Noise control method and noise controller

Abstract

To provide a noise control method and a noise controller, which can suppress a change of a noise level in a cabin.SOLUTION: When it is determined that a noise level is less than a predetermined value if the noise level in a cabin is controlled by output sound output from a speaker 14, output sound is controlled so that the noise level is reduced compared to a case when the noise level is equal to or higher than the predetermined value or output sound for amplifying the noise level is output from the speaker 14.SELECTED DRAWING: Figure 5

Description

[Technical field]

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

[0002] A noise control device is known that acquires road surface information from road information for a road corresponding to the vehicle's position, and generates a reference signal for a control sound that cancels out road noise based on the acquired road surface information (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2008-62804 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the above conventional technology, a reference signal is generated according to the road surface conditions, so when the road surface conditions change, the noise level inside the vehicle cabin also changes along with the change in the road surface conditions. Therefore, when the vehicle moves from a road with low road noise to a road with high road noise, the noise level inside the vehicle cabin changes significantly, causing discomfort to the vehicle occupants.

[0005] An object of the present invention is to provide a noise control method and a noise control device capable of suppressing a change in the noise level inside a vehicle cabin. [Means for solving the problem]

[0006] The present invention solves the above problem by controlling the noise level inside the vehicle cabin by output sound output from a speaker, and when it is determined that the noise level is below a predetermined value, controlling the output sound so that the noise level is lower than when the noise level is above the predetermined value, or by outputting an output sound from the speaker that amplifies the noise level. Effect of the Invention

[0007] According to the present invention, it is possible to suppress a change in the noise level inside the vehicle cabin. [Brief description of the drawings]

[0008] [Figure 1] 1 is a block diagram showing an example of an embodiment of a noise control system including a noise control device according to the present invention. [Diagram 2] 2 is a plan view showing an example of the arrangement of a camera, a microphone, an acceleration sensor, and a speaker in FIG. 1. [Diagram 3] FIG. 1 is a diagram showing an example of noise detected in a certain driving scene. [Figure 4] FIG. 2 is a diagram showing an example of noise level control by the noise control system of FIG. [Diagram 5] 1. FIG. 4 is a diagram showing another example of noise level control by the noise control system of FIG. [Figure 6] 2 is a diagram showing an example of the relationship between a noise level and a silencing ratio for reducing the noise level in the noise control system of FIG. 1. [Figure 7] 1. FIG. 4 is a diagram showing another example of the relationship between the noise level and the silencing ratio for reducing the noise level in the noise control system of FIG. [Figure 8] 1. FIG. 4 is a diagram showing still another example of noise level control by the noise control system of FIG. [Figure 9] 1. FIG. 4 is a diagram showing still another example of noise level control by the noise control system of FIG. [Figure 10] 2 is a flowchart showing an example of a processing procedure in the noise control system of FIG. [Figure 11] 10 is a flowchart showing another example of the processing procedure in the noise control system of FIG. [Figure 12] 10 is a flowchart showing still another example of the processing procedure in the noise control system of FIG. [Figure 13] FIG. 11 is a diagram showing an example of noise level control according to a comparative example of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0010] [Configuration of noise control system] FIG. 1 is a block diagram showing an example of an embodiment of a noise control system according to the present invention. The noise control system 1 is a group of in-vehicle devices that control noise in a vehicle cabin (hereinafter also referred to as in-vehicle noise) by sound output from a speaker (hereinafter also referred to as output sound). The output sound is a sound wave emitted from the speaker into the vehicle cabin, and the waveform of the sound wave is not particularly limited. The vehicle cabin is a living space for occupants in a vehicle, and the shape and size of the living space are not particularly limited. The in-vehicle noise is a sound that may cause discomfort to the occupants of the vehicle. Examples of in-vehicle noise include, but are not limited to, sounds caused by engine vibrations (engine noise), sounds caused by unevenness in the road surface (road noise), and sounds caused by turbulence in the air flow around the vehicle (wind noise).

[0011] Controlling the noise inside the vehicle means, for example, controlling the waveform (frequency and amplitude) of the noise. Examples of controlling the noise inside the vehicle include, but are not limited to, canceling the noise with an output sound having a waveform in the opposite phase to the noise, amplifying the noise with an output sound having the same waveform as the noise, increasing or decreasing the amplitude of the output sound that cancels or amplifies the noise, and raising or lowering the frequency of the output sound that cancels or amplifies the noise.

[0012] 1, the noise control system 1 includes a microphone 11, an acceleration sensor 12, a camera 13, a speaker 14, and a noise control device 2. These devices are mounted on a vehicle and can exchange information with each other.

[0013] The microphone 11 is a device that acquires sounds within the vehicle cabin (hereinafter also referred to as interior sounds) as audio data. Examples of the microphone 11 include, but are not limited to, a small stand microphone, a directional close-talking microphone, a lavalier microphone that can be mounted on the roof or seat of the vehicle. Interior sounds include, but are not limited to, the voices of the passengers, noises such as road noise, and the output sound of the speaker 14. The microphones 11 can be installed at appropriate positions within a range where the interior sounds can be appropriately detected, and the number of microphones 11 is determined appropriately according to the detection range of the microphones 11 and the size of the vehicle cabin.

[0014] The acceleration sensor 12 is a device that detects the acceleration of the vehicle. Examples of the acceleration sensor 12 include, but are not limited to, known sensors such as frequency change type, piezoelectric type, and capacitance type. The acceleration sensor 12 detects, for example, the magnitude and direction of the acceleration of the vehicle, as well as the amount, speed, and direction of movement of the vehicle. The acceleration sensor 12 can be installed at an appropriate position within a range in which the acceleration of the vehicle can be appropriately detected, for example, in the vicinity of each suspension.

