JPH0764564A - Sound isolating structure and sound isolating plate - Google Patents

Abstract

PURPOSE:To prevent the loss of a function as a sound isolating plate even at the time of opening a hole for air passage at a sound isolating plate by forming a resonance system of an air spring between a sound source and the sound isolating plate and an air quantity in the opening of the sound isolating plate, and setting the resonance frequency of the resonance system as a specific value. CONSTITUTION:An opening 12 is provided at a proximity sound isolating plate 11, and an oil pan 2 and the plate 11 are equipped with the model of a vibration system. The resonance frequency of this resonance system is set so as to be less than almost 1/2<1/2> of the main frequency components of a sound emitted by a panel sound source. Then, one end of an air spring 15 constituted between the oil pan (sound source face) 2 being the sound source and the adjacent sound isolating plate 11 is connected with an air mass 16 constituted of the opening 12 of the sound isolating plate 11, and the other end is connected with the sound source face 2, so that the mass spring system of one degree of freedom can be constituted. The rate of perforation of the sound isolating plate 11, the radius of the opening 12, and a distance between the sound source face 2 and the sound isolating plate 11 are decided, so that the sound isolating plate 11 can be equipped with a sufficient sound isolating effect.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound insulation structure for reducing external leakage of sound emitted from a panel sound source such as an oil pan of an automobile engine, a wall surface of a cylinder block, or an exhaust pipe, and a radiation to the outside of the vehicle. The present invention relates to a sound insulation plate used for an undercover or the like for suppressing generated noise.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 29, there is one in which a sound insulating plate 3 is attached in proximity to an oil pan 2 which is one of the main sound producing parts of an automobile engine 1 9300053).

In addition, a sound insulation plate having an opening penetrating the
There is also one that is arranged below the engine in combination with a porous sound absorbing plate (Japanese Utility Model Laid-Open No. 60-131470).

Further, as shown in FIG. 30, in a general vehicle 4, an under cover 6 is attached to the lower surface of the engine room 5. This under cover 6
In addition to preventing the oil pan of the engine from directly contacting the projections on the road surface, it also has a function as a sound insulation wall for suppressing engine noise emitted from the engine room 5 to the outside of the vehicle.

As a matter of course, the larger the mounting area of the undercover 6, the higher the sound insulation effect. However, if the mounting area is widened, the undercover 6 increases the degree of airtightness of the engine room 5 and deteriorates the air permeability, which causes an unfavorable result that the atmospheric temperature of the engine room 5 rises. Therefore, in actuality, even if the sound insulation is sacrificed to some extent, the mounting area of the under cover 6 is reduced to ensure the necessary air permeability.

[0006]

By the way, since there is oil heated to a high temperature in the oil pan, the heat generated by the oil raises the ambient temperature of the space between the oil pan and the sound insulating plate, and the durability of the parts is improved. An unfavorable situation occurs.
In this regard, in the technique disclosed in Japanese Utility Model Laid-Open No. 60-131470,
Although some air permeability is ensured, the function as a sound insulation plate is sacrificed because it is simply provided with an opening mainly for ventilation.

As described above, when a sound insulation plate is to be attached in the vicinity of a sound source that generates heat, if the degree of airtightness is increased in order to improve the sound insulation performance, the ambient temperature of the space between the sound source and the sound insulation plate rises, There has been a problem that the heat insulation performance of parts and the like existing in the vicinity of the space becomes difficult, and if the heat resistance performance is prioritized and the degree of sealing is lowered, the sound insulation performance is deteriorated.

This point also applies to the above-mentioned undercover.

The present invention has been made by paying attention to such a problem, and in order to solve the heat resistance problem and the like that occur when a sound insulating plate is attached in the vicinity of a sound source that generates heat, a vent hole is provided. An object of the present invention is to provide a sound insulation structure and a sound insulation plate that do not lose the function of the sound insulation plate even when the sound insulation plate is opened.

[0010]

According to a first aspect of the present invention, there is provided a sound insulation structure comprising a sound source caused by panel vibration and a sound insulation plate arranged along the sound source and having an opening in a thickness direction. An air spring formed of an air layer between the sound source and the sound insulating plate and an air mass in the opening of the sound insulating plate form a resonance system, and the resonance frequency of the resonance system is approximately 1 of the main frequency component of the sound emitted by the panel sound source. The feature is that it is set to be less than / √2 times.

