EP3875337B1

EP3875337B1 - Railway vehicle noise level reduction

Info

Publication number: EP3875337B1
Application number: EP21159261.3A
Authority: EP
Inventors: Yuta Oura; Koji Agatsuma
Original assignee: Hitachi Rail Ltd
Current assignee: Hitachi Rail Ltd
Priority date: 2020-03-02
Filing date: 2021-02-25
Publication date: 2024-04-17
Anticipated expiration: 2041-02-25
Also published as: EP3875337A1; GB2593148A; GB202002994D0; EP3875337B8; GB2593148B

Description

Field of the disclosure

The present disclosure relates to a method and system for reducing a noise level within a compartment of a railway vehicle.

Background

Electrically powered railway vehicles typically have a traction system including an overhead contactor to contact an overhead line, a voltage transformer to adjust the voltage between the overhead line, and on-board electrical equipment such as a power converter and an electric motor. Between the transformer and the converter it is also common to provide filter equipment for reducing harmonics components, such as ripples on the current generated by the power converter.
Bimodal railway vehicles also include an engine unit which drives a generator. In non-electrified regions of rail network, the overhead contactor is lowered and electrical power generated by the generator supplies the power to the converter. Another approach is to provide the vehicle with battery equipment which supplies power to the converter in non-electrified regions.
Such railway vehicles also generally have an auxiliary power system which uses some of the power to operate apparatuses for passenger comfort and safety, such as ventilation equipment, heaters, air conditioners, lighting, door systems, and audio/visual equipment.
The above-mentioned equipment items are fixed in various manners to structures of the vehicle, for example, to a bogie, a car body frame, or a passenger compartment wall, floor or ceiling. As a result, sound and vibrations may be transmitted into passenger compartments via such structures when the equipment items are operated. Although careful design of vehicle structures can suppress much of this transmission, passenger compartments can nonetheless be affected by operational noise produced by the equipment items.
A known approach to reducing noise level within compartments of railway vehicles is to provide a noise control system that use a speaker to output a generated sound, or "anti-noise", through a speaker to attenuate engine noise. The generated anti-noise is out of phase with the engine noise and combines with the engine noise to reduce the overall noise level from the engine. The resultant mix of engine noise and anti-noise is captured and measured by a microphone, and the output of the microphone is used to determine what the generated anti-noise should be. This approach to noise control requires a feedback loop and relies on actively sensing the noise within a compartment in order to produce the correct anti-noise.
However, railway vehicles are complicated systems, which vary car-to-car in terms of noise level and noise characteristic, and a problem with the known approach is that the sound analysis (typically involving transforms and filters) needed to produce the correct anti-noise in real time in such an environment is difficult to perform.
CN 109501821 A proposes a noise reduction system for a high speed train. Noise suppression is effected by physical intervention to the airflow outside the vehicle by using plasma active flow control technology to change the external surface flow field distribution characteristics of high-speed trains.
US10347236 proposes a system for applying a set of road noise cancellation parameters to a road noise cancellation system in a vehicle traveling from a first road surface type to a second road surface type.
CN10856555 A discloses a train active noise reduction system including noise acquisition, noise processing and generating a canceling soundwave using loudspeakers.
US 10453440 B1 discloses a method of noise filtering on a locomotive comprising comparing, by a controller comprising one or more processors and memory, a value of a signal associated with operation, movement, or both of the locomotive to a reference value; and suppressing one or more amplitudes at frequencies associated with one or more of the following: wind noise, locomotive engine noise, and/or brake system air venting noise.