[0015] The camera 13 is a device that captures an image of an object. Examples of the camera 13 include, but are not limited to, a camera equipped with an imaging element such as a CCD, an ultrasonic camera, and an infrared camera. The camera 13 is mounted on the front grill of the vehicle, under the left and right door mirrors, near the rear bumper, etc. The object is, for example, an object outside the vehicle, and includes the road surface, lane boundary lines, center lines, road markings, median strips, guardrails, curbs, road signs, traffic lights, crosswalks, etc.

[0016] The speaker 14 is a device that converts electrical signal energy into acoustic energy and emits it into space. The speaker 14 may be, but is not limited to, an integrated or separate vehicle speaker. The speaker 14 may be installed at an appropriate position within a range in which the noise inside the vehicle can be appropriately controlled by the output sound, and the number of speakers 14 is determined appropriately according to the settable range of the output volume of the speaker 14 and the size of the vehicle compartment.

[0017] Fig. 2 is a plan view showing an example of the arrangement of the microphone 11, the acceleration sensor 12, the camera 13, and the speaker 14 in Fig. 1. The vehicle 3 shown in Fig. 2 has a driver's seat 31 on the right front side, a passenger seat 32 on the left front side, and rear seats 33, 34 on the rear side. For the sake of explanation, the windshield, roof, rear window, and part of the side windows of the vehicle 3 shown in Fig. 2 are not shown.

[0018] 2 includes a microphone 11a that acquires indoor sounds around the driver's seat 31 and passenger seat 32, and a microphone 11b that acquires indoor sounds around the rear seats 33 and 34. The microphone 11a is attached between the driver's seat 31 and the passenger seat 32 on the front side of the roof of the vehicle 3, and the microphone 11b is attached between the rear seat 33 and the rear seat 34 on the rear side of the roof.

[0019] Acceleration sensors 12a-12d are attached to the suspensions of the right front wheel, left front wheel, right rear wheel, and left rear wheel to detect vibrations transmitted from the road surface to the vehicle body via the tires. A camera 13 is installed on the upper part of the windshield to capture an image of an object in front of the vehicle 3. A speaker 14a that controls noise around the driver's seat 31 is built in the right front door of the vehicle 3 (not shown). Similarly, speakers 14b-14d are built in the left front door, right rear door, and left rear door, respectively.

[0020] Returning to Fig. 1, the noise control device 2 is a device that controls the devices constituting the noise control system 1 to cooperate with each other and output an output sound that controls in-vehicle noise. The noise control device 2 is, for example, a computer, and includes a DSP (Digital Signal Processor) that is a processor, a ROM (Read Only Memory) that stores programs, and a RAM (Random Access Memory) that functions as an accessible storage device. The DSP is an operating circuit that executes the programs stored in the ROM and realizes the functions of the noise control device 2.

[0021] The noise control device 2 has a noise control function for controlling noise inside the vehicle. A program for realizing the noise control function is stored in the ROM of the noise control device 2, and the noise control function is realized by the DSP executing the program stored in the ROM. Fig. 1 shows a determination unit 21, a setting unit 22, and an output unit 23 as functional blocks for realizing the noise control function for convenience. The noise control function of the noise control device 2 will be described below using the example shown in Fig. 3.

[0022] [Noise control device functions] FIG. 3 is a diagram showing an example of the noise inside the vehicle detected by the noise control device 2. In the example shown in FIG. 3, it is assumed that the vehicle 3 shown in FIG. 2 travels on a first road and a second road, which has a larger unevenness of the road surface than the first road and has a larger road noise than the first road. Specifically, it is assumed that the vehicle travels on the first road from time T0 to time T1, enters the second road from the first road at time T1, travels on the second road from time T1 to time T2, enters the first road from the second road at time T2, and travels on the first road from time T2 to time T3. It is also assumed that the noise level inside the vehicle cabin when the vehicle 3 travels on the first road is A1, and the noise level inside the vehicle cabin when the vehicle travels on the second road is B1. In the following, the noise level inside the vehicle cabin is also simply referred to as the noise level.

[0023] Fig. 13 shows an example in which the process of canceling noise by output sound is uniformly performed for the noise shown in Fig. 3. Fig. 13 is a diagram showing an example of noise level control according to a comparative example of the present invention, in which the noise level is reduced from A1 to A2 when the vehicle 3 travels on the first road by the noise canceling process, and the noise level is reduced from B1 to B2 when the vehicle travels on the second road by the noise canceling process. In this case, the noise level is reduced by the noise canceling process, but the difference Dx in the noise levels between the first road and the second road is relatively large. In particular, the noise level suddenly increases when entering the second road from the first road at time T1, and this large change in noise level causes discomfort to the occupants.

[0024] Therefore, the noise control device 2 of this embodiment controls the interior noise with the output sound so as to suppress the increase in the change in the noise level when the noise level changes due to the change in the driving state and driving environment of the vehicle 3. The driving state includes, but is not limited to, the driving speed, acceleration, yaw rate, steering angle, etc. Also, the driving environment includes, but is not limited to, the surrounding weather and outside air temperature, the condition of the road surface, the condition of surrounding objects, etc.

