Noise control method and noise control device

Abstract

This noise control device (1) comprises an engine (11) installed in a vehicle, and a controller (20) that detects the state of the engine (11). In accordance with the state of the engine (11), the controller (20) lowers performance for reducing noise caused by vibration inputted from a road surface.

Description

[Technical field]

[0001] The present invention relates to a noise control method and a noise control device. [Background technology]

[0002] Conventionally, there is known an invention for reducing noise (mainly road noise) inside a vehicle cabin (Patent Document 1). The invention described in Patent Document 1 stops the adaptive operation of a controller when it is determined that the change in the transfer function from the noise source to the evaluation point exceeds a predetermined state. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 5-158487 Summary of the Invention [Problem to be solved by the invention]

[0004] According to the invention described in Patent Document 1, noise inside the vehicle is reduced. However, if the engine is started in a state where the noise inside the vehicle is reduced, the engine noise is emphasized, which may cause discomfort to the passengers.

[0005] The present invention has been made in view of the above problems, and an object of the present invention is to provide a noise control method and a noise control device that make engine noise less noticeable to passengers. [Means for solving the problem]

[0006] A noise control method according to one aspect of the present invention reduces performance for reducing noise caused by vibrations input from a road surface depending on the state of the engine. Effect of the Invention

[0007] According to the present invention, the engine noise becomes less noticeable to the passengers. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 shows an example of the configuration of a noise control device 1 according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a flowchart illustrating an example of an operation of the noise control device 1. [Diagram 3] FIG. 3 is a graph showing the relationship between engine speed and noise level. [Figure 4] FIG. 4 is a flowchart illustrating an example of an operation of the noise control device 1. [Diagram 5] FIG. 5 is a diagram illustrating an example of the timing at which the road noise reduction performance is decreased. [Figure 6] FIG. 6 is a diagram illustrating an example of the timing at which the road noise reduction performance is decreased. [Figure 7] FIG. 7 is a graph showing the relationship between frequency and noise level. [Figure 8] FIG. 8 is a flowchart illustrating an example of an operation of the noise control device 1. [Figure 9] FIG. 9 is a flowchart illustrating an example of an operation of the noise control device 1. [Figure 10] FIG. 10 is a diagram for explaining an example of the timing at which sounds are output. [Figure 11] FIG. 11 is a flowchart illustrating an example of an operation of the noise control device 1. [Figure 12] FIG. 12 is a diagram illustrating another example of the operation of the noise control device 1. In FIG. [Figure 13] FIG. 13 is a diagram illustrating another example of the operation of the noise control device 1. In FIG. [Figure 14] FIG. 14 is a graph showing the relationship between frequency and noise level. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the description of the drawings, the same parts are given the same reference numerals and the description will be omitted.

[0010] An example of the configuration of a noise control device 1 will be described with reference to Fig. 1. The noise control device 1 is installed inside a vehicle. As shown in Fig. 1, the noise control device 1 includes a wheel speed sensor 10, an engine 11, an acceleration sensor 12, a microphone 13, a controller 20, and a speaker 30.

[0011] The wheel speed sensor 10 detects the rotational speed of each tire, and outputs a signal indicative of the detected rotational speed to the controller 20.

[0012] Generally, an engine mounted on a vehicle is used to drive tires. However, the engine 11 according to this embodiment will be described as being used only for generating electricity. That is, the engine 11 according to this embodiment is not connected to tires, but is connected to a generator (not shown). The engine 11 rotates the generator, which generates electricity. However, this is not limited to this. The engine 11 may be connected to tires as usual. The term "connected" here may mean "indirectly connected" or "directly connected". The engine 11 outputs a signal indicating its own state to the controller 20. The state of the engine 11 includes, for example, the number of revolutions of the engine 11, a state in which the engine 11 will start in the future, and a state in which the engine 11 will stop in the future. The signal output by the engine 11 to the controller 20 includes a signal indicating the number of revolutions of the engine 11, a signal indicating that the engine 11 will start in the future, and a signal indicating that the engine 11 will stop in the future.

