A road noise active noise reduction car seat and noise reduction method thereof

Abstract

The present invention discloses a road noise active noise reduction car seat and a noise reduction method thereof, wherein the road noise active noise reduction car seat comprises an active road noise reduction system arranged in the car seat, and the active road noise reduction system comprises: an active noise reduction signal processing controller, a road noise source signal sensor connected to the active noise reduction signal processing controller, an inverted noise reduction speaker and an inverted low-frequency vibrator, an error microphone, and a power amplifier circuit; the road noise source signal sensor is arranged at the bottom of the car seat for collecting road noise signals; the inverted noise reduction speaker and the inverted low-frequency vibrator are arranged on or near the headrest of the car seat for providing an inverted road noise signal; the error microphone is arranged on or near the headrest of the car seat for obtaining the environmental noise near the headrest. The present invention discloses a road noise active noise reduction car seat and a noise reduction method thereof, and reduces the road noise transmitted into the car through the chassis of the car through the active noise reduction method.

Description

Technical Field

[0001] The present invention relates to the technical field of noise reduction, and in particular to a road noise active noise reduction automobile seat and a noise reduction method thereof. Background Art

[0002] In recent years, active noise reduction technology has been widely used in closed headphones. These headphones generally form a small space tightly sealed with the ear or ear canal, and play a sound signal that is inversely proportional to the noise signal through the speaker to offset the spatial noise signal and achieve the purpose of eliminating noise. This is active noise reduction technology. Active noise reduction technology has also been limitedly applied to car cabins, but the aforementioned active noise reduction technology is not effective in reducing noise in a large space throughout the car. Active noise reduction technology in cars relies on signal collection from the main point noise source, such as placing a pickup microphone at the engine, and then emitting inverse noise through the speakers in the car to reduce the noise of specific sound sources. The same method is used to eliminate several relatively large noise sources in the car, such as exhaust pipes, air conditioning outlet noise, etc.

[0003] The noise sources of traditional gasoline or diesel vehicles are relatively complex. The main noise sources are engine noise, exhaust pipe noise, engine air intake noise, air conditioning outlet noise, wind noise, and road noise. In particular, the noise generated by the friction between the car tires and the road surface is transmitted to the car chassis through the four-wheel shock absorbers, and then transmitted to the interior of the car through the chassis. This is the so-called road noise. Since this road noise is mainly bass, it is difficult to be blocked by the passive sound insulation materials designed for the car. Therefore, most of it will still be transmitted into the car, and the volume is very loud. Although this low-frequency noise is not as harsh as mid- and high-frequency noise, because their volume is much louder than mid- and high-frequency noise, it forms a roaring sound. Drivers may be accustomed to this low-frequency road noise and ignore its damage to hearing and body.

[0004] However, the fastest growing vehicles are new energy vehicles, most of which are electric vehicles. Electric vehicles do not have engines, exhaust pipes, or air intakes, and the sound of the electric motors is very low, so a large part of the car noise is reduced. For electric vehicles, road noise caused by the friction between tires and the road surface has become the first noise source. The second noise source is wind noise. Road noise and wind noise are the main noises of electric vehicles. The low-frequency road noise from the car chassis is difficult to isolate through materials and design.

[0005] Therefore, it is necessary to develop a method for active noise reduction of road noise, especially around occupants in car seats, to reduce the road noise perceived by the occupants that is transmitted into the car through the car chassis through the active noise reduction method. This part of the road noise also includes the friction noise generated by the tires and the road surface. Summary of the invention

[0006] The present invention overcomes the shortcomings of the prior art and provides a road noise active noise reduction car seat and a noise reduction method thereof, which reduces the occupant's perception of the road noise transmitted into the car through the car chassis through the active noise reduction method.

[0007] To achieve the above-mentioned object, the technical solution adopted by the present invention is: a road noise active noise reduction car seat, comprising an active road noise reduction system arranged in the car seat, the active road noise reduction system comprising: an active noise reduction signal processing controller, and a road noise source signal sensor connected to the active noise reduction signal processing controller, an inverted noise cancellation speaker and / or an inverted low-frequency vibrator, an error microphone, and a power amplifier circuit;

[0008] The road noise source signal sensor is arranged at the bottom of the car seat or on the frame below the car seat, and is used to collect the road noise signal and feed it back to the active noise reduction signal processing controller;

[0009] The inverted noise cancelling speaker is arranged on or near the headrest of the car seat to provide an inverted road noise signal; and / or the inverted low-frequency vibrator is arranged on or near the headrest, and the active noise reduction signal processing controller is connected to the inverted noise cancelling speaker and / or the inverted low-frequency vibrator through the power amplifier circuit to provide an inverted road noise signal;

[0010] The error microphone is arranged on or near the headrest of the car seat, and is used to obtain the environmental noise near the headrest and feed it back to the active noise reduction signal processing controller.

[0011] In a preferred embodiment of the present invention, the anti-phase low-frequency vibrator is arranged inside the headrest or above the seat back near the headrest; or, the anti-phase low-frequency vibrator is arranged inside the roof and above the headrest.

[0012] In a preferred embodiment of the present invention, the road noise source signal sensor is a noise capture microphone and / or a vibration sensor.

[0013] In a preferred embodiment of the present invention, the inverted noise cancelling speaker comprises a pair of left ear inverted noise cancelling speaker and right ear inverted noise cancelling speaker arranged oppositely on the headrest;

[0014] Or, the inverting noise cancelling speaker comprises a left ear inverting noise cancelling speaker and a right ear inverting noise cancelling speaker which are arranged inside the roof and above the headrest;

[0015] Alternatively, the inverting noise cancelling speaker comprises a left ear inverting noise cancelling speaker and a right ear inverting noise cancelling speaker which are arranged above the seat back and close to the headrest.

[0016] In a preferred embodiment of the present invention, the error microphone is arranged on the headrest of the car seat near the ear; or, the error microphone is arranged above the back of the car seat and near the headrest; or, the error microphone is arranged inside the roof and above the headrest;

[0017] The anti-phase low-frequency vibrator and the error microphone are connected to an active noise reduction signal processing controller to form a noise control loop.

