Device and method for estimating direction of arrival
A device for estimating Direction of Arrival (DOA) of sound from Q≥1 sound sources is provided. The device is configured to obtain a phase difference matrix, which includes measured phase difference values, each of the measured phase difference values being a measured value of a phase difference between two microphone units for a frequency bin in a range of frequencies of the sound. The device is further configured to generate a replicated phase difference matrix by replicating the measured phase difference values to other potential sinusoidal periods, calculate a DOA value for each phase difference value in the replicated phase difference matrix, and determine, as Q DOA results, the Q most prominent peak values in a histogram generated based on the calculated DOA values.
1. A device for estimating Direction of Arrival (DOA) of sound from Q >1 sound sources, the device being a component in a system comprising a plurality of microphone units, the device being configured to:
obtain a phase difference matrix including measured phase difference values, each of the measured phase difference values being a measured value of a phase difference between two microphone units of the plurality of microphone units for a frequency bin in a range of frequencies of the sound,
generate a replicated phase difference matrix by replicating the measured phase difference values to other potential sinusoidal periods,
calculate a DOA value for each phase difference value in the replicated phase difference matrix,
generate a first histogram from the calculated DOA values,
select, as Q+q DOA candidates, Q+q most prominent peak values in the first histogram, wherein q=2,
generate a second histogram based on the selected Q+q DOA candidates, and
determine, as Q DOA results, Q most prominent peak values in the second histogram.
2. The device according to claim 1 , wherein the device is further configured to:
generate the replicated phase difference matrix by replicating the measured phase difference values based on a minimum aliasing frequency defined by
f
a
0
=
c
2
Δ
d
wherein Δd denotes a distance between the two microphone units and c is a speed of the sound.
3. The device according to claim 2 , wherein:
the measured phase difference values in the phase difference matrix are wrapped into [−π, π], and
the device is configured to generate the replicated phase difference matrix according to
C
=
⌈
f
i
-
f
a
0
2
f
a
0
⌉
C
s
=
(
-
C
,
-
C
+
1
,
…
,
0
,
…
,
C
)
μ
(
i
,
j
)
=
μ
0
(
i
)
+
2
π
C
s
(
j
)
i
=
1
,
…
N
;
j
=
1
,
…
(
2
C
+
1
)
wherein μ 0 denotes the phase difference matrix, μ denotes the replicated phase difference matrix, i is a frequency bin index corresponding to frequency f i , j is a replication index, and [*] denotes a ceiling function.
4. The device according to claim 3 , wherein the device is further configured to:
calculate the DOA values based on the formula
θ
(
i
,
j
)
=
arcsin
μ
(
i
,
j
)
2
π
f
Δ
d
wherein θ(i,j) denotes the DOA value for frequency bin index i and replication index j, μ denotes the replicated phase difference matrix and Δd denotes a distance between the two microphone units.
5. The device according to claim 1 , wherein the device is further configured to:
remove complex calculated DOA values, before generating the first histogram.
6. The device according to claim 1 , wherein, for generating the second histogram, the device is configured to:
determine, for each selected DOA candidate, its related DOA values from the calculated DOA values,
generate third histograms from each selected DOA candidate and its related DOA values, and
generate the second histogram by merging the third histograms of all selected DOA candidates.
7. The device according to claim 6 , wherein the device is further configured to:
merge the third histograms of all selected DOA candidates to generate the second histogram by, for each histogram index, using the maximum value from all the third histograms as the value of the second histogram for that histogram index.
8. The device according to claim 6 , wherein the device is further configured to:
determine the related DOA values of a DOA candidate by
determe, as its related phase difference values, the phase difference values in the replicated phase difference matrix that are in supposed correct sinusoidal periods, and
calculate its related DOA values from its related phase difference values.
9. The device according to claim 6 , wherein the device is further configured to:
apply a soft mask to the peak values in each of the third histograms, before merging the third histograms into the second histogram,
wherein the soft mask is designed as a peak filter with a smaller width at a DOA of 0° and larger widths at DOAs of ±90°.
10. The device according to claim 9 , wherein the device is further configured to:
apply a low-pass filter to the second histogram, before determining the Q DOA results.
