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JPH10197332

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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
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DESCRIPTION JPH10197332
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
method and apparatus for measuring the sound transmission characteristics of a member to be
measured, and in particular to a method and apparatus suitable for evaluating the sound
transmission characteristics of a narrow area to be measured. About.
[0002]
2. Description of the Related Art In buildings such as houses and structures such as vehicles, it is
considered to what extent the sound from the outside penetrates and reaches the inside, that is,
the sound transmission characteristics are one of the factors for evaluating the habitability.
Become. Conventionally, the sound transmission characteristics of a vehicle are evaluated by
placing the vehicle to be tested in a reverberation room and collecting the sound radiated in the
reverberation chamber with a microphone placed in the vehicle compartment.
[0003]
As described above, in the test in the reverberation chamber, the sound transmission
characteristics of the entire structure can be evaluated as a result of the sound being emitted
from all directions to the test structure. However, when a partial sound transmission
characteristic is evaluated, there is a problem that the resolution of the sound transmitted
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through the evaluation target portion is deteriorated due to the sound intruding from the other
portion, and the accurate evaluation can not be performed. For example, in the case of a vehicle,
even if it is intended to measure the sound transmission characteristics around the front pillar,
the sound invading from the windshield, the door glass, and also the body members such as the
roof is collected, and the sound intruding from the front pillar periphery Can not be separated
sufficiently, so accurate evaluation can not be made.
[0004]
The present invention has been made to solve the above-mentioned problems, and it is an object
of the present invention to provide a measurement method and a measurement apparatus which
can be evaluated with sufficient resolution with respect to partial sound transmission
characteristics.
[0005]
SUMMARY OF THE INVENTION In order to achieve the above object, according to a method of
measuring sound transmission characteristics of the present invention, sound in an audible area
generated from a speaker is converged to form a point sound source, A sound source is disposed
in the vicinity of a measurement object, and a microphone disposed on the opposite side of the
position of the point sound source with respect to the measurement object collects the sound
from the point sound source, and based on the collected sound The sound transmission
characteristics of the object to be measured are measured.
[0006]
By arranging the point sound source in the vicinity of the measurement object, it is possible to
measure the sound transmission characteristic of this part while reducing the influence of the
sound intruding from the other part.
[0007]
In order to create the point sound source, the point sound source forming device according to the
present invention has a speaker and a case covering the front of the speaker, the case converges
the sound generated from the speaker, and the tip is It has a substantially conical cone portion
that radiates sound from the opening provided in.
Furthermore, it has a nozzle attached directly or indirectly to the opening at the tip of the cone
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part, and the nozzle has a tubular shape and abuts on the measuring object at the end of the tube
facing the measuring object A portion and a non-contacting portion are provided, and the noncontacting portion forms a gap.
[0008]
Furthermore, the case may have a volume adjustment structure that can change its internal
volume.
The sound pressure generated can be adjusted by changing the internal volume.
[0009]
Furthermore, the nozzle may be attached to the tip of the cone through a flexible waveguide.
The position of the point source, ie, the position to be measured, can be easily changed by this
flexible waveguide.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention
(hereinafter referred to as embodiments) will be described below with reference to the drawings.
FIG. 1 is a view showing a schematic configuration of a measurement equipment to which the
sound transmission characteristic measurement method of the present invention is applied. The
object to be measured is the vehicle body 10, and in the drawing, the state of measuring the
sound transmission characteristics around the pillar (A-pillar) in the right front portion is shown.
The sound generation unit 12 generates an oscillation unit 14 that generates a signal having a
flat frequency characteristic in a predetermined frequency region, an equalizer 16 that converts
the generated signal into a signal of a predetermined frequency characteristic, and amplifies the
signal. It includes an amplifier 18 for driving a speaker described later. The signal amplified by
the amplifier 18 is sent to the sound source unit 20.
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[0011]
The detailed configuration of the sound source unit 20 is shown in FIG. The sound source unit 20
is provided with a speaker 22 driven by the above-described amplifier 18, and the speaker 22 is
housed in a case 24. The case 24 further includes a rear case 26 and a front case 28. The rear
case 26 covers the rear of the speaker 22 such as the speaker drive unit 30 provided with a coil
and a magnet, and has an opening substantially coplanar with the opening of the speaker 22. The
front case 28 has an opening that fits into the opening of the rear case 26, and subsequently has
a cone portion whose tip is tapered. A case opening 32 is provided at the tip of the front case 28.
The portion opened in the case 24 is only the case opening 32. Therefore, the sound generated
by the speaker 22 is focused on the case opening 32 by the cone shape of the front case 28, and
a point sound source is formed. . A flexible tube 34 having flexibility is connected to the opening
32, and a nozzle 36 contacting the surface of the object to be measured is connected to the tip of
the opening 32. By the flexible tube 34, the point sound source can be moved to a desired
position without moving the case 24 containing the speaker 22, and the workability is improved.
