JPH08286674A - Method and device for reducing interior sound of car - Google Patents

Abstract

PURPOSE: To evade the increase of weight and especially to reduce an interior sound having a low level frequency of a car by providing partitions for dividing the long-sized area of a pipe structure section so that the frequency of a resonance sound generated in the inside of the pipe structure section is increased up to a frequency band where a vibration and sound proof material inside the car effectively acts. CONSTITUTION: Five partitions 10, which are made of a foamed material of several centimeters in thickness and whose peripheral parts are bonded to the inside wall of a locker 2, are arranged at 40cm intervals from an end face 2a. Similarly, the partition 10 made of the foamed material corresponding to individual sections are disposed at 40cm interval at individual structure sections, too, and the end face of the pipe structure is also taken into consideration so as not to generate the pipe length of >=40cm. Consequently, the generation of the interior sound of the car being resonant with the vibration in the pipe structure section and having the low level frequency corresponding to the original length is suppressed by dividing the long-length area of the pipe structure section. The interior sound of the car caused by resonance of the high level frequency accompanying division is attenuated in a frequency band where the vibration and sound proof material effectively functions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle interior noise reduction method and apparatus for reducing low frequency noise in the vehicle interior.

[0002]

2. Description of the Related Art As a countermeasure for this kind of vehicle interior sound body structure, a reinforcement member is added to the sounding portion and the plate thickness is increased.

[0003]

However, this measure leads to an increase in weight and an increase in cost in order to obtain a sufficient effect against vibrations of low frequencies.

In view of the above points, the present invention has an object to provide a method and apparatus for reducing vehicle interior sound of an automobile capable of avoiding an increase in weight and reducing the interior sound particularly at low frequencies. .

[0005]

SUMMARY OF THE INVENTION In order to achieve this object, the present invention provides that the tubular structure portion of a body is provided with vibration frequencies in the vehicle interior at which the frequencies of resonance sounds that may occur in the tubular structure portion. It is characterized in that a partition wall for dividing the long dimension of the pipe structure portion is provided so as to increase the frequency band in which the soundproof material can effectively operate.

[0006]

With respect to the vehicle interior sound that resonates with the vibration in the pipe structure portion, the division of the length of the pipe structure portion by the partition wall suppresses the generation of the low frequency interior vehicle sound corresponding to the original length. . The vehicle interior sound resulting from the resonance of the high frequency accompanying the division is attenuated in the frequency band in which the vibration and soundproof material effectively functions.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An apparatus for carrying out a method for reducing a vehicle interior sound according to the present invention will be described with reference to FIG. First, the premise principle of the present invention will be described with reference to FIG. In general, a standing wave of a sound wave is generated in the tube according to the opening and closing of both ends of the tube (only the first-order mode is shown by a dotted line in the figure). That is, in the case of A and B in the same figure, the resonance frequency of the primary mode is f and the sound velocity is C (340 m
/ S) and the length of the tube are L, f = C / (2
L). Incidentally, one end is closed and the other end is opened, as shown in FIG.
In the case of, it becomes 4L instead of 2L. Therefore, for example, assuming that the pipe is a rocker with both ends closed and a length dimension of 2.4 m, f is about 70 Hz according to the above equation. According to the invention, this resonant frequency is converted into a reducible frequency as explained below.

In a passenger compartment of a monocoque body of a passenger car, a felt, a vinyl chloride sheet, and a PE are usually provided depending on the location.
An anti-vibration / soundproof material made of T or the like is provided. The vibration-proof and sound-proof characteristics gradually increase from about 100 Hz as a typical characteristic, and become substantially constant after about 600 Hz. Corresponding to this characteristic, partition walls are provided on the rocker, pillar, roof header and roof side rail, which are tubular structures with both ends closed. The distance between each partition wall and the end face of the tube structure is set to about 40 cm by the above formula so that the resonance frequency of the primary mode is converted to, for example, 400 Hz at which the effective frequency band of the vibration and soundproof material is reached.

