JPS608232Y2 - Silencer - Google Patents

Description

[Detailed explanation of the idea] TECHNICAL FIELD The present invention relates to a silencer for air conditioning and other silencers.

Conventionally, ventilation ducts have been equipped with noise reduction techniques to attenuate noise (noise from the blower that is propagated along with the conditioned air flowing through the duct and frictional noise of the conditioned air flowing through the duct) when conditioned air is sent through the ventilation duct. It is known to provide a device.

For example, a bottomed cylindrical sound-absorbing duct made of a sound-absorbing material and having a cross-sectional area approximately equal to the cross-sectional area of the ventilation duct is interposed between the ventilation ducts. Japanese Utility Model Publication No. 45-13243 describes a sound damping device in which the sound absorbing duct is spaced apart from the sound absorbing duct and is surrounded by a sound damping box lined with sound absorbing material and having a cross-sectional area larger than the cross-sectional area of the sound absorbing duct. There is.

In addition, Japanese Utility Model Publication No. 52-8246 discloses that a hollow cylindrical sound absorbing material made of a sound absorbing material such as glass wool has a cross-sectional area approximately equal to the cross-sectional area of the ventilation duct between the ventilation ducts made of a sound insulating material. The ventilation ducts are connected to each other by connecting both ends of the sound absorption duct to the ends of the ventilation duct through a duct, and the sound absorption duct is surrounded by a section having a cross-sectional area larger than that of the sound absorption duct. A sound deadening device is described in which a sound absorbing duct is surrounded by a sound deadening box lined with sound absorbing material while maintaining a space.

However, in the former case, one end of the sound-absorbing duct is covered with a sound-absorbing material, and both ends of the sound-absorbing duct are not connected to the ends of the ventilation duct, but are separated from each other, resulting in increased ventilation resistance and pressure loss. There is.

Furthermore, although the latter type of muffling device avoids the increase in ventilation resistance that occurs in the former type, the attenuation of sound in the low frequency range is not so large.

The present invention eliminates the drawbacks of such conventional noise reduction devices,
The purpose of the present invention is to provide a silencer with low ventilation resistance and high attenuation of sound in the low frequency range.
This purpose is distantly related to the present invention.

That is, in the present invention, a hollow cylindrical sound-absorbing duct made of a sound-absorbing material such as glass wool is interposed between ventilation ducts made of a sound-insulating material and has a cross-sectional area approximately equal to the cross-sectional area of the ventilation duct. The ventilation ducts are connected to each other by connecting both ends of the ducts to the ends of the ventilation duct, and the sound absorption duct is lined with a sound absorbing material that has a cross-sectional area larger than the cross-sectional area of the sound absorption duct. In a sound damping device in which a box surrounds a sound absorbing duct while maintaining space, the end of the ventilation duct on the blower side is placed approximately 0.9 m inside the sound damping box.
This is a sound muffling device characterized in that the length of the end portion is protruded, and the attenuation of sound due to reflection at the open end is increased by the protrusion of the end portion.

An example of implementing the present invention will be explained with reference to the attached drawings.
, 1° is a ventilation duct that sends conditioned air, and the ventilation duct 1
．． , 12, a sound-absorbing duct 2 is made of a sound-absorbing material such as glass wool and has a cross-sectional area S2 that is approximately equal to the cross-sectional area S1 of the ventilation duct.
The sound absorbing duct 2 connects the ventilation ducts 1□, 1□ to each other, and the sound absorbing duct 2 connecting the ventilation ducts has a cross-sectional area S3 larger than the cross-sectional area S2 of the sound absorbing duct 2. It is surrounded by a sound deadening box 4 lined with a sound absorbing material 3 such as glass wool.

The ventilation ducts 1□, 1° are on the side of the blower with respect to the noise-absorbing box 4, and the one 1□ is made of iron plate or a material with a sound insulating property equal to or better than this, and the side of the ventilation ducts 1□ is on the side opposite to the blower with respect to the noise-absorbing box 4. The duct 1□ located at is made of the same material as the ventilation duct 1□ on the blower side or made of a sound absorbing material such as glass wool.

The ventilation duct and the sound absorption duct may have either a circular cross section as shown in the first figure or a square cross section as shown in the third figure.

The sound deadening box 4 is made of a material that has the same sound insulating properties as a steel plate, such as iron plate, concrete, or wood.
This can be done by forming a special box or by using the structure of a building as it is.

For example, in a multi-story building, etc., the ventilation duct 11, 1° and the sound absorption duct 2 are inserted into the space surrounded by the floor, ceiling, and beams, and are installed on the inner wall surface of the space surrounded by the floor, ceiling, and beams. It may be lined with sound absorbing material and used as a sound deadening box.

As described above, in the present invention, a sound-absorbing duct made of a sound-absorbing material such as glass wool is interposed between the ventilation ducts and the cross-sectional area is approximately equal to the cross-sectional area of the ventilation duct. At the same time, the sound absorbing duct that connects the ventilation duct is surrounded by a sound deadening box that has a cross-sectional area larger than the cross-sectional area of the sound absorbing duct and is lined with sound absorbing material to form an air conditioning sound deadening device. It has the effect of

In other words, sound-absorbing materials such as glass wool have excellent sound-absorbing properties but poor sound-insulating properties, and most of the absorbed sound energy is transmitted to the outside. If the ventilation ducts are simply connected to each other by sound absorption ducts, the sound propagating inside the ventilation duct 11 will be absorbed by the sound absorption duct, but most of the energy of the sound will be transmitted to the outside of the sound absorption duct. However, there is a high rate of the sound entering the ventilation duct b again, making it impossible to achieve effective sound attenuation.

