WO2023157379A1 - Noise reduction system for railway vehicle - Google Patents

Abstract

The present invention is a noise reduction system 1 for a railway vehicle for reducing, at a plurality of silencing positions 10 in a railway vehicle 100, noise propagated from a noise source in the exterior of the railway vehicle 100, the plurality of silencing positions 10 being positions that are different in the longitudinal direction of the vehicle, the noise reduction system 1 for a railway vehicle comprising a noise reference sensor 20 for detecting noise propagated from the noise source and/or vibration caused by the noise, and a plurality of silencing devices 30 for respectively reducing noise at each of the plurality of silencing positions 10. Each silencing device 30 is provided with a speaker 31 for emitting sound at the respective silencing position 10 and a control unit 32 for outputting a control signal to cause the speaker 31 to radiate sound such that noise at the respective silencing position 10 is reduced. The noise reference sensor 20 is installed at the same position as, or at a position farther to the front of the vehicle than, the silencing position 10 that is located farthest to the front of the vehicle from among the plurality of silencing positions 10, with respect to the longitudinal direction of the vehicle. Each of the plurality of control units 32 generates the control signal using a reference signal outputted from the noise reference sensor 20.

Description

Noise reduction system for railway vehicles

The present invention relates to a noise reduction system for railway vehicles.

Patent Document 1 discloses a noise reduction device that includes a control sound source, an error detector, and a control section. This noise reduction device operates to cancel the noise by controlling the control sound source to generate a sound having the same sound pressure and the opposite phase as the noise at the position of the error detector. Further, a noise detector is further arranged to detect noise outside the space where the error detector is arranged, a control signal is generated based on the detection results of the error detector and the noise detector, and is output to the control sound source. (FIGS. 14 and 15). It is also disclosed that the speaker, which is the control sound source, is constructed using a glass window (paragraph [0129]).

JP-A-2005-62786

In the noise reduction device of Patent Document 1, when sound is detected only by the error detector, there is a limit to the types of signals that can be acquired by the error detector alone, and there is a problem that noise reduction accuracy is poor. On the other hand, by arranging the noise detector in addition to the error detector, the types of signals that can be acquired increase, and accurate noise reduction can be achieved. However, when both the error detector and the noise detector are arranged in the noise reduction device, there is a problem that the noise reduction device becomes large.

In particular, when introducing the noise reduction device of Patent Document 1 to a railway vehicle, it is necessary to provide a noise reduction device for each of a plurality of noise reduction points. Doing so would significantly increase the installation space of the entire system.

The present invention has been made to solve the above problems, and aims to provide a railway vehicle noise reduction system capable of reducing installation space while achieving accurate noise reduction.

A railroad vehicle noise reduction system of the present invention is a railroad vehicle noise reduction system that reduces noise propagating from a noise source outside the railroad vehicle at a plurality of noise reduction points within the railroad vehicle, The noise reduction points are different points in the longitudinal direction of the vehicle, and the railway vehicle noise reduction system includes a noise reference sensor that detects at least one of noise propagating from the noise source and vibration caused by the noise. and a plurality of mufflers for respectively reducing noise at the plurality of muffling points, wherein the plurality of muffling devices each include a speaker for emitting sound to the muffling points and a noise at the muffling points to be reduced. and a control unit for outputting a control signal for causing the speaker to emit sound, wherein the noise reference sensor is the same as a noise reduction point located furthest forward of the vehicle among the plurality of noise reduction points in the vehicle front-rear direction. Each of the plurality of control units, which are installed at a position or in front of the vehicle from the silencing point thereof, generates the control signal using the reference signal output from the noise reference sensor.

According to the present invention, it is possible to provide a railway vehicle noise reduction system capable of reducing the installation space while achieving accurate noise reduction.

FIG. 1 is a diagram schematically showing an example of a railway vehicle noise reduction system according to Embodiment 1 of the present invention. FIG. 2 is a block diagram showing an example of the configuration of the railway vehicle noise reduction system shown in FIG. FIG. 3 is a flow chart showing an example of signal processing by the railway vehicle noise reduction system shown in FIG. FIG. 4 is a cross-sectional schematic diagram showing an example of the configuration of a silencer for the front window on which the noise reference sensor is installed in the railway vehicle noise reduction system shown in FIG. FIG. 5 is a cross-sectional schematic diagram showing an example of the configuration of a silencer for a window on which no noise reference sensor is installed in the railway vehicle noise reduction system shown in FIG. FIG. 6 is a diagram schematically showing an example of a railway vehicle noise reduction system according to Embodiment 2 of the present invention. FIG. 7 is a diagram schematically showing an example of a railway vehicle noise reduction system according to Embodiment 3 of the present invention.