[0025] As one example, when the vehicle 3 enters the second road from the first road and the road surface changes from a state in which the road surface is less uneven (smooth pavement and less road noise) to a state in which the road surface is more uneven (rough pavement and more road noise), the noise control device 2 controls the noise inside the vehicle to suppress an increase in the difference in noise level before and after the change in road surface condition. As another example, when the engine speed changes in response to the driver's operation, the noise control device 2 controls the noise inside the vehicle to suppress an increase in the change in noise level caused by a change in engine vibration. As yet another example, when the vehicle accelerates, the noise control device 2 controls the noise inside the vehicle to suppress an increase in the change in noise level caused by a change in airflow around the vehicle.

[0026] The noise control device 2 controls the vehicle interior noise by the functions of the determination unit 21, the setting unit 22, and the output unit 23 shown in FIG. 1. First, the noise control device 2 acquires the interior sound from the microphone 11 by the function of the determination unit 21, and detects the vehicle interior noise from the interior sound by frequency analysis based on Fourier transform or the like. The noise control device 2 removes (filters) sounds other than noise, such as the voices of passengers, radio sounds, and music being played, from the interior sound, and detects the vehicle interior noise from the interior sound. The noise control device 2 also calculates the noise level in the vehicle interior from the interior sound acquired from the microphone 11. The noise level is measured in dB units using a known sound level meter, for example, according to JIS C 1509. In this embodiment, the microphone 11 and the noise control device 2 constitute the sound level meter.

[0027] Alternatively or in addition, the noise control device 2 may calculate the noise level from the detection result of the acceleration sensor 12. For example, the noise control device 2 calculates the period and magnitude of the vibration input to the vehicle body from the direction and magnitude of the acceleration detected by the acceleration sensor 12, and estimates the waveform and noise level of the in-vehicle noise from the period and magnitude of the vibration.

[0028] As an example, the noise control device 2 acquires indoor sounds from the microphones 11a and 11b and calculates a noise level from the indoor sounds. The noise control device 2 also calculates the period and magnitude of vibration input to the vehicle body from the detection results of the acceleration sensors 12a, 12b, 12c, and 12d attached to the suspension of the vehicle 3, and estimates the noise level from the period and magnitude of the vibration. The noise level calculated from the detection results of the microphones 11a and 11b and the noise level estimated from the detection results of the acceleration sensors 12a, 12b, 12c, and 12d are then averaged to obtain a final noise level.

[0029] Next, the noise control device 2 determines whether or not the noise level of the in-vehicle noise is below a predetermined value through the function of the determination unit 21. If it is determined that the noise level is below the predetermined value, the noise control device 2 controls the output sound so that the noise level is reduced more than when the noise level is equal to or greater than the predetermined value through the function of the setting unit 22. Specifically, the noise control device 2 sets the rate at which the output sound reduces the noise level of the in-vehicle noise (hereinafter also referred to as the silencing rate) to be smaller than when the noise level is equal to or greater than the predetermined value.

[0030] On the other hand, when it is determined that the noise level is equal to or higher than the predetermined value, the noise control device 2 does not control the output sound to reduce the noise level, but sets the silencing ratio to a higher value than when the noise level is below the predetermined value. Alternatively, when it is determined that the noise level is equal to or higher than the predetermined value, the noise control device 2 may set the silencing ratio to a predetermined ratio.

[0031] The predetermined value can be set to an appropriate value within a range in which the change in noise level caused by the change in the running state and running environment of the vehicle 3 can be suppressed, for example, the noise level is measured on a plurality of road surfaces with different conditions, and the value at which the change in the noise level can be suppressed most is set as the predetermined value based on the measurement results. The road surface condition refers to the properties of the road surface that affect the vibration of the tires and suspension of the vehicle 3, for example, the magnitude of unevenness of the road surface. Examples of the road surface condition include, but are not limited to, a paved condition, an unpaved condition, a packed snow condition, a muddy condition, and a frozen condition.

[0032] The predetermined value may be set by measuring the noise level at a plurality of engine revolution speeds and setting the predetermined value at which the change in the noise level can be most suppressed based on the measurement results, or by measuring the noise level at a plurality of driving speeds and setting the predetermined value at which the change in the noise level can be most suppressed based on the measurement results. Furthermore, the noise control device 2 may set the predetermined value so that the silencing ratio can be set according to the condition of the road surface. For example, the predetermined value is set to a value between the noise level for a smooth pavement condition and the noise level for a rough pavement condition so that the silencing ratio can be switched from a low value to a high value when entering the second road from the first road.

[0033] Canceling the interior noise with the output sound means that an output sound having a waveform in the opposite phase to the interior noise is output from the speaker 14, and the interior noise and the output sound are superimposed to reduce the interior noise. The silencing ratio is an index indicating the degree to which the noise level is reduced by the output sound, and is, for example, the ratio of the noise level reduced by the output sound to the noise level before the output sound is superimposed. In other words, if the noise level becomes 0 (dB) due to the output sound, the silencing ratio is 100%, and if the noise level does not change due to the output sound, the silencing ratio is 0%. The predetermined ratio can be set to an appropriate value within a range in which the discomfort of the occupants due to the interior noise can be suppressed, and is, for example, 10 to 70%.

[0034] The noise control device 2 controls the silencing ratio by increasing or decreasing the amplitude of the output sound. Alternatively or in addition to this, the noise control device 2 may control the silencing ratio by moving the waveform of the output sound in the positive or negative direction along the time axis (horizontal axis). For example, the noise control device 2 generates a waveform in opposite phase to the waveform of the detected interior noise, and multiplies the amplitude of the opposite phase waveform by a positive number greater than 0 and less than 1 so as to obtain a desired silencing ratio. Furthermore, the noise control device 2 may generate a waveform in opposite phase to the waveform of the detected interior noise, and move the period of the opposite phase waveform by 0.05 to 0.25 periods in the positive direction along the time axis so as to obtain a desired silencing ratio.

