JP3961502B2 - Sound insulation panel - Google Patents

Description

The present invention relates to a sound insulating panel.

Conventionally, as shown in FIG. 5, a sound insulation panel 3 is used in an opening 4 of a room 1 surrounded by a wall 2 to reduce indoor noise S ₁ .
The theoretical factors that determine the sound insulation characteristics of a sound insulation panel include panel density and bending rigidity. Theoretically, there are a mass law in which panel density is an element and a stiffness law in which panel rigidity is an element.
According to the mass law, the sound insulation performance is proportional to the panel density and frequency, and according to the stiffness law, the effect appears below the resonance frequency of the panel.

FIG. 6 shows the sound insulation characteristics of a typical panel. In order to improve the sound insulation performance, it is necessary to use a material having a high density and a large plate thickness, and even if a material having a high density is used, it is difficult to cut off so-called low-frequency and mid-range noise. It is shown that.
In an actual sound insulation panel, a heavy glass plate, an iron plate, a concrete wall, etc. are used, but the density (weight per area) of the panel where sound insulation is recognized is about 30 kg / m ² .
In order to supplement the sound insulation effect, a glass wool as a sound absorbing material may be used in an overlapping manner.

Fig. 7 shows the sound absorption characteristics of glass wool, which is very effective at high frequencies, but has no effect on low-frequency noise. Even if glass wool is layered on the sound insulation panel, it is effective for medium and low-frequency noise. It can be seen that is thin.
As described above, since the panel having the sound insulation effect is heavy, there are many places where the sound insulation panel cannot be applied or is difficult to apply, such as ordinary homes, stores, and offices, despite being troubled by noise.
A typical example is a passenger aircraft cabin.
The passenger cabin's cabin noise level is high and impedes passenger comfort. However, due to the strong demand for weight reduction, it is not allowed to give weight to noise countermeasures.

FIG. 8 is a cross-sectional view of a passenger aircraft, showing a noise approach route.
The passenger cabin 10 is surrounded by a fuselage side wall panel 20 and a floor beam 70, and a window 40 is provided on the fuselage. In addition, a ceiling panel 50 and a baggage room 60 are provided in the guest room 10. A heat insulation sound insulation blanket 30 is inserted into the body panel 20.

FIG. 9 is an actual measurement value of the cabin noise spectrum of a typical current passenger aircraft.
As the side wall panel 20 that wraps the guest room, a honeycomb panel having a thickness of about 1 cm, which is called an interior panel, is used, and a characteristic as a sound insulation panel is expected, but the panel density is low (1 kg / m ² or less). It can be seen from the above theory that sound insulation is poor.
A blanket 30 which is a sound-absorbing heat insulating material for heat insulation / sound insulation is attached to the back surface of the panel, and the blanket is filled with glass wool, but the filling amount is limited in terms of weight, Glass wool has no effect on low frequency noise, and as a result, the noise level in the 80 Hz to 800 Hz range is high.
Even in ordinary households, stores, offices, etc., it is estimated that it is difficult to reduce the noise in the low and middle frequencies even if cost and weight are added to the noise reduction.

As a recent noise reduction technique as shown in the following patent document, there is active noise control (Active Noise Control = ANC).
By using the characteristic that the sound is a sparse wave, it emits an antiphase sound at the same level as the noise, and it is a technology that cancels by combining the sparse part with the dense part and the dense part with the sparse part. Practical use is progressing in the field.

The conventional idea of applying ANC to reduce indoor noise is to detect noise entering the room with multiple microphones and reduce the noise by radiating the sound in opposite phases from multiple speakers installed in the room. Met.
However, in a large room, once the noise enters the room, it is repeatedly reflected. Therefore, even if a sound with an antiphase is radiated from the speaker as an electrical signal, the position of the person is different. Since the distance from the person to the person is different, the rate of cancellation is small and not effective.
In particular, it has no effect on high frequency, non-periodic noise.

As for airplanes, ANC has been effective in the Saab 2000 small turboprop passenger aircraft.
The Serve 2000 detects noise with 72 microphones installed in the cabin and radiates sound with anti-phase from 36 speakers, but all of them are propeller noise whose fundamental frequency is 85 Hz. Wind noise with a high frequency of 400 to 1000 Hz called jet noise is not targeted.

