JP7107731B2 - Design method of noise reduction structure - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise reduction structure for reducing noise from ventilation openings and the like in buildings.

In a sound field that propagates one-dimensionally, such as low-frequency noise that propagates through ducts, etc., by arranging acoustic pipes on the walls of the duct, the noise that propagates downstream, that is, on the noise exit side, is reduced. Methods have been proposed in Patent Literature 1, Patent Literature 2, and the like.

In the methods described in Patent Document 1 (Patent No. 3831263) and Patent Document 2 (Patent No. 5454369), the noise reduction effect is obtained at frequencies at which the tube length of the acoustic tube is equal to 1/4 of the wavelength and at odd multiples thereof. is obtained.

However, in the noise reduction structure in the ventilation opening described in Patent Document 1 and Patent Document 2, there are various problems such as a complicated structure, a large number of types and numbers of constituent members, an increase in the weight of the device, and an increase in manufacturing and assembly costs. I had a problem.

Therefore, the inventor proposed an invention according to Patent Document 3 (Japanese Unexamined Patent Application Publication No. 2017-101530) as a noise reduction structure that solves these problems.
Japanese Patent No. 3831263 Japanese Patent No. 5454369 Japanese Patent Application Laid-Open No. 2017-101530 (Japanese Patent Application No. 2016-99316)

In the noise reduction structure using the resonator proposed in Patent Document 3, a large noise reduction effect is obtained at frequencies close to the resonance frequency determined by the cross-sectional shape of the resonator having the slit-shaped opening.

On the other hand, there is a problem that the frequency range in which the noise reduction effect can be obtained is narrow, and the effect is hardly obtained at frequencies far from the resonance frequency. Such a problem becomes particularly conspicuous when trying to reduce noise having components in a wide frequency range, such as road noise.

That is, even if the noise of a specific limited frequency close to the resonance frequency can be reduced, the noise of other frequencies cannot be reduced, so the noise reduction effect on the overall noise is reduced.

In order to solve such problems, Patent Document 3 proposes a noise reduction structure incorporating a plurality of resonators having different resonance frequencies.

However, there is no guidance as to how to set the resonance frequencies of the plurality of resonators for effective noise reduction, which is a problem.

The present invention is intended to solve the above problems, and a method for designing a noise reduction structure according to the present invention includes (n+1) resonators (where n is a natural number), and the resonance frequency of the _n - _th resonator is fn , and the resonance frequency of fn is smaller than the resonance frequency of fn ₊₁ ,
Rn ₌ (fn ₊₁ / _fn )
1< _Rn ≦2
It is characterized by being designed to satisfy

Further, the method for designing a noise reduction structure according to the present invention is characterized by using a pair of resonators having the same resonance frequency and designing such that the slit-shaped openings of the pair of resonators are arranged to face each other. do.

Further, the noise reduction structure designing method according to the present invention is characterized in that the design is such that a partition extending from the slit-shaped opening to the space inside the resonator is provided.

Further, the method for designing a noise reduction structure according to the present invention is characterized in that the resonator is designed so as not to have an air layer.

Further, the method for designing a noise reduction structure according to the present invention is characterized in that the resonator is designed so as to be arranged on a wall surface provided with an opening of the building.

According to the noise reduction structure according to the present invention, a guideline is given as to how to set the resonance frequencies of the plurality of resonators for effective noise reduction.

It is a figure explaining the resonator 10 used for the noise reduction structure 1 which concerns on embodiment of this invention. It is a figure explaining noise reduction structure 1 concerning an embodiment of the present invention. It is a figure (1) which shows the dimension of the dry double wall used for demonstration experiment. It is a figure (2) which shows the dimension of the dry double wall used for demonstration experiment. FIG. 10 is a diagram showing an experimental pattern; It is a figure which shows the result of a demonstration experiment.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present specification is incorporated by reference to the contents described in Japanese Patent Application No. 2016-99316, Japanese Patent Application No. 2016-102062, Japanese Patent Application No. 2016-188010, and Japanese Patent Application No. 2017-181915.

The noise reduction structure 1 according to the present invention uses, as a basic unit, a resonator 10 in which a resonance phenomenon occurs due to a slit structure having a cavity closed behind as shown in FIG. First, this resonator 10 will be described.

FIG. 1A is a perspective view of the resonator 10. FIG. FIG. 1(B) is a cross-sectional view of the slit-shaped opening 50 of the resonator 10 of FIG. 1(A) taken vertically along the longitudinal direction.