[0035] The control of the noise level by the noise control device 2 will be described with reference to Fig. 4. Fig. 4 is a diagram showing the silencing effect when the noise level control by the noise control device 2 is executed for the noise shown in Fig. 3. In the example shown in Fig. 4, it is assumed that the noise level A1 is less than a predetermined value, and the noise level B1 is equal to or greater than the predetermined value. In addition, in the example shown in Fig. 4, when the noise level is less than the predetermined value, the silencing ratio is set to 0%, and when the noise level is equal to or greater than the predetermined value, the silencing ratio is set to a predetermined ratio. That is, in the example shown in Fig. 4, when the noise level is less than the predetermined value, no output sound is output from the speaker 14.

[0036] In this case, while the vehicle 3 is traveling on the first road, the noise level is A1, and since the noise level is less than the predetermined value, control of the noise level by the output sound is not executed. In other words, while the vehicle 3 is traveling on the first road (from time T0 to time T1 and from time T2 to time T3), the noise level is A1. On the other hand, while the vehicle 3 is traveling on the second road (from time T1 to time T2), control of the noise level by the output sound is executed, and the noise level is reduced from B1 to B2. Therefore, as shown in FIG. 4, the difference D1 in the noise levels between the first road and the second road is smaller than the difference Dx shown in FIG. 11, which is a comparative example, and as a result, discomfort to the occupants caused by changes in the noise level can be suppressed.

[0037] Furthermore, when the noise control device 2 determines, through the function of the determination unit 21, that the noise level is less than a predetermined value, the noise control device 2 may output, through the function of the output unit 23, an output sound that amplifies the noise level (hereinafter also referred to as amplified sound) from the speaker 14. In contrast, when the noise control device 2 determines that the noise level is equal to or greater than the predetermined value, it does not output the amplified sound from the speaker 14. The output of the amplified sound may be performed in conjunction with setting the silencing ratio to a smaller value than when the noise level is equal to or greater than the predetermined value, or may be performed instead of such setting. Furthermore, when the noise level is less than the predetermined value, the noise control device 2 may control the amplified sound so that the noise level becomes equal to or greater than the predetermined value.

[0038] The amplified sound is an output sound having a waveform in phase with the noise inside the vehicle, and the noise control device 2 can control the amplitude and period of the amplified sound in the same way as the output sound. In other words, the noise control device 2 can increase or decrease the amplitude of the output sound of the amplified sound, and can shift the period of the waveform of the amplified sound in the positive direction by 0.05 to 0.25 periods along the time axis. The minimum value of the volume of the amplified sound is 0 (dB), and the maximum value is the maximum value of the detected noise level (before the noise reduction process by the output sound).

[0039] Fig. 5 is a diagram showing the noise reduction effect when an amplified sound is output when the noise level is less than a predetermined value in the example shown in Fig. 4. In this case, the noise level is amplified from A1 to A3 while the vehicle 3 is traveling on the first road (time T0 to time T1 and time T2 to time T3), and the noise level is reduced from B1 to B2 while the vehicle 3 is traveling on the second road (time T1 to time T2). Therefore, as shown in Fig. 5, the difference D2 in noise levels between the first road and the second road is smaller than the difference D1 shown in Fig. 4, and as a result, the discomfort felt by the occupants due to the change in noise level can be further suppressed.

[0040] The noise control device 2 may divide the noise level into at least one range equal to or greater than a predetermined value and at least one range below the predetermined value, using the function of the setting unit 22, and set a certain silencing ratio for each range. The ranges are set so that the noise levels do not overlap with each other. The number of set ranges is multiple and within the range that can be processed by the noise control device 2. The noise control device 2 may set the silencing ratio for each range so that it increases in order from the lowest noise level range.

[0041] An example of the relationship between noise level and silencing ratio is shown in Fig. 6. If X2 in Fig. 6 is a predetermined value, in the example shown in Fig. 6, there are two ranges of noise levels equal to or greater than the predetermined value: a range from X2 to X3 and a range greater than X3, and there are two ranges of noise levels less than the predetermined value: a range from X1 to X2 and a range less than X1. The noise control device 2 sets the silencing ratio to Y1 in the range less than noise level X1, sets the silencing ratio to Y2 in the range from noise level X1 to noise level X2, sets the silencing ratio to Y3 in the range from noise level X2 to noise level X3, and sets the silencing ratio to Y4 in the range exceeding noise level X3.

[0042] The noise control device 2 may set, by the function of the setting unit 22, a first noise level equal to or lower than a predetermined value and a second noise level equal to or higher than the predetermined value as thresholds for setting the silencing ratio, and set the silencing ratio to the first ratio when the noise level is lower than the first noise level, set the silencing ratio to a second ratio greater than the first ratio when the noise level is equal to or higher than the second noise level, and set the silencing ratio to a third ratio greater than the first ratio and less than the second ratio and directly proportional to the noise level when the noise level is equal to or higher than the first noise level and less than the second noise level. The first noise level and the second noise level as well as the first ratio and the second ratio can be set to appropriate values ​​within a range in which discomfort felt by the occupants due to changes in the noise level can be suppressed.

