

z_l(t)=Σ

_n=0^L-1[x(t)⊗

R_n(t)]G_n,l,

wherein z_l(t) denotes the output signal as a function of time, x(t) denotes the input audio signal as a function of time, ⊗

denotes the convolution operator, where n can range from 0 to N and N depends on the beam directivity pattern, and G_n,l denotes the n-th gain coefficient for the l-th transducer.

6. The audio signal processing apparatus of claim 5, wherein the n-th gain coefficient for the l-th transducer of the transducer array is obtained through the following:

7. The audio signal processing apparatus of claim 6, wherein the beam directivity pattern is a single beam in a direction defined by an angle ϕ

₀ and wherein the n-th directivity coefficient f_n is obtained through the following;

f_n=√

{square root over (2−

δ

_n)}γ

(ϕ

₀)cos(nϕ

₀),

wherein γ

(ϕ

₀) is an angular dependent factor obtained through the following;

8. The audio signal processing apparatus of claim 5, wherein the beam directivity pattern is defined by multiple beams in respective directions defined by a respective angle ϕ

_j and wherein the output audio signal z_l(t) for the l-th transducer of the transducer array is obtained through the following;

z_l(t)=Σ

_n=0^L-1Σ

_j=1^J[x(t)⊗

R_n(t)⊗

δ

(t−

τ

_j)K_j]G_n,l(ϕ

_j),

wherein J denotes the total number of beams of the beam directivity pattern, τ

_j denotes the time delay for the j-th beam and K_j denotes the gain for the j-th beam.

9. The audio signal processing apparatus of claim 1, wherein the plurality of filters, the plurality of scaling components and the plurality of adders are configured to process at least two audio input audio signals, so as to provide a stereo output audio signal for producing a stereo sound field having the beam directivity pattern defined by the plurality of gain coefficients.

10. The audio signal processing apparatus of claim 1, wherein the plurality of filters, the plurality of scaling components and the plurality of adders are further configured to provide a further output audio signal for producing a further sound field, via a half axisymmetric loudspeaker array, having a further beam directivity pattern defined by the plurality of gain coefficients.

11. The audio signal processing apparatus of claim 1, wherein low-frequency component of each audio input signal is individually processed upstream of the plurality of filters, the plurality of scaling components, and the plurality of adders.

12. The audio signal processing apparatus of claim 1, further comprising a filter network for dividing the input audio signal into two or more divided input audio signals of differing frequency bandwidths, so as to provide at least a first and second input audio signal, and

a further plurality of filters, a further plurality of scaling components, and a further plurality of adders for processing the second input audio signal, so as to provide a second output audio signal for producing the sound field having the beam directivity pattern defined by the plurality of gain coefficients.

13. A sound emission apparatus comprising:

a loudspeaker enclosure comprising a sound emission section and a rear section, wherein the sound emission section is coupled to or integral with the rear section and the sound emission section defines a surface of a half revolution about an axis extending along a length of the loudspeaker enclosure; and

at least one transducer array mounted on the sound emission section of the loudspeaker enclosure, wherein a plane passing through the transducer array is orthogonal to the axis, the at least one transducer array being curved such that the at least one transducer array conforms to the curvature of the surface of the half revolution, where the apparatus comprises filters that use a function describing a radiation polar pattern of a transducer array conforming to the surface of a full revolution comprising the surface of a half revolution.

14. The sound emission apparatus of claim 13, wherein the at least one transducer array spans the width of the sound emission section.

15. The sound emission apparatus of claim 13, wherein the sound emission section defines an aperture for mounting the at least one transducer array.

16. The sound emission apparatus of claim 13, wherein the loudspeaker enclosure defines a half axis-symmetric shape.

17. The sound emission apparatus of claim 13, wherein the loudspeaker enclosure defines one of a half-cylindrical shape or a half-conical shape.

18. The sound emission apparatus of claim 16, wherein the sound emission apparatus comprises:

a further loudspeaker enclosure that defines the half axis-symmetric shape, the further loudspeaker enclosure comprising a sound emission section and a rear section, wherein the sound emission section is coupled to or integral with the rear section and the sound emission section defines a further surface of the half revolution about a further axis extending along a length of the further loudspeaker enclosure; and

at least one further transducer array mounted on the sound emission section of the further loudspeaker enclosure, wherein a further plane passing through the further transducer array is orthogonal to the further axis, the at least one further transducer array being curved such that the at least one further transducer array conforms to the curvature of the further surface of the half revolution,

wherein the rear section of the further loudspeaker enclosure is configured to be coupled to the rear section of the loudspeaker enclosure so as to define an axis-symmetric shape.

19. The sound emission apparatus of claim 13, wherein the at least one transducer array comprises a first transducer array and a second transducer array, wherein a first plane passing through the first transducer array is orthogonal to the axis, a second plane passing through the second transducer array is orthogonal to the axis, and the first and second planes are parallel to each other.

20. The sound emission apparatus of claim 19, wherein the positions of the transducers of the first transducer array have an angular offset relative to the positions of the transducers of the second transducer array.

21. The sound emission apparatus of claim 20, wherein the angular offset is about half of the angular spacing between neighboring transducers of the first transducer array.

22. The sound emission apparatus of claim 13, further comprising the audio signal processing apparatus for processing an input audio signal, wherein the audio signal processing apparatus comprises:

a plurality of filters, each filter configured to filter the input audio signal to obtain a plurality of filtered audio signals, each filter designed according to an extended mode matching beamforming applied to a surface of a half revolution, the surface partially characterizing a loudspeaker enclosure shape;

a plurality of scaling components, each scaling component configured to scale the plurality of filtered audio signals using a plurality of gain coefficients to obtain a plurality of scaled filtered audio signals; and

a plurality of adders, each adder configured to combine the plurality of scaled filtered audio signals, so as to provide an output audio signal for producing a sound field having a beam directivity pattern defined by the plurality of gain coefficients.