As shown in FIG. 1, the resonator 10 used in the noise reduction structure 1 according to the present invention is basically composed of a quadrangular prism-shaped housing 40 having a hollow inner space. One surface of the housing 40 constituting the resonator 10 has a longitudinal slit-shaped opening 50 and partition walls 60 arranged on both sides of the slit-shaped opening 50 and extending into the space inside the resonator 10. And, it is characterized by having. Here, each dimension of the resonator 10 functioning as a resonator is represented by symbols shown in FIG. One surface of the housing 40 in which the slit-shaped opening 50 is formed and the partition wall 60 are perpendicular to each other.

If each dimension of the resonator 10 is sufficiently small with respect to the wavelength, the acoustic impedance ratio Z at the slit-shaped opening 50 can be obtained by the following equation (1).

However, f is the noise frequency, c is the speed of sound, and ρ is the medium (air) density. V _n is the volume of the space surrounded by the slit-shaped opening 50 and the partition wall 60, other than the shaded area in FIG. be done. Note that the second term in [ ] in Equation (2) is a term related to the correction of the opening edge. In addition, the hatched space in FIG. 1(B) corresponds to the air layer of the resonator 10 functioning as a resonator.

Also, V is the volume of the cavity of the resonator 10 (the volume of the air layer) and is calculated by the following equation (3).

Also, S is the area of the slit-shaped opening 50 (slit opening) and is calculated by the following equation (4).

The first term r on the right side of equation (1) is acoustic resistance such as friction generated between the surface of the partition wall 60 of the resonator 10 functioning as a resonator and the air. When the partition wall 60 is made of a material with a smooth surface such as metal, the acoustic resistance r becomes a very small value, and the acoustic impedance ratio Z at the opening of the slit-shaped opening 50 is almost 0 at the resonance frequency f that satisfies the following equation. Become.

When two resonators 10 functioning as such resonators are arranged facing each other, for example, along the upper and lower inner walls 110 of the ventilation opening 100 (see FIG. 5), at the frequency f The opening 50 becomes acoustically "soft", and the noise of frequency f propagating from the upstream side is reflected upstream and does not propagate downstream.

The noise reduction structure 1 according to the present invention is premised on the use of a plurality of resonators 10 having different dimensions and therefore different resonance frequencies. In the present invention, when setting the resonance frequencies of the plurality of resonators 10, it is shown how to set the resonance frequencies of the plurality of resonators 10 in order to achieve effective noise reduction. there is

FIG. 2 is a diagram explaining the noise reduction structure 1 according to the embodiment of the present invention. 2 show the cross-sectional structure of the resonator 10 described in FIG. The designation of the resonators 10 _n using the subscript n will distinguish them from each other and represent resonators of different dimensions. Also, let f _n be the resonance frequency of the resonator 10 _n . The present invention provides a resonance frequency setting method for effectively reducing noise having components in a wide frequency range, in contrast to a noise reduction method using a plurality of elongated slit resonators 10 _n . I will provide a.

FIG. 2(A) is a diagram illustrating a case where two resonators 10 ₁ and 10 ₂ having different resonance frequencies are used. A pair of resonators having the same resonance frequency is used, and the slit-shaped openings 50 ₁ (or 50 ₂ ) of the pair of resonators are arranged to face each other.

When two resonators 10 ₁ and 10 ₂ having different resonance frequencies are used as in this embodiment, the resonance frequencies are denoted as f ₁ and f ₂ , respectively. Of the two resonance frequencies, the smaller one is f ₁ and the larger one is f ₂ .

In the present invention, the ratio of two resonance frequencies is specified as an effective method of setting resonance frequencies.

Specifically, as shown in the box in FIG. 2A, the ratio of the two resonance frequencies is R=f ₂ /f ₁ and 1<R≦2. Note that R=1 means that f ₁ and f ₂ have the same frequency, and R= ₂ means that f ₂ is _twice the frequency of f ₁ . It means that it differs by one octave from the resonance frequency f ₁ of the device 10 ₁ .

In this specification, R as described above is also referred to as "resonance frequency ratio".

FIG. 2B is a diagram illustrating a case where two resonators 10 ₁ , 10 ₂ and 10 ₃ with different resonance frequencies are used. Also in this embodiment, a pair of resonators having the same resonance frequency is used, and the slit-shaped openings 50 ₁ (or 50 ₂ or 50 ₃ ) of the pair of resonators are arranged to face each other.

When three resonators 10 ₁ , 10 ₂ , and _{10 3} with different resonance frequencies are incorporated as in this embodiment, as shown in the box in FIG. , f ₂ and f ₃ , the ratios R ₁ =f ₂ /f ₁ and R ₂ =f ₃ /f ₂ are 1<R ₁ ≦2 and 1<R ₂ ≦2.

Similarly, even when four or more resonators having different resonance frequencies are incorporated, the ratio R of adjacent frequencies when arranging the resonance frequencies in ascending order is 1<R≦2. We generalize this as follows.