[0043] Fig. 7 is a diagram showing another example of the relationship between the noise level and the silencing ratio. In the example shown in Fig. 7, the noise control device 2 sets the silencing ratio to a fixed first ratio when the noise level is less than the first noise level, and sets the silencing ratio to a fixed second ratio when the noise level is equal to or greater than the second noise level. Then, when the noise level is equal to or greater than the first noise level and less than the second noise level, the noise control device 2 calculates the silencing ratio corresponding to the noise level from the straight line L shown in Fig. 7, and sets the calculated silencing ratio as the third ratio.

[0044] The noise control device 2 may set the silencing ratio to a fourth ratio when the noise level is less than a predetermined value, and may set the silencing ratio to a fifth ratio greater than the fourth ratio when the noise level is equal to or greater than the predetermined value, by the function of the setting unit 22. In this case, the noise control device 2 may set the silencing ratio to change from the fourth ratio to the fifth ratio in a first predetermined time when the noise level changes from less than the predetermined value to equal to or greater than the predetermined value, and may set the silencing ratio to change from the fifth ratio to the fourth ratio in a second predetermined time when the noise level changes from equal to or greater than the predetermined value to less than the predetermined value.

[0045] The fourth rate and the fifth rate can be set to appropriate values ​​within a range that can suppress discomfort of the occupants caused by changes in noise level. The first predetermined time is shorter than the second predetermined time, for example, 0.1 to 2 seconds. On the other hand, the second predetermined time is longer than the first predetermined time, and can be set to an appropriate value within a range that can suppress discomfort of the occupants caused by changes in noise level, for example, 3 to 6 seconds.

[0046] Furthermore, when the noise level changes from a predetermined value or more to less than the predetermined value, instead of setting the silencing ratio to change from the fifth ratio to the fourth ratio in a second predetermined time by the function of the setting unit 22, the noise control device 2 may set the silencing ratio to change from the fifth ratio to the fourth ratio in a first predetermined time and output the amplified sound from the speaker for the second predetermined time by the function of the output unit 23. In this case, the ratio at which the amplified sound amplifies the noise level is set to decrease over time. The amplification ratio at which the amplified sound amplifies the noise level is defined as an index indicating the degree to which the noise level is amplified by the amplified sound, similar to the silencing ratio, and is, for example, the ratio of the noise level amplified by the amplified sound to the noise level before the amplified sound is superimposed.

[0047] FIG. 8 is a diagram showing the silencing effect in the example shown in FIG. 4, in which the silencing ratio is changed in a first predetermined time when the noise level changes from less than a predetermined value to more than the predetermined value, and the silencing ratio is changed in a second predetermined time when the noise level changes from more than the predetermined value to less than the predetermined value. In the example shown in FIG. 8, at time T1 when the noise level changes from A1 less than the predetermined value to B1 more than the predetermined value, the silencing ratio is changed from 0% to 30% in about 0.1 seconds. Therefore, the noise level is reduced to B2 immediately after time T1. On the other hand, at time T2 when the noise level changes from B1 more than the predetermined value to A1 less than the predetermined value, the silencing ratio is changed from 30% to 0% in about 5 seconds. Therefore, the silencing effect is gradually reduced between time T2 and time T4, and the noise level becomes A1 at time T4.

[0048] The noise control device 2 may use the function of the setting unit 22 to estimate the timing at which the condition of the road surface on which the vehicle 3 is traveling will change based on an image of the area ahead in the traveling direction of the vehicle 3, and set the silencing ratio to be small or large at the estimated timing. Moreover, instead of or in addition to setting the silencing ratio to be small or large at the estimated timing, the noise control device 2 may start or stop output of the amplified sound using the function of the output unit 23.

[0049] The noise control device 2 acquires an image of the area ahead in the traveling direction of the vehicle 3 from the camera 13, and performs processing such as pattern matching to detect the condition of the road surface. The noise control device 2 acquires an image of an area, for example, 10 to 100 m ahead in the traveling direction of the vehicle 3, depending on the focal length of the camera 13. Then, when the condition of the road surface changes, the noise control device 2 estimates the timing (time) at which the vehicle 3 will reach the position where the condition of the road surface changes, based on the distance to the position where the condition of the road surface changes and the traveling speed of the vehicle 3.

[0050] Furthermore, the noise control device 2 may determine, by the function of the output unit 23, whether or not the noise level changes from less than the predetermined value to a predetermined value or more due to a change in the road surface condition, based on an image of the road ahead in the traveling direction of the vehicle 3, when the noise level is less than the predetermined value. If it is determined that the noise level does not change from less than the predetermined value to a predetermined value or more due to a change in the road surface condition, the noise control device 2 continues the currently executed process. On the other hand, if it is determined that the noise level changes from less than the predetermined value to a predetermined value or more due to a change in the road surface condition, the noise control device 2 estimates a first timing at which the noise level changes from less than the predetermined value to a predetermined value or more, based on an image of the road ahead in the traveling direction of the vehicle 3. Then, the amplified sound is output from the speaker 14 from a second timing, which is a third predetermined time before the first timing, to the first timing. In this case, the amplification rate at which the amplified sound amplifies the noise level is set to increase with time from the second timing to the first timing.