Here, the vibration of the sound insulation panel will be described with reference to FIG. 10 by taking the vibration of the interior panel (side panel, ceiling panel) of the passenger aircraft as an example.
During the flight of the passenger aircraft, the flow of air A1 around the fuselage becomes turbulent, causing the fuselage outer plate 21 to vibrate, the inner air A2 in contact with the outer plate vibrates, and the sound pressure vibrates the interior panel 22. ing.
The flow of air around the fuselage varies depending on the location, and the thickness of the aluminum alloy outer plate varies depending on the location because it depends on strength requirements. Since the frame and the stringer are joined to the inside of the outer plate, the size of the section of the outer plate panel is different, so that the resonance frequency and the vibration form are various. A sound absorbing heat insulating material 30 is inserted inside the outer plate 21.
The pressure change (sound pressure) due to the combined vibrations drives and vibrates the interior panel, and the oscillated interior panel radiates noise S1 into the room.

Therefore, the vibration of the outer plate and the vibration (noise) of the interior panel are not the same.
Therefore, the vibration of the interior panel is detected by detecting the vibration of the interior panel and exciting the interior panel in the opposite phase using this electrical signal.
According to the actual measurement, the sound pressure level is 75 db in the target sound range, but when calculated based on this value, the maximum value of the amplitude is 3 × 10 ⁻⁶ mm and the necessary sound output is also about 0.01 W. Application of ANC is sufficiently possible.
The noise of not only airplanes but also general households and offices is still a composite of various noises, and there is no significant difference in noise level and noise spectrum.
Although the frequency bands are not necessarily the same, since high frequencies can be absorbed by glass wool, an effect can be expected for general noise reduction by targeting the sound range of 80 Hz to 800 Hz.
JP 2002-356817 A

  The problem to be solved by the invention is to reduce noise in a room by blocking a sound that enters a sealed space such as a room or a guest room with a lightweight sound insulation panel.

In the present invention, as a means for solving the problem, a method is adopted in which ANC is applied to the sound insulation panel to suppress the vibration of the sound insulation panel and to block the sound entering the sealed space.
Lightweight sound insulation panels are vibrated by the noise that is entering the cabin, creating inherent noise by the physical characteristics of the panel and radiating it into the room.
In the present invention, by paying attention to this point, by changing the mass, bending rigidity, panel size, aspect ratio, etc. of the sound insulation panel, the vibration form of the panel can be converted into a vibration form that can be easily controlled by the ANC, and the vibration of the panel is picked up. In this way, we used a means to reduce the noise emission by reducing the noise emission by suppressing the vibration of the panel by using the exciter (exciter) attached to the sound insulation panel.
In addition, a sound absorbing material such as glass wool was attached to the sound insulation panel to absorb in advance the energy of high frequency sound that vibrates the sound insulation panel.

According to the present invention, the vibration of the interior panel can be suppressed by the ANC, and as a result, the indoor noise can be reduced.
The first embodiment has a basic configuration and is effective in reducing noise at a low frequency. However, a limit appears at a high frequency due to a time delay of the feedback circuit. In the second to third embodiments, the double panel is used to detect the vibration of the intermediate panel, and the interior panel is driven in the opposite phase. By widening the interval between the panels, the time delay of the feedback circuit is compensated. The effect could be achieved up to a high frequency of 800 Hz.
The present invention is also effective as a method for blocking noise generated in a sealed space and not radiating it to the outside.

FIG. 1 is an explanatory view showing a first embodiment of the present invention.
The fuselage structure 100 of a large jet passenger plane has a fuselage outer plate 110, and an interior panel 200 is attached to the inner side of the fuselage outer plate 110 via a heat insulating sound insulation member 120 such as glass wool.

The interior panel 200 has a pickup coil 310 for vibration detection attached to the body outer plate 110 side, and an exciter 320 as an exciter is attached to the cabin 10 side of the interior panel 200.
The active noise control (ANC) device 300 includes an amplifying unit 330 and a phase inverting unit 340, amplifies the vibration of the interior panel 200 detected by the pickup coil 310, and inverts the phase of the vibration, thereby exchanging the signal with the exciter 320. To excite the exciter. By this action, the vibration of the interior panel due to the noise input through the heat insulating sound insulation member 120 from the body outer plate 110 side is suppressed.
Therefore, noise reaching the passenger compartment 10 is reduced.

By analyzing the vibration situation in the actual machine, the panel bending rigidity value and mass distribution were partially changed to give the panel vibration characteristics that were easy to control.
Since the vibration of the interior panel 200 is not necessarily uniform (simple piston motion), it is necessary to mount a plurality of pickups and corresponding exciters. In Example 1, four sets of pickup coils 310 and exciter 320 were mounted on a 1-meter square panel.

In the configuration of the basic ANC apparatus shown in FIG. 1, the vibration detected by the same panel is amplified, the phase is inverted, and the exciter is driven to stop the vibration of the panel.
This principle is effective at low frequencies such as shaking of a building, but at high frequencies, the phase shift occurs due to the time delay of the amplifier circuit, etc., and the effect can be halved or adversely affected. There is. If the phase that should originally be shifted by 180 ° is further shifted by 30 °, the effect is 86%, if it is shifted by 60 °, it is 70%, and if it is shifted by 90 ° or more, the reduction effect is lost or reversed. In the experiment, the frequency was 200 Hzb.

