Robust voice detector for receive-side automatic gain control
A voice detector improves voice output quality. The voice detector may be incorporated into a cellphone, hands-free car phone, or any other device that provides voice output. The voice detector provides excellent voice output quality even when signal dropouts and other significant signal artifacts are present in the received signal. Not only does the high quality voice output improve the listening experience, it also benefits downstream processing systems that further process the voice signal.
1 . A voice detector comprising:
a noise estimate input;
a frame characteristic input;
a signal-to-noise ratio (SNR) estimator coupled to the noise estimate input and the frame characteristic input and comprising an SNR measurement output;
a smooth voice magnitude estimator coupled to the SNR measurement output and the frame characteristic input and comprising a smooth voice signal output;
voice decision logic coupled to the smooth voice signal output and the frame characteristic input and comprising a voice detection output.
2 . The voice detector of claim 1 , where the frame characteristic input comprises:
a mean absolute value input operable to provide a mean absolute value of a signal sample frame to the SNR estimator.
3 . The voice detector of claim 2 , where the signal sample frame comprises:
frequency domain signal samples, time domain signal samples, or a combination of both frequency domain signal samples and time domain signal samples.
4 . The voice detector of claim 1 , where:
the noise estimate input comprises a background noise estimate input operable to provide a background noise estimate value to the SNR estimator.
5 . The voice detector of claim 1 , where:
the smooth voice magnitude estimator comprises:
adaptation rate selection logic operable to select a current adaptation rate value from multiple available adaptation rate values; and
smooth voice magnitude determination logic operable to generate a current smooth voice signal magnitude taking into consideration the current adaptation rate value.
6 . The voice detector of claim 1 , where:
the SNR measurement output is operable to provide an SNR measurement value to the smooth voice magnitude estimator; and
the smooth voice magnitude determination logic comprises:
a first smooth voice signal magnitude generator;
a second smooth voice signal magnitude generator; and
generator decision logic operable to select between the first and second smooth voice signal magnitude generators based on the SNR measurement value.
7 . The voice detector of claim 5 , where:
the frame characteristic input is operable to provide a frame characteristic value to the smooth voice magnitude estimator; and where:
the multiple adaptation rate values comprise:
a first adaptation rate value;
a second adaptation rate value; and where:
the adaptation rate selection logic comprises:
adaptation rate decision logic operable to select between the first adaptation rate value and the second adaptation rate value as the current adaptation rate value based on the frame characteristic value.
8 . The voice detector of claim 7 , where the adaptation rate decision logic implements:
α
=
{
α
fast
if
x
(
n
)
>
σ
voice
(
n
-
1
)
,
α
slow
otherwise
.
where α comprises the current adaptation rate value, α fast comprises the first adaptation rate value, α slow comprises the second adaptation rate value, ∥x(n)∥ comprises the frame characteristic value, and σ voice (n−1) comprises a prior smooth voice signal magnitude.
9 . A product comprising:
a machine readable medium;
signal-to-noise ratio (SNR) estimator logic stored on the medium and operable to accept a noise estimate value and a frame characteristic value and generate a SNR measurement value;
smooth voice magnitude estimator logic stored on the medium and operable to accept the SNR measurement value and the frame characteristic value and generate a smooth voice signal output value;
voice decision logic stored on the medium and operable to accept the smooth voice signal output value and the frame characteristic value and generate a voice detection value.
10 . The product of claim 9 , where the noise estimate value comprises:
a background noise estimate value.
11 . The product of claim 9 , where the frame characteristic value comprises:
a mean absolute value of a signal sample frame.
12 . The product of claim 9 , where:
the smooth voice magnitude estimator logic comprises:
adaptation rate selection logic operable to select a current adaptation rate value from multiple available adaptation rate values; and
smooth voice magnitude determination logic operable to generate a current smooth voice signal magnitude using the current adaptation rate value.
13 . The product of claim 12 , where:
the multiple adaptation rate values comprise:
a first adaptation rate value;
a second adaptation rate value; and where:
the adaptation rate selection logic comprises:
adaptation rate decision logic operable to select between the first adaptation rate value and the second adaptation rate value as the current adaptation rate value based on the frame characteristic value.
14 . The product of claim 9 , where:
the smooth voice magnitude determination logic comprises:
a first smooth voice signal magnitude generator;
a second smooth voice signal magnitude generator; and
generator decision logic operable to select between the first and second smooth voice signal magnitude generators based on the SNR measurement value.
15 . The product of claim 9 , where the smooth voice magnitude estimator logic implements:
α
=
{
α
fast
if
x
(
n
)
>
σ
voice
(
n
-
1
)
,
α
slow
otherwise
.
where α comprises a current adaptation rate value, α fast comprises a first adaptation rate value, α slow comprises a second adaptation rate value, ∥x(n)∥ comprises the frame characteristic value, and σ voice (n−1) comprises a prior smooth voice signal magnitude.
16 . The product of claim 15 , where the smooth voice magnitude estimator logic implements:
σ
voice
(
n
)
=
{
(
1
-
α
)
σ
voice
(
n
-
1
)
+
α
x
(
n
)
if
γ
>
Γ
,
σ
voice
(
n
-
1
)
otherwise
.
where σ voice (n) comprises the smooth voice signal output value, γ comprises the SNR measurement value, and Γ comprises a SNR threshold.
17 . The product of claim 16 , where the voice decision logic implements:
VD
=
{
1
if
x
(
n
)
>
k
σ
voice
,
0
otherwise
.
where VD comprises the voice detection value, and k comprises a voice detector tuning parameter.
18 . A smooth voice magnitude estimator comprising:
adaptation rate selection logic operable to select a current adaptation rate value from among multiple available adaptation rate values; and
smooth voice magnitude determination logic operable to generate a current smooth voice signal magnitude using the current adaptation rate value.
19 . The smooth voice magnitude estimator of claim 18 , where:
the multiple available adaptation rate values comprise:
a first adaptation rate value; and
a second adaptation rate value approximately 5 to approximately 10 times greater than the first adaptation rate value.
20 . The smooth voice magnitude estimator of claim 18 , where:
the adaptation rate selection logic comprises:
adaptation rate decision logic operable to select among the multiple available adaptation rate values based on a signal sample frame characteristic value and a prior smooth voice magnitude value.
21 . The smooth voice magnitude estimator of claim 20 , where:
the signal sample frame characteristic value comprises a mean absolute value of a signal sample frame.
22 . The smooth voice magnitude estimator of claim 20 , where:
the signal sample frame characteristic value comprises a mean absolute value of: frequency domain signal samples, time domain signal samples, or a combination of both frequency domain signal samples and time domain signal samples.
23 . The smooth voice magnitude estimator of claim 18 , where:
the smooth voice magnitude determination logic comprises:
a first smooth voice signal magnitude generator;
a second smooth voice signal magnitude generator; and
generator decision logic operable to select between the first and second smooth voice signal magnitude generators.
24 . The smooth voice magnitude estimator of claim 23 , where:
the generator decision logic is operable to select the first smooth voice signal magnitude generator when a signal-to-noise ratio (SNR) value exceeds a SNR threshold.
25 . The smooth voice magnitude estimator of claim 24 , where:
the SNR value comprises a SNR value for a signal sample frame generated from a background noise estimate value and a mean absolute value of the signal sample frame.