Method for three-dimensional tracking of sinusoidal acoustic source using a rotating microphone
View Patent ↗A method for determining the location of a first source. A first member is provided. A first tip microphone is attached to a first end of the first member. A first static microphone is provided. An initial frequency is recorded at the static microphone. The first member is rotated at an angular velocity. A tangential distance is calculated from the first tip microphone to the source. A source angle is calculated from the first member to the source. A height of the source is calculated.
1. A method for determining a location of a first source comprising:
providing a first member, wherein a first tip microphone is attached to a first end of said first member;
recording an initial frequency;
rotating the first member at an angular velocity;
calculating a tangential distance from the first tip microphone to the source;
calculating a source angle from the first member to the source; and
calculating a height of the source.
2. The method of claim 1 , further comprising the step of calculating a first tip velocity v 1 according to the relationship
v
1
=
ω
l
2
,
wherein l is a length of the first member and ω is the angular velocity.
3. The method of claim 1 , further comprising the step of recording for each angle of rotation θ a measured frequency f m .
4. The method of claim 1 , further comprising the step of determining a maximum measured frequency f max and a corresponding maximum angle θ max .
5. The method of claim 1 , further comprising the step of determining a minimum measured frequency f min and a corresponding minimum angle θ min .
6. The method of claim 2 , further comprising the step of calculating a maximum possible Doppler shift frequency Δf max according to the relationship
Δ
f
max
=
f
0
v
1
c
,
wherein c is a speed of sound, and wherein f 0 is the initial frequency.
7. The method of claim 6 , further comprising the step of determining a calculated frequency f measured according to the relationship
Δ
f
measured
=
f
0
n
·
v
1
→
c
and the relationship f measured =Δf measured +f 0 , wherein n is a unit vector in the direction from the source to the first tip microphone, and {right arrow over (v 1 )} is a velocity vector of the first tip microphone.
8. The method of claim 7 , wherein the height of the source h is calculated according to the relationship
h
=
±
A
(
Δ
f
max
Δ
f
measured
)
2
-
1
,
wherein A is the tangential distance.
9. The method of claim 1 , further comprising the step of providing a second member with a second tip microphone attached to a second end of said second member.
10. The method of claim 9 , further comprising the step of orienting the second member at an angle different from the first member.
11. The method of claim 10 , further comprising the step of calculating a second height h 2 of the source.
12. The method of claim 11 , further comprising the step of comparing the height of the source h with h 2 to determine whether h is above or below the first member.
13. A method for determining a location of a source comprising:
providing a first member of length l, wherein a first tip microphone is attached to a first end of said first member;
providing a static microphone;
recording at the static microphone an initial frequency f 0 ;
rotating the first member at an angular velocity ω;
calculating a first tip velocity v 1 according to the relationship
v
1
=
ω
l
2
;
recording for each angle of rotation θ a measured frequency f m ;
determining a maximum measured frequency f max and a corresponding maximum angle θ max ;
determining a minimum measured frequency f min and a corresponding minimum angle θ min ;
calculating a tangential distance A and source angle α;
calculating a maximum possible Doppler shift frequency Δf max according to the relationship
h
=
±
A
(
Δ
f
max
Δ
f
measured
)
2
-
1
,
and the relationship f measured =Δf measured +f 0 , wherein c is a speed of sound;
determining a calculated frequency f measured according to the relationship
Δ
f
max
=
f
0
v
1
c
wherein n is a unit vector in the direction from the source to the first tip microphone, and {right arrow over (v 1 )} is a velocity vector of the first tip microphone; and
calculating a height of the source h according to the relationship
Δ
f
measured
=
f
0
n
·
v
1
→
c
,
wherein A is the tangential distance.
14. The method of claim 13 , further comprising the step of providing a second member with a second tip microphone attached to a second end of said second member.
15. The method of claim 14 , further comprising the step of orienting the second member at an angle different from the first member.
16. The method of claim 15 , further comprising the step of calculating a second height h 2 of the source.
17. The method of claim 16 , further comprising the step of comparing h and h 2 to determine whether h is above or below the first member.
18. A method for determining a location of a source comprising:
providing a first member of length l, wherein a first tip microphone is attached to a first end of said first member;
providing a static microphone;
providing a rotary encoder;
measuring at the radial encoder an angle of rotation θ;
recording at the static microphone an initial frequency f 0 ;
rotating the first member at an angular velocity ω;
calculating a first tip velocity v 1 according to the relationship
v
1
=
ω
l
2
;
recording for each angle of rotation θ a measured frequency f m ;
determining a maximum measured frequency f max and a corresponding maximum angle θ max ;
determining a minimum measured frequency f min and a corresponding minimum angle θ min ;
calculating a tangential distance A and source angle α;
calculating a maximum possible Doppler shift frequency Δf max according to the relationship
Δ
f
max
=
f
0
v
1
c
,
wherein c is a speed of sound;
determining a calculated frequency f measured according to the relationship
Δ
f
measured
=
f
0
n
·
v
1
→
c
and the relationship f measured =Δf measured +f 0 , wherein n is a unit vector in the direction from the source to the first tip microphone, and {right arrow over (v 1 )} is a velocity vector of the first tip microphone;
calculating a height of the source h according to the relationship
h
=
±
A
(
Δ
f
max
Δ
f
measured
)
2
-
1
,
wherein A is the tangential distance;
providing a second member with a second tip microphone attached to a second end of said second member;
orienting the second member at an angle different from the first member;
calculating a second height h 2 of the source;
comparing h and h 2 to determine whether h is above or below the first member; and
wherein the initial frequency f 0 , measured frequency f m , and angle of rotation θ are synchronously recorded.
19. The method of claim 18 , further comprising the steps of applying a full rotational discrete Fourier transform to the measured frequency f m , identifying plateau edge frequencies, applying a small window discrete Fourier transform to the measured frequency f m , and identifying a peak signal at plateau edges.
20. The method of claim 18 , further comprising the steps of applying a full rotation discrete Fourier transform to the initial frequency f 0 , and identifying sinusoidal peaks.