FIG. 1 shows rockers 2 of the present invention located on both sides of the floor 1 in the vehicle width direction. The end faces 2a to 40c are shown in FIG.
Five partition walls 10 made of a foam material having an interval of m and a thickness of several cm are adhered to the inner wall of the rocker 2 at the peripheral surface, and five partition walls 10 are arranged. Similarly, the partition walls 10 made of a foam material corresponding to each cross-sectional shape are arranged at intervals of 40 cm in each of the above-mentioned pipe structure portions so that a pipe length of 40 cm or more does not occur even at the end face of the pipe structure.

FIG. 2 shows a passenger car having the aforementioned monocoque body equipped with such a vehicle interior noise reduction device of 40 km.
The test data in a rough surface steady running state of / h are shown.
As is clear from the figure, the sound in the passenger compartment below 100 Hz differs depending on the frequency, but as shown by the dotted line, the improvement of the soundproofing effect of the sound pressure level of 3 dB is confirmed for the maximum specific frequency component. As overall 1.
A soundproofing effect of 4 dB was obtained. At the same time, the high-frequency sound waves of the foam material are absorbed even at high frequencies, and the transmitted sound that passes through the torque box from the front end of the front side member to the rockers and pillars is also blocked by the isolation effect, and the sound level inside the vehicle is reduced. Is improved. Therefore, such an action does not add to the action of the vibration-proof / sound-proof material, and the level does not increase at the resonance frequency of about 400 Hz and its integral multiple frequency.

It should be noted that, from such a test, since the partition wall faces the passenger compartment, a remarkable effect can be obtained even when it is applied only to the rocker, which is a sounding part, and a maximum of 3 dB can be obtained by the same test as in FIG. On the other hand, it is 1.8 dB and overall is 1.
A reduction effect of about 0.8 dB with respect to 4 dB has been confirmed. From this, it is understood that the rocker partition wall is particularly effective for road surface input noise. If the partition wall is not expected to absorb high frequency sound, a resin plate may be used, or a bulkhead may be welded so as to have a reinforcing function.

[0012]

According to the first aspect of the present invention, the vehicle interior sound of the low frequency resonance is suppressed regardless of the vibration and soundproof material in the vehicle interior. Since the sound transmitted through the pipe structure is also blocked, the sound in the vehicle interior in the high frequency range is also reduced. A soundproofing measure can be realized without increasing the weight by adding a reinforcing material in the passenger compartment and increasing the plate thickness, in other words, it is possible to eliminate the obstacle of the weight reduction of the automobile. According to the second aspect of the present invention, the partition wall is light in weight and also has a sound absorbing action with respect to a high frequency sound wave. According to the third aspect of the present invention, by providing the partition wall on the rocker, it is possible to effectively reduce the vehicle interior noise particularly when traveling on the road surface.

[Brief description of drawings]

FIG. 1 is a partial perspective view of a rocker to which a vehicle interior sound reducing method for an automobile according to the present invention is applied.

FIG. 2 is a diagram showing test data for confirming the effect of the present invention.

FIG. 3 is a diagram showing a standing wave mode of a tube structure which is a premise of the present invention.

[Explanation of symbols]

 2 rocker 10 bulkhead

Claims (3)

[Claims] 1. The frequency of a resonance sound that may occur in the pipe structure portion of the body is increased to a frequency band in which the vibration and soundproof material in the vehicle compartment can effectively operate. A method for reducing vehicle interior noise of an automobile, characterized in that a partition wall for dividing the length of the pipe structure portion is provided. 2. The method for reducing vehicle interior sound of an automobile according to claim 1, wherein the partition wall is formed of a foam material. 3. A frequency of a resonance sound that may occur in at least the rocker of the pipe structure portion of the body is increased to a frequency band in which the vibration and soundproof material in the vehicle compartment can effectively operate. A vehicle interior noise reduction device for an automobile, characterized in that a partition wall for dividing the length of the rocker is provided.