Audio signal processing apparatus and method

Patent metadata

Field	Value
Publication number	US-10492017-B2
Application number	US-201816001411-A
Country	US
Kind code	B2
Filing date	Jun 6, 2018
Priority date	Dec 7, 2015
Publication date	Nov 26, 2019
Grant date	Nov 26, 2019

Abstract

An audio signal processing apparatus, comprising a memory configured to store a set of pairs of predefined left ear and right ear transfer functions, which are predefined for a plurality of reference positions relative to the listener, a processor configured to determine a pair of left ear and right ear transfer functions on the basis of the set of predefined pairs of predefined left ear and right ear transfer functions for the azimuth angle and the elevation angle of the virtual target position and an adjustment filter configured to filter the input audio signal on the basis of the determined pair of left ear and right ear transfer functions and an adjustment function configured to adjust a delay between the left ear transfer function and the right ear transfer function to obtain a left ear output audio signal and a right ear output audio signal.

First claim

The invention claimed is:

1. An audio signal processing apparatus for processing an input audio signal, comprising:
a memory configured to store a set of pairs of predefined left ear and right ear transfer functions, wherein each pair of the set of pairs of the predefined left ear and right ear transfer functions is predefined for each reference position of a plurality of reference positions relative to a listener, wherein each of the reference positions lies in a two-dimensional plane;
a processor coupled to the memory and configured to determine a pair of left ear and right ear transfer functions of the set of pairs of the predefined left ear and right ear transfer functions according to an azimuth angle and an elevation angle of a virtual target position relative to the listener; and
an adjustment filter coupled to the memory and the processor and configured to filter the input audio signal on a basis of the determined pair of the left ear and right ear transfer functions and an adjustment function, wherein the adjustment function is configured to:
adjust a delay between a determined left ear transfer function and a determined right ear transfer function of the determined pair of the left ear and right ear transfer functions; and
adjust a frequency dependence of the determined left ear transfer function and the determined right ear transfer function as a function of the azimuth angle or the elevation angle on the basis of a plurality of infinite impulse response filters in order to obtain a left ear output audio signal and a right ear output audio signal, wherein a frequency dependence of each infinite impulse response filter of the plurality of infinite impulse response filters is defined by a plurality of predefined filter parameters, wherein for an infinite impulse response filter, the predefined filter parameters are selected by determining a frequency and the azimuth angle or the elevation angle at which a measured left ear transfer function or a measured right ear transfer function of pairs of measured left ear and right ear transfer functions has a minimal or a maximal magnitude; and

a transmitter coupled to the memory and the processor and configured to transmit the left ear output audio signal and the right ear output audio signal to the listener to enable the listener to perceive the input audio signal as arriving from the virtual target position.

2. The audio signal processing apparatus of claim 1 , wherein the adjustment filter is further configured to adjust the delay between the determined left ear transfer function and the determined right ear transfer function as a function of the azimuth angle and the elevation angle of the virtual target position by compensating for sound travel time differences associated with a first distance between the virtual target position and a left ear of the listener and a second distance between the virtual target position and a right ear of the listener.

3. The audio signal processing apparatus of claim 1 , wherein the adjustment filter is further configured to adjust the delay between the determined left ear transfer function and the determined right ear transfer function as a function of the azimuth angle of the virtual target position by compensating for sound travel time differences associated with a first distance between the virtual target position and a left ear of the listener and a second distance between the virtual target position and a right ear of the listener.

4. The audio signal processing apparatus of claim 1 , wherein the adjustment filter is further configured to adjust the delay between the determined left ear transfer function and the determined right ear transfer function as a function of the elevation angle of the virtual target position by compensating for sound travel time differences associated with a first distance between the virtual target position and a left ear of the listener and a second distance between the virtual target position and a right ear of the listener.

5. The audio signal processing apparatus of claim 1 , wherein the adjustment filter is further configured to adjust the delay between the determined left ear transfer function and the determined right ear transfer function as a function of the azimuth angle or the elevation angle of the virtual target position on a basis of the following equations:

τ
L

⁡

(
Θ
)

=

τ
⁡

(

Θ
+

π
2

)

;
and

τ
R

⁡

(
Θ
)

=

τ
⁡

(

Θ
-

π
2

)

,

wherein the τ L denotes a delay applied to the left ear transfer function, wherein the τ R denotes a delay applied to the right ear transfer function, wherein the τ and the Θ is defined on a basis of the following equations:

τ
⁡

(
Θ
)

=

a
c

⁢
sin
⁢

⁢
Θ

;
and

Θ
=

{

arc
⁢

⁢

sin
⁡

(

sin
⁢

⁢
θ
⁢

Assignees

• Huawei Tech Co Ltd

Inventors

• Pang Liyun
• Grosche Peter
• Faller Christof
• Favrot Alexis

Classifications

• H04S7/303 Primary

  Tracking of listener position or orientation · CPC title

• H04S2400/11

  Positioning of individual sound objects, e.g. moving airplane, within a sound field (H04S2420/13 takes precedence) · CPC title

• H04S1/005 Primary

  For headphones · CPC title

• H04S2420/01

  Enhancing the perception of the sound image or of the spatial distribution using head related transfer functions [HRTF's] or equivalents thereof, e.g. interaural time difference [ITD] or interaural level difference [ILD] · CPC title