[0013] A plurality of acceleration sensors 12 are installed. The installation location of the acceleration sensors 12 is not particularly limited, but may be, for example, on or near the tires, or on or near the engine 11. The acceleration sensors 12 detect vibrations input from the road surface when the vehicle is traveling. The acceleration sensors 12 output the detected vibration data to the controller 20. The acceleration sensors 12 installed on or near the engine 11 detect the acceleration (vibration) of the engine 11. The greater the output and rotation speed of the engine 11, the greater the vibration of the engine 11. The greater the vibration of the engine 11, the greater the noise of the engine 11. The acceleration sensor 12 outputs the detected acceleration of the engine 11 to the controller 20.

[0014] A plurality of microphones 13 are installed inside the vehicle. The locations where the microphones 13 are installed are not particularly limited, but may be, for example, the ceiling or seats (headrests) inside the vehicle. Sound input to the microphones 13 is converted into an electrical signal and output as sound data to the controller 20. The microphones 13 installed on the ceiling, seats, etc. inside the vehicle detect the noise of the engine 11.

[0015] The controller 20 is a general-purpose microcomputer equipped with a CPU, a memory, and an input / output unit. A computer program for functioning as the noise control device 1 is installed in the microcomputer. By executing the computer program, the microcomputer functions as a plurality of information processing circuits equipped in the noise control device 1. Note that, although an example of implementing the plurality of information processing circuits equipped in the noise control device 1 by software is shown here, it is of course possible to configure the information processing circuits by preparing dedicated hardware for executing each information process shown below. The plurality of information processing circuits may also be configured by individual hardware. The controller 20 includes an engine state detection unit 21, an environment detection unit 22, and a noise control unit 23 as examples of the plurality of information processing circuits.

[0016] The engine state detection unit 21 detects the state of the engine 11 by using data acquired from the wheel speed sensor 10, the engine 11, the acceleration sensor 12, and the microphone 13. An example of the state of the engine 11 has been described above. The engine state detection unit 21 outputs a signal corresponding to the state of the engine 11 to the noise control unit 23.

[0017] The environment detection unit 22 detects the vehicle environment using data acquired from the wheel speed sensor 10, the engine 11, the acceleration sensor 12, and the microphone 13. The "vehicle environment" in this embodiment will be described later. The environment detection unit 22 outputs a signal corresponding to the vehicle environment to the noise control unit 23.

[0018] The noise control unit 23 analyzes the vibration data acquired from the acceleration sensor 12 and the sound data acquired from the microphone 13. The noise control unit 23 generates a sound signal of an opposite phase to the analyzed vibration data and sound data. The noise control unit 23 outputs the generated sound signal from the speaker 30. As a result, the noise is canceled by the opposite phase wave, so that the noise is reduced. This type of noise control method is called "active noise control" and is a well-known technology. In the following, "active noise control" may be abbreviated to simply "ANC". The noise control unit 23 changes the performance of the ANC based on the signal acquired from the engine state detection unit 21 or the environment detection unit 22.

[0019] Next, an operation example of the noise control device 1 will be described with reference to FIG. 2. In step S101, the engine state detection unit 21 judges whether the state of the engine 11 has changed. When the engine state detection unit 21 judges that the state of the engine 11 has changed, it outputs a signal related to the judgment to the noise control unit 23 (YES in step S101). On the other hand, when the engine state detection unit 21 judges that the state of the engine 11 has not changed, it outputs a signal related to the judgment to the noise control unit 23 (NO in step S101). In step S103, the noise control unit 23 performs normal noise control. An example of "normal noise control" is the ANC itself. In step S105, the noise control unit 23 reduces the road noise reduction performance. "Road noise" is noise caused by vibration input from the road surface. Specifically, "road noise" is noise generated by friction and collision between the road surface and the tires when the vehicle is traveling. In this embodiment, the ANC reduces this "road noise".