11. The device according to claim 1 , wherein:
each microphone unit of the two microphone units includes an array of one or more microphones, and
the one or more measured phase difference values of the phase difference matrix are obtained from measured phase differences between the one or more microphones of one of the microphone units and the one or more microphones of the other one of the microphone units.
12. An apparatus for determining Direction of Arrival (DOA) of sound from Q>1 sound sources, the apparatus comprising:
a device configured to:
obtain a phase difference matrix including measured phase difference values, each of the measured phase difference values being a measured value of a phase difference between two microphone units of a plurality of microphone units for a frequency bin in a range of frequencies of the sound,
generate a replicated phase difference matrix by replicating the measured phase difference values to other potential sinusoidal periods,
calculate a DOA value for each phase difference value in the replicated phase difference matrix,
generate a first histogram from the calculated DOA values,
select, as Q+q DOA candidates, Q+q most prominent peak values in the first histogram, wherein q=2,
generate a second histogram based on the selected Q+q DOA candidates, and
determine, as Q DOA results, Q most prominent peak values in the second histogram and
a sound receiver, including the two microphone units, configured to receive the sound, generate the phase difference matrix, and provide the phase difference matrix to the device.
13. A method of estimating Direction of Arrival (DOA) of sound from Q >1 sound sources, in a system comprising a plurality of microphone units, the method comprising:
obtaining a phase difference matrix including measured phase difference values, each of the measured phase difference values being a measured value of a phase difference between two microphone units of the plurality of microphone units for a frequency bin in a range of frequencies of the sound,
generating a replicated phase difference matrix by replicating the measured phase difference values to other potential sinusoidal periods,
calculating a DOA value for each phase difference value in the replicated phase difference matrix,
generating a first histogram from the calculated DOA values,
selecting, as Q+q DOA candidates, Q+q most prominent peak values in the first histogram, wherein q=2,
generating a second histogram based on the selected Q+q DOA candidates, and
determining, as Q DOA results, Q most prominent peak values in the second histogram.
14. The device according to claim 10 , wherein the low-pass filter is a Gaussian filter with a standard deviation σ according to
σ
=
arccos
(
1
-
c
f
s
Δ
d
)
wherein f s denotes the sampling rate.
15. The apparatus according to claim 12 , wherein the device is further configured to:
generate the replicated phase difference matrix by replicating the measured phase difference values based on a minimum aliasing frequency defined by
f
a
0
=
c
2
Δ
d
wherein Δd denotes a distance between the two microphone units and c is a speed of the sound.
16. The apparatus according to claim 15 , wherein:
the measured phase difference values in the phase difference matrix are wrapped into [−π, π], and
the device is configured to generate the replicated phase difference matrix according to
C
=
⌈
f
i
-
f
a
0
2
f
a
0
⌉
C
s
=
(
-
C
,
-
C
+
1
,
…
,
0
,
…
,
C
)
μ
(
i
,
j
)
=
μ
0
(
i
)
+
2
π
C
s
(
j
)
i
=
1
,
…
N
;
j
=
1
,
…
(
2
C
+
1
)
wherein μ 0 denotes the phase difference matrix, μ denotes the replicated phase difference matrix, i is a frequency bin index corresponding to frequency f i , j is a replication index, and [*] denotes a ceiling function.
17. The method according to claim 13 , further comprising:
generating the replicated phase difference matrix by replicating the measured phase difference values based on a minimum aliasing frequency defined by
f
a
0
=
c
2
Δ
d
wherein Δd denotes a distance between the two microphone units and c is a speed of the sound.
18. The method according to claim 17 , wherein:
the measured phase difference values in the phase difference matrix are wrapped into [−π, π], and the method further comprises:
generating the replicated phase difference matrix according to
C
=
⌈
f
i
-
f
a
0
2
f
a
0
⌉
C
s
=
(
-
C
,
-
C
+
1
,
…
,
0
,
…
,
C
)
μ
(
i
,
j
)
=
μ
0
(
i
)
+
2
π
C
s
(
j
)
i
=
1
,
…
N
;
j
=
1
,
…
(
2
C
+
1
)
wherein μ 0 denotes the phase difference matrix, μ denotes the replicated phase difference matrix, i is a frequency bin index corresponding to frequency f i , j is a replication index, and [*] denotes a ceiling function.