[0018] In a preferred embodiment of the present invention, the error microphone includes a group of left-ear error microphone and right-ear error microphone relatively arranged on the headrest of the car seat, which are used to obtain the environmental noise on both sides of the headrest near the passenger's ear canal, and feed it back to the active noise reduction signal processing controller; or, the error microphone includes a group of left-ear error microphone and right-ear error microphone relatively arranged above the back of the car seat and near the headrest, which are used to obtain the environmental noise on both sides of the headrest near the passenger's ear canal, and feed it back to the active noise reduction signal processing controller; or, the error microphone includes a group of left-ear error microphone and right-ear error microphone relatively arranged inside the roof and above the headrest, which are used to obtain the environmental noise on both sides of the headrest near the passenger's ear canal, and feed it back to the active noise reduction signal processing controller;

[0019] The left ear inverted noise cancellation speaker and the left ear error microphone, as well as the right ear inverted noise cancellation speaker and the right ear error microphone are respectively connected to the active noise reduction signal processing controller to form two independent noise control loops.

[0020] In a preferred embodiment of the present invention, a method for reducing noise of a road noise active noise reduction vehicle seat is implemented by using a road noise active noise reduction vehicle seat, and comprises the following steps:

[0021] Step 1: The active noise reduction signal processing controller of the active road noise reduction system sends a command to obtain road noise. The road noise source signal sensor located at the bottom of the car seat picks up and feeds back to the active noise reduction signal processing controller. The active noise reduction signal processing controller generates a predicted inverse road noise signal through the feedforward active noise reduction algorithm in the active noise reduction algorithm.

[0022] Step 2: The active noise reduction signal processing controller sends the predicted inverted road noise signal to the inverted noise cancellation speaker and / or the inverted low-frequency vibrator through the power amplifier circuit, and collects real-time noise information through the error microphone. Through the hybrid feedback adaptive active noise cancellation algorithm, the active road noise reduction control is implemented to suppress the road noise through the inverted noise generated by the secondary channel to achieve noise reduction.

[0023] In a preferred embodiment of the present invention, the active noise reduction algorithm includes: a feedforward active noise reduction method, a feedback active noise reduction method, or a hybrid feedback active noise reduction method;

[0024] The feedforward active noise cancellation method includes: a noise capture microphone and / or a vibration sensor is arranged at the bottom of the car seat, and a noise signal obtained by the noise capture microphone and / or the vibration sensor is mapped to a noise frequency response through a digital signal processor and / or an analog signal processor and a linear filter circuit in an active noise reduction signal processing controller, and then the inverted road noise signal is driven by the active noise reduction signal processing controller to broadcast the inverted noise signal through an inverted noise cancellation speaker and / or an inverted low-frequency vibrator on the headrest of the car seat or outside the headrest of the car seat to offset the sound wave vibration of the car road noise;

[0025] Or, the feedback active noise cancellation method includes: an error microphone is placed on the headrest or on the periphery of the headrest to extract the car noise caused by road noise; the feedback active noise cancellation method uses a digital signal processor and / or an analog signal processor in an active noise reduction signal processing controller and a linear filter circuit to drive the anti-phase noise signal to broadcast through an anti-phase noise cancellation speaker and / or an anti-phase low-frequency vibrator to offset the sound wave vibration of the car road noise;

[0026] Alternatively, a hybrid feedback active noise cancellation method uses a feedforward active noise cancellation method and a feedback active noise cancellation method that cooperate with each other. The digital signal processor and / or analog signal processor and the linear filter circuit in the active noise reduction signal processing controller map the noise signal to the actual noise frequency response, and then drive the anti-phase noise cancellation speaker and / or the anti-phase low-frequency vibrator to broadcast the anti-phase noise signal to offset the sound wave vibration of the car road noise; a noise capture microphone and / or a vibration sensor at the bottom of the seat is used to monitor the road noise signal, and another error microphone is used to monitor the error signal of the noise cancellation effect at any time, and these two signals are used to adaptively adjust the active noise reduction filter circuit.

[0027] In a preferred embodiment of the present invention, the active noise reduction algorithm also includes: a VAD module for speech detection; when an occupant on a car seat speaks, the speech signal detected by the error microphone that is close is much larger than the speech signal detected by the noise capture microphone at the bottom of the car seat; the occupant's speech is detected by the energy ratio of the two microphone signals of the noise capture microphone and the error microphone; when it is detected that the occupant is speaking, the adaptive process of the mixed feedback adaptive active noise cancellation algorithm is stopped, and at this time, the response function of the feedforward signal of the feedforward active noise cancellation method is temporarily fixed and stops updating until it is detected that the occupant stops speaking, and then the adaptive process of the mixed feedback adaptive active noise cancellation algorithm resumes updating.

[0028] In a preferred embodiment of the present invention, the hybrid feedback adaptive active noise cancellation algorithm includes: a filter-x least mean square (FxLMS) adaptive algorithm, including the following steps:

[0029] The reference signal x(n) is picked up by the road noise reference sensor, and the filtered signal x'(n) is generated through the secondary path model. The reference signal x(n) generates a secondary signal y(n) through the adaptive filter W(n) to drive the noise cancellation speaker. The anti-phase noise response generated by the noise cancellation speaker passes through the secondary path h(n) in the space and is superimposed on the primary road noise field d(n). The error signal e(n) is obtained through the error microphone as the feedback input of the system. The LMS algorithm performs iterative calculations and continuously adjusts the adaptive filter W(n), so that the mean square error continues to decrease and the adaptive process converges.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The present invention discloses a road noise active noise reduction automobile seat and a noise reduction method thereof, which reduces the road noise transmitted into the vehicle through the vehicle chassis by means of the active noise reduction method.

[0032] 1. The current RNC active road noise cancellation system can only cancel limited road noise (3dB+) at low speeds. It cannot achieve a perceptible noise cancellation effect at high speeds. The active road noise cancellation method of the present invention can achieve a significant road noise cancellation effect at both low and high speeds, with a noise cancellation effect of more than 10dB.

[0033] 2. Eliminate noise pollution in the interior of the car and eliminate the largest sources of car noise: road noise and tire noise. The road noise elimination bandwidth of the present invention is wide, suitable for eliminating low-medium frequency road noise with the largest energy in the cabin noise, and improving the intelligibility of conversations in the cabin.