[0020] The acceleration sensor 12 is mainly used to detect vibrations related to "road noise". "Reducing road noise reduction performance" means reducing the performance for reducing "road noise" (reducing the effect of ANC). As a specific example, it means suppressing the sound of the opposite phase output from the speaker 30. "Suppressing the sound of the opposite phase" means reducing the amplitude of the sound output from the speaker 30, or making the amplitude and frequency of the sound output from the speaker 30 different from the state in which the effect of ANC is maximized. By suppressing the sound output from the speaker 30 in this way, the effect of ANC is weakened and the noise inside the vehicle increases. As a result, the start-up sound (noise) of the engine 11 blends in with the noise inside the vehicle, making it difficult for the occupants to notice the noise of the engine 11. Another effect is that the occupants do not notice that the engine 11 has started. The engine 11 according to this embodiment is used only for power generation. Therefore, if the SOC (STATE OF CHARGE) of the battery is sufficient, whether the engine 11 is running or not has little impact on the occupants. Therefore, in order to provide a comfortable driving environment for the occupants, it is necessary to make it difficult for the occupants to notice the noise of the engine 11. This can be achieved according to the present embodiment.

[0021] An example of the "change in the state of the engine 11" in step S101 shown in FIG. 2 is the rotational speed of the engine 11. When the rotational speed of the engine 11 changes between 0 and a predetermined rotational speed, the noise control unit 23 reduces the load noise reduction performance. This will be described with reference to FIG. 3. The horizontal axis in FIG. 3 indicates the rotational speed of the engine 11, and the vertical axis indicates the in-vehicle noise level. The higher the in-vehicle noise level is on the upper side of the graph. "ANC OFF" means that ANC is not functioning. When ANC is not functioning, the in-vehicle noise is naturally large. "Maximum effect of ANC" means that the effect of ANC is maximally exerted. When the effect of ANC is maximally exerted, the in-vehicle noise is small. "Normal control" in step S103 may mean "maximum effect of ANC". As shown in FIG. 3, when the rotational speed of the engine 11 changes between 0 and a predetermined rotational speed, the noise control unit 23 reduces the load noise reduction performance according to the rotational speed. For example, at the moment when the engine 11 starts, the noise control unit 23 stops ANC. As the rotational speed of the engine 11 gradually increases, the noise control unit 23 reduces the reduction width. When the rotational speed of the engine 11 reaches the predetermined rotational speed A, the noise control unit 23 returns ANC to normal control. In other words, when the rotational speed of the engine 11 is less than the predetermined rotational speed A, the noise control unit 23 reduces the load noise reduction performance. Further, the noise control unit 23 may set B between 0 and A, and reduce the load noise reduction performance when the rotational speed of the engine 11 reaches the predetermined rotational speed B. Further, the noise control unit 23 may set C and D (C < D) between 0 and A, and reduce the load noise reduction performance when the rotational speed of the engine 11 is between the predetermined rotational speed C and the predetermined rotational speed D.

[0022] An example of the "change in state of the engine 11" in step S101 shown in FIG. 2 is not limited to the number of revolutions of the engine 11. The "change in state of the engine 11" in step S101 may indicate that the engine 11 changes to a state in which it will be started in the future. This point will be described with reference to FIGS. 4 and 5. In step S201 in FIG. 4, the engine state detection unit 21 judges whether the engine 11 is in a state in which it will be started in the future. For this judgment, a signal output from the engine 11 is used. When the engine state detection unit 21 acquires a signal indicating that the engine 11 will be started in the future from the engine 11, it judges that the engine 11 has changed to a state in which it will be started in the future (YES in step S201). Thereafter, the process proceeds to step S205. When NO in step S201, the process proceeds to step S203. The processes of steps S203 and S205 are the same as those of steps S103 and S105, and therefore the description will be omitted. The "future" referred to here is not particularly limited, but is, for example, 5 seconds later. Time T1 shown in FIG. 5 indicates the time when the engine state detection unit 21 acquires a signal from the engine 11 indicating that the engine will be started in the future. Time T2 indicates the time when the engine 11 is started. As shown at time T1, the noise control unit 23 reduces the road noise reduction performance before the engine 11 is started. As a result, as shown at time T2, the start-up sound of the engine 11 blends in with the noise inside the vehicle, so that the passengers are less likely to notice the noise of the engine 11. Note that in FIG. 5, the noise control unit 23 stops the ANC immediately after time T1, but this is not limited thereto. For example, as shown in FIG. 6, the noise control unit 23 may gradually reduce the road noise reduction performance from time T1 to time T2, and stop the ANC immediately before the engine 11 starts (time T2). This makes it possible to reduce the noise inside the vehicle between time T1 and time T2, as compared to FIG. 5. Note that an example of the timing when the system mounted on the vehicle starts the engine 11 is when the SOC of the battery becomes equal to or lower than a predetermined value.