However, in the present invention, the sound-absorbing duct connecting the ventilation duct is surrounded by a sound-absorbing box lined with sound-absorbing material and having a cross-sectional area larger than the cross-sectional area of the sound-absorbing duct.
The energy of the sound transmitted to the outside of the sound-absorbing duct is absorbed by the sound-absorbing material on the inner wall of the sound-absorbing box, and is also insulated by the sound-absorbing box and does not leak to the outside. Therefore, the energy of the sound transmitted through the sound-absorbing duct is is ventilation duct 1
There is no risk of sound entering the room, and a high sound attenuation rate can be obtained.

In addition, since the cross-sectional area of the sound deadening box is larger than the cross-sectional area of the ventilation duct, a part of the sound energy (especially the proportion of low-frequency sounds) propagated inside the ventilation duct 11 along with the conditioned air is absorbed. Due to the phenomenon of sound reflection at the opening end, the sound is transmitted from the sound absorption duct into the sound deadening box and then returned to the ventilation duct 11, which also increases the attenuation of low frequency sound in particular.

The present inventor believes that this phenomenon of sound reflection at the open end occurs in almost the same way even when a sound absorbing duct made of sound absorbing material such as glass wool is interposed at the open end of a duct that opens into a large space. It has been proven by experiment.

(See Figures 4 and 5) Therefore, in the present invention, the sound absorption duct absorbs noise, and at the same time, by utilizing the poor sound insulation property of the sound absorption duct, most of the sound energy is transferred outside the sound absorption duct. The energy of the transmitted sound is absorbed and insulated by a sound-absorbing box surrounding the sound-absorbing duct, and the phenomenon of sound reflection at the opening end is used to attenuate low-frequency sound in particular. By taking this into consideration, it is possible to efficiently attenuate any of medium and high frequency sounds, high frequency sounds, and low frequency sounds.

In addition, it is possible to attenuate noise by simply interposing a sound-absorbing box lined with sound-absorbing material between ventilation ducts without intervening the sound-absorbing duct as described above; Since the cross-sectional area of the sound deadening box is large compared to the cross-sectional area of the silencing box, there is a problem in that ventilation resistance increases, and therefore the output of the blower must be increased, resulting in a large pressure loss when sending conditioned air.

However, in the present invention, the ventilation ducts in the sound-absorbing box are connected to each other by a sound-absorbing duct with a cross-sectional area that is approximately equal to the cross-sectional area of the ventilation duct, so regardless of the difference in the cross-sectional views of the ventilation duct and the sound-absorbing box, The cross-sectional area of the flow path for conditioned air is almost uniform without changing, so there is no increase in ventilation resistance at the location where the silencing box is placed as described above, and the pressure loss for sending conditioned air is reduced. Can be made smaller.

In addition, the length of the noise reduction box 4 is 11, the protrusion length in the noise reduction box between the ventilation ducts (on the blower side) is 11, and the protrusion length in the noise reduction box of the ventilation duct 1 is 12.
Then, in order to maximize the silencing effect (obtain the theoretical value of the sound attenuation rate), 1 must be (11 + 1 □ +
1) It is desirable that the cross-sectional area S3 of the noise reduction box 4 is at least W times the cross-sectional area S1 of the ventilation duct 11.

This means that if the length of the sound-absorbing duct 2 that connects the ventilation ducts 11 and 12 is 1 m or more between the ends of the ventilation ducts 11 and 1□, almost all the sound energy will be transmitted to the outside of the sound-absorbing duct 2. This is because it is possible.

By causing the tip of the ventilation duct 11 on the blower side to protrude by a predetermined length l□ inside the sound deadening box, sounds in the low frequency range can be significantly attenuated compared to the case where it does not protrude.

Figure 5 is based on the case where the protrusion length 1□ is set to zero.
This shows the attenuation of sound when 11 is 0.9 m.

Note that 12 may be approximately 0.1 m.

[Brief explanation of the drawing]

The drawings show an example of the implementation of the present invention; FIG. 1 is a perspective view, FIG. 2 is a vertical sectional view of FIG. 1, FIG. 3 is a perspective view showing another embodiment, and FIGS. 4 and 5. The figure is an explanatory diagram of the experimental results. 11.1゜...Ventilation duct, 2...Sound absorbing duct, 3...Sound absorbing material, 4...Sound deadening box.

Claims (1)

[Scope of Claim for Utility Model Registration] 1. A hollow cylindrical sound-absorbing duct made of sound-absorbing material such as glass wool is interposed between ventilation ducts made of sound-insulating material and has a cross-sectional area approximately equal to the cross-sectional area of the ventilation duct. The ventilation ducts are connected to each other by connecting both ends of the sound absorption duct to the ends of the ventilation duct, and
In the sound-absorbing device, the sound-absorbing duct is surrounded by a sound-absorbing box having a cross-sectional area larger than the cross-sectional area of the sound-absorbing duct and lined with sound-absorbing material, while maintaining a space around the entire periphery of the sound-absorbing duct. A sound muffling device characterized in that an end of the duct on the blower side projects inside a sound deadening box by a length of about 0.9 m, and the protrusion of the end increases attenuation of sound due to reflection at the open end. 2. The sound deadening device according to claim 1, wherein the sound deadening box has a cross-sectional area that is at least twice as large as the cross-sectional area of the sound absorbing duct. 3. The silencer according to claims 1 and 2, wherein the length of the sound absorbing duct is 1 rrL or more in terms of the distance between the ends of the two ventilation ducts.