[0034] 3. The present invention does not require distributed arrangement of sensors and car wiring. All components of the present invention can be inside the car seat. The independent product design leads to simpler implementation and lower cost, and is also more flexible. In particular, it does not require complex and lengthy car wiring and expensive A2B audio communication chips, which is very meaningful.

[0035] 4. The present invention is suitable for use in both traditional gasoline vehicles and new energy electric vehicles, which have sufficient power and widely distributed batteries. The active road noise cancellation system of the present invention is input through the power supply line, and installation, debugging and testing are very convenient. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0037] Figure 1 This is a schematic diagram of the structure of a road noise active noise reduction car seat of the present invention Figure 1 (Using two anti-phase noise-cancelling speakers);

[0038] Figure 2It is a signal processing flow chart when a road noise source signal sensor in a road noise active noise reduction automobile seat of the present invention adopts a noise capture microphone;

[0039] Figure 3 This is a schematic diagram of the structure of a road noise active noise reduction car seat of the present invention Figure 2 (Using anti-phase low-frequency vibrator);

[0040] Figure 4 It is a signal processing flow chart when an inverted road noise signal in a road noise active noise reduction automobile seat of the present invention is divided into two signals by a frequency division filter and transmitted to an inverted low-frequency vibrator and an inverted noise reduction speaker;

[0041] Figure 5 This is a schematic diagram of the structure of a road noise active noise reduction car seat of the present invention Figure 3 (Using inverse phase low frequency vibrator and inverse phase noise canceling speaker);

[0042] Figure 6 It is a general framework diagram of a system for a road noise active noise reduction vehicle seat of the present invention (inverted phase noise reduction speaker);

[0043] Figure 7 is a general framework diagram of another system of a road noise active noise reduction vehicle seat of the present invention (anti-phase low-frequency vibrator);

[0044] Figure 8 It is a hybrid feedback adaptive active noise cancellation algorithm and VAD module flow chart of a road noise active noise reduction automobile seat of the present invention;

[0045] Fig. 9 It is a schematic diagram of the structure of a road noise active noise reduction automobile seat of the present invention;

[0046] Among them, 1-headrest, 11-left side of headrest, 12-middle part of headrest, 13-right side of headrest, 2-shoulder rest, 21-left side of shoulder rest, 22-middle part of shoulder rest, 23-right side of shoulder rest, 3-seat backrest, 4-car seat, 41-bottom, 5-frame, 6-roof, 61-left side of roof, 62-middle part of roof, 63-right side of roof,

[0047] 7- road noise source signal sensor, 8- inverted low frequency vibrator, 82- left ear inverted noise cancellation speaker, 83- right ear inverted noise cancellation speaker, 91- left ear error microphone, 92- right ear error microphone. DETAILED DESCRIPTION

[0048] The technical solution of the present invention is described in detail below through the accompanying drawings and specific embodiments. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical solution of the present invention, rather than limitations on the technical solution of the present invention. The embodiments of the present invention and the technical features in the embodiments may be combined with each other unless there is a conflict.

[0049] The term "and / or" is only a description of the association relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " generally indicates that the related objects are in an "or" relationship.

[0050] The existing active road noise reduction technology places a three-axis acceleration sensor on the car body above the tire, picks up the vibration signal caused by the car road noise, and uses the inverse signal of this signal to emit inverse noise through the car audio speaker to offset the noise in the car cabin. At the same time, an error microphone is placed near the ear of the occupant to monitor the noise reduction effect and adjust the amplitude and phase of the broadcast inverse noise at any time to achieve the optimal effect of reducing the car cabin road noise. However, due to the large space inside the car, the noise at each spatial point is different, and it is difficult to eliminate the noise through active noise reduction methods.

[0051] First, because the correlation between the noise inside the car and the vibration signal above the wheel is not high, the existing RNC active road noise cancellation technology is not efficient in eliminating road noise. Secondly, due to cost issues, the RNC system often shares speakers with the car audio system, and the car speakers are far away from the error microphone, so the power required to release the reverse phase noise is relatively high, the noise cancellation efficiency is low, and it is easy to form unstable howling.

[0052] In addition, this distributed RNC active noise reduction method requires different sensors, microphones and speakers to be placed in different places in the car, lengthy signal wiring and expensive A2B signal transmission chips, which increase signal delay and cost. In addition, the active noise reduction algorithm of the existing RNC method is relatively complex, requiring expensive high-computing signal processing chips, but the dB reduction of road noise is limited and the convergence time is too long. The result is half the effort with twice the effort.

[0053] Aiming at these characteristics of automobile road noise, the present invention invents a new active road noise reduction RNC method, which aims to overcome the above defects of the existing RNC method, so as to achieve better noise reduction effect, faster convergence, more stable performance, more targeted components, more reasonable system layout, and lower overall cost. Embodiment 1

[0054] like Figure 3As shown, the present invention discloses a road noise active noise reduction car seat, including an active road noise reduction system arranged in a car seat 4, the active road noise reduction system including: an active noise reduction signal processing controller, and a road noise source signal sensor 7 connected to the active noise reduction signal processing controller, an inverted low-frequency vibrator 8, an error microphone, and a power amplifier circuit.

[0055] Specifically, the road noise source signal sensor 7 is arranged at the bottom 41 of the car seat 4, or the road noise source signal sensor 7 is arranged on the frame 5 below the car seat 4, for collecting the road noise signal and feeding it back to the active noise reduction signal processing controller. Further, in this embodiment, the road noise source signal sensor 7 is arranged at the bottom 41 of the car seat 4. Moreover, the road noise source signal sensor 7 adopts a noise capture microphone and / or a vibration sensor. In this embodiment, a noise capture microphone is adopted.

[0056] Specifically, the anti-phase low-frequency vibrator 8 is arranged on the headrest 1, for example, on the left side 11, the middle 12, or the right side 13 of the headrest 1. In this embodiment, the anti-phase low-frequency vibrator 8 is arranged at the middle 12 of the headrest 1. The active noise reduction signal processing controller is connected to the anti-phase low-frequency vibrator 8 through the power amplifier circuit to provide an anti-phase road noise signal. Furthermore, in other embodiments, the anti-phase low-frequency vibrator 8 can also be arranged inside the headrest 1 or above the seat back near the headrest 1.