According to a second aspect of the present invention, there is provided the sound insulation structure according to the first aspect, wherein the peripheral edge of the opening of the sound insulation plate projects toward the panel sound source, and the height of the projection is the sound insulation between the panel sound source and the sound source. It is characterized in that the distance between the plates is approximately 1/2.

The invention of claim 3 is the sound insulation structure according to claim 1, wherein the resonance frequency of the vibration system is approximately 2 ^1/2 times,
The main frequency band of the sound emitted from the panel sound source exists in the frequency range between the panel sound source and the inter-plate resonance frequency generated between the sound insulation plates.

The invention of claim 4 is the sound insulation structure according to claim 1, wherein the resonance frequency of the vibration system is approximately 2 ^1/2 times,
It is characterized in that the main frequency band of the sound emitted from the panel sound source exists at approximately the center value of the frequency range between the panel sound source and the plate resonance frequency generated between the sound insulation plates.

According to a fifth aspect of the present invention, in the sound insulation structure according to the first aspect, when the sound emitted from the panel sound source is a combination of several panel resonance frequencies, at least one of the resonance frequencies is set. One is included in a frequency range between approximately 2 ^1/2 times the resonance frequency of the vibration system and the inter-plate resonance frequency generated between the panel sound source and the sound insulation plate.

According to a sixth aspect of the present invention, in a sound insulating plate that blocks the propagation of sound from the space A to the space B, the sound insulating plate has an opening penetrating in the thickness direction, and the cross-sectional area of the opening is from the space A side. It is characterized in that it gradually increases in size as it reaches the space B side.

The invention of claim 7 is the sound insulating plate according to claim 6, wherein the cross-sectional area S of the opening is defined by an exponential function with the distance in the thickness direction as a variable. There is.

According to an eighth aspect of the present invention, the sound insulation plate according to the sixth or seventh aspect is used as an undercover for partitioning the lower part of the engine room of the vehicle from the outside.

[0018]

According to the invention of claim 1, a vibration system having one degree of freedom is constituted by the air spring formed by the air layer between the panel sound source and the sound insulation plate and the air mass at the opening of the sound insulation plate. , The vibration due to the sound wave is attenuated, and the transmitted sound wave is reduced. In this case, since air can freely flow in and out through the opening, sufficient air permeability is naturally ensured.

Further, according to the invention of claim 2, since the air mass of the opening becomes large and the distance between the sound insulation plate and the sound source becomes large, the air spring becomes small, and the sound insulation performance is improved in a lightweight and compact manner. be able to. Moreover, since the projecting height of the opening edge portion is 1/2 times the plate-to-plate distance, the opening end comes into contact with the odd-order plate-to-plate resonance node, so that the influence of plate-to-plate resonance is reduced.

According to the third aspect of the invention, since the main frequency band of the sound source is placed in the area where the sound insulation effect is obtained, a reliable sound insulation effect can be obtained.

Further, according to the invention of claim 4, since the frequency for the purpose of sound insulation exists in the central portion of the region where the sound insulation effect is high, naturally the high sound insulation effect can be obtained.

Further, according to the invention of claim 5, when the sound from the sound source is composed of a combination of several resonance frequencies, at least one of them is in a region having a high sound insulation effect, so at least that frequency As for the sound insulation effect is obtained.

Further, according to the invention of claim 6, since the real part of the acoustic impedance at the end surface of the sound insulation plate on the sound source side can be brought close to zero, the sound insulation function can be achieved for the sound in the low frequency region. it can.

Further, according to the invention of claim 7, the boundary of frequencies where the sound insulation effect can be expected becomes clear.

Further, according to the invention of claim 8, the sound from the engine room can be shielded to the outside and can be radiated from the opening.

[0026]

Embodiments of the present invention will be described below with reference to the drawings.

