JP3402711B2 - Sound intensity measurement device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to noise control and sound field visualization.
In the field of acoustic measurement, such as computerization, sound source search, and radiation power measurement
The present invention relates to a sound intensity measuring device used. [0002] 2. Description of the Related Art Sound intensity is measured in a sound field.
A sound that passes through a unit area perpendicular to the direction of sound travel in a unit time
Energy. Measures sound intensity
To measure the sound pressure, which is the amount of scalar
The sound field that was impossible with the method of
It becomes possible to visualize. This allows noise control
In the field, it is easier to find sound sources and to take measures against noise.
You. Also, in the measurement of radiated power in actual use conditions
Is not affected by ambient reflections or external noise.
Measurement of power. [0003] Conventionally, as a sound intensity measurement method,
It is known that the so-called two-microphone method is
Have been. This technique places two microphones in the sound field.
Place them apart from each other by a predetermined distance d.
Assuming that the sound field varies linearly between the crophones
The sound input at the midpoint of the two microphones
It measures the strength. However, these two
In the icrophone method, the above assumption,
Including errors, especially in the high frequency band
The difference in the phase of the sound input to each phone is
It is a difference factor. As a method of correcting this error, (A) The sound wavelength λ, the distance d between two microphones and
Using a predetermined amount before measurement
Kd / sin (kd),
(Where k represents the wave number (2π / λ)). (B) Sound signal obtained by each of two microphones
The sound intensity calculated using the phase difference φ
The tee is multiplied by φ / sin φ. There are two methods
is there. [0005] These two approaches are based on the sound energy flow.
Direction (hereinafter sometimes simply referred to as "sound direction")
And the direction of the line connecting the two microphones
Direction).
In addition, under the condition that there is no sound reflection,
However, accurate correction is performed. [0006] However, the sound direction and
Probe orientation mismatch or sound reflection
Correction may not be possible if is present. FIG.
Is a system for confirming the effects of the above-described corrections (a) and (b).
It is a graph showing a simulation result. The vertical axis is sound
Is the sound intensity (dB) (relative value), where 0 dB is
Indicates that there is no error. The horizontal axis is the traveling wave
And the phase difference between the reflected wave and the reflected wave. That is, this group
Roughness is measured at each measurement point where the phase difference between the traveling wave and the reflected wave is different.
Error of sound intensity when probe is placed
It represents. Simulation for obtaining the graph of FIG.
The condition of the sound is f = 1.2kHz, traveling wave
Relative intensity r = 0.0 (no reflection)
The distance d between two microphones d = 0.05
m, the angle θ = 45 ° between the direction of the probe and the direction of the sound
It is. Obtained without any correction
The sound intensity was about-as shown by the solid line in FIG.
It has an error of 0.5 dB. This was mentioned above
(A), that is, by multiplying kd / sin (kd), FIG.
Results in an error of about 0.5 dB as shown by the broken line
Becomes On the other hand, the above (b), that is, φ / sin φ is raised to the power
By calculation, as shown by the dashed line in FIG.
It is. That is, the direction of the probe and the direction of the sound are not
When there is a match and there is no sound reflection
Is correctly corrected by multiplying by φ / sinφ.
In kd / sin (kd), correct correction is not performed.
No. FIG. 9 shows the intensity ratio of the reflected wave to the traveling wave, r = 0.
5. The angle θ = 0 ° between the direction of the probe and the direction of the sound
FIG. 8 shows the case where the directions match.
It is a graph showing a simulation result similar to. When no correction has been made, it is indicated by a solid line.
Has an error of about -0.5 dB, and kd / sin (k
multiplying by d) corrects correctly and multiplies by φ / sin φ
Then, the error greatly fluctuates according to the phase difference. Sand
That is, the condition that the direction of the probe and the direction of the sound match
Then, even if sound reflection exists, kd / sin (k
d) is correctly corrected by multiplying by
Correct correction is not performed for φ. FIG. 10 shows the intensity ratio of the reflected wave to the traveling wave.
r = 0.5, the angle θ between the direction of the probe and the direction of the sound =
Simulation similar to FIGS. 8 and 9 at 45 °
It is a graph showing a result. As shown in FIG.
There is a wave and the direction of the probe and the direction of the sound do not match.
Under certain conditions, kd / sin (kd),
Correct correction is performed using either φ / sin φ.
Absent. Here, even if a reflected wave exists, the probe
Kd / sin when the direction of
Correction is correctly performed by multiplying (kd)
Therefore, this kd / sin (kd) indicates the direction of the probe.
The angle θ between the sound and the direction of the sound
Equivalent distance between the two microphones by an amount corresponding to
Considering that the separation is reduced, kdcos θ / sin (kdcos
θ) may be used for correction. FIG. 11 shows a state under the same conditions as in FIG.
