US 9,177,566 B2Granted

Noise suppression method and apparatus

AssigneeTelefonaktiebolaget L M Ericsson (publ)

InventorsPer Åhgren, Anders Eriksson

Life of this patent

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Abstract

The present invention relates to a method and apparatus of a digital filter for noise suppression of a signal representing an acoustic recording. The method comprises determining a desired frequency response (H(ω)) of the digital filter; and generating a noise suppression filter based on the desired frequency response. The desired frequency response is determined in a manner so that the desired frequency response does not exceed a maximum level, wherein the maximum level is determined in response to the signal to be filtered.

Claims19

Dependent claims

A method implemented by a digital filter design processor of designing a noise suppression filter to filter an input signal representing an acoustic recording, the method comprising:

determining, by a digital filter design processor, a desired frequency response of the noise suppression filter by:
determining a maximum level of the desired frequency response in response to the input signal to be filtered and in dependence on a minimum level, wherein the maximum level determined by:
H
max
⁡
(
ω
)
=
max
⁢
{
H
min
2
β
⁢
(
Φ
^
y
⁡
(
ω
)
-
Φ
^
n
⁡
(
ω
)
)
Φ
^
n
⁡
(
ω
)
,
H
min
}
,
wherein Hmax(ω) is the maximum level as a function of frequency, Hmin is a minimum level of the desired frequency response, β is a tolerance threshold representing a maximum acceptable signal-to-noise ratio, {circumflex over (Φ)}y(ω) is a spectral density of the input signal as a function of frequency, {circumflex over (Φ)}n(ω) is a spectral density of a noise component of the input signal as a function of frequency, ({circumflex over (Φ)}y(ω)−{circumflex over (Φ)}n(ω) is a spectral density of an estimated desired component of the input signal as a function of frequency, and
(
(
Φ
^
y
⁡
(
ω
)
-
Φ
^
n
⁡
(
ω
)
)
Φ
^
n
⁡
(
ω
)
)
is an estimate of a signal-to-noise ratio of the input signal to be filtered as a function of frequency;
determining an approximation of the desired frequency response using the input signal;
comparing the approximation with the maximum level;
and
determining the desired frequency response based on the comparison of the approximation with the maximum level such that the desired frequency response does not exceed the maximum level and does not take a value lower than the minimum level;
generating, by the digital filter design processor, a noise suppression filter based on the desired frequency response;
and
filtering, by the noise suppression filter, the input signal representing the acoustic recording for use in recording and/or playback of the filtered input signal.

78 more elements

A digital filter design processor arranged to design a noise suppression filter to filter an input signal representing an acoustic recording, the digital filter design processor comprising:

a desired frequency response determination processor for determining a desired frequency response for the noise suppression filter, said desired frequency response determination processor configured to:
determine a maximum level of the desired frequency response in response to the input signal to be filtered and in dependence on a minimum level of the desired frequency response, wherein the maximum level is determined by:
H
max
⁡
(
ω
)
=
max
⁢
{
H
min
2
β
⁢
(
Φ
^
y
⁡
(
ω
)
-
Φ
^
n
⁡
(
ω
)
)
Φ
^
n
⁡
(
ω
)
,
H
min
}
,
wherein Hmax(ω) is the maximum level as a function of frequency, Hmin is a minimum level of the desired frequency response, β is a tolerance threshold representing a maximum acceptable signal-to-noise ratio, {circumflex over ({circumflex over (Φ)}y(ω) is a spectral density of the input signal as a function of frequency, {circumflex over (Φ)}n(ω) is a spectral density of a noise component of the input signal as a function of frequency, ({circumflex over (Φ)}y(ω)−{circumflex over (Φ)}n(ω)) is a spectral density of an estimated desired component of the input signal as a function of frequency, and
(
(
Φ
^
y
⁡
(
ω
)
-
Φ
^
n
⁡
(
ω
)
)
Φ
^
n
⁡
(
ω
)
)
is an estimate of a signal-to-noise ratio of the input signal to be filtered as a function of frequency;
determine an approximation of the desired frequency response using the input signal;
compare the approximation of the desired frequency response with the maximum level;
and
determine the desired frequency response based on the comparison of the approximation with the maximum level so that the desired frequency response does not exceed the maximum level and does not take a value lower than the minimum level;
a filter signal generation processor configured to generate the noise suppression filter based on the desired frequency response;
and
the noise suppression filter configured to filter the input signal representing the acoustic recording for use in recording and/or playback of the filtered input signal.