[0057] Specifically, the error microphone is disposed on the headrest 1 of the car seat 4 or near the headrest 1 to obtain the ambient noise near the headrest 1 and feed it back to the active noise reduction signal processing controller.

[0058] Specifically, the error microphone uses a single error microphone arranged on the headrest 1 of the car seat 4 near the ear. In this embodiment, the error microphone uses a group of left ear error microphones 91 and right ear error microphones 92 arranged relatively on the headrest 1 of the car seat 4, which are used to obtain the ambient noise on both sides of the headrest 1 near the passenger's ear canal and feed it back to the active noise reduction signal processing controller. In addition, the anti-phase low-frequency vibrator 8 and any one of the error microphones are connected to the active noise reduction signal processing controller to form a noise control loop. Embodiment 2

[0059] like Figure 1 As shown, the present invention discloses a road noise active noise reduction car seat, including an active road noise reduction system arranged in a car seat 4, the active road noise reduction system including: an active noise reduction signal processing controller, and a road noise source signal sensor 7 connected to the active noise reduction signal processing controller, an inverting noise cancellation speaker, an error microphone, and a power amplifier circuit.

[0060] Specifically, the road noise source signal sensor 7 is disposed at the bottom 41 of the car seat 4, for collecting road noise signals and feeding them back to the active noise reduction signal processing controller. In this embodiment, the road noise source signal sensor 7 is a noise capture microphone.

[0061] Specifically, the inverted noise cancelling speaker is located on the headrest 1, and the active noise reduction signal processing controller is connected to the inverted noise cancelling speaker through the power amplifier circuit to provide an inverted road noise signal. Further, the inverted noise cancelling speaker includes a pair of left ear inverted noise cancelling speakers 82 and right ear inverted noise cancelling speakers 83 arranged on the headrest 1 relatively; or, the inverted noise cancelling speaker includes a left ear inverted noise cancelling speaker 82 and a right ear inverted noise cancelling speaker 83 arranged inside the roof and above the headrest 1. Further, the inverted noise cancelling speaker uses a pair of left ear inverted noise cancelling speakers 82 and right ear inverted noise cancelling speakers 83 with low delay bass, which are placed near the two ears of the headrest 1 of the car seat 4. The right ear inverted noise cancelling speaker 83 is placed near the right ear, and the output inverted noise forms a noise canceling quiet zone in the right ear. The other left ear inverted noise cancelling speaker 82 is placed near the left ear, and the output inverted noise forms a noise canceling quiet zone in the left ear. Specifically, the setting position of the inverted noise cancelling speaker can be varied. It can be located at the upper, middle, or lower part of the headrest 1, or at the upper part of the seat back and adjacent to the headrest 1. It can even be located on the roof 6 (including the left side 61, the middle 62, and the right side 63) above the seat. When a single inverted noise cancelling speaker is used, it can be set at the middle 62 of the roof. When a pair of left ear inverted noise cancelling speakers 82 and right ear inverted noise cancelling speakers 83 are used, the left ear inverted noise cancelling speakers 82 and the right ear inverted noise cancelling speakers 83 can be installed at the left side 61 and the right side 63 of the roof, respectively. As long as it is close to the occupant's head and also close to the position where the error microphone is placed, it will be fine.

[0062] Specifically, the error microphone is arranged on the headrest 1 of the car seat 4 or near the headrest 1, and is used to obtain the environmental noise near the headrest 1, and feed it back to the active noise reduction signal processing controller. Further, the error microphone includes at least one group of left ear error microphone 91 and right ear error microphone 92 arranged relatively on the headrest 1 of the car seat 4, or the left ear error microphone 91 and the right ear error microphone 92 can also be arranged on the shoulder rest left side 21 and the shoulder rest right side 23 of the shoulder rest 2 of the car seat 4 respectively. The left ear error microphone 91 and the right ear error microphone 92 are used to obtain the environmental noise near the passenger's ear canal on both sides of the headrest 1, and feed it back to the active noise reduction signal processing controller; the left ear anti-phase noise reduction speaker 82 and the left ear error microphone 91, and the right ear anti-phase noise reduction speaker 83 and the right ear error microphone 92 are respectively connected to the active noise reduction signal processing controller to form two independent noise control loops. Embodiment 3

[0063] like Figure 5 As shown, the present invention discloses a road noise active noise reduction car seat, including an active road noise reduction system arranged in a car seat 4, the active road noise reduction system including: an active noise reduction signal processing controller, and a road noise source signal sensor 7 connected to the active noise reduction signal processing controller, an inverted noise cancellation speaker and an inverted low-frequency vibrator 8, an error microphone, and a power amplifier circuit.

[0064] Specifically, the road noise source signal sensor 7 is arranged at the bottom 41 of the car seat 4, and is used to collect the road noise signal and feed it back to the active noise reduction signal processing controller. Furthermore, the road noise source signal sensor 7 adopts a noise capture microphone and / or a vibration sensor. In this embodiment, the road noise source signal sensor 7 adopts a noise capture microphone.

