Audio processing
An audio processing arrangement ( 200 ) comprises a plurality of audio sources ( 101, 102 ) generating input audio signals, a processing circuit ( 110 ) for deriving processed audio signals from the input audio signals, a combining circuit ( 120 ) for deriving a combined audio signal from the processed audio signals, and a control circuit ( 130 ) for controlling the processing circuit in order to maximize a power measure of the combined audio signal and for limiting a function of gains of the processed audio signals to a predetermined value. In accordance with the present invention, the audio processing arrangement ( 200 ) comprises a pre-processing circuit ( 140 ) for deriving pre-processed audio signals from the input audio signals to minimize a cross-correlation of interferences comprised in the input audio signals. The pre-processed signals are provided to the processing circuit ( 110 ) instead of the input audio signals.
1. An audio processing arrangement comprising:
a pre-processing circuit for deriving pre-processed audio signals from the input audio signals to minimize a cross-correlation of interferences comprised in input audio signals; wherein the pre-processing circuit is arranged to minimize the cross-correlation of interferences by multiplication of the input audio signals by an inverse of a regulation matrix, wherein the regulation matrix guarantees that the cross-correlation of interferences is minimized;
a processing circuit for deriving processed audio signals from the pre-processed input audio signals;
a combining circuit for deriving a combined audio signal from the processed audio signals; and
a control circuit for controlling the processing circuit to maximize a power measure of the combined audio signal, and for limiting a function of gains of the processed audio signals to a predetermined value.
2. An audio processing arrangement comprising:
a pre-processing circuit for deriving pre-processed audio signals from the input audio signals to minimize a cross-correlation of interferences comprised in input audio signals;
a processing circuit for deriving processed audio signals from the pre-processed input audio signals;
a combining circuit for deriving a combined audio signal from the processed audio signals; and
a control circuit for controlling the processing circuit to maximize a power measure of the combined audio signal, and for limiting a function of gains of the processed audio signals to a predetermined value, wherein the pre-processing circuit is arranged to minimize a cross-correlation of the interferences by multiplication of input audio signals by an inverse of a regulation matrix, wherein the regulation matrix is a function of a correlation matrix, and wherein entries of the correlation matrix are correlation measures between respective pairs of plurality of audio sources.
3. The audio processing arrangement according to claim 2 , wherein the regulation matrix is the correlation matrix.
4. The audio processing arrangement according to claim 2 , wherein the regulation matrix is given by:
Γ reg (ω)=ηΓ(ω)+(1−η) I
wherein Γ reg (ω) is the regulation matrix, Γ(ω) is the correlation matrix, η is a predetermined parameter, I is an identity matrix, and ω is a radial frequency.
5. The audio processing arrangement according to claim 4 , wherein the parameter η is given by:
η
=
σ
v
2
σ
v
2
+
σ
n
2
wherein σ ν 2 is a variance of the correlated interference in the input audio signals, and σ n 2 is the variance of an uncorrelated electronic noise contained in the input audio signals.
6. The audio processing arrangement according to claim 4 , wherein the parameter η is a predetermined fixed value.
7. The audio processing arrangement according to claim 2 , wherein the (p,q) entry of the regulation matrix is given by:
Γ
reg
pq
(
ω
)
=
E
{
V
p
*
(
ω
)
V
q
(
ω
)
}
E
{
V
p
*
(
ω
)
V
p
(
ω
)
}
E
{
V
q
*
(
ω
)
V
p
(
ω
)
}
wherein V p (ω) is the interference in the input audio signal p, V q (ω) is the interference in the input audio signal q, ω is a radial frequency, and E is an expectation operator.
8. The audio processing arrangement according to claim 2 , wherein the (p,q) entry of the correlation matrix is given by:
Γ
pq
(
ω
)
=
sin
c
(
ω
d
pq
c
)
wherein d pq is a distance between microphones p and q, c is a speed of sound in air, and ω is a radial frequency.
9. The audio processing arrangement according to claim 1 , wherein the processing circuit comprises a plurality of adjustable filters for deriving the processed audio signals from the pre-processed audio signals, the control circuit comprises a plurality of further adjustable filters for deriving from the combined audio signals filtered combined audio signals, the further adjustable filters having a transfer function being a conjugate of a transfer function of the adjustable filters, and the control circuit is arranged for limiting a function of gains of the processed audio signals to the predetermined value by controlling the transfer functions of the adjustable filters and the further adjustable filters in order to minimize a difference measure between the input audio signals and the filtered combined audio signal corresponding to the input audio signals.
10. The audio processing arrangement according to claim 1 , further comprising:
delay elements for compensating a delay difference of a common audio signal present in the input audio signals.
11. An audio signal processing arrangement comprising:
a plurality of audio sources generating input audio signals; and
an audio processing arrangement as claimed in claim 1 .
12. An audio processing method comprising
receiving a plurality of input audio signals from a plurality of audio sources;
deriving pre-processed audio signals from the input audio signals, to minimize a cross-correlation of interferences comprised in the input audio signals, wherein deriving to minimize the cross-correlation of interferences includes multiplication of the input audio signals by an inverse of a regulation matrix, wherein the regulation matrix guarantees that the cross-correlation of interferences is minimized;
deriving processed audio signals from the pre-processed audio signals;
deriving a combined audio signal from the processed audio signals;
controlling the deriving of processed audio signals in order to maximize a power measure of the combined audio signal; and
controlling the deriving of processed audio signals for limiting a function of gains of the processed audio signals to a predetermined value.
13. A hearing aid comprising the audio processing arrangement according to claim 11 .
14. The audio processing arrangement according to claim 2 , wherein the processing circuit comprises a plurality of adjustable filters for deriving the processed audio signals from the pre-processed audio signals, the control circuit comprises a plurality of further adjustable filters for deriving from the combined audio signals filtered combined audio signals, the further adjustable filters having a transfer function being a conjugate of a transfer function of the adjustable filters, and the control circuit is arranged for limiting a function of gains of the processed audio signals to the predetermined value by controlling the transfer functions of the adjustable filters and the further adjustable filters in order to minimize a difference measure between the input audio signals and the filtered combined audio signal corresponding to the input audio signals.
15. The audio processing arrangement according to claim 2 , further comprising:
delay elements for compensating a delay difference of a common audio signal present in the input audio signals.
16. An audio signal processing arrangement comprising:
a plurality of audio sources generating input audio signals; and
an audio processing arrangement as claimed in claim 2 .
17. A hearing aid comprising the audio signal processing arrangement according to claim 16 .
18. The audio processing arrangement according to claim 1 , wherein the regulation matrix is a correlation matrix.
19. The audio processing arrangement according to claim 1 , wherein the regulation matrix is given by:
Γ reg (ω)=ηΓ(ω)+(1−η) I
wherein Γ reg (ω) is the regulation matrix, Γ(ω) is a correlation matrix, η is a predetermined parameter, I is an identity matrix, and ω is a radial frequency.
20. The audio processing arrangement according to claim 19 , wherein the parameter η is given by:
η
=
σ
υ
2
σ
υ
2
+
σ
n
2
wherein σ ν 2 is a variance of the correlated interference in the input audio signals, and σ n 2 is the variance of an uncorrelated electronic noise contained in the input audio signals.