78 more elements

A user equipment for processing of an acoustic signal, the user equipment including a digital filter design processor arranged to design a noise suppression filter to filter an input signal representing an acoustic recording, the digital filter design processor comprising:

a desired frequency response determination processor for determining a desired frequency response for the noise suppression filter, said desired frequency response determination processor configured to:
determine a maximum level of the desired frequency response in response to the input signal to be filtered and in dependence on a minimum level of the desired frequency response, wherein the maximum level is determined by:
H
max
⁡
(
ω
)
=
max
⁢
{
H
min
2
β
⁢
(
Φ
^
y
⁡
(
ω
)
-
Φ
^
n
⁡
(
ω
)
)
Φ
^
n
⁡
(
ω
)
,
H
min
}
,
wherein Hmax(ω) is the maximum level as a function of frequency, Hmin is a minimum level of the desired frequency response, β is a tolerance threshold representing a maximum acceptable signal-to-noise ratio, {circumflex over (Φ)}y(ω) is a spectral density of the input signal as a function of frequency, {circumflex over (Φ)}n(ω) is a spectral density of a noise component of the input signal as a function of frequency, ({circumflex over (Φ)}y(ω)−{circumflex over (Φ)}n (ω)) is a spectral density of an estimated desired component of the input signal as a function of frequency, and
(
(
Φ
^
y
⁡
(
ω
)
-
Φ
^
n
⁡
(
ω
)
)
Φ
^
n
⁡
(
ω
)
)
is an estimate of a signal-to-noise ratio of the input signal to be filtered as a function of frequency;
determine an approximation of the desired frequency response using the input signal;
compare the approximation with the determined maximum level;
and
determine the desired frequency response based on the comparison of the approximation with the maximum level so that the desired frequency response docs does not exceed the maximum level and does not take a value lower than the minimum level;
and
a filter signal generation processor configured to generate the noise suppression filter based on the desired frequency response;
and
the noise suppression filter configured to filter the input signal representing the acoustic recording for use in recording and/or playback of the filtered input signal.

79 more elements

A node for relaying a signal representing voice in a communications system, the node including a digital filter design processor arranged to design a noise suppression filter to filter an input signal representing voice, the digital filter design processor comprising:

a desired frequency response determination processor for determining a desired frequency response for the noise suppression filter, said desired frequency response determination processor configured to:
determine a maximum level of the desired frequency response in response to the input signal to be filtered and in dependence on a minimum level of the desired frequency response, wherein the maximum level is determined by:
H
max
⁡
(
ω
)
=
max
⁢
{
H
min
2
β
⁢
(
Φ
^
y
⁡
(
ω
)
-
Φ
^
n
⁡
(
ω
)
)
Φ
^
n
⁡
(
ω
)
,
H
min
}
,
wherein Hmax(ω) is the maximum level as a function of frequency, Hmin is a minimum level of the desired frequency response, β is a tolerance threshold representing a maximum acceptable signal-to-noise ratio, {circumflex over (Φ)}y(ω) is a spectral density of the input signal as a function of frequency, {circumflex over (Φ)}n(ω) is a spectral density of a noise component of the input signal as a function of frequency, ({circumflex over (Φ)}y(ω)−{circumflex over (Φ)}n (ω)) is a spectral density of an estimated desired component of the input signal as a function of frequency, and
(
(
Φ
^
y
⁡
(
ω
)
-
Φ
^
n
⁡
(
ω
)
)
Φ
^
n
⁡
(
ω
)
)
is an estimate of a signal-to-noise ratio of the input signal to be filtered as a function of frequency;
determine an approximation of the desired frequency response using the input signal;
compare the approximation with the determined maximum level;
and
determine the desired frequency response based on the comparison of the approximation with the maximum level, so that the desired frequency response does not exceed the maximum level and does not take a value lower than the minimum level;
and
a filter signal generation processor configured to generate the noise suppression filter based on the desired frequency response;
and
the noise suppression filter configured to filter the input signal representing the acoustic recording for use in recording and/or playback of the filtered input signal.

