Active road noise reduction automobile seat and noise reduction method thereof

Abstract

Disclosed in the present invention discloses are an active road noise reduction automobile seat and a noise reduction method thereof. The active road noise reduction automobile seat comprises an active road noise reduction system provided in an automobile seat, the active road noise reduction system comprising: an active noise reduction signal processing controller, a road noise source signal sensor connected to the active noise reduction signal processing controller, an anti-phase noise cancellation speaker, an anti-phase low-frequency vibrator, an error microphone and a power amplifier circuit; the road noise source signal sensor is arranged at the bottom of the automobile seat, and is configured to acquire a road noise signal; the anti-phase noise cancellation speaker and the anti-phase low-frequency vibrator are arranged on or near a headrest of the automobile seat, and are configured to provide anti-phase road noise signals; and the error microphone is arranged on or near the headrest of the automobile seat, and is configured to acquire ambient noise near the headrest. Disclosed in the present invention are the active road noise reduction automobile seat and the noise reduction method thereof. By means of the active noise reduction method, road noise conducted into automobiles by means of automobile chassis is reduced.

Description

A road noise active noise reduction car seat and its noise reduction method Technical Field

[0001] This invention relates to the field of noise reduction technology, and in particular to an active road noise reduction car seat and its noise reduction method. Background Technology

[0002] In recent years, active noise cancellation technology has been widely used in closed-back headphones. These headphones typically form a small, tightly sealed space with the ear or ear canal, playing a sound signal that is inversely phase to the noise signal through a speaker, thus canceling out the ambient noise and achieving noise reduction. This is active noise cancellation technology. Active noise cancellation technology has also been applied to a limited extent in car cabins, but it is not very effective for reducing noise in the larger spaces of a vehicle. Active noise cancellation technology in cars relies on signal acquisition from key noise sources, such as placing a microphone near the engine, and then playing inversely phased noise through the car's speakers to reduce noise from specific sources. The same method is applied to eliminate several major noise sources in a car, such as exhaust pipes and air conditioning vents.

[0003] The noise sources in traditional gasoline or diesel vehicles are quite complex. The main sources include engine noise, exhaust pipe noise, engine air intake noise, air conditioning vent noise, wind noise, and road noise. In particular, the noise generated by the friction between the car tires and the road surface is transmitted through the four-wheel shock absorbers to the car chassis, and then from the chassis into the car's interior. This is what is known as road noise. Because this road noise is predominantly low-frequency, it is difficult to block by the passive sound insulation materials designed into the car. Therefore, most of it still reaches the car's interior, and at a considerable volume. Although this low-frequency noise is not as harsh as mid-to-high-frequency noise, its volume is much louder, creating a booming sound. Drivers may become accustomed to this low-frequency road noise and ignore its potential damage to hearing and health.

[0004] However, the fastest-growing segment is currently new energy vehicles, most of which are electric vehicles. Electric vehicles lack engines, exhaust pipes, and air intakes, and their electric motors are very quiet, thus significantly reducing vehicle noise. For electric vehicles, road noise caused by tire-road friction becomes the primary noise source. The second source is wind noise. Road noise and wind noise are the main sources of noise in electric vehicles. Low-frequency road noise from the vehicle chassis is difficult to isolate through materials and design.

[0005] Therefore, there is a need to develop a method for active road noise reduction, especially for occupants in car seats. This method aims to reduce the road noise perceived by occupants as transmitted into the car through the chassis, including friction noise generated by tires and the road surface. Summary of the Invention

[0006] This invention overcomes the shortcomings of the prior art and provides a road noise active noise reduction car seat and its noise reduction method. By actively reducing noise, the occupants reduce their perception of road noise transmitted into the car through the car chassis.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: an active road noise reduction car seat, including an active road noise reduction system installed in the car seat, the active road noise reduction system including: an active noise reduction signal processing controller, and a road noise source signal sensor, an anti-phase noise cancellation horn and / or an anti-phase low-frequency vibrator, an error microphone, and a power amplifier circuit connected to the active noise reduction signal processing controller;

[0008] The road noise source signal sensor is installed at the bottom of the car seat or on the frame below the car seat to collect road noise signals and feed them back to the active noise cancellation signal processing controller.

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

[0010] The error microphone is positioned on or near the headrest of the car seat to acquire ambient noise in the vicinity of the headrest and feed it back to the active noise cancellation signal processing controller.