FIG. 2 shows an embodiment in which the interior panel has a double structure. That is, a panel 202 (herein referred to as an intermediate panel) having a size and material configuration that is completely equal to that of the interior panel 200 is disposed on the back side (body outer plate side) of the interior panel. The intermediate panel 202 has the same physical characteristics as the interior panel 200.

The vibration is detected by the pickup coil 410 attached to the intermediate panel 202, amplified by the amplification unit 430 of the ANC device 400, and the electric power having the opposite phase at the phase inversion unit is added to the exciter 420 attached to the interior panel 200. This is a method of suppressing 200 vibrations.
The effect of suppressing the vibration of the interior panel 200 is detected by the pickup coil 415 attached to the interior panel 200 and sent to the amplifying unit 430 to change the voltage level and phase of the electric power in the opposite phase and add to the exciter to achieve the maximum effect. Get.

FIG. 3 shows the principle of this scheme.
In this method, since the intermediate panel 202 and the interior panel 200 have the same physical characteristics, the vibration of the interior panel 200 is stopped by detecting the vibration of the intermediate panel 202 and vibrating the interior panel 200 in the opposite phase. Is.
The glass wool 120 is disposed outside the intermediate panel 202 and absorbs high-frequency components of noise from the body outer plate 110 in advance.

FIG. 4 shows a third embodiment of the present invention, where the space between the intermediate panel 202 and the interior panel 200 is widened, the time for transmitting sound pressure from the intermediate panel 202 to the interior panel 200 is lengthened, and the time of the feedback circuit is increased. The structure which solved the delay is shown.
In this figure, the ANC control device is omitted.

Disposing the glass wool 120 between the two panels eliminates the disadvantage of increasing the thickness, and at the same time, the glass wool 120 is fixed to the interior panel 200 to increase the mass of the glass wool 120 to increase the sound insulation effect. It is useful for.
When the glass wool 120 is fixed to the interior panel 200, there is a difference in vibration between the intermediate panel 202 and the interior panel 200 in a high frequency sound range, but there is no problem because it is outside the scope of ANC application.

It is desirable that the distance L between the two panels is long, but if the practical distance is 68 millimeters, it takes 0.2 milliseconds (m Sec) when calculated from the speed of sound. This value is sufficient to compensate for the time delay of the electrical feedback circuit.
In other words, a distance of 68 millimeters corresponds to two wavelengths (720 °) of a sound of 10,000 Hz, one wavelength (360 °) at 5,000 Hz, half wavelength (180 °) at 2,500 Hz, 1, This corresponds to 90 ° at 250 Hz, 60 ° at 833 Hz, and 30 ° at 416 Hz.
When the ANC effect is expected up to a high sound range, the distance between both panels should be wide.

The figure which shows the example which applied ANC to the interior panel The figure which shows the other example which applied ANC to an interior panel Diagram showing vibration of interior panel and intermediate panel The figure which shows the other example which applied ANC to an interior panel Figure showing a room with sound insulation panels Sound insulation characteristic diagram of a typical panel Sound absorption characteristics of glass wool Passenger plane cross section Figure showing an example (measured value) of the noise spectrum of a passenger cabin Diagram showing vibration and noise emission of passenger aircraft interior panels

Explanation of symbols

10 Passenger Aircraft Guest Room 100 Airframe Structure 110 Outer Plate 200 Interior Panel 300 ANC Device 310 Pickup Coil 320 Exciter 330 Amplifying Unit 340 Phase Inverting Unit

Claims (3)

A first sound insulation panel disposed on the indoor side formed by the honeycomb panel, and a second sound insulation panel having the same characteristics as the first sound insulation panel disposed on the sound source side in parallel to the first sound insulation panel; a second sound insulating panel of the sound source side surface to the mounted is oscillating managed by an urban known device, a first sound insulating panel of the sound source side surface to the mounted is vibrator of, electrically connected to the vibration detector and shaker Active noise control device
The active noise control device is a sound insulation panel including an amplifying unit that amplifies an electric signal of a vibration detector and a phase inverting unit that inverts the phase of the amplified vibration and supplies power to the vibrator. The sound insulation panel according to claim 1, further comprising a correction pack-up coil attached to a surface of the first sound insulation panel opposite to the exciter . The sound insulation panel of Claim 1 or 2 provided with the sound- absorbing heat insulating material inserted in the space between a 1st sound insulation panel and a 2nd sound insulation panel.

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