[0023] The "change in state of the engine 11" in step S101 shown in FIG. 2 may include a change in data detected by the acceleration sensor 12 or the microphone 13. The acceleration sensor 12 detects the acceleration (vibration) of the engine 11. The microphone 13 detects the noise of the engine 11. The engine state detection unit 21 determines whether the data detected by the acceleration sensor 12 or the microphone 13 is greater than a predetermined value. If the data detected by the acceleration sensor 12 or the microphone 13 is greater than the predetermined value, the noise control unit 23 may reduce the road noise reduction performance. The data detected by the acceleration sensor 12 or the microphone 13 being greater than the predetermined value means that the engine 11 is running. Therefore, according to this method, the passengers are less likely to notice the noise of the engine 11. Note that, as shown in FIG. 7, if the noise level related to a specific frequency (the 1.5th order component of the engine 11) among the frequencies related to the acceleration or noise exceeds the noise level indicated by the reference symbol 40, the noise control unit 23 may reduce the road noise reduction performance.

[0024] Next, another operation example of the noise control device 1 will be described with reference to FIG. 8. However, the processes of steps S303 and S307 are the same as the process of step S103 shown in FIG. 2, and therefore the description will be omitted. Also, the process of step S309 is the same as the process of step S105 shown in FIG. 2, and therefore the description will be omitted. In step S301, if the engine 11 is running (YES in step S301), the process proceeds to step S305. On the other hand, if the engine 11 is not running (NO in step S301), the process proceeds to step S303. In step S305, the environment detection unit 22 detects the environment of the vehicle. If the environment of the vehicle is a predetermined environment (YES in step S305), the process proceeds to step S307. On the other hand, if the environment of the vehicle is not the predetermined environment (NO in step S305), the process proceeds to step S309. Here, an example of the "environment of the vehicle" will be described. An example of the "environment of the vehicle" is the speed of the vehicle. If the speed is greater than the predetermined speed, the process of step S305 becomes YES. A speed greater than a predetermined speed means that road noise is loud. In this case, even if ANC is used, the noise inside the vehicle is still loud. Therefore, the noise of the engine 11 blends in with the noise inside the vehicle, so there is no need to reduce the road noise reduction performance. Therefore, when the speed is greater than a predetermined speed, the noise control unit 23 does not reduce the performance for reducing noise. "Do not reduce the performance for reducing noise" means that normal ANC is performed. On the other hand, when the speed is equal to or lower than the predetermined speed (NO in step S305), the noise control unit 23 reduces the road noise reduction performance (step S309).

[0025] The "vehicle environment" may include data detected by the acceleration sensor 12 or the microphone 13 immediately before the engine 11 starts. If the data detected by the acceleration sensor 12 or the microphone 13 immediately before the engine 11 starts is greater than a predetermined value, the process of step S305 is YES. If the data detected by the acceleration sensor 12 or the microphone 13 immediately before the engine 11 starts is greater than a predetermined value, it means that the road noise is large. Therefore, since the noise of the engine 11 blends in with the noise inside the vehicle, there is no need to reduce the road noise reduction performance. Therefore, if the data detected by the acceleration sensor 12 or the microphone 13 immediately before the engine 11 starts is greater than a predetermined value, the noise control unit 23 does not reduce the performance for reducing noise. On the other hand, if the data detected by the acceleration sensor 12 or the microphone 13 immediately before the engine 11 starts is equal to or less than the predetermined value (NO in step S305), the noise control unit 23 reduces the road noise reduction performance (step S309).