It is a graph showing a simulation result, and kd /
sin (kd), with correction by φ / sinφ, k
The correction result by dcosθ / sin (kdcosθ) is
It is shown. As shown in FIG. 11, kdcos θ / s
By using in (kdcosθ), the reflected wave
And the direction of the probe and the direction of the sound do not match,
Correction is also made. However, kdcos θ / sin (kdco
sθ), the probe direction and
It is necessary to know in advance the angle between the sound and the direction.
Is usually unknown. Know the direction of the sound
Change the probe direction by trial and error.
Attempt to maximize the required sound intensity value
There is a way to find the direction, but it is very troublesome
It is not realistic. In view of the above circumstances, the present invention
Corrected correctly without repeating errors
Sound in which the required sound intensity can be obtained
An object of the present invention is to provide a strength measuring device. [0015] [MEANS FOR SOLVING THE PROBLEMS]
Ming's sound intensity measurement device (1) The line connecting the two microphones is tertiary
To extend in at least three different directions
At least four microphones located at fixed points (2) The sound signals obtained by the microphone
Loss spectrum G_mn(M and n are the numbers of each microphone
Means for calculating the cross spectrum (3) Crosss calculated by the cross spectrum calculation means
Vector G_mnThe sound energy at the measurement point
Sound direction calculation means for determining the direction of the flow of lugie (3) Flow of sound energy obtained by sound direction calculation means
And the line segment connecting each of the two microphones m and n
Angle θ_mn, The cross spectrum G
_mnInstead of the expression   G '_mn= G_mn・ ｛Kd_mncos θ_mn/ Sin (kd_mncos θ_mn)｝… (1) Here, k is the wave number of the sound (2π / λ; λ is the wavelength of the sound), d_mn
Represents the distance between the two microphones m and n. so
The required corrected cross spectrum G '_mnUsing
Sound intensity operator who seeks sound intensity
It is characterized by having a step. [0016] According to the above-mentioned at least four microphones,
Of each of the two microphones (allowing overlap)
Cross spectrum G of different sound signals_mnAnd calculate it
Cross spectrum G_mnIn the x, y, and z directions
A sound intensity component can be determined. These sound intensities are related to the errors described above.
There are some that include the difference, but the sound in the x, y, and z directions
The sound component, the approximate direction of the sound
Can be determined. The direction is determined in this way.
The angle between the direction of the sound and the direction of each pair is θ _mnage
The correction term kd_mncos θ_mn/ Sin (k
d_mncos θ_mn) Using the cross spectrum G_mnCorrect
And the corrected cross spectrum G ' _mnSound using
Find the sound intensity. This allows you to try and
Correct correction without repeated measurement like error
The calculated sound intensity can be obtained. [0018] Embodiments of the present invention will be described below. This
Here, four matrices are placed at each vertex position of the regular tetrahedron.
Probe having an microphone (Japanese Patent Laid-Open No. 5-28859)
No. 8) will be described. FIG. 1 shows four micro-cells in this embodiment.
Phone P₁ , P_Two , P_Three , P_Four FIG. these
4 microphones P₁ , P_Two , P_Three , P_Four Is one side
It is arranged at each vertex of a regular tetrahedron of length d. X axis, Y
The axis and Z axis may be determined in any manner, but here,
The position of the center of gravity of the plane is set to origin 0, and three microphones P
₁ , P_Two, P_Three Is on a plane that extends parallel to the XY plane.
And microphone P_Four Coordinates so that is on the Z axis
Set the axis and the microphone P₁ From position to Z axis
The Y axis is defined in the direction of a line segment that intersects at right angles with the extending Z axis. Book
In an embodiment, four microphones are
Attached to an axis extending in the Z-axis direction so that
You. FIGS. 2 and 3 show three-dimensional sound intensity measurement of the present invention.
Four microphones mounted in one embodiment of the device
Front view showing the probe in a deflected state, and the left side of FIG.
It is a side view seen from the side. Micro at the tip of mounting shaft 20
Phone P_Four With three microphones
P₁ , P_Two , P_Three Is attached so as to surround the mounting shaft 20.
Each arm 22, 24, 26 fixed to the shaft 20
It is attached. These four microphones P₁ , P
_Two , P_Three , P_Four Are the vertices of the regular tetrahedron
Located in. 4 microphones P₁ , P_Two , P_Three ,
P_Four Configure the probe with this attached, where
Indicates the direction in which the mounting shaft 20 extends, the Z axis, and the microphone P
₁ Let the direction in which the arm 22 for fixing the
You. The X-axis direction is not particularly specified, but the mounting shaft 20 and the arm
The direction perpendicular to both directions is the X-axis direction. Accordingly
The probe in measuring the sound intensity
It can be easily arranged in the direction. Also, these four
Microphone P₁ , P_Two , P_Three , P_Four Composed of
The position of the center of gravity of the tetrahedron (the position and coordinates of the measured sound intensity)
Microphone P at the origin of the axis)_Four Extends in the Z-axis direction of
Only the axis 20a is present, so the disturbance of the sound field is minimized
Can be held down. FIG. 4 shows the sound intensity measurement of the present invention.