Summary

It would thus be desirable to provide an alternative approach to noise level reduction that overcomes this problem.
According to a first aspect there is provided a method of reducing a noise level within a compartment of a railway vehicle according to claim 1.
Advantageously, the method can create the noise cancellation signal, quickly and straightforwardly via the sound database, i.e. without complex sound analysis. In addition, non-equipment noise in the compartment, such as passenger noise, does not affect the creation of the cancellation signal.
Conveniently, the sound database may store, for each equipment item, plural noise signatures which are related by the database to values of a respective operational state of that equipment item. In this case, each operational state of the vehicle may be formed by a pattern of values of operational states of the equipment items. Further, plural noise signatures may be selected from the database, the selected noise signatures corresponding to the pattern of values of operational states of the equipment items which form the operational state of the vehicle.
The method may further include: sensing noise within the compartment; determining an overall noise level of the sensed noise; and adjusting the level of the transmitted noise cancellation signal to reduce the overall noise level. For example, the noise may be sensed by one or more microphones distributed through the compartment. In particular, when the noise cancellation signal is transmitted into the compartment by one or more speakers distributed through the compartment, each microphone may be located adjacent a respective speaker. The level of the noise cancellation signal from each speaker can then be adjusted independently based on feedback from the adjacent microphone.
Generally, the transmitted noise cancellation signal should be out of phase with the noise within the compartment produced by the noise-producing equipment items. For example, one option to achieve this is for the sound database to store, for each noise signature and its respective operational state, a corresponding phase related to a state of a reference equipment item of the vehicle. Then, when the one or more noise signatures are selected from the database, their corresponding phases are also selected. Moreover, when the noise cancellation signal is created from the selected noise signatures and transmitted into the compartment, the selected phases can then be used to set the phases of the signatures within the signal relative to the present states of their reference equipment item. For example, the phase of a noise signature for reducing the noise from an engine can be related to a positional state of that engine, e.g. a crank shaft position of a diesel engine. Thus this approach requires pre-knowledge of the relationships between states of the reference equipment items and the phases in the compartment, relative to those states, of the noise within the compartment produced by the noise-producing equipment items.
However, another option to achieve having the transmitted noise cancellation signal be out of phase with the noise within the compartment produced by the noise-producing equipment items is based on measurement of the phase of the noise. For example, the method can further include: sensing noise within the compartment produced by the noise-producing equipment items; determining one or more phases of the sensed noise; and adjusting corresponding phases of the selected noise signatures within the transmitted noise cancellation signal such that they are out of phase with the determined phases.
Yet another option to achieve having the transmitted noise cancellation signal be out of phase with the noise within the compartment produced by the noise-producing equipment items is simply to make ad hoc adjustments of the phases of the selected noise signatures within the transmitted noise cancellation signal until the overall noise level within the compartment is reduced. Thus more particularly, the method may further include: sensing noise produced within the compartment by the noise-producing equipment items and the noise cancellation signal; determining an overall noise level of the sensed noise; and adjusting the phases of the selected noise signatures within the transmitted noise cancellation signal to reduce the overall noise level.
According to a second aspect there is provided a system for reducing a noise level within a compartment of a railway vehicle according to claim 6.
The system of the second aspect thus corresponds to the method of the first aspect.
Conveniently, the controller may be a computer-based controller, e.g. comprising one or more processors, which is configured by being suitably programmed. The controller may be part of a train's overall TCMS (train control and management system).
The database can be stored on a suitable computer readable medium of the system. The term "computer readable medium" may represent one or more devices for storing data, including read only memory (ROM), random access memory (RAM), magnetic RAM, core memory, magnetic disk storage mediums, optical storage mediums, flash memory devices and/or other machine readable mediums for storing information. The term "computer-readable medium" includes, but is not limited to portable or fixed storage devices, optical storage devices, wireless channels and various other mediums capable of storing, containing or carrying instruction(s) and/or data.
Conveniently, the sound database may store, for each equipment item, plural noise signatures which are related by the database to values of a respective operational state of that equipment item. In this case, each operational state of the vehicle may be formed by a pattern of values of operational states of the equipment items. Further, plural noise signatures may be selected from the database by the controller, the selected noise signatures corresponding to the pattern of values of operational states of the equipment items which form the operational state of the vehicle.
The controller may be further configured to: receive a sensed noise within the compartment; determine an overall noise level of the sensed noise; and adjust the level of the transmitted noise cancellation signal to reduce the overall noise level. For example, the system may further include one or more microphones for distribution through the compartment to sense the noise within the compartment. In particular, when the system has one or more speakers for distribution through the compartment, each microphone may be for location adjacent a respective speaker, the level of the noise cancellation signal from each speaker being adjusted independently based on feedback from the adjacent microphone.
As previously mentioned, generally, the transmitted noise cancellation signal should be out of phase with the noise within the compartment produced by the noise-producing equipment items. According to one option, the sound database may further store, for each noise signature and its respective operational state, a corresponding phase related to a state of a reference equipment item of the vehicle. The controller may then be further configured to: also select the corresponding phases to the one or more selected noise signatures; and to create the noise cancellation signal from the selected noise signatures with the selected phases being used to set the phases of the signatures within the signal relative to the present states of their reference equipment item. However, according to another option, the controller can be further configured to: receive a sensed noise produced within the compartment by the noise-producing equipment items, determine one or more phases of the sensed noise, and adjust corresponding phases of the selected noise signatures within the transmitted noise cancellation signal such that they are out of phase with the determined phases. And according to yet another option, the controller can be further configured to: receive sensed noise produced within the compartment by the noise-producing equipment items and the noise cancellation signal, determine an overall noise level of the sensed noise; and adjust the phases of the selected noise signatures within the transmitted noise cancellation signal to reduce the overall noise level.
According to a third aspect there is provided a railway vehicle having a compartment affected by noise-producing equipment items and fitted with the system of the second aspect for reducing a noise level within the compartment.
Further aspects of the present disclosure provide: a computer program comprising code according to claim 12; and a computer readable medium storing that computer program.