[0026] Next, with reference to FIG. 9, another operation example of the noise control device 1 will be described. However, since the processing of steps S401 to S405 is the same as the processing of steps S101 to S105 shown in FIG. 2, the description will be omitted. In step S407, the noise control unit 23 outputs a sound from the speaker 30. The road noise reduction performance is reduced by the processing of step S405. However, for example, when the road noise itself is small, even if the road noise reduction performance is reduced, the effect is limited (the road noise does not become so large). In this case, the start-up sound of the engine 11 is less likely to be blended into the noise inside the vehicle. That is, the passengers are more likely to notice the noise of the engine 11. Therefore, in order to drown out the start-up sound of the engine 11, the noise control unit 23 outputs a sound from the speaker 30 in step S407. This makes it possible to drown out the start-up sound of the engine 11. As for what kind of sound to output, for example, the noise control unit 23 may output a sound louder than the road noise from the speaker 30. By analyzing the vibration acquired by the acceleration sensor 12, the amplitude and frequency of the road noise are known. The noise control unit 23 uses a sound having a larger amplitude than the amplitude of the road noise, so that a sound louder than the road noise can be output from the speaker 30. The process of step S407 may be expressed as outputting a sound louder than the road noise from the speaker 30. An example of the timing of outputting the sound will be described with reference to FIG. 10. Time T1 in FIG. 10 indicates the timing when the degradation of the road noise reduction performance starts. Time T2 indicates the timing when the ANC is stopped. As shown in FIG. 10, the noise control unit 23 gradually decreases the road noise reduction performance, and then stops the road noise reduction performance and simultaneously outputs the sound from the speaker 30. Reference numeral 50 indicates that the noise level inside the vehicle has increased due to the output of the sound. By outputting the sound in this way and increasing the noise level inside the vehicle, it is possible to drown out the startup sound of the engine 11.

[0027] The "change in state of the engine 11" in step S101 shown in FIG. 2 may include an abnormality of the engine 11. In this embodiment, "abnormal" means that the engine 11 is not normal. "Abnormal" is a concept that includes not only a failure that prevents a part from performing its original function, but also a malfunction that does not result in a failure and a sign of a failure. The process when an abnormality of the engine 11 is detected will be described with reference to FIG. 11. When an abnormality of the engine 11 is detected, a command to stop the ANC is output (YES in step S501). In step S505, the noise control unit 23 outputs sound from the speaker 30. The sound output method is the same as in FIG. 9. This makes it possible to inform the occupant that an abnormality has occurred in the engine 11. In step S507, the noise control unit 23 stops the ANC. The process in FIG. 11 is not limited to an abnormality of the engine 11. Many devices are mounted on the vehicle in addition to the engine 11. Specifically, the devices include the above-mentioned generator, motor, inverter, battery, ANC system, etc. When an abnormality of these devices or the functions of the devices is detected, the same process as when an abnormality of the engine 11 is detected is also performed. Such processing is based on a fail-safe viewpoint. Note that in step S507, the noise control unit 23 may notify an occupant (a user in the vehicle) of an ANC stop guidance instead of stopping the ANC. The stop guidance may be displayed on a display (for example, a display of a navigation device) or may be output as a sound from the speaker 30. The occupant who receives the stop guidance can stop the ANC by pressing a virtual switch displayed on the display or a physical switch installed in the vehicle.

[0028] (Action and effect) As described above, the noise control device 1 according to this embodiment provides the following advantageous effects.

[0029] The noise control device 1 includes an engine 11 mounted on a vehicle and a controller 20 that detects the state of the engine 11. The controller 20 reduces the performance for reducing noise caused by vibrations input from the road surface according to the state of the engine 11. An example of "noise caused by vibrations input from the road surface" is the above-mentioned "road noise." According to the noise control device 1, the noise of the engine 11 blends in with the noise inside the vehicle, making it difficult for passengers to notice the noise of the engine 11. The "noise of the engine 11" includes the "start-up sound of the engine 11" and the "driving sound of the engine 11." Another effect is that the passengers will not notice that the engine 11 has started.

[0030] The state of the engine 11 includes the rotation speed of the engine 11. When the rotation speed of the engine 11 reaches a predetermined rotation speed, the controller 20 reduces the performance for reducing noise. An example of the "predetermined rotation speed" is the above-mentioned "predetermined rotation speed B." According to the noise control device 1, the noise of the engine 11 blends in with the noise inside the vehicle, making it difficult for passengers to notice the noise of the engine 11.

