Adaptive mode control apparatus and method for adaptive beamforming based on detection of user direction sound
An adaptive mode control apparatus and method for adaptive beamforming based on detection of a user direction sound are provided. The adaptive mode control apparatus includes a signal intensity detector that searches for signal intensity of each designated direction to detect signal intensity having a maximum value when a voice signal of each direction is input through at least one microphone; and an adaptive mode controller that compares the signal intensity having the maximum value detected through the signal intensity detector with a threshold value and determines whether to perform an adaptive mode of a Generalized Sidelobe Canceller (GSC) according to the comparison results. Therefore, a lack of control of adaptation of an adaptive filter of the conventional art is solved. That is, as one condition for guaranteeing performance of adaptive beamforming, adaptation of an adaptive filter is not performed when noise of a sound with a high autocorrelation is cancelled.
1. An adaptive mode control apparatus for adaptive beamforming based on detection of a user direction sound, comprising:
a signal intensity detector configured to search for signal intensity of each designated direction to detect signal intensity having a maximum value when a voice signal of each direction is input through at least one microphone; and
an adaptive mode controller configured to compare the signal intensity having the maximum value detected through the signal intensity detector with a threshold value and determine whether to perform an adaptive mode of a Generalized Sidelobe Canceller (GSC) according to results of the comparison.
2. The adaptive mode control apparatus of claim 1 , wherein the signal intensity detector comprises:
a window processor configured to apply a Hanning window of a predetermined length to a voice having noise input to each microphone of a microphone array to be divided into frames;
a Discrete Fourier Transform (DFT) processor configured to apply a DFT for each microphone and each frame for frequency analysis of the frames divided by the window processor;
a correlation computer configured to steer a beam in a detection direction in pairs of microphones which configures the microphone array and estimates a cross-power spectrum;
a weight estimator configured to compute a phase-transform weight for normalizing a cross-power spectrum from a frame output through the DFT processor; and
a signal intensity measuring unit configured to measure intensity of a sound input from microphones which configures the microphone array from a corresponding direction for detecting a voice signal.
3. The adaptive mode control apparatus of claim 1 , wherein the adaptive mode controller determines not to perform the adaptive mode of the GSC when the signal intensity having the maximum value exceeds the threshold value and determines to perform the adaptive mode of the GSC when the signal intensity having the maximum value does not exceed the threshold value.
4. The adaptive mode control apparatus of claim 3 , wherein it is determined before adaptive beamforming processing whether to perform the adaptive mode of the GSC.
5. The adaptive mode control apparatus of claim 3 , further comprising,
a fixed beamformer configured to steer the microphones which configure the microphone array to a user direction;
a signal blocking unit configured to compute a side-lobe noise input through the microphones that configure the microphone array; and
an adaptive filter configured to cancel a directional noise using a signal blocking output value that is computed by adaptively estimating a spatial path transfer function.
6. The adaptive mode control apparatus of claim 5 , wherein an average value of user voice signals input from the front through the microphones of the microphone array is computed through the fixed beamformer using the following Equation:
Z
fb
(
k
,
l
)
=
1
4
∑
i
=
1
4
Z
i
aec
(
k
·
l
)
,
where Z fb denotes a fixed beamformer output, k denotes a discrete frequency index, l denotes a frame index, Z aec denotes an echo-canceled signal, and i denotes a microphone index.
7. The adaptive mode control apparatus of claim 5 , wherein the side-lobe noise computed through the signal blocking unit is a side-lobe noise in which a front sound is canceled and only noise is acquired using the following Equation:
[
Z
1
sb
(
k
,
l
)
Z
2
sb
(
k
,
l
)
Z
3
sb
(
k
,
l
)
]
=
[
1
-
1
0
0
0
1
-
1
0
0
0
1
-
1
]
[
Z
1
aec
(
k
,
l
)
Z
2
aec
(
k
,
l
)
Z
3
aec
(
k
,
l
)
Z
4
aec
(
k
,
l
)
]
,
where Z sb is a signal blocking output, Z aec an echo-canceled signal, k denotes a discrete frequency index, and l denotes a frame index.
8. The adaptive mode control apparatus of claim 5 , wherein a length of the Hanning window applied through the window processor is 256 milliseconds (ms).
9. An adaptive mode control method for adaptive beamforming based on detection of a user direction sound, comprising:
searching for signal intensity of each designated direction to detect signal intensity having a maximum value when an array input signal input through at least one microphone that is provided to a fixed beamformer and a signal blocking unit is received;
comparing the detected signal intensity having the maximum value with a threshold and determining whether to perform an adaptive mode of a GSC according to results of the comparison.