[0065] Specifically, the inverted noise cancelling speaker and the inverted low-frequency vibrator 8 are arranged on the headrest 1 of the car seat 4 or near the headrest 1 to provide an inverted road noise signal. Among them, the inverted low-frequency vibrator 8 is arranged on the headrest 1. Specifically, the inverted low-frequency vibrator 8 is arranged inside the headrest 1, or the inverted low-frequency vibrator 8 is arranged above the back of the seat near the headrest 1. The inverted noise cancelling speaker is arranged on the headrest 1 or inside the roof and above the headrest 1. Further, the inverted noise cancelling speaker includes a pair of left-ear inverted noise cancelling speakers 82 and right-ear inverted noise cancelling speakers 83, which are relatively arranged on the left side 11 of the headrest and the right side 13 of the headrest on the headrest 1; or, the inverted noise cancelling speaker includes a left-ear inverted noise cancelling speaker 82 and a right-ear inverted noise cancelling speaker 83 arranged inside the roof and above the headrest 1. The active noise reduction signal processing controller is connected to the left ear inverted noise cancellation speaker 82, the right ear inverted noise cancellation speaker 83 and the inverted low-frequency vibrator 8 through a number of power amplifier circuits to provide an inverted road noise signal. Furthermore, there are three inverted sound-emitting devices (the left ear inverted noise cancellation speaker 82, the right ear inverted noise cancellation speaker 83 and the inverted low-frequency vibrator 8), the left ear inverted noise cancellation speaker 82 and the right ear inverted noise cancellation speaker 83 on the left and right sides of the headrest 1, and an inverted low-frequency vibrator 8 in the middle. The inverted road noise signal is divided into two signals by the frequency division filter. One subwoofer signal below 100Hz drives an inverted low-frequency vibrator 8 located in the middle of the headrest 1 through a low-frequency power amplifier. The other bass signal above 100Hz drives the bass speaker on the left or right side of the headrest 1 through a bass power amplifier. In this embodiment, (100Hz) is one of the examples, and it can also be other similar frequencies. The present invention provides three different implementation cases, wherein one sound-generating device, two sound-generating devices, and three sound-generating devices are installed near the headrest 1 , respectively, and at least one of the sound-generating devices is an anti-phase low-frequency vibrator 8 .

[0066] Specifically, the error microphone is arranged on the headrest 1 of the car seat 4 or near the headrest 1, and is used to obtain the environmental noise near the headrest 1 and feed it back to the active noise reduction signal processing controller. The error microphone includes at least one group of left ear error microphone 91 and right ear error microphone 92 arranged relatively on the headrest 1 of the car seat 4; or, the left ear error microphone 91 and the right ear error microphone 92 can also be arranged on the shoulder rest left side 21 and the shoulder rest right side 23 of the shoulder rest 2 of the car seat 4 respectively. The left ear error microphone 91 and the right ear error microphone 92 are used to obtain the environmental noise near the passenger's ear canal on both sides of the headrest 1 and feed it back to the active noise reduction signal processing controller; the left ear anti-phase noise reduction speaker 82 and the left ear error microphone 91, and the right ear anti-phase noise reduction speaker 83 and the right ear error microphone 92 are respectively connected to the active noise reduction signal processing controller to form two independent noise control loops.

[0067] Furthermore, a pair of left ear error microphones 91 and right ear error microphones 92 are placed near the two ears on the seat headrest 1. The right ear error microphone 92 is placed near the right ear to pick up the residual noise in the right ear area after noise cancellation, and the other left ear error microphone 91 is placed near the left ear to pick up the residual noise in the left ear area after noise cancellation. The specific error microphone positions can be varied, but they are all in the same area as the noise cancellation speaker. The error microphone can be located at the upper, middle, or lower part of the headrest 1, or at the upper part of the seat back and adjacent to the headrest 1. It can even be located on the roof above the seat. As long as it is close to the occupant's head. The relative position of the error microphone and the noise cancellation speaker can be above the noise cancellation speaker, below the noise cancellation speaker, or side by side with the noise cancellation speaker. The best position of the error microphone is as close to the occupant's ear as possible. The two error microphones are respectively distributed near the left ear and the right ear. The error microphone of the present invention can also be a single one. Unlike the error microphones for each ear, a single error microphone only needs to be close to the head to pick up the residual noise after the head area is de-noised. The error microphone and the anti-phase noise-cancelling speaker or vibrator are both located near the head of the seat, in a similar noise-cancelling area. The signal processing method of the error microphone is also similar to the signal processing method of the road noise collection microphone.

[0068] One seat has two sets of noise cancelling speakers and error microphones, but they share a road noise source signal, forming two local noise cancelling quiet areas around the two ears, making noise cancelling more accurate. Because the noise cancelling speakers do not share the original audio speakers of the car, but install independent noise cancelling speakers in the seat headrest 1, it is conducive to optimizing the performance selection of the noise cancelling speakers. At the same time, because it is close to the occupant's head, it does not require a high-power amplifier. Active noise cancellation is carried out locally, and it is not easy to interfere with each other and couple to form unstable states such as howling. The speakers and error microphones that output anti-phase sound waves are located near the head, which is convenient for forming a local noise cancelling quiet bubble around the driver or passenger's head, avoiding the problem of active noise reduction in a large space, and reducing the difficulty of implementing the active road noise cancellation system. The entire active noise cancellation system can be placed independently in the car seat 4, eliminating the complex long wiring in the car, reducing the wiring harness, and no longer requiring expensive A2B audio communication chips. Reduce costs and increase flexibility. Embodiment 4

[0069] A method for reducing noise of a road noise active noise reduction vehicle seat is implemented by using a road noise active noise reduction vehicle seat of embodiment 1, comprising the following steps:

[0070] Step 1: The active noise reduction signal processing controller of the active road noise reduction system sends an instruction to obtain road noise, and the road noise source signal sensor 7 located at the bottom 41 of the car seat 4 feeds back to the active noise reduction signal processing controller. The active noise reduction signal processing controller generates a predicted inverse road noise signal through the feedforward active noise reduction algorithm in the active noise reduction algorithm.

[0071] Step 2: The active noise reduction signal processing controller sends the predicted inverse road noise signal to the inverse noise reduction speaker and / or the inverse low-frequency vibrator 8, and collects real-time noise information through the error microphone, and uses a hybrid feedback adaptive active noise reduction algorithm to achieve active road noise reduction control by suppressing the road noise through the inverse noise generated by the secondary channel to achieve noise reduction.