[0031] The state of the engine 11 includes a state in which the engine 11 will start in the future. When the controller 20 receives a signal indicating that the engine 11 will start in the future, the controller 20 reduces the performance for reducing noise. As a result, the start-up sound of the engine 11 blends in with the noise inside the vehicle, making it difficult for passengers to notice the noise of the engine 11.

[0032] When the controller 20 receives a signal indicating that the engine 11 will be started in the future, the controller 20 gradually reduces the performance for reducing noise before the engine 11 starts, and stops the performance for reducing noise immediately before the engine 11 starts. This makes it possible to reduce road noise until immediately before the engine 11 starts. Furthermore, since the start-up sound of the engine 11 blends in with the noise inside the vehicle, it becomes difficult for passengers to notice the noise of the engine 11.

[0033] The state of the engine 11 includes vibration data detected by the acceleration sensor 12 or noise data detected by the microphone 13. When the noise level indicated by the vibration data related to the engine 11 or the noise level indicated by the noise data related to the engine 11 is greater than a predetermined value, the controller 20 reduces the performance for reducing noise. As a result, the noise of the engine 11 blends in with the noise inside the vehicle, making it difficult for passengers to notice the noise of the engine 11.

[0034] The controller 20 reduces the performance for reducing noise when the noise level of a predetermined frequency among the frequencies indicated by the vibration data related to the engine 11 or the noise data related to the engine 11 is greater than a predetermined value. This causes the noise of the engine 11 to blend in with the noise inside the vehicle, making it difficult for passengers to notice the noise of the engine 11.

[0035] The controller 20 detects the environment of the vehicle. After the engine 11 starts, the controller 20 does not reduce the performance for reducing noise according to the detected environment of the vehicle. This is because, when the noise inside the vehicle is large, the noise of the engine 11 is mixed with the noise inside the vehicle.

[0036] The vehicle environment includes the speed of the vehicle. After the engine 11 starts, the controller 20 does not reduce the performance for reducing noise if the speed is greater than a predetermined speed. A speed greater than the predetermined speed means that road noise is large. Since the noise of the engine 11 is blended into the noise inside the vehicle, there is no need to reduce the road noise reduction performance.

[0037] The vehicle environment includes vibration data detected by the acceleration sensor 12 or noise data detected by the microphone 13. When the noise level indicated by the vibration data detected immediately before the engine 11 starts or the noise level indicated by the noise data is greater than a predetermined value, the controller 20 does not reduce the performance for reducing noise. The fact that these noise levels are greater than the predetermined value means that the road noise is loud. Since the noise of the engine 11 blends in with the noise inside the vehicle, there is no need to reduce the road noise reduction performance. The "vibration data" here means "vibration data excluding the engine 11". Similarly, the "noise data" here means "noise data excluding the engine 11".

[0038] The controller 20 reduces the performance for reducing noise according to the state of the engine 11, and then stops the performance for reducing noise and simultaneously outputs sound from the speaker 30. This makes it possible to drown out the noise of the engine 11.

[0039] When an abnormality is detected in a device or function of the device mounted on the vehicle, a command to stop the performance for reducing noise is output to the controller 20. When the controller 20 receives the command, it stops the performance for reducing noise after outputting sound from the speaker 30, or notifies the occupant of a guide to stop the performance for reducing noise after outputting sound from the speaker 30. This makes it possible to inform the occupant that an abnormality has occurred in the device or function of the device.

[0040] Each of the functions described in the above embodiments may be implemented by one or more processing circuits. A processing circuit includes a programmed processing device, such as a processor including electrical circuitry. A processing circuit also includes devices such as application specific integrated circuits (ASICs) or circuit components arranged to perform the described functions.

[0041] As described above, the embodiment of the present invention has been described, but the description and drawings forming a part of this disclosure should not be understood as limiting this invention. From this disclosure, various alternative embodiments, examples and operating techniques will become apparent to those skilled in the art.

