Method of denoising signal mixtures
View Patent ↗Disclosed is a method of denoising signal mixtures so as to extract a signal of interest, the method comprising receiving a pair of signal mixtures, constructing a time-frequency representation of each mixture, constructing a pair of histograms, one for signal-of-interest segments, the other for non-signal-of-interest segments, combining said histograms to create a weighting matrix, rescaling each time-frequency component of each mixture using said weighting matrix, and resynthesizing the denoised signal from the reweighted time-frequency representations.
1. A method of denoising signal mixtures so as to extract a signal of interest, the method comprising:
receiving a pair of signal mixtures;
constructing a time-frequency representation of each mixture;
constructing a pair of histograms, one for signal-of-interest segments, the other for non-signal-of-interest segments;
combining said histograms to create a weighting matrix;
rescaling each time-frequency component of each mixture using said weighting matrix; and
resynthesizing the denoised signal from the reweighted time-frequency representations.
2. The method of claim 1 wherein said receiving of mixing signals utilizes signal-of-interest activation.
3. The method of claim 2 wherein said signal-of-interest activation detection is voice activation detection.
4. The method of claim 1 wherein said histograms are a function of amplitude versus a function of relative time delay.
5. The method of claim 1 wherein said combining of histograms to create a weighting matrix comprises:
subtracting said non-signal-of-interest segment histograms from said signal-of-interest segment histogram so as to create a difference histogram; and
rescaling said difference histogram to create a weighting matrix.
6. The method of claim 5 wherein said rescaling of said difference histogram to create the weighting matrix comprises rescaling said difference histogram with a rescaling function ƒ(x) that maps x to [0,1].
7. The method of claim 6 wherein said rescaling function ƒ(x) is given by the equation:
f
(
x
)
=
{
tanh
(
x
)
,
0
,
x
>
0
x
≤
0
}
.
8. The method of claim 6 wherein said rescaling function ƒ(x) maps a largest p percent of histogram values to unity and the remaining values to zero.
9. The method of claim 5 wherein said histograms and weighting matrix are a function of amplitude versus a function of relative time delay.
10. The method of claim 1 wherein said constructing of a time-frequency representation of each mixture is given by the equation:
[
X
1
(
ω
,
τ
)
X
2
(
ω
,
τ
)
]
=
[
1
…
1
a
1
ⅇ
-
ⅈ
ωδ
1
…
a
N
ⅇ
-
ⅈ
ωδ
N
]
[
S
1
(
ω
,
τ
)
⋮
S
N
(
ω
,
τ
)
]
+
[
N
1
(
ω
,
τ
)
N
2
(
ω
,
τ
)
]
where X(ω, τ) is the time-frequency representation of x(t) constructed using the equation for said constructing of a time-frequency representation of each given mixture, ω is the frequency variable (in both the frequency and time-frequency domains), τ is the time variable in the time-frequency domain that specifies the alignment of the window, a 1 is the relative mixing parameter associated with the i th source, N is the total number of sources, S(ω, τ) is the time-frequency representation of s(t), N 1 (ω, τ) or N 2 (ω, τ) are the noise signals n 1 (t) and n 2 (t) in the time-frequency domain.
11. The method of claim 10 wherein said histograms are constructed according to an equation selected from the group:
H
v
(
m
,
n
)
=
∑
ω
,
τ
|
X
1
w
(
ω
,
τ
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|
+
|
X
2
w
(
ω
,
τ
)
|
,
and
H
v
(
m
,
n
)
=
∑
ω
,
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|
X
1
w
(
ω
,
τ
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|
·
|
X
2
w
(
ω
,
τ
)
|
,
where m=Â(ω, τ), n={circumflex over (Δ)}(ω, τ); and
wherein
 (ω, τ)=[ a num ( â (ω, τ)− a min )/( a max −a min )], and
{circumflex over (Δ)}(ω, τ)=[δ num ({circumflex over (δ)}(ω, τ)−δ min )/(δ max −δ min )]
where a min , a max , δ min , δ max are the maximum and minimum allowable amplitude and delay parameters, a num , δ num are the number of histogram bins to use along each axis, and [ƒ(x)] is a notation for the largest integer smaller than ƒ(x).
12. The method of claim 1 further comprising a preprocessing procedure comprising:
realigning said mixtures so as to reduce relative delays for the signal of interest; and
rescaling said realigned mixtures to equal power.
13. The method of claim 1 further comprising a postprocessing procedure comprising a blind source separation procedure.
14. The method of claim 1 wherein said histograms are constructed in a mixing parameter ratio plane.
15. A program storage device readable by machine, tangibly embodying a program of instructions executable by the machine to perform method steps for denoising signal mixtures so as to extract a signal of interest, said method steps comprising:
receiving a pair of signal mixtures;
constructing a time-frequency representation of each mixture;
constructing a pair of histograms, one for signal-of-interest segments, the other for non-signal-of-interest segments;
combining said histograms to create a weighting matrix;
rescaling each time-frequency component of each mixture using said weighting matrix; and
resynthesizing the denoised signal from the reweighted time-frequency representations.
16. A system for denoising signal mixtures so as to extract a signal of interest, comprising:
means for receiving a pair of signal mixtures;
means for constructing a time-frequency representation of each mixture;
means for constructing a pair of histograms, one for signal-of-interest segments, the other for non-signal-of-interest segments;
means for combining said histograms to create a weighting matrix;
means for rescaling each time-frequency component of each mixture using said weighting matrix; and
means for resynthesizing the denoised signal from the reweighted time-frequency representations.