[0072] Furthermore, a road noise source signal sensor 7 located at the bottom 41 of the car seat 4 obtains the road noise signal source near the chassis of the car and divides it into two paths. One path generates an anti-noise signal with a phase opposite to the road noise signal on the right side of the head through the right-path anti-phase filter, and then emits an anti-phase sound wave through the noise cancellation speaker on the right side of the seat headrest 1, which cancels the road noise transmitted to the right side of the head through the air, forming a noise cancellation quiet area near the right ear of the occupant. At the same time, an error microphone near the right ear picks up the residual noise after noise cancellation and feeds it back to an adaptive active noise reduction algorithm, automatically adjusting the coefficient of the anti-phase noise cancellation filter to minimize the residual noise after noise cancellation. The basic active noise reduction algorithm can use the FxLMS adaptive hybrid feedback active noise cancellation method, or other algorithms such as the FxAP affine projection active noise cancellation algorithm or corresponding algorithms in the frequency domain. At the same time, the same road noise signal source generates an anti-noise signal with the opposite phase to the road noise signal on the left side of the head through the left-side anti-phase filter, and then sends out an anti-phase sound wave through the noise cancellation speaker on the left side of the seat headrest 1, which cancels the road noise transmitted to the left side of the head through the air, forming a noise cancellation quiet area near the left ear of the occupant. At the same time, an error microphone near the left ear picks up the residual noise after noise cancellation and feeds it back to an adaptive active noise reduction algorithm, automatically adjusting the coefficient of the anti-phase noise cancellation filter to minimize the residual noise after noise cancellation.

[0073] Furthermore, the active noise reduction algorithm includes: a hybrid feedback active noise reduction method, including a feedforward active noise reduction method and a feedback active noise reduction method, the digital signal processor and / or analog signal processor in the active noise reduction signal processing controller and the linear filter circuit map the noise signal to the actual noise frequency response, and then drive the inverted noise reduction speaker and / or the inverted low-frequency vibrator 8 to broadcast the inverted noise signal to offset the sound wave vibration of the car road noise. It uses the noise capture microphone and / or vibration sensor at the bottom of the seat to monitor the road noise signal, and uses another error microphone to monitor the error signal of the noise reduction effect at any time, and uses these two signals to adaptively adjust the active noise reduction filter circuit to achieve the best noise reduction effect.

[0074] Among them, in the feedforward active noise cancellation method, the noise capture microphone and / or the vibration sensor are set at the bottom of the car seat 4, and the noise signal obtained by the noise capture microphone and / or the vibration sensor is mapped to the noise frequency response through the digital signal processor and / or the analog signal processor and the linear filter circuit in the active noise reduction signal processing controller, and then the inverted road noise signal is driven by the active noise reduction signal processing controller to broadcast the inverted noise signal through the inverted noise cancellation speaker and / or the inverted low-frequency vibrator 8 on the headrest 1 of the car seat 4 or the periphery of the headrest 1 of the car seat 4 to offset the sound wave vibration of the car road noise. Further, the linear filter circuit is automatically debugged to ensure that this mapping is correctly applicable to the maximum noise elimination; the advantage of the feedforward active noise cancellation method is that because the noise source signal and the noise signal have a temporal causal relationship, the linear system of the noise conduction path can be simulated, and active noise cancellation can be better achieved. However, there is no adaptive automatic adjustment with only feedforward, and changes and disturbances in the acoustic path are likely to cause the noise reduction effect to deteriorate.

[0075] Among them, the feedback active noise cancellation method, contrary to the feedforward active noise cancellation method, the error microphone is placed on the headrest 1 or the periphery of the headrest 1 to extract the car noise caused by road noise; the feedback active noise cancellation method uses the digital signal processor and / or analog signal processor in the active noise reduction signal processing controller and the linear filter circuit to drive the anti-phase noise signal through the anti-phase noise cancellation speaker and / or the anti-phase low-frequency vibrator 8 to broadcast to offset the sound wave vibration of the car road noise. Furthermore, the distance between the error microphone and the noise cancellation speaker is very short, and the processing time of the feedback design is also less; the feedback active noise cancellation method is most effective for eliminating low-frequency road noise with a longer wavelength. Because there is a delay in the feedback path, there is a limit on the bandwidth of effective noise cancellation, and only low-frequency noise with a longer wavelength can be eliminated.

[0076] Since the road noise source signal sampling microphone and the error sampling microphone of the present invention are both located in the car cabin and in the same space, the anti-phase sound waves emitted by the noise cancellation speaker may be transmitted to the road noise sampling microphone under the seat, resulting in signal coupling. Therefore, the road noise signal collected in this way may be "impure", resulting in system instability or even howling. In the traditional RNC method, because the road noise signal is collected by the acceleration sensor outside the cabin, there is no problem of signal cross-linking. In order to solve this problem, the present invention adopts improvements in both acoustics and algorithms to reduce the impact of acoustic signal coupling on the active noise cancellation effect. In the arrangement of acoustic devices, the noise cancellation speaker and the error microphone are arranged in a very close space, near the headrest 1. In this way, the power of the anti-phase noise played by the noise cancellation speaker does not need to be very large. At the same time, because the road noise sampling microphone is located at the bottom of the seat, it is far away from the noise cancellation speaker, so the sound pressure broadcast by the noise cancellation speaker has little chance of feedback to the road noise microphone.

[0077] Furthermore, the active noise reduction algorithm also includes: a VAD module for speech detection; when the occupant on the car seat 4 speaks, the speech signal detected by the close error microphone is much larger than the speech signal detected by the noise capture microphone at the bottom of the car seat 4; the occupant's speaking voice is detected by the energy ratio of the two microphone signals of the noise capture microphone and the error microphone; when the occupant is detected to be speaking, the mixed feedback adaptive active noise cancellation algorithm processing process is stopped, and at this time the response function of the feedforward signal of the feedforward active noise cancellation method is temporarily fixed and stops updating until the occupant stops speaking, and then the mixed feedback adaptive active noise cancellation algorithm processing process resumes updating.

[0078] Specifically, in this embodiment, the algorithm used by the hybrid feedback adaptive active noise cancellation algorithm includes: filter-x least mean square (FxLMS) adaptive algorithm. The filter-x least mean square (FxLMS) adaptive algorithm includes the following steps: pick up the reference signal x(n) through the road noise reference sensor, generate the filter-x signal x'(n) through the secondary path model, the reference signal x(n) generates the secondary signal y(n) through the adaptive filter W(n) to drive the noise cancellation speaker, the anti-phase noise response generated by the noise cancellation speaker passes through the secondary path h(n) in the space and is superimposed with the primary road noise field d(n), and the error signal e(n) is obtained through the error microphone as the feedback input of the system. The LMS algorithm performs iterative operations and continuously adjusts the adaptive filter W(n), so that the mean square error is continuously reduced and the adaptive process converges. However, it is not limited to this. In other embodiments, other adaptive algorithms can be used to implement the hybrid feedback adaptive active noise cancellation algorithm according to actual usage requirements. The adaptive active noise reduction algorithm adopted by the present invention adds a VAD speech detection module. When it detects that the passenger is speaking, the updating of the adaptive filter coefficient is suspended, so that the road noise elimination effect is not disturbed by the speaking sound.