[0012]
The detailed shape of the nozzle 36 is shown in FIG. The nozzle 36 is formed of a rubber-based
soft material and engaged so that the base 38 covers the outer diameter of the flexible tube 34.
The tip end portion 40 continuing to the base portion 38 is provided with unevenness in the
axial direction, the convex portion 40a abuts on the surface of the measurement object, and the
concave portion 40b forms a gap with the surface of the measurement object. The nozzle 36 is
made of a soft material in order to prevent the vehicle 10, which is an object to be measured,
from being scratched. Further, by providing the recess 40 b to provide a gap, the surface area to
which sound is applied can be increased, and the energy of sound can be increased. By making
the shape of the nozzle 36 appropriate, it is possible to obtain the characteristics of the sound
source according to the characteristics of the measurement object and the measurement site.
[0013]
Next, the configuration of the sound collection unit 42 for collecting and analyzing the sound
emitted from the sound generation unit 12 will be described. The sound emitted from the nozzle
36 is collected by the microphone 44 disposed in the vehicle compartment, amplified by the
amplifier 46, and then analyzed by the fast Fourier transformer (FFT) 48 for frequency
characteristics and the like.
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[0014]
In the above embodiment, the nozzle 36 is connected to the case 24 via the flexible tube 34.
However, the nozzle 36 can be directly attached to the opening 32 of the case 24.
[0015]
Another embodiment of the case for housing the speaker 22 is shown in FIG.
The case 50 of the present embodiment is capable of changing the volume inside the case. The
rear case 52 houses the speaker 22 similarly to the rear case 26 of FIG. 2, and further, a screw
portion 52 a is provided in a portion projecting to the front portion of the speaker 22. The front
case 54 has a cone portion 56 and a case opening 58 similarly to the front case 28 of FIG.
Furthermore, a threaded portion 54 a is formed on the inner surface of the cylindrical portion of
the front case 54. The rear case 52 and the front case 54 are connected by screwing together the
screw portions 52a and 54a, and the relative rotation of these causes the volume of the space in
front of the speaker 22 inside the case 50 to be 4 (a) can be changed to a state in which the
volume in FIG. 4 (b) is small. By having such a volume change structure, the sound output can be
adjusted.
[0016]
FIG. 5 shows still another embodiment of a case for housing the speaker 22. In the case 60 of the
present embodiment, as in the case 50 shown in FIG. 4, the volume inside the case can be
changed. The rear case 62 accommodates the speaker 22 like the rear case 26 of FIG. 2 and is
further provided with an engagement ridge 62a having a substantially triangular cross section
provided in a circumferential direction at a portion projecting to the front portion of the speaker
22. . The front case 64 has a cone 66 and a case opening 68 similarly to the front case 28 of FIG.
Further, on the inner surface of the cylindrical portion of the front case 64, an engagement
groove 64a having a substantially triangular cross section is formed in the circumferential
direction. The rear case 62 and the front case 64 are connected by the engagement of the
engagement ridges 62a and the engagement grooves 64a, and the sliding movement in the axial
direction of these causes the speaker in the case 60 The volume of the front space 22 can be
changed from the state of large volume in FIG. 5A to the state of small volume in FIG. 5B. By
having such a volume change structure, the sound output can be adjusted.
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[0017]
6 and 7 show the detailed dimensions of the sound source section 20 shown in FIG. In FIG. 6, the
nozzle 36 is directly attached to the tip of the case 24. The frequency characteristic of the sound
generated by the sound source unit 20 is shown in FIG. Graph A shows the characteristics when
the nozzle 36 is directly attached to the case 24. Graph B is a characteristic when the nozzle 36 is
attached via the flexible tube 34 with an inner diameter of 12 mm and a length of 5 m. When the
flexible tube 34 is used, the sound pressure tends to be lower as the frequency is higher, but this
is corrected by using the equalizer 16. That is, before actual measurement, a microphone is
disposed in front of the nozzle 36, frequency analysis is performed by FFT, and the equalizer 16
is adjusted based on the analysis result. As a result, substantially flat characteristics are obtained
at 500 Hz to 4 kHz as shown in the graph B described above. This frequency range is an area of
wind noise that becomes a problem in vehicles.
[0018]
10 and 11 show the characteristics of the resolution of the sound source unit 20 of this
embodiment. As shown in FIG. 9, the microphone 44 is moved along the orthogonal plane P at a
distance h from the tip of the nozzle 36, and the relationship between the movement amount x
(distance from the nozzle 36 to the microphone 44) and the sound pressure is measured Do. The
result for the case where the distance h is 0 is shown in FIG. 10. In the case where the flexible
tube 34 is not used, an attenuation of 25 dB can be obtained at 100 mm, and in the case where
the flexible tube 34 is used, an attenuation of 30 dB is obtained. Further, FIG. 11 shows the
amount of attenuation when the microphone is moved 100 mm when the distance h is changed.