79 more elements

A non-transitory computer-readable medium including program code for designing a noise suppression filter to filter an input signal representing an acoustic recording, the program code comprising computer-executable instructions that when executed by a computer causes the computer to perform operations, wherein the operations are configured to:

determine a maximum level of the desired frequency response in response to the input signal to be filtered and in dependence on a minimum level, wherein the maximum level is determined by:
H
max
⁡
(
ω
)
=
max
⁢
{
H
min
2
β
⁢
(
Φ
^
y
⁡
(
ω
)
-
Φ
^
n
⁡
(
ω
)
)
Φ
^
n
⁡
(
ω
)
,
H
min
}
,
wherein Hmax (ω) is the maximum level as a function of frequency, Hmin is a minimum level of the desired frequency response, β is a tolerance threshold representing a maximum acceptable signal-to-noise ratio, {circumflex over (Φ)}y(ω) is a spectral density of the input signal as a function of frequency, {circumflex over (Φ)}n(ω) is a spectral density of a noise component of the input signal as a function of frequency, ({circumflex over (Φ)}y(ω)−{circumflex over (Φ)}n(ω)) is a spectral density of an estimated desired component of the input signal as a function of frequency, and
(
(
Φ
^
y
⁡
(
ω
)
-
Φ
^
n
⁡
(
ω
)
)
Φ
^
n
⁡
(
ω
)
)
is an estimate of a signal-to-noise ratio of the input signal to be filtered as a function of frequency;
determine an approximation of the desired frequency response using the input signal;
compare the approximation with the maximum level;
determine the desired frequency response based on the comparison of the approximation with the maximum level, such that the desired frequency response does not exceed a maximum level and does not take a value lower than a minimum level;
and
generate a noise suppression filter based on the desired frequency response;
and
filter the input signal representing the acoustic recording for use in recording and/or playback of the filtered input signal.

77 more elements

Dependencies are inferred from the claim text.

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Abstract

A method implemented by a digital filter design processor of designing a noise suppression filter to filter an input signal representing an acoustic recording, the method comprising:

determining, by a digital filter design processor, a desired frequency response of the noise suppression filter by:
determining a maximum level of the desired frequency response in response to the input signal to be filtered and in dependence on a minimum level, wherein the maximum level determined by:
H
max
⁡
(
ω
)
=
max
⁢
{
H
min
2
β
⁢
(
Φ
^
y
⁡
(
ω
)
-
Φ
^
n
⁡
(
ω
)
)
Φ
^
n
⁡
(
ω
)
,
H
min
}
,
wherein Hmax(ω) is the maximum level as a function of frequency, Hmin is a minimum level of the desired frequency response, β is a tolerance threshold representing a maximum acceptable signal-to-noise ratio, {circumflex over (Φ)}y(ω) is a spectral density of the input signal as a function of frequency, {circumflex over (Φ)}n(ω) is a spectral density of a noise component of the input signal as a function of frequency, ({circumflex over (Φ)}y(ω)−{circumflex over (Φ)}n(ω) is a spectral density of an estimated desired component of the input signal as a function of frequency, and
(
(
Φ
^
y
⁡
(
ω
)
-
Φ
^
n
⁡
(
ω
)
)
Φ
^
n
⁡
(
ω
)
)
is an estimate of a signal-to-noise ratio of the input signal to be filtered as a function of frequency;
determining an approximation of the desired frequency response using the input signal;
comparing the approximation with the maximum level;
and
determining the desired frequency response based on the comparison of the approximation with the maximum level such that the desired frequency response does not exceed the maximum level and does not take a value lower than the minimum level;
generating, by the digital filter design processor, a noise suppression filter based on the desired frequency response;
and
filtering, by the noise suppression filter, the input signal representing the acoustic recording for use in recording and/or playback of the filtered input signal.

78 more elements