1 and 2 show a first embodiment of the present invention.
In FIG. 1, the sound insulation plate 1 is provided around the lower portion of the oil pan 2 of the engine 1 so as to surround the oil pan 2 closely.
1 is attached. The sound insulation plate 11 is formed in a box shape as shown in FIG. 2, and has a large number of circular openings 12 that completely penetrate in the thickness direction. Here, by providing the opening 12 in the proximity sound insulation plate 11, the oil pan 2 and the proximity sound insulation plate 11 have a vibration system model as shown in FIG.

In this model, one end of an air spring 15 formed between an oil pan (hereinafter also referred to as a sound source surface) 2 which is a sound source and a proximity sound insulating plate 11 has air formed by an opening 12 of the sound insulating plate 11. A mass spring system with one degree of freedom is connected to the mass (air mass) 16 and the other end is connected to the sound source surface 2.

Here, by vibrating the sound source surface 2,
This vibration excites the air mass 16 via the air spring 15, and the vibration of the air mass 16 excites the outside air, which becomes noise radiated to the outside.

At this time, paying attention to the vibration transmissibility between the sound source surface 2 and the air mass 16, in the one-degree-of-freedom vibrating system such as this model, the vibration transmissibility is as follows.

[0031]

[Equation 1] From this, when the condition that the vibration transmissibility is less than 1, that is, the condition to enter the anti-vibration area is calculated,

[Equation 2] Is required.

Therefore, from the equation (2), the resonance point 2
It can be said that in the frequency range exceeding ^1/2 times, the vibration transmissibility falls below 1 and enters the vibration isolation region.

Here, the resonance frequency of this vibration system includes the thickness t of the sound insulating plate 11, the radius a of the opening 12, the distance d between the sound source surface 2 and the sound insulating plate 11, and the aperture ratio α (α = πa ² / L ^{2 (} where L is determined by the pitch of the openings), and the resonance frequency fo within the vibration isolation region is determined by the following equation.

[0034]

[Equation 3] However, even within this vibration isolation region, the sound insulation effect is significantly reduced in the vicinity of the inter-plate resonance frequency fn between the sound source surface 2 and the adjacent sound insulation plate 11 shown in the following equation.

[0035]

[Equation 4] That is, the main frequency f for the purpose of sound insulation is expressed by
If so, this proximity sound insulation plate has a sufficient effect.

[0036]

[Equation 5] For example, in the case of an oil pan, the main frequency range of engine noise is 1 to 2.5 kHz, so the vibration isolation frequency fo expressed by the formula (3) is 1 kHz or less, and the plate resonance expressed by the formula (4). Of the frequencies, the aperture ratio of the sound insulating plate 11, the plate thickness, the radius of the opening 12, the distance between the sound source surface 2 and the sound insulating plate 11 are determined so that the resonance frequency of the first order, that is, n = 1 is 2.5 kHz or more. If so, this proximity sound insulation plate 11 will have a sufficient sound insulation effect.

FIG. 4 shows the sound insulation effect of the sound insulation plate structure of the embodiment. This represents a reduction amount of the noise level when the sound insulation plate 11 is provided, compared to the noise level when the sound insulation plate 11 is not provided. The shaded area in this figure shows the effect of sound insulation. As is clear from this figure, the sound insulation structure of the embodiment has an effect as a sound insulation plate because the noise level is lowered in the frequency range represented by the above formula (4).
In addition, although there is a region where the effect is small at some frequencies, this region is a region where humans do not care about outside noise, and when viewed as a whole, noise can be greatly reduced, which is a particular problem. Never.

At the same time, since it also has an opening 12 for ventilation, it also has the effect of solving the heat resistance problem.

FIG. 5 shows a second embodiment of the present invention. In the sound insulation structure of the second embodiment, the sound absorbing material 13 is provided in a place other than the opening 12 between the sound insulation plate 11 and the sound source surface 2 of the first embodiment.
Is provided. According to this embodiment, the sound absorbing material 13
The interposition of the plates prevents plate-to-plate resonance and improves sound insulation performance.