Hereinafter, a noise reduction system for railway vehicles according to the present invention will be described.
However, the present invention is not limited to the following configurations, and can be appropriately modified and applied without changing the gist of the present invention. Combinations of two or more of the individual desirable configurations described below are also part of the present invention.

Also, each embodiment shown below is an example, and it goes without saying that partial replacement or combination of configurations shown in different embodiments is possible. Descriptions of items common to multiple embodiments will be omitted, and only different points will be described.

In this specification, "railway vehicle" means a vehicle (preferably a passenger car) that runs on a predetermined track (regardless of material), and its power source is not particularly limited. Specifically, railway vehicles include, for example, trains (including streetcars, monorails, magnetic levitation railways, etc.), diesel trains, passenger cars of locomotives, and the like.

[Embodiment 1]
FIG. 1 is a diagram schematically showing an example of a railway vehicle noise reduction system according to Embodiment 1 of the present invention.

The railway vehicle noise reduction system 1 shown in FIG. is reduced at a plurality of silencing points 10 of .

The railway vehicle 100 is composed of a plurality of vehicles 110, and a plurality of windows 120 are provided on one side of each vehicle 110. The positions of the plurality of windows 120 in the vehicle front-rear direction are different from each other.

A plurality of windows are similarly provided on the other side of each vehicle 110, and each of these windows is similarly provided with a silencer, which will be described later. , the description of the configuration of the other side of the railcar 100 is omitted.

In this specification, the "vehicle front-back direction" corresponds to the traveling direction of the railway vehicle and its opposite direction. That is, the "vehicle front" corresponds to the traveling direction of the railway vehicle, and the "vehicle rearward" corresponds to the direction opposite to the traveling direction of the railway vehicle. In addition, "one side and the other side" respectively mean one side and the other side with respect to the traveling direction of the railway vehicle.

The noise reduction points 10 are points where noise propagating from the noise source is mainly reduced, and the multiple noise reduction points 10 are set at different points in the longitudinal direction of the vehicle. Here, the positions in the longitudinal direction of the vehicle are respectively set corresponding to the plurality of windows 120 of the railway vehicle 100 that are different from each other.

The railway vehicle noise reduction system 1 includes a noise reference sensor 20 and a plurality of silencers 30 .

The noise reference sensor 20 is a reference signal acquisition sensor that detects at least one of noise propagating from a noise source and vibration caused by the noise, and outputs the detection result as a reference signal. Here, as the noise reference sensor 20, a microphone (noise reference microphone) for detecting noise propagating from a noise source is installed.

Note that the noise reference sensor 20 is not particularly limited to a microphone, and may be, for example, a vibration sensor that detects vibration caused by noise propagating from a noise source. In this case, a vibration sensor may be installed in the window 120 of the railroad vehicle 100 and the vibration of the window 120 generated in response to noise may be detected by the vibration sensor.

The noise reference sensor 20 is installed in the longitudinal direction of the vehicle at the same position as the silencing point 10 located furthest forward of the vehicle among the plurality of silencing points 10, or installed in front of the silencing point 10. Thus, the noise reference sensor 20 is installed in the leading vehicle 110 . Further, in this embodiment, the noise reference sensor 20 is installed only at the same position as the silencing point 10 located furthest forward of the vehicle, that is, only at the front window 120 of the front vehicle 110 .

A plurality of muffling devices 30 are devices for reducing noise at a plurality of muffling points 10 , and one muffling device 30 is provided for each muffling point 10 .

Each silencer 30 includes a speaker 31 (for example, a transparent flat panel speaker 31a to be described later) and a control section (control circuit) 32. It should be noted that both silencers 30 have the same configuration.

Each speaker 31 emits sound to the muffling point 10 (the muffling point 10 targeted for muffling by the muffling device 30 including the speaker 31).