Brief description of the drawings

Embodiments will now be described by way of example only, with reference to the Figures, in which:

Figure 1 shows schematically a train formed of plural vehicles providing respective passenger compartments;
Figure 2 shows schematically a noise cancellation controller of one of the vehicles of Figure 1;
Figure 3 shows schematically a sound database of the noise cancellation controller of Figure 2; and
Figure 4 shows a variant noise cancellation controller.

Detailed description

Figure 1 shows schematically a train formed of plural vehicles 1 providing respective passenger compartments. Each vehicle has equipment items, such as traction control systems 2, engines 3 etc., joined to the structure of the vehicle. In operation, these equipment items are sources of acoustic noise within the passenger compartments.
However, each vehicle 1 has a noise cancellation controller 4 (discussed in more detail below), which can conveniently be implemented as a part of the train's overall TCMS. In addition, each vehicle has one or more speakers 5 for projecting sound into the passenger compartment under the control of its noise cancellation controller. Optionally, each vehicle further has one or more microphones 6 for detecting sound within the compartment and providing the detected sound to the noise cancellation controller.
Each noise cancellation controller 4 also receives operational information (e.g. via the TCMS) about the current state of the train, such as the power notching level selected by the driver, the auxiliary equipment loading, the engine speed etc.
One of the noise cancellation controllers is shown schematically in Figure 2. It contains or is operatively connected to a sound database which relates operational states of the vehicle to respective noise signatures produced by the equipment items. For example, one noise source is the power converter of the traction control system. The power converter transforms AC power from the overhead line via a voltage transformer into DC power. The power converter normally operates, and thus produces noise, continuously. In contrast, the transformer only produces noise when power is supplied from the overhead line. Propulsion equipment is another noise source, but is more dependent on operational situations. For example, an inverter and a motor may generate acoustic noise during acceleration or deceleration, but not during coasting. If the train has an engine, this generates acoustic noise when it is being operated, but conversely these periods of operation generally coincide with interruption of power from the overhead line, and hence absence of noise from the transformer. The train's auxiliary power system (which runs internal equipment such as air conditioners, ventilators, and passenger information display and announcement systems) generally operates continuously, but its power consumption level may vary as necessary to maintain a stable passenger environment.
Consequently, different operational states of the vehicle correspond to different patterns of values of operational states of noise-producing equipment items and hence different combinations of noise signatures produced within each passenger compartment. Accordingly, the sound database of the noise cancellation controller provides a lookup table which stores suitable anti-noise signatures to cancel the noise produced by different equipment items depending on the values of operational states of those items. For example, as shown in Figure 3, Sound A is anti-noise for cancelling engine noise, and the database stores different Sound A signatures (A-1, A-2, A-3 etc.) depending on a value of the engine speed operational state. As a second example, Sound B is anti-noise for cancelling noise produced by propulsion equipment, and the database stores different Sound B signatures (B-1, B-2, B-3 etc.) depending on a value of the notch level operational state. As a third example, Sound C is anti-noise for cancelling noise from the auxiliary power system, and the database stores different Sound C signatures (C-1, C-2, C-3 etc.) depending on a value of the loading operational state of the auxiliary power system. Although not shown in Figure 3, the lookup table may also store for each signature a corresponding phase.
When the noise cancellation controller receives the present operational state of the vehicle (for example, electric drive mode or non-electric drive mode, speed of train, notch position, workload of auxiliary power system), it can thus select from the database suitable anti-noise signatures for the equipment items implicated in the operational state (e.g. one or none of type A, one or none of type B and one or none of type C), and combine the different sounds via a summing unit (SUM) and a sound creation unit to create a noise cancellation signal which is transmitted into the passenger compartment through the one or more speakers to reduce the noise level within the compartment. The relative phases of the combined signatures can be set according to their corresponding phases, and these can also be used to set the overall phase of the transmitted signal relative to states of one or more reference equipment items of the vehicle, i.e. so that the noise cancellation signal is out of phase with the noise in the compartment produced by the equipment items.
The anti-noise signatures are stored in the database before service operation of the vehicle. For example, some or all of the signatures can be configured from real monitored noise data, aggregated by driving the vehicle on a route. The signatures (and their phases if present) can be updated regularly (e.g. on a daily basis). However, another option is to create some or all of the signatures (and their phases if present) by simulation based on workload information of equipment items and knowledge of vibration transmission formulae for the vehicle.
Compared to known approaches for reducing noise level within passenger compartments, the above approach has an advantage that is it does not require complex sound analysis (i.e. transforms and filters) to create the noise cancellation signal, but rather can create the signal quickly and straightforwardly via the sound database. Having said that, the above approach can be combined with a sound analysis approach to improve the quality of the noise cancellation signal and providing a form of dynamic feedback.
A further advantage of the above approach is that non-equipment noise in the compartment, such as passenger noise or door operation noise, does not affect the creation of the cancellation signal.
In order to set the level of the noise cancellation signal, as shown in Figure 4, one or more microphones in the compartment may sense the overall noise level within the compartment. The sound creation unit can then use this sensed level as feedback to adjust the level of the signal to better reduce the overall noise level. Preferably the compartment has at least two such microphones, for example set in the ceiling at fore and aft positions in the compartment. Indeed, more preferably each speaker has an adjacent and corresponding microphone so that the level of the noise cancellation signal from each speaker can be adjusted independently based on feedback from its own microphone.
The noise sensed by the microphones can also be used to set the phases of the signatures within the noise cancellation signal. For example, phases of the noise produced by the noise-producing equipment items can be determined from the sensed noise so that the phases of the signatures can be set out of phase therewith. Alternatively, the relative phasing of the signatures within the noise cancellation signal can simply be adjusted until the overall noise level of the sensed within the compartment is reduced.
Conveniently, the TCMS can use the speakers 5 for purposes other than noise cancellation. For example, routine and emergency passenger announcements can be relayed over the speakers. Such announcements typically take priority over the noise cancellation signal, which may be suspended for the duration of an announcement. Noise cancellation may also be suspended when the doors of the train are open.