FIG. 6 shows a cross section of the essential parts of a third embodiment of the present invention. In the sound insulation structure of the third embodiment, the peripheral edge portion 14 of the opening 12 is projected to the sound source surface 2 side to increase the air mass of the opening 12 and increase the distance d between the sound source surface 2 and the sound insulating plate 11. By doing so, the air spring is made small, and the sound insulation performance is improved in a lightweight and compact form. In this case, by setting the protrusion height t to be 1/2 of the plate-to-plate distance, the opening end hits the node of odd-order plate-to-plate resonance, so that the influence of plate-to-plate resonance can be reduced.

7 and 8 show a fourth embodiment of the present invention.
This embodiment is a modification of the third embodiment, and the peripheral portion of the opening 12a at the portion with the lowest ground clearance is not projected and can be used as a drainage hole, and the resonance frequency of the opening 12a is The resonance frequency of the opening 12 is set to be equal to or lower than the resonance frequency. According to this embodiment, water can be drained while maintaining sound insulation.

9 and 10 show a fifth embodiment of the present invention. In this embodiment, the sound insulation structure of the present invention is applied to an under cover of an engine room. In this embodiment, the proximity sound insulation plate 11 is supported on the vehicle body 17 side. According to this embodiment, since the sound insulation plate 11 does not directly contact the sound source 2, it is possible to prevent the sound insulation plate 11 itself from vibrating due to the vibration of the sound source and causing noise.

Incidentally, in an acceleration state where engine noise is particularly large, the engine rolls and an angular displacement occurs. Therefore, in the case of the present embodiment, the aperture ratio of the sound insulating plate 11, the plate thickness, the radius of the opening 12, the space between the oil pan surface 2 and the sound insulating plate 11 are maximized so that the effect is maximized in the state where the angular displacement occurs. It is desirable to determine the distance.

11 and 12 show a sixth embodiment of the present invention. The sixth embodiment is an improvement of the fifth embodiment. In the fifth embodiment, when the vehicle is in an accelerating state, the engine position changes and the sound source surface 2 and the proximity sound insulation plate 11 are changed.
Even if the distance between and changes, the area of the opening 12 is changed by driving the movable portion 18 by the motor 19 so that the set frequency does not change. A motor 19 for driving the movable portion 18 is controlled by a motor controller 20, and an output signal of an acceleration / deceleration sensor 21 is input to the motor controller 20.

Therefore, in this embodiment, the movement of the movable portion 18 is controlled by the control shown in the flow chart of FIG.

[0046] That is, the vehicle speed at step S ₁ is read, the motor rotation angle at step S ₂ is calculated. The motor rotation angle is calculated, for example, by associating the movement amount of the engine 1 with the acceleration / deceleration of the vehicle with the area of the opening 12, and the correspondence between the area of the opening 12 and the movement amount of the movable portion 18 (motor rotation angle). This is done by obtaining in advance.

In step S ₃ , the motor is driven by the output from the motor control device 20, and when the motor rotation angle reaches the calculated rotation angle (YES in step S ₄ ), the control ends. The judgment in step S ₄ is made by the motor 19
It is carried out by feedback of the signal from.

According to this embodiment, even if the position of the engine 1 changes due to acceleration of the vehicle or the like, the set frequency is adjusted so as not to change, and a stable sound insulation effect can be obtained.

14 and 15 show a seventh embodiment of the present invention. In the seventh embodiment, ventilation type sound insulation walls 20 are arranged on both sides of the sound insulation plate 11 of the fifth embodiment. The ventilation type sound insulation wall 20 is composed of a combination of at least two perforated plates facing each other with a space therebetween, and is an air spring due to the air mass at the opening of the perforated plate and the air layer between the perforated plates. The plate thickness, aperture ratio, and plate spacing of the perforated plates are set so that the resonance frequency of the vibration system configured by and is lower than the main frequency of the sound for sound insulation.

According to this embodiment, the sound leakage from the side of the proximity sound insulation plate 11 is also reduced by the ventilation type sound insulation wall 20, and the overall sound insulation effect is enhanced.

16A and 16B show an eighth embodiment of the present invention. In the eighth embodiment, the sound insulation structure of the present invention is applied to a flat under cover arranged below a transmission (panel sound source) 25. In this embodiment, at the bottom of the transmission 25,
A flat plate sound insulating plate 11 having an opening 12 as an under cover is arranged so as to satisfy a predetermined condition.