FIG. 2 is a block diagram showing the overall configuration of an embodiment of the device.
The microphone probe 1 has four microphones P
₁ , P_Two , P_Three , P_FourAre provided and these
Crophon P₁ , P_Two , P_Three , P_Four Is shown in FIGS. 2 and 3.
Is arranged and fixed. These microphones
P₁ , P_Two , P_Three , P_Four The signal obtained at
The signal is input to the FFT analyzer 3 via the loop 2. In the FFT analyzer 3, the A / D converter 4
Is converted to a digital signal in the
Is input to the cross spectrum calculator 5. Cross spec
In the vector calculation unit 5, each microphone P₁ , P_Two , P
_Three , P_Four Are Fourier-transformed respectively,
And a cross corresponding to each combination of two microphones
Power spectrum G_mn(M, n = 1, 2, 3, 4)
Can be Where G_mnIs two microphones P_m , P
_n In the cross power spectrum of the signal obtained in
is there. The cross spectrum calculated by the cross spectrum calculator 5
Loss power spectrum G_mn(M, n = 1, 2, 3, 4)
Is input to the sound direction calculation unit 6, and the sound direction calculation unit 6
Is performed, and the direction of the sound is obtained. Sound direction calculation
In the output section 6, the noise calculated by the cross spectrum calculation section 5 is obtained.
Loss power spectrum G_mn(M, n = 1, 2, 3, 4)
First, the sound intensity in each of the X, Y, and Z directions is used.
Ingredients are required. The direction i component I of the sound intensity_i Is
In general, I_i = Im (a_i G₁₂+ B_i G₁₃+ C_i G₁₄+ D_i G_{twenty three}
+ E_i G_{twenty four}+ F_i G₃₄) Here, Im (...) is an imaginary part of one-sided spectrum of ...,
a_i , B_i , C_i, D_i , E_i , F_i Represents each coefficient
You. ... (2) Is represented by This is applied to the coordinate system shown in Figs.
Then, each component in the X, Y, and Z directions of the sound intensity I is obtained.
Minute I_x , I_y , I_z Is [0026] (Equation 1) Here, Im {G}: One-sided cross spec of G
The imaginary part of Khutor ω: angular frequency ρ: density of the medium d: spacing between microphones It is. Here, each direction of X, Y, Z is positive.
May be selected, in this case, depending on how to select
What is necessary is to reverse the sign of the operation result of the equations (3) to (5).
No. The sound direction calculator 6 calculates the sound direction in accordance with the equations (3) to (5).
Each component of X, YZ axis direction of sound intensity based on sound
Of the sound from the measurement point where the probe is located
A direction is required. Direction cosine of the direction of the sound as seen from the measurement point
Is the angle between the direction of the sound and the X, Y, and Z axes.
α, β, γ, cosα = I_x / I cosβ = I_y / I cosγ = I_z / I (6) Given by Where I is the magnitude of the sound intensity
And I = (I_x ^Two+ I_y ^Two+ I_z ^Two)^1/2           …… (7) Given by Using the three directional cosines shown in equation (6)
And four microphones P₁ , P_Two, P_Three , P_Four To
Microphones m, n (m, m,
n = 1,2,3,4) and the direction of the sound
Angle θ_mnIs required. [0030] (Equation 2)In the sound direction calculation section 6, based on equation (8)
Angle θ_mn, And cross spectrum calculation
Cross spectrum G obtained by part 5_mnIs the sound intensity
It is input to the city calculation unit 7. Sound intensity calculation
In the unit 7, the input angle θ_mnAnd cross spectrum G_mn
And the expression   G '_mn= G_mn・ ｛Kdcosθ_mn/ Sin (kdcosθ_mn)｝… (9) Cross spectrum G 'corrected by_mnIs required,
Further, the corrected cross spectrum G '_mnUsing
And G in the above equations (3) to (5)_mnTo G '_mnChanged to
Equation: [0032] (Equation 3) The sound intensity corrected based on the
Each component I in the X, Y, and Z directions_x ', I_y ', I_z But
Desired. In the sound intensity calculation unit 7,
The calculated sound intensity (I _x ', I_y ', I_z
′) Is returned to the sound direction calculation unit 6 again, and the equations (6) to (8) are used.
Therefore, the angle θ again_mnAnd the angle θ obtained again_mnTo
The sound intensity is input to the sound intensity calculation unit 7 and the sound intensity is calculated again.
And correct several times in this way
After that, the sound intensity may be obtained. Next, the simulation results of the present invention will be described.
Will be explained. FIG. 5 shows the effect of the correction according to the present invention.
