JPH05173580A - Sound insulating panel - Google Patents

Abstract

PURPOSE:To provide the sound insulating panel which can reduce the vibration level on a panel so that the radiation sound from the panel becomes small. CONSTITUTION:The sound insulating panel 1 consists of the panel 1, an actuator 3 which excites it, vibration sensors 5 which detect the vibration of the panel 1, a noise detection sensor 8, and a driving part 4 which processes electric signals of a noise inputted from the sensors 5 and 8 and drives the actuator 3 so as to excite the panel 1 in the opposite phase from the noise; and the driving part 4 has a converting circuit 6 which converts the electric signals from the vibration sensors 5 into the sound pressure value of the radiation sound from the panel 1 and the panel 1 is so excited that the radiation sound pressure converted value becomes small. High sound insulation performance is obtained over a wide frequency range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound insulation panel for canceling panel vibration due to noise by exciting the panel in a phase opposite to that of noise.

[0002]

2. Description of the Related Art In recent years, noise prevention has become an important issue in the environment of living environment due to the increasing density and aggregation of houses in urban areas, and various sound insulation panels have been used along with it. Generally, a double structure having an air layer in the middle is used because of its light weight and relatively good sound insulation. However, in this case, since there is a resonance transmission phenomenon in the low frequency region due to the spring action of the middle air layer, it cannot be said that the sound insulation performance in the middle and low frequency regions is sufficient.

For this reason, a sound insulation panel having an active sound insulation effect has been proposed. This is, as shown in FIG. 3, a panel 1, an actuator 3 for excitation attached to the panel 1, a drive unit 4 for driving the actuator 3, and a vibration attached to the panel 1 for detecting the vibration of the panel 1. It is composed of a sensor 5 and a noise detection sensor 8 that detects a sound or a vibration emitted from a noise source 9, and the drive unit 4 calculates an electric signal of noise input from the vibration sensor 5 and the noise detection sensor 8. The vibration of the panel 1 caused by the noise is canceled by exciting the panel 1 in the opposite phase to the noise, and as a result, the vibration of the panel 1 is stopped and the stationary state is maintained.

[0004]

Since the conventional sound insulation panel as described above works to reduce the vibration level at the point where the vibration sensor 5 is installed, the panel 1
The vibration level at points other than the point where the vibration sensor 5 is installed is not concerned at all. Therefore, in some cases, by suppressing the vibration of the point where the vibration sensor 5 is installed, the vibration of the point other than this position may be increased. That is,
In the frequency range of vibration modes other than the primary resonance mode, many peaks and valleys are distributed on the plane of the two-dimensional panel,
In other words, a node of vibration and an antinode are generated, and even if the vibration is controlled so that the vibration at the point where the vibration sensor 5 is installed becomes zero, as shown by the broken line in FIG. 4, the vibration increases at other points. Since the sound insulation of the panel is determined by the vibration state of the entire panel surface, the sound insulation may be deteriorated. Therefore, it is conceivable to increase the number of points for suppressing the vibration level on the panel 1 by using a plurality of vibration sensors 5, but nevertheless, the higher the vibration mode, the higher the vibration mode (the mode with a large number of nodes / bellys). However, it is not a fundamental solution.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a sound insulation panel capable of reducing the vibration level on the panel so that the sound emitted from the panel is reduced. Especially.

[0006]

According to the present invention, in order to solve the above problems, as shown in FIG.
An excitation actuator 3 attached to the panel 1, a vibration sensor 5 attached to the panel 1 for detecting vibration of the panel 1, a noise detection sensor 8 for detecting sound or vibration emitted from a noise source 9, The actuator 3 is driven so as to cancel the vibration of the panel 1 due to the noise by calculating the electric signal of the noise inputted from the vibration sensor 5 and the noise detection sensor 8 to excite the panel 1 in a phase opposite to the noise. In the sound insulation panel including the drive unit 4 for driving the drive unit 4, the drive unit 4 has a conversion circuit 6 for converting an electric signal from the plurality of vibration sensors 5 into a radiated sound pressure value radiated from the panel 1. 6 is Am (t) for the acceleration signal from the m-th vibration sensor 5, P (t) for the sound pressure signal at the point for evaluating the radiated sound pressure, N for the number of vibration sensors 5, and m for the m-th vibration sensor. The impulse response of the transfer characteristic from acceleration to sound pressure from the dynamic sensor 5 to the point where the radiated sound pressure is evaluated is Dm (t), Sm is a constant relating to m, * is a convolution integral, t is time, and g is arbitrary. Is a constant of It is characterized by being a circuit that realizes.

[0007]

The operation of the present invention will be described below with reference to FIG.
In FIG. 2, the XY plane is the panel surface. The emission of sound from the vibrating panel is determined by the vibration state of the panel surface, so that a finite number of minute elements d are formed on this panel surface.
If each element dS is divided into S and each element dS is considered to be oscillating, if each element dS is sufficiently small with respect to the wavelength, the sound wave is radiated spherically to the space. According to the elastic wave theory, the sound pressure at an arbitrary point E in this space is expressed as a function of the distance from the sound source and the time, and when the coordinates shown in FIG. It is represented by the formula 1.