Each control unit 32 is connected to a speaker 31, and outputs sound to the speaker 31 so as to reduce noise at the muffling point 10 (the muffling point 10 targeted for muffling by the muffling device 30 including the control unit 32). Outputs a control signal to emit. Specifically, a control signal is output so as to cause the speaker 31 to generate a sound having the same sound pressure and the opposite phase as the noise at the sound deadening point 10 .

In addition, each control unit 32 is connected to the noise reference sensor 20 and uses the reference signal output from the noise reference sensor 20 to generate a control signal. That is, the reference signal of the noise reference sensor 20 acquired in front of the vehicle is used by a plurality of silencers 30 for a plurality of silence points 10 located in the same or more rearward direction than the noise reference sensor 20 in the longitudinal direction of the vehicle. be. Therefore, it is not necessary to install the noise reference sensor 20 at each muffling point 10 (each window 120), and the installation space for the railway vehicle noise reduction system 1 can be reduced. It also leads to an improvement in the degree of freedom in installation of the railroad vehicle noise reduction system 1 and a cost reduction. Furthermore, since each muffler 30 uses the reference signal of the noise reference sensor 20, it is possible to achieve accurate noise reduction.

It should be noted that even if the reference signal acquisition point and the position of the silencing point 10 are different, the railway vehicle 100 is moving at high speed, and basically the same noise (for example, passing through a rail joint) is present at each silencing point 10 . (noise generated when a vehicle crashes or rushes into a tunnel), it is possible to use (reproduce) a reference signal at each muffling point 10 . That is, the reference signal is processed based on the running speed of the railroad vehicle 100 and the distance between the noise reference sensor 20 (reference signal acquisition point) and each silence point 10 (hereinafter sometimes referred to as distance between points). (correction) can be used. Specifically, the reference signal at each silence point 10 is reproduced by passing through a filter that considers the running speed of the railroad vehicle 100, the distance between points, and the acoustic characteristics of each silence point 10. FIG.

FIG. 2 is a block diagram showing an example of the configuration of the railway vehicle noise reduction system shown in FIG.

As shown in FIG. 2, the railroad vehicle noise reduction system 1 performs reference signal processing for processing the reference signal output from the noise reference sensor 20 in order to appropriately process the reference signal and propagate it to each noise reduction point 10. It comprises a device 40 , a plurality of delay devices 50 and a plurality of error sensors 60 respectively connected to the plurality of mufflers 30 .

The reference signal processing device 40 receives the reference signal acquired from the noise reference sensor 20 and the speed information indicating the traveling speed of the railway vehicle 100 . The reference signal processing device 40 is composed of an acoustic filter 41, a signal amplifier 42, a delay device 43, etc. in consideration of the acoustic characteristics of each silence point 10 in order to reproduce the reference signal. The reference signal processed by the reference signal processing device 40 is input to the mufflers 30 (mufflers _{1 to n 1} ) of each muffling point 10 . At that time, the signal passes through the delay devices 50 (delay devices _{1 to n 2} ) having a delay amount calculated from the distance from the position where the reference signal is acquired to each silence point 10 . Note that n represents an integer of 2 or more.

FIG. 3 is a flowchart showing an example of signal processing by the railway vehicle noise reduction system shown in FIG.

As shown in FIG. 3, in the railway vehicle noise reduction system 1, first, the noise reference sensor 20 acquires a reference signal (S01), the acquired reference signal is processed by the acoustic filter 41 (S02), and the acoustic filter The reference signal processed by 41 is amplified by the signal amplifier 42 (S03).

In parallel with this, the reference signal processing device 40 acquires velocity information (S04), and each error sensor 60 acquires an error signal (S05).

Then, the reference signal processing device 40 calculates the delay time based on the speed information (S06), and the delay device 43 delays the amplified reference signal by the calculated delay time (S07). Note that this delay time is inversely proportional to the running speed of the railway vehicle 100 . That is, the delay time becomes shorter as the traveling speed of the railway vehicle 100 becomes faster, and becomes longer as the traveling speed of the railway vehicle 100 becomes slower.

The delayed reference signal is further delayed by the delay device 50 for each window 120 (each silence point 10) (S08). The delay time by the delay device 50 is calculated by the delay device 50 based on the distance between each point measured in advance and the speed information. This delay time is proportional to the point-to-point distance and inversely proportional to the traveling speed of the railway vehicle 100 . That is, the delay time is shorter as the point-to-point distance is shorter and the traveling speed of the railway vehicle 100 is faster, and longer as the point-to-point distance is longer and the traveling speed of the railway vehicle 100 is lower.