[0051] Similarly, the noise control device 2 may determine whether the noise level changes from a predetermined value or more to less than a predetermined value due to a change in the road surface condition based on an image of the area ahead of the vehicle 3 in the traveling direction when the noise level is equal to or more than the predetermined value. If it is determined that the noise level does not change from a predetermined value or more to less than the predetermined value due to a change in the road surface condition, the noise control device 2 continues the currently executed process. On the other hand, if it is determined that the noise level changes from a predetermined value or more to less than the predetermined value due to a change in the road surface condition, the noise control device 2 estimates a third timing at which the noise level changes from a predetermined value or more to less than the predetermined value based on an image of the area ahead of the vehicle 3 in the traveling direction. Then, the amplified sound is output from the speaker 14 for a third predetermined time from the third timing. In this case, the amplification rate at which the amplified sound amplifies the noise level is set to decrease with time from the third timing until the third predetermined time has elapsed. The third predetermined time can be set to an appropriate value within a range in which the discomfort of the occupants due to the change in the noise level can be suppressed, for example, 3 to 6 seconds.

[0052] Fig. 9 is a diagram showing the silencing effect in the case where an amplified sound is outputted when the noise level changes in the example shown in Fig. 4 to make the change in the noise level gentle. In the example shown in Fig. 9, the noise control device 2 estimates that the vehicle 3 will enter the second road from the first road at time T1 from the image of the vehicle 3 in the forward traveling direction between time T0 and time T5. Then, the noise control device 2 outputs the amplified sound from the speaker 14 from time T5, which is a third predetermined time before time T1, to time T1. The amplification ratio at which the amplified sound amplifies the noise level is set to gradually increase from time T5 to time T1, and the silencing process is executed at a predetermined silencing ratio after time T1, so that the noise level changes gently from A1 to B2 when entering the second road from the first road.

[0053] Furthermore, from an image of the vehicle 3 ahead in the traveling direction, the noise control device 2 estimates that the vehicle 3 will enter the first road from the second road at time T2, between time T1 and time T2. Then, from time T2 to time T4, which is a third predetermined time after time T2, the noise control device 2 outputs an amplified sound from the speaker 14. The amplification rate at which the amplified sound amplifies the noise level is set to gradually decrease from time T2 to time T4, and no output sound is output after time T4, so that when the vehicle enters the first road from the second road, the noise level changes gradually from B2 to A1.

[0054] [Processing in noise control systems] 10 to 12, a procedure for processing information by the noise control device 2 will be described. The process described below is executed at predetermined time intervals (for example, every 0.1 to 1 milliseconds) by a processor (DSP) included in the noise control device 2.

[0055] FIG. 10 is an example of a flowchart showing information processing executed in the noise control system 1 of the present embodiment.

[0056] First, in step S1, indoor sound is acquired from microphone 11 using the function of determination unit 21, and in the following step S2, noise is detected from the indoor sound, and in the following step S3, it is determined whether or not the noise level is below a predetermined value. If it is determined in step S3 that the noise level is below the predetermined value, the process proceeds to step S4, where the setting unit 22 sets the silencing ratio to a first ratio that is smaller than the second ratio. On the other hand, if it is determined in step S3 that the noise level is equal to or greater than the predetermined value, the process proceeds to step S5, where the silencing ratio is set to the second ratio. Then, in step S6, the output unit 23 functions to output an output sound corresponding to the set silencing ratio from speaker 14.

[0057] Next, Fig. 11 is another example of a flowchart showing information processing executed in the noise control system 1 of the present embodiment. The flowchart shown in Fig. 11 is obtained by replacing steps S4 to S6 of the flowchart shown in Fig. 10 with steps S7 and S8.

[0058] Steps S1 to S3 in Fig. 11 are the same as steps S1 to S3 in Fig. 10, and therefore a description thereof will be omitted. In the flowchart shown in Fig. 11, if it is determined in step S3 that the noise level is less than a predetermined value, the process proceeds to step S7, and the amplified sound is output from speaker 14 by the function of output unit 23. On the other hand, if it is determined in step S3 that the noise level is equal to or greater than the predetermined value, the process proceeds to step S8, and the amplified sound is not output.

[0059] Next, FIG. 12 is yet another example of a flowchart showing information processing executed in the noise control system 1 of the present embodiment.

[0060] First, in step S11, the determination unit 21 acquires an image of the area ahead of the vehicle 3 from the camera 13, and in the next step S12, the timing at which the road surface condition will change is estimated, and in the next step S13, in consideration of a predetermined value, it is determined whether or not it is necessary to change the sound deadening ratio in accordance with the change in the road surface condition. If it is determined in step S13 that the sound deadening ratio needs to be changed, the process proceeds to step S14, where the setting unit 22 changes the sound deadening ratio, and in the next step S15, the output unit 23 changes the output sound at the estimated timing. On the other hand, if it is determined in step S13 that the sound deadening ratio does not need to be changed, the process proceeds to step S16, where the current sound deadening process is continued.

[0061] [Embodiments of the present invention] As described above, according to this embodiment, in the noise control method for controlling the noise level inside the vehicle cabin by the output sound output from the speaker 14, it is determined whether the noise level is below a predetermined value, and when it is determined that the noise level is below the predetermined value, the output sound is controlled so as to reduce the noise level more than when the noise level is equal to or higher than the predetermined value. This makes it possible to suppress changes in the noise inside the vehicle.

[0062] Moreover, according to the noise control method of the present embodiment, the noise level is calculated from the detection results of the microphone 11 and the acceleration sensor 12 of the vehicle 3. This makes it possible to calculate the noise level more accurately.

[0063] Furthermore, according to the noise control method of the present embodiment, the timing at which the condition of the road surface on which the vehicle 3 travels will change is estimated based on an image of the road ahead in the traveling direction of the vehicle 3, and the silencing ratio at which the output sound reduces the noise level is set to be small or large at the timing. This makes it possible to further suppress changes in the interior noise.

