Automatic utterance detector with high noise immunity
View Patent ↗An utterance detector for speech recognition is described. The detector consists of two components. The first part makes a speech/non-speech decision for each incoming speech frame. The decision is based on a frequency-selective autocorrelation function obtained by speech power spectrum estimation, frequency filter, and inverse Fourier transform. The second component makes utterance detection decision, using a state machine that describes the detection process in terms of the speech/non-speech decision made by the first component.
1. An utterance detector comprising:
a frame-level detector for making speech/non-speech decisions for each frame, and
an utterance detector coupled to said frame-level detector and responsive to said speech/non-speech decisions over a period of frames to detect an utterance; said frame-level detector includes frequency-selective autocorrelation.
2. The utterance detector of claim 1 , wherein said frame-level frame detector includes means for calculating power spectrum of an input signal, performing frequency shaping, performing inverse FFT and determining maximum value of periodicity.
3. The utterance detector of claim 2 , wherein calculating power spectrum includes the steps of filtering the signal, applying a Hamming window and performing FFT on the signal from the Hamming window.
4. The utterance detector of claim 2 , wherein said performing frequency shaping step includes the step of:
F
(
k
)
=
{
α
F
l
-
k
if
0
≤
k
<
F
l
1
if
F
l
≤
k
<
F
h
β
k
-
F
h
if
F
h
≤
k
<
N
2
where F l and F h are low and high frequency indices respectfully. R(k) is the autocorrelation, F(k) is a filter, and α and β are constants
with
α=0.70
β=0.85
to get R(k).
5. An utterance detector comprising:
a frame-level detector for making speech/non-speech decisions for each frame, and
an utterance detector coupled to said frame-level detector and responsive to said speech/non-speech decisions over a period of frames to detect an utterance; said frame-level detector includes autocorrelation; said utterance detector including filter means for performing frequency-selective autocorrelation.
6. The utterance detector of claim 5 , wherein said autocorrelation and filtering is performed in DFT domain by taking the signal and applying DFT, performing frequency domain windowing and then inverse DFT.