17 (a) and 17 (b) show an example in which the above-mentioned ventilation type sound insulation walls 20 are provided on both sides of the under cover 26 of the transmission 25. When the air permeability is low by itself, the air permeability can be ensured by not reducing the sound insulation performance by combining with the sound insulation structure using the proximity sound insulation plate of the eighth embodiment.

18 (a) and 18 (b) show a ninth embodiment. In this embodiment, a proximity sound insulation plate 31 that is curved according to the curved surface of the case of the transmission 25 is directly fixed to the transmission case with a vibration-proof rubber 32 by bolts.

19A and 19B show a tenth embodiment of the present invention. In this embodiment, an L-shaped proximity sound insulating plate 33 with an opening 12 is provided below and on the side surface of the differential device (panel sound source) 26 so as to cover them. In this case, the proximity sound insulation plate 33 is directly fixed to the rear suspension members 34 and 35 via the vibration damping rubber 32.

20 (a) and 20 (b) show an eleventh embodiment of the present invention. In this embodiment, the proximity sound insulating plate 11 is provided on the side surface of the cylinder block 27 so as to cover it. In this case, the proximity sound insulation plate 11 is directly fixed to the cylinder block 27 via the anti-vibration rubber 32.

21A and 21B show a twelfth embodiment of the present invention. In this embodiment, a proximity sound insulating plate 35 having an opening 12 that is curved according to the shape of the muffler is arranged around the lower portion of the muffler 28.

FIG. 22 shows a thirteenth embodiment of the present invention. In this embodiment, a combination of flat sound insulation plates 11 is arranged around a lower portion of a curved sound source surface 2 such as a muffler. In this case, since the sound source surface 2 is a curved surface,
The distance between the sound source surface 2 and the sound insulation plate 11 differs depending on the place. For this reason, the aperture ratio and the radius of the opening 12 are adjusted by the plate-to-plate distance so that fo in the equation (3) becomes constant.

FIG. 23 shows a fourteenth embodiment of the present invention. In the fourteenth embodiment, the peripheral edge of the opening 12 in the thirteenth embodiment is projected toward the sound source surface 2 side by ½ of the plate-to-plate distance. Also at this time, as in Example 13, the aperture ratio and the opening radius are adjusted by the plate-to-plate distance so that fo in the formula (3) is constant regardless of the location.

In the above description, the opening 12
Although the case where the shape is circular is shown, the shape of the opening 12 may not be circular, but another shape may be used as long as the frequency setting is reliable.

Next, examples of the inventions according to claims 6 to 8 will be described. In the following examples, serial numbers that are continuous with the examples described above are attached.

FIG. 24 is a sound insulation plate 5 of the fifteenth embodiment of the present invention.
1 is shown. As shown in FIGS. 25 and 26, the sound insulating plate 51 is applied to the rear portion of the under cover 60 attached to the lower surface of the engine room (first space) 5 of the vehicle 4. On the sound insulation plate 51 at the rear of the under cover 60,
Opening 5 for ventilation of cooling air flowing outside the vehicle (second space)
Many 2 are open.

As shown in FIGS. 24 (a), 24 (b) and 26, the opening 52 is gradually opened from the engine room (first space) 5 side to the outside of the vehicle (second space) side. It has a horn shape with a large area.

FIG. 27 shows a sound insulation plate according to the 16th embodiment of the present invention. The sound insulation plate 55 of this embodiment changes so that the cross-sectional area S of the opening 56 satisfies the following exponential function with the distance x in the thickness direction as a variable from the engine room side (sound source side) toward the vehicle exterior side. is doing.

[0064]

[Equation 6] Next, the operation of the sound insulating plates 51 and 55 of the 15th and 16th embodiments in which the cross-sectional area of the opening is gradually changed will be described.

As is well known, the sound insulation performance of a general sound insulation wall is drastically lowered by providing an opening.

However, the fifteenth embodiment or the first
By configuring as in the sixth embodiment, the acoustic impedance on the sound source side of the sound insulation wall is as shown in FIG. 28 (b) at the sound source side end face.

FIG. 28A shows an example of the model compared in FIG. Here, the case where the shape of the opening is a simple cylindrical hole is compared with the case of the fifteenth embodiment and the case of the sixteenth embodiment.