After that, the control unit 32 of each silencer 30 generates a control signal based on the reference signal input from the delay device 50 and the error signal input from the error sensor 60 (S09), and the generated control signal is output to the speaker 31 (S10). By generating the control signal based not only on the reference signal but also on the error signal, the types of signals that can be acquired increase, so noise reduction with higher accuracy can be achieved.

Each control unit 32 may have any configuration as long as it controls the speaker 31 so as to reduce the sound detected by the error sensor 60 as much as possible. Similar to the reduction device, it may comprise an FX filter (filtered X filter), a coefficient updater and an adaptive filter. In this case, a reference signal is input to the FX filter from the corresponding delay device 50 , and the characteristics of the FX filter are set to characteristics equivalent to the transfer function from the speaker 31 to the error sensor 60 . The coefficient updater receives the error signal from the corresponding error sensor 60 and the output signal of the FX filter. The adaptive filter receives an output signal (filter coefficient described later) from the coefficient updater and a reference signal output from the corresponding delay unit 50, and outputs a control signal based on these signals. The coefficient updater is composed of an LMS (Least Mean Square) algorithm or the like, and performs arithmetic processing to update the filter coefficients of the adaptive filter so that the error input from the error sensor 60 is always small. Then, the adaptive filter generates a control signal based on the filter coefficient updated by the coefficient updater, and outputs the generated control signal to the speaker 31 .

In this specification, each signal and its processing may be a digital signal and digital signal processing, or may be an analog signal and analog signal processing. Alternatively, some signals and their processing may be analog signals and analog signal processing, and other signals and their processing may be digital signals and digital signal processing.

In this embodiment, a plurality of silencers 30 are provided for a plurality of windows 120 whose positions in the vehicle front-rear direction are different from each other. Accordingly, it is possible to more effectively reduce the noise propagating from the noise source outside the railroad vehicle 100 . This is because noise from the outside tends to enter the interior of the railcar 100 through the window 120 .

FIG. 4 is a cross-sectional schematic diagram showing an example of the configuration of a silencer for the front window on which the noise reference sensor is installed in the railway vehicle noise reduction system shown in FIG. FIG. 5 is a cross-sectional schematic diagram showing an example of the configuration of a silencer for a window on which no noise reference sensor is installed in the railway vehicle noise reduction system shown in FIG.

As shown in FIGS. 4 and 5, each window 120 of the railcar 100 includes an external windowpane 121 and a window frame 122 that supports the windowpane 121 .

The noise reference sensor 20 is installed only for the front window 120, and is installed, for example, on the inner side (vehicle interior) of the lower portion of the window glass 121 of the front window 120. Although the specific location of the noise reference sensor 20 installed with respect to the window 120 is not particularly limited, it is preferably installed at the center of the windowpane 121 from the viewpoint of improving the accuracy of the reference signal.

The silencer 30 is provided for each window 120 and may include a transparent flat panel speaker 31 a as the speaker 31 . The transparent flat panel speaker 31 a is fitted in the window frame 122 inside the window glass 121 .

The error sensor 60 is provided for each silencing point 10 (each window 120), and is installed, for example, inside (inside the vehicle) below the transparent flat panel speaker 31a.

The error sensor 60 is an error signal acquisition sensor that detects at least one of sound and vibration at the sound deadening point 10 and outputs the detection result as an error signal. Here, as the error sensor 60, a microphone (error microphone) for detecting the sound at the sound deadening point 10 is installed.

Note that the error sensor 60 is not particularly limited to a microphone, and may be, for example, a vibration sensor that detects vibration at the sound deadening point 10 . In this case, a vibration sensor may be installed on the window frame 122 in the vicinity of the transparent flat speaker 31a and the vibration of the window frame 122 may be detected by the vibration sensor.

Then, the reference signal output from the noise reference sensor 20 is input to the control section 32 of each silencer 30 through the above-described signal processing, and the error signal output from the error sensor 60 is input to the control section of each silencer 30. 32. Also, each control unit 32 generates a control signal based on the reference signal and the error signal, outputs it to the speaker 31, and the speaker 31 emits sound to the sound deadening point 10 based on the control signal. As a result, noise from the outside interferes with the sound from the speaker 31 at the muffling point 10 and cancels out, thereby reducing the noise.
Here, the noise may be reduced by directly canceling the vibration of the transparent flat panel speaker 31a by the control signal without causing the speaker 31 to emit sound.