[0079] Working principle:

[0080] The present invention is composed of several parts, a road noise sensor unit, one or more inverted noise cancellation speakers, one or more error microphones, an active noise cancellation ANC (Active Noise Cancellation) circuit, and a noise cancellation speaker driving amplifier circuit. The active road noise reduction method of the present invention is different from the previous distributed active road noise cancellation RNC (Road Noise Cancellation) method. The entire active road noise reduction system of the present invention is completely and independently placed in the car seat 4, or near the seat. No complicated in-car wiring and long-distance signal transmission are required. This active noise reduction system includes a road noise source signal sensor 7 placed at the bottom of the car seat, an inverted noise cancellation speaker placed near the headrest 1 of the car seat 4, an error microphone placed at the ear of the headrest 1 of the car seat 4, and an active noise reduction signal processing controller and speaker amplifier circuits. This circuit controller is often located at the bottom of the car seat together with the road noise sensor.

[0081] The microphone or sensor at the bottom of the car seat picks up the road noise of the car. The signal passes through the active road noise reduction system to generate an inverted road noise signal, which is played out through the noise reduction speaker near the headrest 1 to cancel the road noise transmitted to the head through the air. The residual noise in the noise reduction area near the headrest 1 is picked up by the error microphone placed near the headrest 1. This error signal is passed to the adaptive algorithm, which automatically adjusts the parameters of the active noise reduction system to adjust the inverted noise pressure played by the noise reduction speaker to minimize the signal detected by the error microphone. Such an active road noise reduction system can generate a local noise reduction quiet area in a limited space at the head position of the person in the car seat 4, greatly reducing the road noise heard by the person in the seat.

[0082] The present invention abandons the acceleration sensor and uses the road noise microphone as the road noise source signal sensor, which is placed in the car cabin near the chassis and not easily touched or blown by the air conditioner. In this way, the vibration collected is not the vibration outside the car or the body structure, but the road noise signal transmitted into the car. In this way, the collected road noise signal is more correlated with the road noise heard by the occupants. Therefore, the bottom of the seat is an ideal place to place the sensor and collect road noise. At the same time, because the road noise signal collection microphone is closer to the chassis and farther away from the inverted speaker of the occupant's head, it is less disturbed by the inverted signal of the speaker, and it is not easy to form howling and instability interference caused by signal coupling. Therefore, collecting road noise signals at the bottom of the seat is a more suitable position. After the road noise signal is collected, it must be pre-processed by a DC isolation circuit and a low-pass filter. The typical bandwidth of the formed road noise signal is between 5Hz and 500Hz. This is the main energy frequency band of the road noise signal. Under the seat is also a good place to place the active noise reduction circuit board and the power amplifier. The noise reduction circuit and the road noise microphone or the road noise sensor can be made in a box.

[0083] The road noise source signal is collected from the place where the road noise near the chassis is transmitted to the cockpit. It has a high correlation with the road noise heard by the occupants and can achieve a good noise reduction effect. The traditional RNC method uses road noise collected from the mechanical vibration above the wheels outside the car, which is not highly correlated with the noise in the cockpit. This is the main reason for its poor noise reduction performance. Because the noise is reduced in the local space of the occupant's head, it is easier to generate a local space with better noise reduction effect. Because the space inside the car is relatively large, it is difficult to actively reduce noise at all spatial points in a large space through an anti-phase sound source, and the sound field of the active noise reduction speaker in a large space is also difficult to control. Therefore, the method of active noise reduction in the sound field in a large space is a matter of twice the result with half the effort.

[0084] Furthermore, the road noise active noise reduction car seat and the noise reduction method thereof of the present application are not only applicable to cars, but also to situations where the main noise of trains, high-speed railways, etc. comes from the noise of the bottom wheels and rails of the car.

[0085] Based on the ideal embodiment of the present invention, through the above description, relevant personnel can make various changes and modifications without departing from the technical concept of the present invention. The technical scope of the present invention is not limited to the content in the specification, and the technical scope must be determined according to the scope of the claims.

Claims

1. A road noise active noise reduction car seat, characterized in that: An active road noise reduction system is provided in a car seat, the active road noise reduction system comprising: an active noise reduction signal processing controller, and a road noise source signal sensor, an inverted noise cancellation speaker and / or an inverted low-frequency vibrator, an error microphone, and a power amplifier circuit connected to the active noise reduction signal processing controller; The road noise source signal sensor is arranged at the bottom of the car seat inside the car or on the frame below the car seat, and is used to collect the road noise signal and feed it back to the active noise reduction signal processing controller; An inverted noise cancelling speaker is arranged on or near the headrest of the car seat to provide an inverted road noise signal; and / or an inverted low-frequency vibrator is arranged on or near the headrest, and the active noise reduction signal processing controller is connected to the inverted noise cancelling speaker and / or the inverted low-frequency vibrator through the power amplifier circuit to provide an inverted road noise signal; The error microphone is arranged on or near the headrest of the car seat, and is used to obtain the ambient noise near the headrest and feed it back to the active noise reduction signal processing controller; The inverted noise cancelling speaker comprises a pair of left ear inverted noise cancelling speaker and right ear inverted noise cancelling speaker which are arranged on the headrest opposite to each other; Or, the inverting noise cancelling speaker comprises a left ear inverting noise cancelling speaker and a right ear inverting noise cancelling speaker which are arranged inside the roof and above the headrest; Or, the inverted noise cancelling speaker comprises a left ear inverted noise cancelling speaker and a right ear inverted noise cancelling speaker arranged above the seat back and close to the headrest; The left ear inverted noise cancellation speaker and the left ear error microphone in the inverted noise cancellation speaker, and the right ear inverted noise cancellation speaker and the right ear error microphone in the inverted noise cancellation speaker are respectively connected to the active noise reduction signal processing controller to form two independent noise control loops.