In the case of a cylindrical hole, the acoustic impedance Z of the end surface on the sound source side is Re (real part) dominant, has no change with frequency, and has a certain constant value.

On the other hand, the Re (real part) component of the acoustic impedance Z of the sound source side end face of the fifteenth and sixteenth embodiments is near zero on the low frequency side and converges to a constant value in the high frequency region.

Particularly, in the case of the sixteenth embodiment, the Re (real part) component changes rapidly and changes at a certain frequency fc. At this time, fc is calculated as follows.

[0071]

[Equation 7] The fact that the Re (real part) component of the acoustic impedance of the end surface of the sound insulation wall on the sound source side is zero means that the sound of that frequency is reflected and not transmitted.

The component is ρC (ρ: air density,
Equal to (C: speed of sound) means that all are transmitted. That is, it is difficult for the sound insulation wall having a simple cylindrical hole to fulfill the function of the sound insulation wall.

However, in the fifteenth and sixteenth embodiments, since the Re (real part) component is close to zero in the low frequency region, it is difficult to transmit sound. In other words, it will function as a sound insulation wall.

Therefore, in the fifteenth embodiment, the Re (real part) component of the acoustic impedance is close to zero in the low frequency region, and in the sixteenth embodiment, the sound frequency f of the sound source requiring sound insulation is , F <fc, the function as a sound insulation wall is obtained.

[0075]

As described above, according to the first aspect of the present invention, it is possible to have both air permeability and sound insulation, and it is possible to solve the heat resistance problem without losing the sound insulation function.

Further, according to the invention of claim 2, the influence of the plate-to-plate resonance between the sound source and the sound insulation plate is reduced, and the sound insulation performance is further improved.

According to the third aspect of the invention, the sound insulation effect is enhanced by strictly setting the resonance frequency of the vibration system.

According to the invention of claim 4, the sound insulation effect is further enhanced by making the setting of the resonance frequency of the vibration system more strict.

According to the fifth aspect of the invention, by narrowing down a specific frequency in the sound emitted by the sound source, a sound insulation effect can be obtained at least for that frequency.

According to the sixth aspect of the invention, the sound insulation performance can be improved especially for sounds in the low frequency range.

Further, according to the invention of claim 7, since the boundary of the frequency where the sound insulation effect can be expected can be clarified, it is possible to obtain a clear sound insulation performance by narrowing down the sound to be sound insulation.

According to the invention of claim 8, both the air permeability and the sound insulation of the engine room can be improved.

[Brief description of drawings]

FIG. 1 is a side sectional view of a first embodiment of the present invention.

FIG. 2 is a perspective view of the sound insulation plate in the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of a vibration model used for analyzing sound insulation performance according to the first embodiment of this invention.

FIG. 4 is a characteristic diagram showing an effect of the first embodiment of the present invention.

FIG. 5 is a side sectional view of a second embodiment of the present invention.

FIG. 6 is a side sectional view of a third embodiment of the present invention.

FIG. 7 is a side sectional view of a fourth embodiment of the present invention.

FIG. 8 is a perspective view of a sound insulation plate used in a fourth embodiment of the present invention.

FIG. 9 is a side sectional view of a fifth embodiment of the present invention.

FIG. 10 is a perspective view of a sound insulating plate used in a fifth embodiment of the present invention.

FIG. 11 is a side sectional view of a sixth embodiment of the present invention.

FIG. 12 is a perspective view of a sound insulating plate used in a sixth embodiment of the present invention.

FIG. 13 is a flow chart showing control of the motor of the sixth embodiment.

FIG. 14 is a side sectional view of a seventh embodiment of the present invention.

FIG. 15 is a perspective view of a sound insulation plate used in a seventh embodiment of the present invention.

FIG. 16 is a configuration diagram of an eighth embodiment of the present invention, (a)
Is a bottom view and (b) is a side sectional view.

17A and 17B are configuration diagrams of an under cover in which an effect is further improved by applying an eighth embodiment of the present invention, FIG. 17A is a bottom view, and FIG. 17B is a side sectional view.

