close

Вход

Забыли?

вход по аккаунту

?

JPH05288598

код для вставкиСкачать
Patent Translate
Powered by EPO and Google
Notice
This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
financial decisions, should not be based on machine-translation output.
DESCRIPTION JPH05288598
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
three-dimensional sound intensity measuring apparatus for measuring sound intensity by
recording sound with four microphones disposed at positions of respective vertices of a regular
tetrahedron.
[0002]
2. Description of the Related Art Heretofore, as a sensor for measuring the sound intensity of
various sounding bodies, there has been known a pair microphone consisting of two
microphones disposed back and forth toward the sounding body. The sound intensity is
calculated based on the cross power spectrum obtained by Fourier transforming the output of
this pair of microphones.
[0003]
That is, the cross power spectrum Gba (f) obtained by the above-mentioned Fourier transform
processing is Gba (f) = Sb · Sa * (1) where Sb: Fourier transform spectrum Sa * of the output of
one microphone: the other Complex conjugate spectrum of the Fourier transform spectrum of the
output of the microphone, and based on the cross power spectrum Gba (f), the acoustic intensity I
(f1 to f2) between the frequencies f1 and f2 is determined as follows: Be
03-05-2019
1
[0005]
Here, Im {Gba (f)}: imaginary part of one side cross spectrum of cross power spectrum Gba ρ:
density of medium Δr: distance between both microphones The acoustic intensity determined by
this equation (2) is both microphones The component of the sound intensity in the X direction or
Y direction which is a component in the linear direction connecting both microphones (for
example, this is taken as the Z direction) at the center point between them is not determined.
When trying to obtain each component of the sound intensity in the X, Y, Z directions using the
principle of this pair microphone, simply, in the Z direction and -Z direction, etc., centering on a
predetermined point where the sound intensity is to be obtained. The microphones are arranged
at a distance apart to form one pair of microphones, and in the same manner, they are equally
spaced in the X and -X directions and equally spaced in the Y and -Y directions. It is conceivable
to arrange the microphones at the positions, respectively, and to arrange a total of three pairs of
microphones, that is, six microphones.
[0006]
However, since the number of microphones is too large in this case, it is considered to obtain
each three-dimensional component of the sound intensity by combining four microphones. FIG. 5
is a layout diagram of four microphones arranged to obtain three-dimensional components of
acoustic intensity. One microphone P4 is disposed at the origin where the three axes of X, Y and
Z intersect, and the microphones P3, P1 and P2 are disposed on the X, Y and Z axes separated by
a distance L from the origin. By arranging four microphones in this manner, two microphones P4,
P3; P4, P1; P4, P2 constitute respective paired microphones, and each paired microphone makes
up each component in the X, Y, Z direction of acoustic intensity. Is required.
[0007]
However, in this case, the X component of the sound intensity is obtained at a point shifted by L /
2 in the X direction from the origin, and similarly, the Y component and the Z component are
only L / 2 in the Y direction and Z direction from the origin. The shifted points are determined,
and thus the acoustic intensities of different points in space are determined for each component.
In order to avoid this, it is proposed to arrange four microphones as follows (Newport Beach, CA,
USA “INTER-NOISE” 1989 December 4-6 '89 'MEASURINGTHE THREE-DIMENSIONAL
03-05-2019
2
ACOUSTIC INTENSITY' VECTOR WITH A FOUR-See MICROPHONE PROBE L. M. C. Santos, C. C.
Rodrigues, J. L. Bento Celho).
[0008]
FIG. 6 is a layout diagram of four microphones arranged so as to obtain three-dimensional
components of acoustic intensity at the same point in three directions. Here, as shown in FIG. 6
(a), four microphones P1, P2, P3, P4 are disposed at the respective apexes of a regular
tetrahedron with a side length d, and FIG. And (c), the X, Y, and Z axes are defined so as to appear
square when viewed from the X and Z axes (not shown but also the Y axis).
[0009]
By arranging in this way and performing predetermined processing on the signals obtained by
the four microphones, the X, Y, and Z direction components of the acoustic intensity at the origin
where the X, Y, and Z axes intersect are determined. Be
[0010]
Here, when actually measuring the sound intensity, it is properly known which direction of the
sound field (for example, the room) each component of the measured sound intensity is. It is
important that, in order to do this, the four microphones need to be oriented correctly with a
good knowledge of the X, Y and Z axes.
[0011]
FIG. 7 is a graphic representation of a photograph of four microphones fixed to an axis, which is
published in the above-mentioned reference, for which the method of measuring the acoustic
intensity described with reference to FIG. 6 has been proposed.
Although the above document does not explicitly describe the positional relationship of the four
microphones P1, P2, P3 and P4 on the photograph, it is arranged as shown in FIG. 6, and the
central axis extends in the Z axis direction. It is considered to be a direction.
If this arrangement is considered, although the direction of the Z-axis is known, the directions of
03-05-2019
3
both the X-axis and the Y-axis are unclear, and they are integrated as shown in FIG. 7 when
actually measuring the acoustic intensity. It is unclear at first glance how to arrange the
microphones in the sound field, and there is a problem that it is difficult to arrange the
microphones in the correct orientation.
[0012]
In order to solve this, it is conceivable, for example, to attach a pointer indicating the X direction
or Y direction similar to the arm 12 at the tip of the shaft 10 and to know the direction by the
pointer. However, in the case of measuring the sound intensity, it is necessary to reduce
members that disturb the sound field as much as possible in order to make the measurement
accurate. However, in the arrangement shown in FIG. 7, the arm 12 is present near the origin of
the coordinate axis which is the measurement point, and in addition to that, the indicator stick