FIG. 2(C) is a diagram for explaining the case of using two _resonators 10 ₁ , 10 ₂ , . . Also in this embodiment, a pair of resonators having the same resonance frequency is used, and the slit-shaped openings 50 of the pair of resonators are arranged to face each other.

The invention can be defined as follows. That is, a noise reduction structure in which (n+1) resonators (where n is a natural number) having slit-shaped openings with mutually different resonance frequencies are arranged, and the resonance frequency of the n-th resonator is f _n and _if the resonant frequency of fn is less than the resonant frequency of fn _{+1 (} i.e., if f1<f2<...< _fn <fn _{+1 )} , then
Rn ₌ (fn ₊₁ / _fn )
1< _Rn ≦2
is characterized by satisfying

As described above, according to the noise reduction structure according to the present invention, a guideline is given as to how to set the resonance frequencies of the plurality of resonators for effective noise reduction.

In the embodiments described so far, a case where a pair of resonators having the same resonance frequency is used and the slit-like openings of the pair of resonators are "opposed" has been described as an example. There is also an arrangement in which the resonators are arranged only on one side (also referred to as “one-sided (parallel) arrangement”; for example, in FIG. 2, an arrangement example in which only resonators having slit-shaped openings are arranged on the upper side of the paper surface). It can be included in the embodiment.

It has been confirmed that the method of "opposing arrangement" of the resonators 10 is effective as a noise reduction method compared to other arrangement methods, but it is also sufficient for arrangement methods such as "one side (parallel) arrangement". A noise reduction effect can be expected. If only "one-sided (parallel) arrangement" can be adopted due to layout reasons, such an arrangement can be adopted as appropriate.

Such a “one-side (parallel) arrangement” also includes (n+1) resonators (where n is a natural number) having slit-shaped openings with mutually different resonance frequencies under the definition as above. configured as follows.

In addition, in the embodiments described so far, a case where a pair of resonators having the same resonance frequency is used and the slit-shaped openings of the pair of resonators are "opposed to each other" has been described as an example. An embodiment using a pair of resonators having resonance frequencies is also included in the noise reduction structure 1 of the present invention.

In the embodiments described so far, the resonator 10 has partition walls 60 arranged on both sides of the slit-shaped opening 50 and extending into the space inside the resonator 10 . However, such partition walls 60 on both sides are not necessarily essential. The partition wall 60 may be provided on one side of the slit-shaped opening 50, or may not be provided at all.

When adopting the resonator 10 in which the partition wall portions 60 on both sides of the slit portion 50 are omitted, the front plate of the resonator 10 including the slit portion 50 has a large thickness (for example, a plate thickness l). Good to use.

Due to such a plate thickness l, V _n described in the previous embodiment also occurs in the resonator 10 used in this embodiment. As a result, the noise reduction structure 1 according to the present embodiment, in which the resonator 10 without the partition wall 60 is used, can obtain the same effect as the noise reduction structure 1 described above.

The resonator 10 used in the embodiments described so far has an air layer indicated by the shaded area in FIG. 1(B). However, the resonator 10 having such an air layer is also not essential in the present invention.

A substantially U-shaped resonator partitioned by plates in three of four directions, ie, a resonator without an air layer behind it, functions as an acoustic tube. Even in such a resonator that does not have an air layer behind it, under the definition above, there are (n+1) resonators (where n is a natural number ) are arranged side by side.

The noise reduction structure 1 according to the present invention was verified by experiments. The results of demonstrating the effect of the noise reduction method to which the resonance frequency setting method according to the present invention is applied by sound insulation experiments are shown below. A dry double wall was adopted as a member for providing the ventilation opening 100, and various resonators were attached to the interior wall 110 side of the wall for experiments. Further, the experiment was conducted in the TYPE II laboratory described in JIS A 1416:2000 "Method for measuring aerial sound insulation performance of building members in laboratory".

In the experiment, the sound transmission loss of a dry double wall provided with a slit-shaped ventilation opening 100 with a width of 100 mm, a depth of 300 mm, and a height of 1,600 mm shown in FIGS. It was measured according to the method.