When the flexible tube 34 is not used (graph A), it is possible to obtain a distance h of 25 mm
and -10 dB which is one standard of resolution. When the flexible tube 34 is used (graph B), -10
dB can be obtained at a distance h of 40 mm.
[0019]
As described above, regarding the resolution, better characteristics are obtained when the
flexible tube 34 is used, and it is considered that there is an influence of the sound emitted from
the surface of the case when this is not used. Therefore, by covering the case 24 with the sound
insulation covers 70 and 72 as shown in FIG. 12, the resolution can be further enhanced even
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when the flexible tube 34 is not used.
[0020]
Finally, the results of measuring the sound transmission characteristics of the conventional
apparatus and the apparatus of the present embodiment using a vehicle are shown. The sound
transmission characteristics in the vicinity of the rear side molding portion (see FIG. 13) of the
vehicle 10 were evaluated. The details of this part are shown in FIG. Point sound sources, i.e.,
nozzles were defined at five positions DA, DB, DC, DD, DE, and at each nozzle position,
microphones were arranged at positions D1 to D11, and the sound pressure of each was
measured. The numbers displayed between the nozzle positions DA to DE in the figure represent
the distance (in mm) between adjacent nozzle positions.
[0021]
In FIG. 15, the attenuation amount obtained by subtracting the sound pressure Pi measured in
the vehicle compartment from the generated sound pressure P0 is displayed on the vertical axis.
FIG. 16 shows the amount of attenuation when the vehicle 10 is placed in the conventional
reverberation chamber, and sound is emitted from all directions to measure the inside of the
vehicle cabin. The measurement data groups GA to GE shown in FIGS. 15 and 16 are considered
to be data indicating sound transmission characteristics near the nozzle positions DA to DE,
respectively. Even in the conventional method, even in the present embodiment, it can be seen
that the sound transmission characteristics near the nozzle position DD are not good, but the
difference between the good portion and the bad portion is larger in the case of the present
embodiment (conventional 8 dB And 14 dB), it can be seen that the accuracy in evaluating local
sound transmission characteristics is high.
[0022]
Also, when the nozzle is placed at the position DC, comparing the attenuation amount at the
microphone position D9 between the present embodiment and the conventional example, the
conventional example can not distinguish superiority from the other parts, but according to the
present embodiment, the microphone It can be seen that the amount of attenuation is larger than
the position D8.
[0023]
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As described above, since it is possible to measure local sound transmission characteristics, it is
possible to surely specify a site to which a measure of sound transmission is to be taken, and to
provide useful information at the time of product development.
[0024]
Brief description of the drawings
[0025]
FIG. 1 is a schematic configuration view of a measurement equipment of sound transmission
characteristics to which the present invention is applied.
[0026]
FIG. 2 is a configuration diagram of a sound source unit of the present embodiment.
[0027]
3 is a detailed view of the tip shape of the sound source unit shown in FIG. 2;
[0028]
FIG. 4 is a block diagram of another sound source unit according to the present embodiment, in
which the internal volume of the case can be changed.
[0029]
[FIG. 5] A configuration diagram of still another sound source unit of the present embodiment, in
which the internal volume of the case can be changed.
[0030]
FIG. 6 is a view showing an embodiment of a sound source unit shown in FIG. 2;
[0031]
7 is a view showing an example of the tip shape of the sound source unit shown in FIG. 3; FIG.
[0032]
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FIG. 8 is a diagram showing frequency characteristics of the sound source unit of the present
embodiment.
[0033]
FIG. 9 is a diagram showing an outline of a test on resolution of the sound source unit of the
present embodiment.
[0034]
FIG. 10 is a diagram showing the characteristics of the resolution of the sound source unit of the
present embodiment.
[0035]
FIG. 11 is a diagram showing the characteristics of the resolution of the sound source unit of the
present embodiment.
[0036]
12 is a diagram showing the details of the cover for preventing sound leakage from the case.
[0037]
13 is an explanatory view of a measurement example using the apparatus of the present
embodiment.
[0038]
FIG. 14 is an explanatory view of a measurement example using the apparatus of the present
embodiment.
[0039]
15 is a diagram showing the results of measurement using the apparatus of the present example.
[0040]
FIG. 16 is a diagram showing the results of measurement using a conventional device.
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[0041]
Explanation of sign
[0042]
10 vehicle body, 12 sound generation unit, 20 sound source unit, 28 front case (cone unit), 34
flexible tubes, 42 sound collection unit, 44 microphones.
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