[0064] According to the noise control method of the present embodiment, the noise level is divided into at least one range equal to or greater than the predetermined value and at least one range less than the predetermined value, which do not overlap with each other, and a certain silencing ratio for reducing the noise level of the output sound is set for each range. This makes it easy to set the silencing ratio.

[0065] According to the noise control method of the present embodiment, a first noise level equal to or lower than the predetermined value and a second noise level equal to or higher than the predetermined value are set as thresholds for setting a silencing ratio at which the output sound reduces the noise level, and when the noise level is lower than the first noise level, the silencing ratio is set to the first ratio, when the noise level is equal to or higher than the second noise level, the silencing ratio is set to the second ratio higher than the first ratio, and when the noise level is equal to or higher than the first noise level and lower than the second noise level, the silencing ratio is set to the third ratio higher than the first ratio and lower than the second ratio and directly proportional to the noise level. This makes it possible to set a silencing ratio according to the noise level.

[0066] According to the noise control method of the present embodiment, when the noise level is less than the predetermined value, the silencing ratio for reducing the noise level of the output sound is set to a fourth ratio, when the noise level is equal to or greater than the predetermined value, the silencing ratio is set to a fifth ratio greater than the fourth ratio, when the noise level changes from less than the predetermined value to equal to or greater than the predetermined value, the silencing ratio is set to change from the fourth ratio to the fifth ratio in a first predetermined time, and when the noise level changes from equal to or greater than the predetermined value to less than the predetermined value, the silencing ratio is set to change from the fifth ratio to the fourth ratio in a second predetermined time longer than the first predetermined time. This makes it possible to make the change in the noise level more gradual.

[0067] Moreover, according to the noise control method of the present embodiment, when it is determined that the noise level is less than the predetermined value, the output sound that amplifies the noise level is output from the speaker 14. This makes it possible to suppress changes in the in-vehicle noise.

[0068] According to the noise control method of the present embodiment, when the noise level is less than the predetermined value, the silencing ratio at which the output sound reduces the noise level is set to a fourth ratio, when the noise level is equal to or greater than the predetermined value, the silencing ratio is set to a fifth ratio greater than the fourth ratio, when the noise level changes from less than the predetermined value to equal to or greater than the predetermined value, the silencing ratio is set to change from the fourth ratio to the fifth ratio in a first predetermined time, when the noise level changes from equal to or greater than the predetermined value to less than the predetermined value, the silencing ratio is set to change from the fifth ratio to the fourth ratio in the first predetermined time, and when the noise level changes from equal to or greater than the predetermined value to less than the predetermined value, the output sound that amplifies the noise level is output from the speaker 14 for a second predetermined time longer than the first predetermined time, and the amplification ratio at which the output sound that amplifies the noise level amplifies the noise level is set to decrease over time. This makes it possible to make the noise level change more gradual.

[0069] According to the noise control method of the present embodiment, when the noise level is less than the predetermined value, a first timing at which the noise level changes from less than the predetermined value to equal to or greater than the predetermined value is estimated based on an image of the area ahead in the traveling direction of the vehicle 3, and the output sound that amplifies the noise level is output from the speaker 14 from a second timing that is a third predetermined time before the first timing to the first timing, and an amplification ratio at which the output sound that amplifies the noise level amplifies the noise level is set to increase over time from the second timing to the first timing, and when the noise level is equal to or greater than the predetermined value, a third timing at which the noise level changes from equal to or greater than the predetermined value to less than the predetermined value is estimated based on the image, and the output sound that amplifies the noise level is output from the speaker 14 from the third timing to the third predetermined time, and an amplification ratio at which the output sound that amplifies the noise level amplifies the noise level is set to decrease over time from the third timing to the third predetermined time. This makes it possible to make the noise level change more gradual.

[0070] Furthermore, according to the present embodiment, there is provided a noise control method for controlling a noise level inside a vehicle cabin by an output sound output from a speaker 14, which determines whether the noise level is below a predetermined value, and when it is determined that the noise level is below the predetermined value, outputs the output sound that amplifies the noise level from the speaker 14. This makes it possible to suppress changes in the noise inside the vehicle.

[0071] Furthermore, according to the noise control method of the present embodiment, the timing at which the condition of the road surface on which the vehicle 3 is traveling will change is estimated based on an image of the area ahead in the traveling direction of the vehicle 3, and the output of the output sound that amplifies the noise level is started or stopped at that timing. This makes it possible to further suppress changes in the noise inside the vehicle.

[0072] Furthermore, according to the present embodiment, there is provided a noise control device 2 that controls the noise level inside the vehicle cabin by the output sound output from the speaker 14, the noise control device 2 including a determination unit 21 that determines whether the noise level is below a predetermined value, and a setting unit 22 that controls the output sound when the determination unit 21 determines that the noise level is below the predetermined value so as to reduce the noise level more than when the noise level is equal to or higher than the predetermined value. This makes it possible to suppress changes in the vehicle interior noise.