[0011] In a preferred embodiment of the present invention, the anti-phase low-frequency vibrator is disposed inside the headrest or above the seat back near the headrest; or, the anti-phase low-frequency vibrator is disposed 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 phase-reversing noise cancellation speaker includes a pair of left-ear phase-reversing noise cancellation speakers and a right-ear phase-reversing noise cancellation speaker disposed opposite to each other on the headrest;

[0014] Alternatively, the anti-phase noise cancellation horn includes a left-ear anti-phase noise cancellation horn and a right-ear anti-phase noise cancellation horn installed inside the roof and above the headrest;

[0015] Alternatively, the anti-phase noise cancellation speaker includes a left-ear anti-phase noise cancellation speaker and a right-ear anti-phase noise cancellation speaker located above the seat back and near the headrest.

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

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

[0018] In a preferred embodiment of the present invention, the error microphone includes a set of left-ear and right-ear error microphones disposed opposite each other on the headrest of the car seat, for acquiring ambient noise on both sides of the headrest near the passenger's ear canal and feeding it back to the active noise cancellation signal processing controller; or, the error microphone includes a set of left-ear and right-ear error microphones disposed opposite each other above the back of the car seat and near the headrest, for acquiring ambient noise on both sides of the headrest near the passenger's ear canal and feeding it back to the active noise cancellation signal processing controller; or, the error microphone includes a set of left-ear and right-ear error microphones disposed opposite each other inside the roof and above the headrest, for acquiring ambient noise on both sides of the headrest near the passenger's ear canal and feeding it back to the active noise cancellation signal processing controller.

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

[0020] In a preferred embodiment of the present invention, a noise reduction method for an active road noise cancellation car seat is implemented using an active road noise cancellation car seat, comprising the following steps:

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

[0022] Step 2: The active noise cancellation signal processing controller predicts the inverted road noise signal and sends it to the inverted noise cancellation speaker and / or inverted low-frequency vibrator through the power amplifier circuit. It also collects real-time noise information through the error microphone and realizes active road noise control by using the inverted noise generated by the secondary channel to suppress road noise and 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 vibration sensor are installed at the bottom of the car seat; the noise signal acquired by the noise capture microphone and / or vibration sensor is mapped to the noise frequency response by a digital signal processor and / or analog signal processor and a linear filter circuit in the active noise cancellation signal processing controller; and the inverted road noise signal is driven by an inverted noise cancellation speaker and / or inverted low-frequency vibrator on or around the headrest of the car seat to cancel the sound wave vibration of the car road noise.

[0025] Alternatively, the feedback active noise cancellation method includes: placing an error microphone on or around the headrest to extract vehicle noise caused by road noise; the feedback active noise cancellation method uses a digital signal processor and / or analog signal processor in the active noise cancellation signal processing controller and a linear filter circuit to drive the inverted noise signal through an inverted noise cancellation speaker and / or an inverted low-frequency vibrator to cancel the sound wave vibration of vehicle road noise.

[0026] Alternatively, the hybrid feedback active noise cancellation method employs a combination of feedforward active noise cancellation and feedback active noise cancellation. The digital signal processor and / or analog signal processor in the active noise cancellation signal processing controller, along with the linear filter circuit, maps the noise signal to the actual generated noise frequency response. Then, an inverted noise cancellation horn and / or an inverted low-frequency vibrator drive the playback of an inverted noise signal to cancel out the acoustic vibration of the vehicle road noise. A noise-capturing microphone and / or vibration sensor under the seat are used to monitor the road noise signal, while another error microphone continuously monitors the error signal of the noise cancellation effect. These two signals are used to adaptively adjust the active noise cancellation filter circuit.

[0027] In a preferred embodiment of the present invention, the active noise reduction algorithm further includes: a VAD module for speech detection; when an occupant in the car seat speaks, the speech signal detected by the nearby error microphone is much greater 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 the occupant is detected speaking, the adaptive process of the hybrid feedback adaptive active noise reduction algorithm is stopped, and at this time the response function of the feedforward signal of the feedforward active noise reduction method is temporarily fixed and stops updating until the occupant stops speaking, and then the adaptive process of the hybrid feedback adaptive active noise reduction 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 root (FxLMS) adaptive algorithm, comprising the following steps:

[0029] A reference signal x(n) is picked up by a road noise reference sensor. A filter-x signal x'(n) is generated by a secondary path model. The reference signal x(n) is passed through an adaptive filter W(n) to generate a secondary signal y(n) which drives a noise-canceling speaker. The inverse noise response generated by the noise-canceling speaker is superimposed on the primary road noise field d(n) after passing through a secondary path h(n) in space. The error signal e(n) is obtained by an error microphone and used 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 is continuously reduced, and the adaptive process converges.