[0042] (Other embodiments) Another operation example of the noise control device 1 will be described with reference to FIG. 12. Time T1 in FIG. 12 indicates the timing when the engine 11 is started. Time T2 indicates the timing when the engine 11 transitions to a steady state. The period between time T1 and time T2 indicates the period from when the engine 11 is started to when it transitions to the steady state. The "steady state" refers to a state in which the engine 11 maintains a constant rotation speed. The "steady state" may also be expressed as a state in which the time change in the engine 11 rotation speed is smaller than a predetermined value. The controller 20 reduces noise related to the engine 11 when the engine 11 is started, and reduces noise caused by vibration input from the road surface when the engine 11 is stopped. That is, the controller 20 reduces noise caused by vibration input from the road surface until time T1. The controller 20 reduces noise related to the engine 11 after time T2. As a result, road noise is reduced until the engine 11 is started, and noise related to the engine 11 is reduced after the engine 11 is started.

[0043] There are cases where the engine 11 transitions to a steady state and then continues to operate. Time T1 in FIG. 13 indicates the timing when the engine 11 is started. Time T2 is an arbitrary point indicating that the engine 11 continues to operate after transitioning to the steady state. The controller 20 detects the time change in the number of revolutions of the engine 11. When the time change in the number of revolutions of the engine 11 is smaller than a predetermined value and the engine 11 is operating, the controller 20 does not reduce noise caused by vibration input from the road surface, but reduces only the noise related to the engine 11. This makes it difficult for passengers to notice the noise of the engine 11. Note that "when the time change in the number of revolutions of the engine 11 is smaller than a predetermined value and the engine 11 is operating" indicates that the engine 11 continues to operate after transitioning to the steady state as at time T2. Reference numeral 60 in FIG. 14 indicates that the engine 11 is started and the ANC is stopped. Reference numeral 61 indicates that the engine 11 is stopped and the ANC is stopped. Reference numeral 62 indicates that ANC is operating using all sensors. Reference numeral 63 indicates that only data detected by the acceleration sensor 12 and the microphone 13 installed on the engine 11 is used. By reducing only the noise related to the engine 11 as shown by reference numeral 63, the noise level inside the vehicle becomes smaller, and the passengers become less likely to notice the noise of the engine 11.

[0044] "Engine 11 is stopped" may be defined as the number of revolutions of engine 11 being zero. "Noise related to engine 11" may be defined as noise indicated by data detected by acceleration sensor 12 or microphone 13 installed on engine 11. "Noise caused by vibrations input from the road surface" may be defined as noise indicated by data detected by acceleration sensor 12 or microphone 13 installed in a location other than engine 11. When the number of revolutions of engine 11 is zero, controller 20 may not reduce the noise related to engine 11, but may reduce the noise caused by vibrations input from the road surface. This efficiently reduces road noise.

[0045] When the time change in the rotation speed of the engine 11 is smaller than a predetermined value and the engine 11 is operating, the controller 20 may reduce the noise related to the engine 11 by using only the data detected by the acceleration sensor 12 installed on the engine 11 among the data detected by the multiple acceleration sensors 12. This makes it difficult for passengers to notice the noise of the engine 11.

[0046] In the ANC, only the data from the acceleration sensor 12 may be used, only the data from the microphone 13 may be used, or both the data from the acceleration sensor 12 and the microphone 13 may be used. [Explanation of symbols]

[0047] 1 Noise control device, 10 Wheel speed sensor, 11 Engine, 12 Acceleration sensor, 13 Microphone, 20 Controller, 21 Engine state detection unit, 22 Environment detection unit, 23 Noise control unit, 30 Speaker

Claims

1. A noise control method for a noise control device including an engine mounted on a vehicle and selectively operated and stopped while the vehicle is traveling, and a controller for detecting a state of the engine, comprising: The controller reduces a performance for reducing noise caused by vibration input from a road surface depending on whether the engine is operating or stopped. A noise control method comprising:

2. A noise control method for a noise control device including an engine mounted on a vehicle and a controller for detecting a state of the engine, comprising: the engine state includes a future start state of the engine; The controller: Decreasing a performance for reducing noise caused by vibration input from a road surface according to a state of the engine; When a signal is received indicating that the engine will be started in the future, the noise reduction performance is reduced. A noise control method comprising:

3. The engine status includes the engine speed; The controller reduces the performance for reducing the noise when the engine speed reaches a predetermined speed.

