ONLINE TARGET-SPEECH EXTRACTION METHOD FOR ROBUST AUTOMATIC SPEECH RECOGNITION
Provided is a target speech signal extraction method for robust speech recognition including: (a) receiving information on a direction of arrival of the target speech source with respect to the microphones; (b) generating a nullformer by using the information on the direction of arrival of the target speech source to remove the target speech signal from the input signals and to estimate noise; (c) setting a real output of the target speech source using an adaptive vector w(k) as a first channel and setting a dummy output by the nullformer as a remaining channel; (d) setting a cost function for minimizing dependency between the real output of the target speech source and the dummy output using the nullformer by performing independent component analysis (ICA); and (e) estimating the target speech signal by using the cost function, thereby extracting the target speech signal from the input signals.
1 . A target speech signal extraction method of extracting a target speech signal from input signals input to at least two or more microphones for robust speech recognition, comprising:
(a) receiving information on a direction of arrival of the target speech source with respect to the microphones;
(b) generating a nullformer for removing the target speech signal from the input signals and estimating noise by using the information on the direction of arrival of the target speech source;
(c) setting a real output of the target speech source using an adaptive vector w(k) as a first channel and setting a dummy output by the nullformer as a remaining channel;
(d) setting a cost function for minimizing dependency between the real output of the target speech source and the dummy output using the nullformer by performing independent component analysis (ICA); and
(e) estimating the target speech signal by using the cost function, thereby extracting the target speech signal from the input signals.
2 . The target speech signal extraction method according to claim 1 , wherein the direction of arrival of the target speech source is a separation angle θ target formed between a vertical line in the microphone and the target speech source.
3 . The target speech signal extraction method according to claim 1 , wherein the nullformer is a “delay-subtract nullformer” and cancels out the target speech signal from the input signals input from the microphones.
4 . The target speech signal extraction method according to claim 3 ,
wherein a nullformer U m (k,τ) for removing the target speech signal from signals input from first and m-th microphones is expressed by the following Mathematical Formula, and
U
m
(
k
,
τ
)
=
X
m
(
k
,
τ
)
-
exp
{
jω
k
(
m
-
1
)
sin
θ
target
c
}
X
1
(
k
,
τ
)
,
m
=
2
,
…
,
M
.
wherein, X m (k,τ) denotes the input signal input from the m-th microphone, θ target denotes a direction of arrival of the target speech source, and k and τ denote a frequency bin number and a frame number, respectively.
5 . The target speech signal extraction method according to claim 1 ,
wherein a time domain waveform y(k) of an estimated target speech signal is expressed by the following Mathematical Formula, and
y
(
t
)
=
∑
τ
∑
k
=
1
K
Y
(
τ
,
k
)
jw
k
(
t
-
τ
H
)
wherein Y(k,τ)=w(k)x(k,τ), w(k) denotes an adaptive vector for generating a real output with respect to the target speech source, and k and τ denote a frequency bin number and a frame number, respectively.