indicating the direction is too far out of the sound field and accurate measurement can not be
performed. There is a fear.
[0013]
An object of the present invention is to provide a three-dimensional sound intensity measuring
apparatus provided with a microphone which is arranged so that the disturbance of the sound
field is small and the directions of coordinate axes can be grasped at first glance.
[0014]
FIG. 1 is a layout view of four microphones P1, P2, P3 and P4 in the present invention.
These four microphones P1, P2, P3 and P4 are disposed at each vertex of a regular tetrahedron
of length d. Here, the coordinate position is determined such that the center of gravity of this
regular tetrahedron is the origin point 0, and that the three microphones P1, P2, P3 are on a
plane extending parallel to the XY plane and the microphone P4 is on the Z axis. And, from the
position of the microphone P1 to the Z-axis, the Y-axis is defined in the direction of the line
segment intersecting the Z-axis at right angles. In the present invention, four microphones are
attached to an axis extending in the Z-axis direction in such a manner. Of course, the X, Y and Z
axes may be interchanged with one another.
03-05-2019
4
[0015]
The three-dimensional sound intensity measuring apparatus of the present invention has a probe
in which four microphones are fixed as shown in FIG. 1, so that the axis extends as in the
conventional case (FIG. 7). The direction is the Z-axis direction and the extension direction of the
arm is the Y-axis direction for attaching the microphone P1 shown in FIG. 1 corresponding to the
arm 12 shown in FIG. Since it is a direction orthogonal to both, it can be grasped at a glance, and
it becomes easy to arrange the microphone in the correct direction when measuring the sound
intensity. Further, it is easy to arrange an arm for attaching the microphones P1, P2 and P3 at a
position away from the origin 0, and the disturbance of the sound field is also reduced.
[0016]
EXAMPLES Examples of the present invention will be described below. 2 and 3 are a front view
showing a probe in a state in which four microphones are attached according to an embodiment
of the three-dimensional sound intensity measuring device of the present invention, and a side
view seen from the left of FIG.
[0017]
The microphone P4 is attached to the end of the attachment shaft 20, and the three microphones
P1, P2, P3 are attached to the respective arms 22, 24 and 26 fixed to the attachment shaft 20 so
as to surround the attachment shaft 20. It is done. The sensor portions of these four microphones
P1, P2, P3 and P4 are the apexes of a regular tetrahedron. When a probe having four
microphones P1, P2, P3 and P4 attached in this way, the extending direction of the mounting
shaft 20 is taken as Z axis, and the extending direction of the arm 22 for fixing the microphone
P1 as Y axis. And the X-axis direction is not explicitly specified, but can be immediately grasped
as a direction perpendicular to both the mounting shaft 20 and the arm 22 so that the probe can
be easily oriented in the correct direction for measuring the acoustic intensity it can. Also, at the
barycentric position (position of measured acoustic intensity, origin of coordinate axis) of a
tetrahedron formed of these four microphones P1, P2, P3 and P4, only the axis 20a extending in
the Z-axis direction of the microphone P4 Is present, and thus the disturbance of the sound field
can be minimized.
[0018]
03-05-2019
5
FIG. 4 is a block diagram showing the overall configuration of an embodiment of the threedimensional acoustic intensity measurement device of the present invention. The microphone
probe 1 is provided with four microphones P1, P2, P3 and P4, and these microphones P1, P2, P3
and P4 are arranged and fixed as shown in FIGS. The signals obtained by these microphones P 1,
P 2, P 3 and P 4 are inputted to the FFT analyzer 3 via the microphone amplifier 2.
[0019]
In the FFT analyzer 3, the A / D converter 4 converts the digital signal into a digital signal, and
the digital signal is input to the FFT calculator 5. In the FFT operation unit 5, the signals obtained
by the respective microphones P1, P2, P3 and P4 are respectively subjected to the Fourier
transform, and cross power spectra Gij (i, j = 1, 2, 3) corresponding to the respective
combinations of two microphones. , 4) are required. Where G ij is the cross power spectrum for
the signal obtained with the two microphones P i and P j.
[0020]
The cross power spectrum G ij (i, j = 1, 2, 3, 4) obtained by the FFT operation unit 5 is input to
the intensity operation unit 6, and the intensity operation unit 6 performs an operation according
to the following equation. The components SIX, SIY and SIZ in the X, Y and Z directions of the
acoustic intensity are obtained.
[0022]
Here, the imaginary part: of the one-side cross spectrum of Im {G}: G: density of the medium d:
distance between the microphones The acoustic intensity (SIX, SIY, SIZ) thus determined is the
display unit 7 Is input and displayed.
Here, each direction of X, Y, and Z may be selected as positive. In this case, the sign of the
calculation result of the equations (3) to (5) may be reversed depending on how to select.
[0023]
03-05-2019
6
In the above embodiment, as shown in FIG. 2, the central microphone P4 is arranged to project
more than the plane formed by the other microphones P1, P2 and P3, but four microphones P4
are provided. The microphone may be placed at a retracted position where a regular tetrahedron
is formed. In this case, the axis 20a does not exist at the position of the center of gravity of the
regular tetrahedron, so that the disturbance of the sound field is further reduced.
[0024]
As described above, according to the three-dimensional sound intensity measuring apparatus of
the present invention, the first microphone attached to the tip of the shaft and the first
microphone equidistantly spaced from the shaft are square faces together with the first
microphone. Because it is equipped with a probe consisting of the second, third and fourth
microphones attached to the positions that make up each vertex of the body, it is easy to set this
probe in the correct direction when measuring the acoustic intensity. It becomes possible to
arrange, and accurate measurement with less disturbance of the sound field becomes possible.
03-05-2019
7
Документ
Категория
Без категории
Просмотров
0
Размер файла
16 Кб
Теги
jph05288598
1/--страниц
Пожаловаться на содержимое документа