2. The road noise active noise reduction car seat according to claim 1, characterized in that: The anti-phase low-frequency vibrator is arranged inside the headrest or above the seat back near the headrest; or, the anti-phase low-frequency vibrator is arranged inside the roof and above the headrest.

3. The road noise active noise reduction car seat according to claim 1, characterized in that: The road noise source signal sensor adopts a noise capture microphone and / or a vibration sensor.

4. The road noise active noise reduction car seat according to claim 1, characterized in that: The error microphone is arranged on the headrest of the car seat close to the ear; or, the error microphone is arranged above the back of the car seat and close to the headrest; or, the error microphone is arranged inside the roof and above the headrest; The anti-phase low-frequency vibrator and the error microphone are connected to an active noise reduction signal processing controller to form a noise control loop.

5. The road noise active noise reduction car seat according to claim 1, characterized in that: The error microphone includes a group of left-ear error microphones and right-ear error microphones relatively arranged on the headrest of the car seat, which are used to obtain the environmental noise on both sides of the headrest near the passenger's ear canal and feed it back to the active noise reduction signal processing controller; or, the error microphone includes a group of left-ear error microphones and right-ear error microphones relatively arranged above the back of the car seat and close to the headrest, which are used to obtain the environmental noise on both sides of the headrest near the passenger's ear canal and feed it back to the active noise reduction signal processing controller; or, the error microphone includes a group of left-ear error microphones and right-ear error microphones relatively arranged inside the roof and above the headrest, which are used to obtain the environmental noise on both sides of the headrest near the passenger's ear canal and feed it back to the active noise reduction signal processing controller.

6. A method for reducing road noise in an active noise reduction vehicle seat, characterized in that: The method is implemented by using a road noise active noise reduction automobile seat as claimed in any one of claims 1 to 5, comprising the following steps: Step 1: The active noise reduction signal processing controller of the active road noise reduction system sends a command to obtain road noise. The road noise source signal sensor located at the bottom of the car seat picks up and feeds back to the active noise reduction signal processing controller. The active noise reduction signal processing controller generates a predicted inverse road noise signal through the feedforward active noise reduction algorithm in the active noise reduction algorithm. Step 2: The active noise reduction signal processing controller sends the predicted inverted road noise signal to the inverted noise cancellation speaker and / or the inverted low-frequency vibrator through the power amplifier circuit, and collects real-time noise information through the error microphone. Through the hybrid feedback adaptive active noise cancellation algorithm, the active road noise reduction control is implemented to suppress the road noise through the inverted noise generated by the secondary channel to achieve noise reduction.

7. The method for reducing road noise in an active noise reduction vehicle seat according to claim 6, characterized in that: The active noise reduction algorithm includes: a feedforward active noise reduction method, a feedback active noise reduction method, or a hybrid feedback active noise reduction method; The feedforward active noise cancellation method includes: a noise capture microphone and / or a vibration sensor is arranged at the bottom of the car seat, and a noise signal obtained by the noise capture microphone and / or the vibration sensor is mapped to a noise frequency response through a digital signal processor and / or an analog signal processor and a linear filter circuit in an active noise reduction signal processing controller, and then the inverted road noise signal is driven by the active noise reduction signal processing controller to broadcast the inverted noise signal through an inverted noise cancellation speaker and / or an inverted low-frequency vibrator on the headrest of the car seat or outside the headrest of the car seat to offset the sound wave vibration of the car road noise; Or, the feedback active noise cancellation method includes: an error microphone is placed on the headrest or on the periphery of the headrest to extract the car noise caused by road noise; the feedback active noise cancellation method uses a digital signal processor and / or an analog signal processor in an active noise reduction signal processing controller and a linear filter circuit to drive the anti-phase noise signal to broadcast through an anti-phase noise cancellation speaker and / or an anti-phase low-frequency vibrator to offset the sound wave vibration of the car road noise; Alternatively, a hybrid feedback active noise cancellation method uses a feedforward active noise cancellation method and a feedback active noise cancellation method that cooperate with each other. The digital signal processor and / or analog signal processor and the linear filter circuit in the active noise reduction signal processing controller map the noise signal to the actual noise frequency response, and then drive the anti-phase noise cancellation speaker and / or the anti-phase low-frequency vibrator to broadcast the anti-phase noise signal to offset the sound wave vibration of the car road noise; a noise capture microphone and / or a vibration sensor at the bottom of the seat is used to monitor the road noise signal, and another error microphone is used to monitor the error signal of the noise cancellation effect at any time, and these two signals are used to adaptively adjust the active noise reduction filter circuit.

8. The method for reducing road noise in an active noise reduction vehicle seat according to claim 7, characterized in that: The active noise reduction algorithm also includes: a VAD module for speech detection; when an occupant on a car seat speaks, the speech signal detected by a close error microphone is much larger than the speech signal detected by a noise capture microphone at the bottom of the car seat; the occupant's speech is detected by the energy ratio of the two microphone signals of the noise capture microphone and the error microphone; when it is detected that the occupant is speaking, the adaptive process of the hybrid feedback adaptive active noise cancellation algorithm is stopped, and at this time, the response function of the feedforward signal of the feedforward active noise cancellation method is temporarily fixed and stops updating until it is detected that the occupant stops speaking, and then the adaptive process of the hybrid feedback adaptive active noise cancellation algorithm resumes updating.

9. A method for reducing road noise in an active noise reduction vehicle seat according to claim 8, characterized in that: The hybrid feedback adaptive active noise cancellation algorithm includes: a filter-x minimum mean square root adaptive algorithm, including the following steps: The reference signal x(n) is picked up by the road noise reference sensor, and the filtered signal x'(n) is generated through the secondary path model. The reference signal x(n) generates a secondary signal y(n) through the adaptive filter W(n) to drive the noise cancellation speaker. The anti-phase noise response generated by the noise cancellation speaker passes through the secondary path h(n) in the space and is superimposed on the primary road noise field d(n). The error signal e(n) is obtained through the error microphone as the feedback input of the system. The LMS algorithm performs iterative calculations and continuously adjusts the adaptive filter W(n), so that the mean square error continues to decrease and the adaptive process converges.

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