10. The adaptive mode control method of claim 9 , wherein searching for signal intensity of each designated direction to detect signal intensity having a maximum value comprises:
at a window processor, applying a Hanning window of a predetermined length to a voice having noise input to each microphone of a microphone array to be divided into frames;
at a DFT processor, performing a DFT: for each microphone and each frame for frequency analysis;
at a correlation computer, steering a beam in a detection direction in pairs of microphones which configure the microphone array and estimating a cross-power spectrum;
at a weight estimator, computing a phase-transform weight for normalizing a cross-power spectrum from the frame output through the DFT processor; and
measuring intensity of a sound input through the microphones which configure the microphone array from a corresponding direction when the directions of the microphones which configure the microphone array are searched.
11. The adaptive mode control method of claim 9 , wherein in determining whether to perform the adaptive mode, it is determined that the adaptive mode of the GSC is not performed when the signal intensity having the maximum value exceeds the threshold value, and it is determined that the adaptive mode of the GSC is performed when the signal intensity having the maximum value does not exceed the threshold value.
12. The adaptive mode control method of claim 9 , wherein it is determined before adaptive beamforming processing whether to perform the adaptive mode of the GSC.
13. The adaptive mode control method of claim 9 , wherein at a fixed beamformer, steering the microphones which configures the microphone array to a user direction comprises, at the fixed beamformer, computing an average value of user voice signals input from the front through the microphones of the microphone array using the following Equation:
Z
fb
(
k
,
l
)
=
1
4
∑
i
=
1
4
Z
i
aec
(
k
·
l
)
,
where Z fb denotes a fixed beamformer output, k denotes a discrete frequency index, l denotes a frame index, Z aec denotes an echo-canceled signal, and i denotes a microphone index.
14. The adaptive mode control method of claim 9 , further comprising,
at a fixed beamformer, steering the microphones which configures the microphone array to a user direction;
at a signal blocking unit, computing a side-lobe noise; and
at an adaptive filter, canceling a directional noise using a signal blocking output value that is computed by adaptively estimating a spatial path transfer function.
15. The adaptive mode control method of claim 14 , wherein at a signal blocking unit, computing a side-lobe noise comprises computing a side-lobe noise in which a front sound is canceled and only noise is acquired using the following Equation:
[
Z
1
sb
(
k
,
l
)
Z
2
sb
(
k
,
l
)
Z
3
sb
(
k
,
l
)
]
=
[
1
-
1
0
0
0
1
-
1
0
0
0
1
-
1
]
[
Z
1
aec
(
k
,
l
)
Z
2
aec
(
k
,
l
)
Z
3
aec
(
k
,
l
)
Z
4
aec
(
k
,
l
)
]
,
where Z sb is a signal blocking output, Z aec an echo-canceled signal, k denotes a discrete frequency index, and l denotes a frame index.
16. A system for adaptive beamforming, the system comprising
an adaptive mode control apparatus configured to perform adaptive beamforming based on detection of a user direction sound, the adaptive mode control comprising:
a signal intensity detector configured to search for signal intensity of each designated direction to detect signal intensity having a maximum value when a voice signal of each direction is input through at least one microphone; and
an adaptive mode controller configured to compare the signal intensity having the maximum value detected through the signal intensity detector with a threshold value and determines whether to perform an adaptive mode of a Generalized Sidelobe Canceller (GSC) according to results of the comparison.
17. The system of claim 16 , wherein the signal intensity detector comprises:
a window processor that applies a Hanning window of a predetermined length to a voice having noise input to each microphone of a microphone array to be divided into frames;
a Discrete Fourier Transform (DFT) processor that performs a DFT for each microphone and each frame for frequency analysis of the frames divided by the window processor;
a correlation computer that steers a beam in a detection direction in pairs of microphones which configures the microphone array and estimates a cross-power spectrum;
a weight estimator that computes a phase-transform weight for normalizing a cross-power spectrum from a frame output through the DFT processor; and
a signal intensity measuring unit that measures intensity of a sound input from microphones which configures the microphone array from a corresponding direction for detecting a voice signal.
18. The system of claim 16 , wherein the adaptive mode controller determines not to perform the adaptive mode of the GSC when the signal intensity having the maximum value exceeds the threshold value and determines to perform the adaptive mode of the GSC when the signal intensity having the maximum value does not exceed the threshold value.
19. The system of claim 18 , wherein it is determined before adaptive beamforming processing whether to perform the adaptive mode of the GSC.
20. The system of claim 18 , further comprising,
a fixed beamformer that steers the microphones which configure the microphone array to a user direction;
a signal blocking unit that computes a side-lobe noise input through the microphones that configure the microphone array; and
an adaptive filter that cancels a directional noise using a signal blocking output value that is computed by adaptively estimating a spatial path transfer function.