6 is a graph showing a simulation result for the second embodiment. Shi
The condition of the simulation is that the sound frequency f = 1.2 kHz.
z, relative intensity of the reflected wave with respect to the traveling wave r = 0.5, 2 for each
Distance between two microphones d = 0.06 m, Z axis and X
The angle 方向 between the sound direction and the Z axis in a plane including the axis
= 0 °, the direction of sound in a plane including the X axis and the Y axis
Angle ζ = 0 ° with X axis, all microphones
The phase difference between the pump systems (phase difference between channels) is zero.
Is the case. That is, the simulation shown in FIG.
Indicates that the reflected wave exists but the sound direction matches the Z axis.
Is the case. In this case, an error of about -1.0 dB before correction.
Although there is a difference, even if a reflected wave exists, the method of the present invention is used.
Has been corrected correctly. FIG. 6 shows a supplement according to the present invention.
Another simulation result to confirm the positive effect
FIG. Simulation conditions are shown in the figure.
And the simulation of FIG.
Is ξ = 45 °, that is, in the X direction (horizontal) with respect to the Z axis.
It is assumed that sound is incident from a direction that is 45 °
Have been. FIG. 6 shows the sound intensity in the X direction.
Component and the component in the Z direction are shown.
When the size of the key (see equation (7)) is 1.0,
Component I in the Z direction_x , I_z Is in decibels, I_x = I_z = 10 · log1.0 / √2 = -1.5 (d
B) Becomes Therefore, the position at -1.5 dB in FIG.
Means that is correctly corrected, in the present invention,
In this way, there is a reflected wave, and the sound enters obliquely.
However, correct correction is performed. FIG. 7 shows the effect of the correction according to the present invention.
A graph showing another simulation result
And there is a reflected wave, the sound enters obliquely, and
Microphone P_Four The other three channels including the amplifier
E = kd / 50 ≒ 1.5 °
It is assumed that. In this case, the phase error e
The error caused by this remains, but even in this case, the reflected wave,
The error due to the oblique incidence of the sound is correctly corrected. The above uses four microphones.
A description of the 3D intensity probe
There is a probe with six microphones.
However, exactly the same method can be applied. [0039] As described above, according to the present invention,
The difference between the error due to the reflected wave and the error due to the oblique incidence of sound
To find correct corrected sound intensity
Can be.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows four microphones P ₁ ,
P _2, P _3, is a schematic representation of a P _4. FIG. 2 is a front view showing a probe with four microphones attached thereto according to one embodiment of the three-dimensional sound intensity measuring apparatus of the present invention. FIG. 3 is a side view of the three-dimensional sound intensity measuring device shown in FIG. 2 as viewed from the left side of FIG. 2; FIG. 4 is a block diagram showing an overall configuration of an embodiment of the sound intensity measuring device according to the present invention. FIG. 5 is a graph showing a simulation result for confirming the effect of correction according to the present invention. FIG. 6 is a graph showing another simulation result for confirming the effect of correction according to the present invention. FIG. 7 is a graph showing another simulation result for confirming the effect of the correction according to the present invention. FIG. 8 is a graph showing a simulation result for confirming the effect of correction. FIG. 9 is a graph showing a simulation result for confirming the effect of correction. FIG. 10 is a graph showing a simulation result for confirming the effect of correction. FIG. 11 is a graph showing a simulation result for confirming the effect of correction. [Description of Signs] 1 Microphone probe 2 Microphone amplifier 3 FFT analyzer 4 A / D converter 5 Cross spectrum calculator 6 Sound direction calculator 7 Sound intensity calculator

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Shozo Anzai 1-16-1 Hakusan, Midori-ku, Yokohama-shi, Kanagawa Prefecture Inside Ono Sokki Technical Center (56) References JP-A-5-288598 (JP, A JP, 5-79899 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01H 3/10

Claims (1)

(57) [Claim 1] At least four microphones arranged at measurement points such that line segments connecting each two microphones extend in at least three directions different from each other three-dimensionally. , cross-spectral G _mn of the sound signals to each other obtained by said microphone (m, n represents the number of the microphones) based and cross-spectral calculation means for determining, in cross spectrum G _mn obtained in the cross-spectral calculation means A sound direction calculating means for determining the direction of the flow of sound energy at the measurement point; and a line segment connecting the direction of the flow of sound energy obtained by the sound direction calculating means and each of the two microphones m and n. And θ _mn , the cross spectrum G _mn
Instead of the formula G ′ _mn = G _mn · {kd _mn cos θ _mn / sin (kd _mn cos θ _mn )} where k is the sound wave number (2π / λ; λ is the sound wavelength), d _mn
Represents the distance between the two microphones m and n. And a sound intensity calculating means for obtaining sound intensity using the corrected cross spectrum G ′ _mn obtained in step (a).