The experimental pattern is shown in FIG. FIG. 5 is a schematic diagram of a plan view of a dry double-walled ventilation opening 100 vicinity. In the experiment, elongated resonators with a length of 1,600 mm are installed on both the left and right sides of the ventilation opening 100 on the dry double-wall sound receiving room side. Each experimental pattern is described below.
case A:
A pattern in which the same resonators with a resonance frequency of 500 Hz are arranged facing each other. An example using a resonator having a single resonance frequency as a comparison target for cases B to E below.
case B:
A pattern in which resonators having two resonance frequencies of 500 Hz and 630 Hz are arranged facing each other. This corresponds to the embodiment described in FIG. 12 of Japanese Patent Application No. 2016-099316. The resonance frequency ratio is R=1.26, corresponding to 1/3 octave.
case C:
A pattern in which resonators having two resonance frequencies of 400 Hz and 800 Hz are arranged facing each other. This corresponds to the embodiment described in FIG. 12 of Japanese Patent Application No. 2016-099316. The resonance frequency ratio is R=2, corresponding to one octave.
case D:
A pattern in which resonators with resonance frequencies of 500 Hz and 630 Hz are arranged opposite to each other. The resonance frequency ratio is R=1.26, corresponding to 1/3 octave.
case E:
A pattern in which resonators with resonance frequencies of 500 Hz and 1 kHz are arranged opposite to each other. The resonance frequency ratio is R=1.26, corresponding to 1/3 octave.
case O:
A pattern used for comparison when no resonator is arranged. In order to avoid the influence of case A to case E and the change in the depth of the ventilation opening 100, a simple elongated box is arranged.

FIG. 6A shows the measurement results of the sound transmission loss for each ⅓ octave band of cases A, B, and C. FIG.

It can be seen that case A has greatly improved sound transmission loss compared to case O in the vicinity of the 500 Hz band, which is the resonant frequency of the resonator. This is the noise reduction effect of the slit resonator.

In case B where the resonance frequency ratio is R=1.26, although the maximum value of the effect is lower than that in case A, it can be confirmed that the noise reduction effect is obtained in a wider frequency band.

When you want to reduce noise that has components in a wide frequency range, such as road noise, overall noise reduction is achieved by having a wide frequency range where the effect can be obtained rather than having a large maximum effect at the pinpoint frequency. It is often effective from the viewpoint of

On the other hand, in case C where the resonance frequency ratio is R=2, the frequency range in which the effect can be obtained is further widened.

FIG. 6B shows the measurement results of sound transmission loss for each ⅓ octave band of cases A, D, and E. FIG.

Similar to the above, case D, which has a resonance frequency ratio of R = 1.26, has a lower noise reduction effect in a wider frequency range than case A, although the maximum effect is lower. can be confirmed.

In addition, this result shows that an embodiment in which two resonators having a resonance frequency ratio of 1<R≦2 are arranged facing each other is effective as an application of the one-sided arrangement.

On the other hand, in case E where the resonance frequency ratio is R=2, the frequency range in which the effect can be obtained is further widened.

As described above, it was confirmed that the noise reduction method using the resonator 10 having the elongated slit-shaped opening 50 according to the present invention can expand the frequency range in which the noise reduction effect can be obtained.

Further, according to the noise reduction structure 1 according to the present invention, a stable noise reduction effect can be obtained as a whole frequency characteristic.

Further, according to the noise reduction structure 1 according to the present invention, when it is desired to reduce noise having components in a wide frequency range, such as road noise, an effective combination of resonance frequencies can be set, and a resonator for achieving the combination can be used. can be designed.

As described above, according to the noise reduction structure according to the present invention, a guideline is given as to how to set the resonance frequencies of the plurality of resonators for effective noise reduction.

In the above embodiment, the noise reduction structure 1 according to the present invention has been described based on an example of applying it to an opening in the wall surface of a building, but the present invention is applicable to building doors, louvers, and double-skin structures. It can also be applied to openings and the like.

Reference Signs List 1 Noise reduction structure 10, 10 ₁ , 10 ₂ , 10 _n Resonator 40 Housing 50 Slit-shaped opening 60 Partition wall 100 Ventilation opening 110... Interior wall 120... Exterior wall

Claims (5)

A method for designing a noise reduction structure in which (n+1) resonators (where n is a natural number) having slit-shaped openings with mutually different resonance frequencies are arranged,
Let fn be the resonant frequency of the _n -th resonator, and _if the resonant frequency of fn is less than the resonant frequency of fn ₊₁ ,
Rn ₌ (fn ₊₁ / _fn )
1< _Rn ≦2
A method of designing a noise reduction structure, characterized by designing to satisfy 2. The method of designing a noise reduction structure according to claim 1, wherein a pair of resonators having the same resonance frequency are used, and the slit-like openings of the pair of resonators are designed to face each other. 3. The method for designing a noise reduction structure according to claim 1, wherein the design is such that a partition extending from the slit-shaped opening into a space inside the resonator is provided. 4. The method for designing a noise reduction structure according to any one of claims 1 to 3, wherein the resonator is designed so as not to have an air layer. 5. The method for designing a noise reduction structure according to any one of claims 1 to 4, wherein the resonator is designed to be arranged on a wall surface provided with an opening of the building.

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