[0073] Furthermore, according to the present embodiment, there is provided a noise control device 2 that controls the noise level inside the vehicle cabin by an output sound output from a speaker 14, the noise control device 2 including a determination unit 21 that determines whether the noise level is below a predetermined value, and an output unit 23 that outputs the output sound that amplifies the noise level from the speaker 14 when the determination unit 21 determines that the noise level is below the predetermined value. This makes it possible to suppress changes in the noise inside the vehicle. [Explanation of symbols]

[0074] 1. Noise control system 11, 11a, 11b...Microphone 12, 12a, 12b, 12c, 12d...Acceleration sensors 13. Camera 14, 14a, 14b, 14c, 14d...Speakers 2. Noise control device 21…Judgment section 22. Setting section 23...Output section 3. Vehicle 31…Driver’s seat 32…Passenger seat 33,34…Rear seats

Claims

1. A noise control method for controlling a noise level in a vehicle cabin by an output sound output from a speaker, comprising: determining whether the noise level is less than a predetermined value; When it is determined that the noise level is less than the predetermined value, the output sound is controlled so as to reduce the noise level more than when the noise level is equal to or greater than the predetermined value.

2. The noise control method according to claim 1 , wherein the noise level is calculated from detection results of a microphone and an acceleration sensor of a vehicle.

3. estimating a timing when a road surface condition of a road on which the vehicle is traveling will change based on an image of a road ahead in a traveling direction of the vehicle; 3. The noise control method according to claim 1, further comprising setting a silencing ratio at which the output sound reduces the noise level to be smaller or larger at the timing.

4. Dividing the noise level into at least one range equal to or greater than the predetermined value and at least one range less than the predetermined value, the ranges being non-overlapping with each other; The noise control method according to claim 1 or 2, further comprising: setting a constant silencing ratio for reducing the noise level of the output sound for each of the ranges.

5. A first noise level equal to or lower than the predetermined value and a second noise level higher than the predetermined value are set as thresholds for setting a silencing ratio at which the output sound is reduced, If the noise level is less than the first noise level, the silencing ratio is set to a first ratio; When the noise level is equal to or higher than the second noise level, the silencing ratio is set to a second ratio greater than the first ratio; 3. The noise control method according to claim 1, wherein, when the noise level is equal to or greater than the first noise level and less than the second noise level, the silencing ratio is set to a third ratio that is greater than the first ratio, less than the second ratio, and directly proportional to the noise level.

6. When the noise level is less than the predetermined value, a noise reduction ratio at which the output sound reduces the noise level is set to a fourth ratio; When the noise level is equal to or higher than the predetermined value, the noise silencing ratio is set to a fifth ratio greater than the fourth ratio; When the noise level changes from less than the predetermined value to equal to or greater than the predetermined value, the silencing ratio is set to change from the fourth ratio to the fifth ratio in a first predetermined time period, 3. The noise control method according to claim 1, wherein, when the noise level changes from equal to or greater than the predetermined value to less than the predetermined value, the silencing rate is set to change from the fifth rate to the fourth rate in a second predetermined time period that is longer than the first predetermined time period.

7. 3. The noise control method according to claim 1, further comprising the step of: outputting, from the speaker, the output sound that amplifies the noise level when it is determined that the noise level is less than the predetermined value.

8. When the noise level is less than the predetermined value, a noise reduction ratio at which the output sound reduces the noise level is set to a fourth ratio; When the noise level is equal to or higher than the predetermined value, the noise silencing ratio is set to a fifth ratio greater than the fourth ratio; When the noise level changes from less than the predetermined value to equal to or greater than the predetermined value, the silencing ratio is set to change from the fourth ratio to the fifth ratio in a first predetermined time period, When the noise level changes from equal to or greater than the predetermined value to less than the predetermined value, the silencing ratio is set to change from the fifth ratio to the fourth ratio in the first predetermined time, and the output sound that amplifies the noise level is output from the speaker for a second predetermined time that is longer than the first predetermined time, 3. The noise control method according to claim 1, further comprising setting an amplification rate at which the output sound amplifies the noise level so as to decrease over time.

9. When the noise level is less than the predetermined value, a first timing at which the noise level changes from less than the predetermined value to equal to or greater than the predetermined value is estimated based on an image of a forward area in a traveling direction of the vehicle; outputting the output sound from the speaker, the output sound amplifying the noise level, from a second timing, which is a third predetermined time before the first timing, to the first timing; an amplification rate at which the output sound for amplifying the noise level is amplified is set to increase with time from the second timing to the first timing; When the noise level is equal to or greater than the predetermined value, estimating, based on the image, a third timing at which the noise level changes from equal to or greater than the predetermined value to less than the predetermined value; outputting the output sound from the speaker, the output sound amplifying the noise level, for the third predetermined time from the third timing; 3. The noise control method according to claim 1, further comprising setting an amplification rate at which the output sound amplifies the noise level so as to decrease over time from the third timing until the third predetermined time has elapsed.

10. A noise control method for controlling a noise level in a vehicle cabin by an output sound output from a speaker, comprising: determining whether the noise level is less than a predetermined value; When it is determined that the noise level is less than the predetermined value, the output sound that amplifies the noise level is output from the speaker.

11. estimating a timing when a road surface condition of a road on which the vehicle is traveling will change based on an image of a road ahead in a traveling direction of the vehicle; The noise control method according to claim 10 , further comprising starting or stopping the output of the output sound, the noise level of which is amplified, at the timing.

12. A noise control device that controls a noise level in a vehicle cabin by an output sound output from a speaker, a determination unit that determines whether the noise level is less than a predetermined value; A noise control device comprising: a setting unit that controls the output sound so that, when the judgment unit determines that the noise level is less than the predetermined value, the noise level is reduced more than when the noise level is equal to or greater than the predetermined value.

13. A noise control device that controls a noise level in a vehicle cabin by an output sound output from a speaker, a determination unit that determines whether the noise level is less than a predetermined value; an output unit that outputs the output sound from the speaker, which amplifies the noise level, when the determination unit determines that the noise level is less than the predetermined value.

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