At least one error sensor 60 may be provided for the entire railway vehicle 100, and may be provided for each silencer 30 as shown in FIGS. You may provide one. In the latter case, for example, one may be provided for each vehicle of the railway vehicle 100, or only one may be provided for a plurality of adjacent muffling points 10, and the error signal from the error sensor 60 is sent to a plurality of muffling points. It may be used in device 30 . In the latter case, the error signal may be appropriately corrected according to the distance between the error sensor 60 (error signal acquisition point) and each silence point 10 or the like.

[Embodiment 2]
FIG. 6 is a diagram schematically showing an example of a railway vehicle noise reduction system according to Embodiment 2 of the present invention.

In the railway vehicle noise reduction system 2 according to this embodiment shown in FIG. In this case, the noise reference sensor 20 may be changed to a larger and more powerful one than if installed in the window 120 . Also, as the noise reference sensor 20, a microphone and a vibration sensor may be used together.

By not installing the noise reference sensor 20 on the window 120, it is possible to reduce the number of components in all the windows 120. As a result, the transparent flat panel speaker 31a can be installed closer to the window glass, and the structure can be made thinner.

In the window 120 where the noise reference sensor 20 is not provided, the transparent flat panel speaker 31a can be installed closer to the window glass 121, and the structure can be made thinner.

Also, by changing the noise reference sensor 20 to a higher performance one or using a microphone and a vibration sensor together, the accuracy of the reference signal obtained can be improved. Thereby, the effect of noise reduction can be improved.

Even if the measurement environment at the point where the reference signal is acquired and the noise reduction point 10 are different, the reference signal can be used (reproduced) at each noise reduction point 10 as in the first embodiment. Specifically, the reference signal at each silence point 10 is reproduced by passing through a filter that considers the running speed of the railroad vehicle 100, the distance between points, and the acoustic characteristics of each silence point 10. FIG. Also, to reproduce the reference signal, a device for signal processing such as a signal amplifier, a delay device, etc. may be interposed.

In the first and second embodiments, only one noise reference sensor 20 is installed in the entire railroad vehicle 100, specifically, only in the leading vehicle 110. However, in these embodiments, the noise reference sensor 20 One sensor 20 may be installed for each vehicle of the railroad vehicle 100 . In this case, the railway vehicle noise reduction system 1 or 2 may be constructed in each vehicle. Further, a plurality of noise reference sensors 20 may be installed for the entire railway vehicle 100, and one may be installed for each of the plurality of vehicles.

[Embodiment 3]
FIG. 7 is a diagram schematically showing an example of a railway vehicle noise reduction system according to Embodiment 3 of the present invention.

In the railway vehicle noise reduction system 3 according to this embodiment shown in FIG.

More specifically, the railcar 100 includes, as the cars 110, a first car 110a and a second car 110b positioned behind the first car 110a. has a plurality of first windows 120a with different positions in the vehicle front-rear direction as the windows 120, and a second vehicle 110b has a plurality of second windows 120 with different positions in the vehicle front-rear direction as the windows 120. It has a window 120b. The noise reference sensors 20 are respectively installed in the plurality of first windows 120a of the first vehicle 110a.

Also, the plurality of silencers 30 are provided for the plurality of first windows 120a and the plurality of second windows 120b, respectively, and the plurality of noise reference sensors 20 installed in the plurality of first windows 120a. Each reference signal output from is used (inputted) to the silencer 30 provided for the first window 120a in which the noise reference sensor 20 is installed and the second window 120b located at the same position in the vehicle. be.

By installing the noise reference sensors 20 in a plurality of windows 120 in this way, it is possible to correct errors in the reference signal due to differences in the installation positions of the windows 120 and the vehicle shape around the windows 120 . Thereby, the effect of noise reduction can be improved.

Here, the fact that the positions in the vehicle are the same between the first window 120a and the second window 120b is, more specifically, for example: (1) the first vehicle 110a and the second vehicle 110a; 110b is provided with a first window 120a and a second window 120b at corresponding positions, and if the first window 120a and the second window 120b are windows corresponding to each other, (2) each vehicle is evenly divided into a plurality of regions in the longitudinal direction of the vehicle, the first window 120a and the second window 120b exist within corresponding regions.

