JPH07217978A - Silencer - Google Patents

Abstract

PURPOSE:To obtain a silencer causing a pressure loss and producing a large temperature-raising effect by providing a twisted partition plate in a passage in a central part, in a sound-absorbing duct type silencer prepared by fitting a layered sound-absorbing material inside a cylindrical casing. CONSTITUTION:This sound-absorbing duct type silencer being suitable for reduction of noise in an air conditioning duct has a structure wherein a sound- absorbing material 2 is fitted inside an outer-tube casing 1 and a partition plate 3 twisted at an angle of 180 deg. and fitted with a sound-absorbing material 4 on the opposite sides is provided in a passage formed inside the sound- absorbing material 2. In this silencer, air flows under the guidance of the twisted partition plate 3. Since a change in the area of the passage and a change in the shape thereof are small, accordingly, a draft loss is not caused nearly at all, the quantity of sound wave coming into contact with the sound-absorbing materials increases and thus an excellent silencing effect can be produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to noise reduction in an air-conditioning duct, and more particularly to a sound-absorbing duct type silencer suitable for a large noise-eliminating effect with a small ventilation pressure loss.

[0002]

2. Description of the Related Art A conventional sound absorbing duct type silencer is a noise countermeasure handbook, Japan Acoustic Materials Association, Gihodo, 400-40.
As shown in page 3, by partitioning the cross section of the flow path into several flow paths, sound is absorbed even in a high frequency region having a short wavelength, so that a large sound deadening effect is obtained.

[0003]

According to the above-mentioned prior art, if the partition is made so that the flow path becomes small, a large noise reduction effect can be obtained, but the pressure loss becomes large, and conversely, the size of the flow path is reduced so as to suppress the pressure loss. The larger the value, the smaller the muffling effect. Therefore, it cannot be said that the consideration of compatibility between the muffling effect and the pressure loss is sufficient, and there is a problem that either one is preferentially used depending on the purpose.

An object of the present invention is to provide a muffler which has a large muffling effect and a small pressure loss.

[0005]

The above object can be achieved by forming the partition plate of the flow path into a twisted shape.

[0006]

With the twisted shape of the partition plate of the flow path, the flow path is formed not by a straight line but by a curved line, so that the passage of sound waves is reduced and the sound deadening effect is great. In addition, the change in area of the flow path is small and the change in shape is not rapid, so that the pressure loss is small.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. The sound absorbing material 2 is attached to the inside of the outer cylinder casing 1, and the partition plate 3 twisted by 180 ° is provided in the flow path formed inside the sound absorbing material 2. Further, sound absorbing materials 4 are attached to both sides of the partition plate 3.

According to this embodiment, the air is guided by the twisted partition plate 3 and flows, and since the change in the area and shape of the flow path is small, the ventilation pressure loss is almost eliminated.
In addition, since a sound wave that travels linearly has a large amount of contact with the sound absorbing material, a high frequency sound wave having a short wavelength also has a small amount of passing through, and thus has a large sound deadening effect.

[0009]

According to the present invention, the change in area and shape of the flow path is small due to the twisting of the partition plate, and the sound waves are prevented from going straight, so that the pressure loss is small and a large volume of sound can be obtained.

[Brief description of drawings]

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

FIG. 2 is an explanatory view of the partition plate of FIG.

[Explanation of symbols]

 1 ... Outer cylinder casing, 2, 4 ... Sound absorbing material, 3 ... Partition plate.

Claims (1)

[Claims] 1. A sound-absorbing duct type silencer in which a layered sound-absorbing material is attached to the inside of a cylindrical casing, characterized in that a twist partition plate is provided in the flow path at the center.