[0008]

[Equation 1]

In Expression 1, P is the sound pressure expressed in the frequency domain, A (x, y) is the vibration acceleration in the z direction expressed in the frequency domain at the point (x, y), and dS is the area of the minute element. , K is the wave number, and R is the distance to an arbitrary point in space. If the distance R from the minute element dS to the sound pressure evaluation point E is considered to be constant within the element, the conversion formula is simplified to
become that way.

[0010]

[Equation 2]

Further, when the vibration acceleration is considered to be uniform within the minute element dS,

[0012]

[Equation 3]

When there are N minute elements dS, the area of the element m is Sm,

[0014]

[Equation 4]

It is expressed as Here, g = jρ / 2π. If the expression expressed in this frequency domain is expressed in the time domain,

[0016]

[Equation 5]

[0017] Here, Dm (t) is exp (-
jkRm) / Rm inverse Fourier transform. In this way, the sound pressure value at an arbitrary point in space is obtained from the time signal of the vibration on the panel surface divided into elements.

Therefore, rather than detecting the vibration acceleration at each finite element point on the panel and activating the control to reduce the vibration itself, the signal P ( If the control is operated so as to reduce t), the sound emitted to the evaluation point will be reduced.

[0019]

Embodiment An embodiment of the present invention will be described with reference to FIG.
Reference numeral 1 denotes a rectangular panel, the peripheral edge of which is fixed by a peripheral member 2. A plurality of electromagnetic type excitation actuators 3 are attached to the panel 1. In the illustrated embodiment, four excitation actuators 3 are attached. Further, 36 vibration acceleration sensors 5 are installed at equal intervals. The drive unit 4 that drives the excitation actuator 3 has a conversion circuit 6 that uses a DSP (digital signal processor). A noise detection sensor 8 for detecting vibrations or sounds emitted by a noise source 9 is connected to the drive unit 4, and signals Am (t) from 36 acceleration sensors 5 on the panel 1 are input. The drive unit 4 has a circuit unit that performs the calculation expressed by the equation 6 on the 36 acceleration signals Am (t), and further, the sound pressure value P (t) calculated here. Is input to an adaptive digital filter that works to minimize it.

[0020]

[Equation 6]

This adaptive digital filter is a Filt.
It operates according to the ered-X LMS algorithm.
In Expression 6, Sm means the area shared by each acceleration sensor 5, and is a constant value here. Since the peripheral edge of the panel 1 is fixed to the peripheral member 2, it is considered that the vibration level is small and is not taken into consideration in the calculation of the radiated sound pressure.
Further, Dm (t) has a frequency characteristic that is a complex number Dm (t).
Use Dm (t) expressed as (ω) = exp (−jωRm / c) / Rm. This Dm (t) can also be obtained by measurement.

Note that it is possible to directly detect the sound pressure at the radiated sound evaluation point using a microphone and operate the control so as to reduce the sound pressure. As in the invention, the S / N ratio is poor as compared with the configuration in which the vibration is detected by the vibration sensor, which is not practical. In addition, installing a microphone in an outdoor space is not suitable because it has a problem of durability. If the vibration sensor on the panel is used as in the present invention, the sound insulation panel does not have such a problem.

[0023]

As described above, in the present invention, the vibration of the panel is detected at a plurality of points, the vibration detection signal is converted into the sound pressure radiated from the panel, and the radiated sound pressure conversion value becomes small. Since the panel is excited as described above, there is an effect that high sound insulation performance can be obtained over a wide frequency range.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of the present invention.

FIG. 2 is a diagram showing a coordinate system of plane elements and radiated sound pressure evaluation points.

FIG. 3 is a diagram showing a schematic configuration of a conventional example.

FIG. 4 is an explanatory diagram of a vibration mode.

[Explanation of symbols]

 1 Panel 2 Peripheral part 3 Actuator 4 Drive part 5 Vibration sensor 6 Conversion circuit 7 Control circuit 8 Noise detection sensor 9 Noise source

Claims (2)

[Claims] 1. A panel, an excitation actuator attached to the panel, a vibration sensor attached to the panel to detect vibration of the panel, a noise detection sensor to detect sound or vibration emitted from a noise source, and vibration. The sensor and the noise detection sensor are composed of a drive unit that drives the actuator so as to cancel the vibration of the panel due to the noise by performing an operation on the electrical signal of the noise and exciting the panel in a phase opposite to the noise. In the sound insulation panel, the drive unit has a conversion circuit that converts an electric signal from a plurality of vibration sensors into a radiated sound pressure value radiated from the panel, and the conversion circuit includes an acceleration signal from the m-th vibration sensor. Is the sound pressure signal at the point where the sound pressure to be radiated is evaluated, P (t), the number of vibration sensors is N, and the sound emitted from the m-th vibration sensor is The impulse response of the transfer characteristic from the acceleration to the sound pressure up to the point where the pressure is evaluated is Dm (t), Sm
Is a constant relating to m, * is a convolution integral, t is time, g
Is an arbitrary constant, A sound insulation panel that is a circuit that realizes 2. The impulse response Dm (t) of the transfer characteristic
Is the frequency characteristic Dm (ω) expressed by the complex number,
ω is the angular frequency, c is the speed of sound, Rm is the distance from the m-th vibration sensor to the point at which the radiated sound pressure is evaluated, j is the imaginary unit,
Let exp be the base of the natural logarithm and h be an arbitrary constant, then the complex number Dm (ω) = (h / Rm) exp (−jωRm / c)
The sound insulation panel according to claim 1, wherein