Method and apparatus for detecting and locating noise sources whether correlated or not

• US 6,999,881 B2
• Filed: 12/17/2003
• Issued: 02/14/2006
• Est. Priority Date: 12/17/2003
• Status: Active Grant

• Current Assignee: 01 DB - METRAVIB
• Original Assignee: Metravib R.D.S.
• Inventors: Permuy, Alfred, Millet, Joël
• Primary Examiner(s): Nghiem, Michael
• Assistant Examiner(s): LE, JOHN H
• Application Number:
  US10/736,894
• Publication Number:
  US 20050137804A1
• Time in Patent Office: 790 Days
• Field of Search: 702/14, 702/17, 702/38, 702/57, 702/69, 702/74, 702/152, 324/326, 324/520, 324/536, 73/405.A, 736/24, 381/71.13, 381/71.14, 381/94.7, 381/92, 381/71.2
• US Class Current: 702/17
• CPC Class Codes: G01V 1/362 Effecting static or dynamic corrections; Stacking

Abstract

A method of detecting and locating noise sources each emitting respective signals S_j with j=1 to M, detection being provided by a sound wave or vibration sensors each delivering a respective time-varying electrical signal s_i with i in the range 1 to N, wherein the method steps include: (a) taking the time-varying electrical signals delivered by the sensors, each signal s_i(t) delivered by a sensor being the sum of the signals S_j emitted by the noise sources; (b) amplifying and filtering the time-varying electrical signals as taken; (c) digitizing the electrical signals; (d) calculating a functional; and (e) minimizing the functional relative to the vectors n_j for j=1 to M so as to determine the directions of vector n_j of the noise sources.

Claims

1. A method of detecting and locating noise sources each emitting a respective signal S_j with j=1 to M, detection being provided by means of acoustic wave or vibration sensors each delivering a respective time-varying electrical signal s_i with i lying in the range 1 to N, the method comprising:

taking the time-varying electrical signals delivered by the sensors, each signal s_i(t) delivered by a sensor being the sum of the signals S_j emitted by the noise sources;

amplifying and filtering the time-varying electrical signals as taken;

digitizing the electrical signals;

calculating the functional f, such that;

$f<br><br>\left(n_l,\mathrm{\dots <br><br>}<br><br>,n_j,\mathrm{\dots <br><br>}<br><br>,n_M\right)=\frac{\det <br><br>\left(<<br><br>T_k<br><br>\left(\mathrm{\omega <br><br>}\right),T_l^{*}<br><br>\left(\mathrm{\omega <br><br>}\right)><br><br>k,l=0<br><br><br><br>\mathrm{to}<br><br><br><br>M\right)}{\det <br><br>\left(<<br><br>T_k<br><br>\left(\mathrm{\omega <br><br>}\right),T_l^{*}<br><br>\left(\mathrm{\omega <br><br>}\right)><br><br>k,l=1<br><br><br><br>\mathrm{to}<br><br><br><br>M\right)}$

 

with ${\left(T_k<br><br>\left(\mathrm{\omega <br><br>}\right)\right)}_i={\mathrm{e<br><br>}}^{J<br><br><br><br>\mathrm{\omega <br><br>}<br><br>\frac{<<br><br>n_k,c_i><br><br>}{c}}$

<

.,.>

being the scalar product;

c_i being the vector constructed between the center of gravity of the sensors and the position of sensor i;

n_j being the unit vector in the direction defined by the center of gravity of the senors and source j;

with T₀=s; and

with c=the speed of sound; and

in minimizing the functional f relative to the vectors n_j for j=1 to M in such a manner as to determine the directions n_j of the noise sources, wherein ω

is angular frequency,

<

T_k(ω

), T_i*(ω

)>

is the scalar product between T_k(ω

), and T_l*(ω

),

J corresponds to the imaginary number in mathematics.

2. A method according to claim 1, wherein, in order to minimize the functional f when the noise sources are narrow band sources, the method comprises:

calculating the Fourier transforms of the signals s_i(t) delivered by the sensors;

using the expressions for the determinants of the matrices of general term;

<

T_k(ω

),T_l*(ω

)>

 

to calculate the functional;

$f_1=\underset{k}{\sum <br><br>}<br><br>{<br><br>{B<br><br>\left(\mathrm{\omega <br><br>}\right)}_k<br><br>}^2$

and after selecting a determined number of noise sources, minimizing the functional f₁ to determine the directions n_j of the selected noise sources, wherein B is the noise vector which depends on ω

.

3. A detection method according to claim 1, wherein, in order to minimize the functional f when the noise sources are broad band, the method comprises:

calculating the Fourier transforms of the signals s_i(t) delivered by the sensors;

using the expressions of the determinants of the matrices of general term;

<

T_k(ω

),T_l*(ω

)>

 

to calculate the functional;

f₂=∫

∥

B(ω

)∥

²dω

and after selecting a determined number of noise sources, minimizing the functional f₂ to determine the directions n_j of the selected noise sources, wherein dω

is the derived term in the integral mathematics formulation.

4. A detection method according to claim 1, wherein, in order to minimize the functional f, the method comprises:

simplifying the expression for the functional ƒ

to minimize the following functional f₃;

f₃=∫

det(<

T_k,T_l*>

k, l=0 to M)dω

calculating cross-correlation functions γ

_ij of the signals s_i and s_j; and

after selecting a determined number of noise sources, minimizing the functional f₃, wherein

<

T_k, T_l*>

is the scalar product between T_k and T_i*.

5. A detection method according to claim 1, wherein, after the minimization operation, the method comprises calculating the source vector:

S(ω

)=(^tT*.T)<sup>−

1</sup>.^tT*.s(ω

)

in order to discover the characteristics of the noise sources, wherein

^tT* is the conjugate transposed matrix of T and T is a matrix,

S(ω

) is the vector of S which depends on ω

.