In this embodiment, the reference signal output from each noise reference sensor 20 is also used (input) to the silencer 30 provided for the first window 120a on which the noise reference sensor 20 is installed.

Further, in the present embodiment, each reference signal output from the plurality of noise reference sensors 20 installed in the plurality of first windows 120a has a shape similar to that of the first windows 120a in which the noise reference sensors 20 are installed. It may be used with the silencer 30 provided for substantially the same second window 120b.

In each embodiment, the railway vehicle 100 shows a case of a two-car train, but the railway vehicle 100 may be three or more, and the third and subsequent vehicles are similar to the second vehicle. You can build a system.

Further, in each embodiment, each silencing point 10 and each silencing device 30 are provided for the window 120 of the vehicle 110 , but each silencing point 10 and each silencing device 30 are provided for a plurality of windows other than the windows 120 of the vehicle 110 . location, for example, a plurality of locations on a wall or ceiling. Further, the sound deadening point 10 and sound deadening device 30 may be provided on different types of vehicle components, such as vehicle windows and walls. In that case, it is preferable to process the reference signal with a filter that considers the material of the installation location.

Reference Signs List 1, 2, 3 Railway vehicle noise reduction system 10 Silence point 20 Noise reference sensor 30 Silencer 31 Speaker 31a Transparent plate speaker 32 Control unit 40 Reference signal processor 41 Acoustic filter 42 Signal amplifier 43 Delayer 50 Delayer 60 Error sensor 100 rail car 110 car 110a first car 110b second car 120 window 120a first window 120b second window 121 window glass 122 window frame

Claims (7)

1. A railway vehicle noise reduction system for reducing noise propagating from a noise source external to the railway vehicle at a plurality of noise reduction points within the railway vehicle,
   The plurality of noise reduction points are different points in the longitudinal direction of the vehicle,
   The railway vehicle noise reduction system includes a noise reference sensor that detects at least one of noise propagating from the noise source and vibration caused by the noise;
   a plurality of mufflers that respectively reduce noise at the plurality of muffling points,
   each of the plurality of muffling devices includes a speaker that emits sound to the muffling point;
   a control unit that outputs a control signal that causes the speaker to emit sound so that the noise at the muffling point is reduced;
   The noise reference sensor is installed at the same position as, in the longitudinal direction of the vehicle, a noise reduction point located furthest forward of the vehicle among the plurality of noise reduction points, or installed in front of the vehicle from the noise reduction point,
   The railway vehicle noise reduction system, wherein each of the plurality of control units generates the control signal using a reference signal output from the noise reference sensor.
2. The railroad vehicle noise reduction system according to claim 1, wherein the plurality of silencers are provided for a plurality of windows of the railroad vehicle whose positions in the vehicle longitudinal direction are different from each other.
3. The railway vehicle noise reduction system according to claim 1 or 2, wherein the noise reference sensor is installed at a location other than a window of the railway vehicle.
4. The railway vehicle according to any one of claims 1 to 3, wherein the noise reference sensor is installed only one for the entire railway vehicle or one for each vehicle of the railway vehicle. noise reduction system.
5. The railway vehicle comprises a first vehicle and a second vehicle located behind the first vehicle,
   The first vehicle includes a plurality of first windows having different positions in the vehicle front-rear direction,
   the second vehicle includes a plurality of second windows having different positions in the vehicle front-rear direction;
   The noise reference sensor is installed in each of the plurality of first windows,
   the plurality of silencers are provided for the plurality of first windows and the plurality of second windows, respectively;
   Each reference signal output from the plurality of noise reference sensors installed on the plurality of first windows is transmitted to a second window at the same position in the vehicle as the first window on which the noise reference sensors are installed. 3. The railway vehicle noise reduction system according to claim 1 or 2, which is used in a muffler provided against the railway vehicle.
6. The reference signal output from the noise reference sensor is processed based on the running speed of the railcar and the distance between the noise reference sensor and each of the silence points. 2. The railway vehicle noise reduction system according to claim 1.
7. An error sensor that detects at least one of sound and vibration at any one of the plurality of silencing points,
   The railway according to any one of claims 1 to 6, wherein each of the plurality of control units generates the control signal using an error signal output from the error sensor in addition to the reference signal. Vehicle noise reduction system.
   
   

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