Claims

A method of reducing a noise level within a compartment of a railway vehicle (1) affected by noise-producing equipment items (2, 3), the method including:
providing a sound database which relates operational states of the vehicle to respective noise signatures produced by the equipment items;

determining the present operational state of the railway vehicle;

selecting one or more noise signatures from the database corresponding to the present operational state;

creating a noise cancellation signal from the selected noise signatures; and

transmitting the noise cancellation signal into the compartment by one or more speakers (5) distributed through the compartment to reduce the noise level within the compartment.
The method of claim 1, wherein:
the sound database stores, for each equipment item, plural noise signatures which are related by the database to values of a respective operational state of that equipment item;

each operational state of the vehicle is formed by a pattern of values of operational states of the equipment items; and

plural noise signatures are selected from the database, the selected noise signatures corresponding to the pattern of values of operational states of the equipment items which form the operational state of the vehicle.
The method of claim 1 or 2, further including:
sensing noise within the compartment;

determining an overall noise level of the sensed noise; and

adjusting the level of the transmitted noise cancellation signal to reduce the overall noise level.
The method of claim 3, wherein the noise is sensed by one or more microphones (6) distributed through the compartment.
The method of claim 4 as dependent on claim 2, wherein each microphone located adjacent a respective speaker, the level of the noise cancellation signal from each speaker being adjusted independently based on feedback from the adjacent microphone.
A system for reducing a noise level within a compartment of a railway vehicle (1) affected by noise-producing equipment items (2, 3), the system including:
a sound database which relates operational states of the vehicle to respective noise signatures produced by the equipment items;

a controller (4) which is configured to determine the present operational state of the railway vehicle, select one or more noise signatures from the database corresponding to the present operational state, and create a noise cancellation signal from the selected noise signatures for transmission into the compartment to reduce the noise level within the compartment; and

one or more speakers (5) for distribution through the compartment, the noise cancellation signal being transmitted into the compartment by the speakers.
The system of claim 6, wherein:
the sound database stores, for each equipment item, plural noise signatures which are related by the database to values of a respective operational state of that equipment item;

each operational state of the vehicle is formed by a pattern of values of operational states of the equipment items; and

plural noise signatures are selected from the database by the controller, the selected noise signatures corresponding to the pattern of values of operational states of the equipment items which form the operational state of the vehicle.
The system of claim 6 or 7, wherein the controller is further configured to:
receive a sensed noise within the compartment;

determine an overall noise level of the sensed noise; and

adjust the level of the transmitted noise cancellation signal to reduce the overall noise level.
The system of claim 8, further including one or more microphones (6) for distribution through the compartment to sense the overall noise level within the compartment.
The system of claim 9 as dependent on claim 8, wherein each microphone is for location adjacent a respective speaker, the level of the noise cancellation signal from each speaker being adjusted independently based on feedback from the adjacent microphone.
A railway vehicle (1) having a compartment affected by noise-producing equipment items (2, 3) and fitted with the system of any one of claims 6 to 10 for reducing a noise level within the compartment.
A computer program comprising code which, when the code is executed on a computer, causes the computer to perform a method of reducing a noise level within a compartment of a railway vehicle (1) affected by noise-producing equipment items (2, 3), the method including
providing a sound database which relates operational states of the vehicle to respective noise signatures produced by the equipment items;

determining the present operational state of the railway vehicle;

selecting one or more noise signatures from the database corresponding to the present operational state; and

creating a noise cancellation signal from the selected noise signatures for transmission into the compartment by one or more speakers (5) distributed through the compartment to reduce the noise level within the compartment.
A computer readable medium storing the computer program of claim 12.