FIG. 18 is a configuration diagram of a ninth embodiment of the present invention, (a)
Is a vertical sectional view, and (b) is a horizontal sectional view.

FIG. 19 is a configuration diagram of a tenth embodiment of the present invention,
(A) is a bottom view and (b) is a side sectional view.

FIG. 20 is a configuration diagram of an eleventh embodiment of the present invention,
(A) is a side sectional view and (b) is a perspective view.

FIG. 21 is a configuration diagram of a twelfth embodiment of the present invention,
(A) is a plan view and (b) is a side sectional view.

FIG. 22 is a side sectional view of a thirteenth embodiment of the present invention.

FIG. 23 is a side sectional view of a fourteenth embodiment of the present invention.

FIG. 24 is a configuration diagram of a sound insulation plate of a fifteenth embodiment of the present invention, (a) is a plan view and (b) is a sectional view.

FIG. 25 is a bottom view of the vehicle to which the fifteenth embodiment of the present invention is applied.

FIG. 26 is a side view of the front half of a vehicle to which the fifteenth embodiment of the present invention has been applied.

27A and 27B are configuration diagrams of a sound insulation plate according to a sixteenth embodiment of the present invention, in which FIG. 27A is a sectional view and FIG. 27B is an enlarged sectional view of an opening.

28 (a) and 28 (b) are comparative explanatory views of the operation of the fifteenth embodiment and the sixteenth embodiment of the present invention, (a) showing a model of a sound insulation plate for comparison, and (b) showing acoustic impedance of comparison contents. It is a characteristic view which shows a difference.

FIG. 29 is a side sectional view of a conventional example.

FIG. 30 is a bottom view of a conventional vehicle.

[Explanation of symbols]

 2 oil pan (panel sound source, sound source surface) 11, 31, 33, 35 sound insulation plate 12 opening 15 air spring 16 air mass (air mass) 14 edge of opening 25 transmission (panel sound source) 26 differential device (panel sound source) ) 27 cylinder block (panel sound source) 28 muffler (panel sound source) 51,55 sound insulation plate 52,56 opening

Claims (8)

[Claims] 1. An air spring, comprising: a sound source caused by panel vibration; and a sound insulating plate arranged close to the sound source and having an opening in the thickness direction, the air spring comprising an air layer between the sound source and the sound insulating plate. A resonance system is formed with the air mass in the opening of the sound insulation plate,
A sound insulation structure, wherein a resonance frequency of the resonance system is set to be lower than approximately 1 / √2 times a main frequency component of a sound emitted from the panel sound source. 2. The sound insulating plate according to claim 1, wherein a peripheral portion of an opening of the sound insulating plate projects toward the panel sound source, and a projecting height is approximately ½ of a distance between the panel sound source and the sound insulating plate. Sound insulation structure. 3. The sound emitted from the panel sound source in a frequency range between approximately 2 ^1/2 times the resonance frequency of the vibration system and the inter-plate resonance frequency generated between the panel sound source and the sound insulation plate. The sound insulation structure according to claim 1, wherein a main frequency band exists. 4. The panel sound source is set to a substantially central value of a frequency range between approximately 2 ^1/2 times the resonance frequency of the vibration system and a plate resonance frequency generated between the panel sound source and the sound insulation plate. The sound insulation structure according to claim 1, wherein a main frequency band of emitted sound is present. 5. When the sound emitted from the panel sound source is composed of a combination of several panel resonance frequencies, at least one of the resonance frequencies is about 2 ^1/2 times the resonance frequency of the vibration system. The sound insulation structure according to claim 1, wherein the sound insulation structure is included in a frequency range between the panel sound source and an inter-plate resonance frequency generated between the sound insulation plates. 6. A sound insulating plate that blocks the propagation of sound from a first space to a second space, having an opening penetrating in the thickness direction, and the cross-sectional area of this opening is on the side of the first space. The sound insulating plate is characterized in that it is gradually formed larger from the side to the second space side. 7. The sound insulation board according to claim 6, wherein the cross-sectional area S of the opening is defined by an exponential function with a distance in the thickness direction as a variable. 8. The sound insulating plate according to claim 6, which is used as an undercover for partitioning a lower portion of a vehicle engine room from the outside.