3. The noise control method according to claim 1 or 2.

4. The controller, upon receiving a signal indicating that the engine will be started in the future, gradually reduces the performance for reducing the noise before the engine starts and stops the performance for reducing the noise immediately before the engine starts.

3. The noise control method according to claim 2.

5. The engine state includes vibration data detected by an acceleration sensor or noise data detected by a microphone; The controller reduces a performance for reducing the noise when a noise level indicated by the vibration data related to the engine or a noise level indicated by the noise data related to the engine is greater than a predetermined value.

5. The noise control method according to claim 1, wherein the noise control method is a noise control method for controlling a noise generated by a noise source.

6. The controller reduces a performance for reducing the noise when a noise level at a predetermined frequency among frequencies indicated by the vibration data related to the engine or the noise data related to the engine is greater than a predetermined value.

6. The noise control method according to claim 5.

7. The controller: Detecting an environment of the vehicle; After the engine is started, the performance for reducing the noise is not reduced according to the detected environment of the vehicle.

7. The noise control method according to claim 1, wherein the noise control method is a noise control method for controlling a noise generated by a noise source.

8. The environment of the vehicle includes the speed of the vehicle; The controller does not reduce the performance for reducing the noise when the speed is greater than a predetermined speed after the engine starts.

8. The noise control method according to claim 7.

9. The environment of the vehicle includes vibration data detected by an acceleration sensor or noise data detected by a microphone; The controller does not reduce the performance for reducing the noise when a noise level indicated by the vibration data detected immediately before the engine is started or a noise level indicated by the noise data is greater than a predetermined value.

9. The noise control method according to claim 7 or 8.

10. The controller reduces the performance for reducing the noise according to the state of the engine, and then stops the performance for reducing the noise and simultaneously outputs a sound from a speaker. The noise control method according to any one of claims 1 to 9.

11. When an abnormality is detected in a device mounted on the vehicle or in a function of the device, a command to stop the performance for reducing the noise is output to the controller, When the controller receives the command, the controller stops the performance for reducing the noise after outputting the sound from the speaker, or notifies a user riding in the vehicle of a guide to stop the performance for reducing the noise after outputting the sound from the speaker. The noise control method according to any one of claims 1 to 10.

12. The controller reduces noise associated with the engine when the engine is running, and reduces noise caused by vibrations input from the road surface when the engine is stopped. The noise control method according to any one of claims 1 to 11.

13. The controller: Detecting a change in the engine speed over time; When the detected time change is smaller than a predetermined value and the engine is operating, the noise caused by the vibration input from the road surface is not reduced, and only the noise related to the engine is reduced. A noise control method according to any one of claims 1 to 12.

14. The engine being stopped is defined as the engine speed being zero; The engine noise is defined as noise indicated by data detected by an acceleration sensor or a microphone installed in the engine, The noise caused by vibration input from the road surface is defined as noise indicated by data detected by an acceleration sensor or a microphone installed in a location other than the engine, The controller does not reduce noise related to the engine when the engine speed is zero, and reduces noise caused by vibration input from the road surface.

13. The method of claim 12.

15. Multiple acceleration sensors are installed. When the time change is smaller than a predetermined value and the engine is operating, the controller reduces noise related to the engine by using only data detected by an acceleration sensor installed on the engine among data detected by a plurality of acceleration sensors.

14. The method of claim 13.

16. an engine mounted on a vehicle and selectively operated and stopped while the vehicle is traveling; A controller for detecting a state of the engine, The controller reduces a performance for reducing noise caused by vibration input from a road surface depending on whether the engine is operating or stopped. A noise control device comprising:

17. An engine mounted in a vehicle; A controller for detecting a state of the engine, the engine state includes a future start state of the engine; The controller: Decreasing a performance for reducing noise caused by vibration input from a road surface according to a state of the engine; When a signal is received indicating that the engine will be started in the future, the noise reduction performance is reduced. A noise control device comprising:

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