[0030] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0031] This invention discloses an active road noise reduction car seat and its noise reduction method, which reduces road noise transmitted into the car through the car chassis by active noise reduction.

[0032] 1. Current active road noise cancellation systems (RNC) can only reduce limited road noise (3dB+) under low-speed conditions. At high speeds, they cannot achieve a perceptible noise reduction effect. The active road noise cancellation method of this invention achieves significant road noise reduction effects under both low-speed and high-speed conditions, with a noise reduction effect exceeding 10dB.

[0033] 2. Eliminate noise pollution inside the vehicle, specifically the largest sources of automotive noise: road noise and tire noise. This invention has a wide bandwidth for road noise reduction, making it suitable for eliminating low-to-mid-frequency road noise with the highest energy in the cabin, thus improving the intelligibility of conversations within the cabin.

[0034] 3. This invention eliminates the need for distributed sensor placement and automotive wiring. All components of this invention can be located within the car seat. This stand-alone product design leads to simpler implementation, lower costs, and greater flexibility. In particular, the elimination of complex and lengthy automotive wiring and expensive A2B audio communication chips is highly significant.

[0035] 4. This invention is suitable for use in both traditional gasoline vehicles and new energy electric vehicles. New energy vehicles have ample power and widely distributed batteries. The active road noise cancellation system of this invention is input via a power line, making installation, debugging, and testing very convenient. Attached Figure Description

[0036] The present invention will be further described below with reference to the accompanying drawings and embodiments.

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

[0038] Figure 2 is a signal processing flowchart of a road noise source signal sensor in an active road noise reduction car seat according to the present invention, which uses a noise capture microphone.

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

[0040] Figure 4 is a signal processing flowchart of an active road noise reduction car seat according to the present invention, in which the anti-phase road noise signal is split into two signals by a frequency division filter and transmitted to an anti-phase low-frequency vibrator and an anti-phase noise reduction horn.

[0041] Figure 5 is a structural schematic diagram of a road noise active noise reduction car seat according to the present invention (using an anti-phase low-frequency vibrator and an anti-phase noise reduction horn);

[0042] Figure 6 is a general framework diagram of a road noise active noise reduction car seat system according to the present invention (inverting noise cancellation speaker);

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

[0044] Figure 8 is a schematic diagram of the hybrid feedback adaptive active noise cancellation algorithm and VAD module of a road noise active noise cancellation car seat according to the present invention.

[0045] Figure 9 is a schematic diagram of a road noise active noise reduction car seat structure according to 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 backrest, 21-left side of shoulder backrest, 22-middle part of shoulder backrest, 23-right side of shoulder backrest, 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, 7-road noise source signal sensor, 8-inverting low-frequency vibrator, 82-left ear inverting noise cancellation speaker, 83-right ear inverting noise cancellation speaker, 91-left ear error microphone, 92-right ear error microphone. Detailed Implementation

[0047] The technical solution of the present invention will be described in detail below with reference to 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 thereof. In the absence of conflict, the embodiments of the present invention and the technical features in the embodiments can be combined with each other.

[0048] The term "and / or" simply describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. Additionally, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0049] Existing active road noise cancellation technology places a triaxial accelerometer on the vehicle body above the tires to pick up vibration signals caused by road noise. The inverse signal of this accelerometer is then played through the car audio speakers to produce inverse noise, which is used to cancel out noise inside the car cabin. Simultaneously, an error microphone is placed near the occupant's ear to monitor the noise cancellation effect and adjust the amplitude and phase of the played inverse noise as needed to achieve optimal reduction of road noise inside the cabin. However, due to the large size of the car interior and the varying noise levels at different points, it is difficult to completely eliminate noise using active noise cancellation methods.

[0050] Firstly, because the correlation between in-car noise and vibration signals above the wheels is not high, existing RNC active road noise cancellation technology is not very efficient at canceling road noise. Secondly, due to cost issues, RNC systems often share speakers with car audio systems. Since car speakers are relatively far from the error microphone, the power requirement for dissipating out-of-phase noise is relatively high, resulting in low noise cancellation efficiency and a tendency to generate unstable howling.

[0051] Furthermore, this distributed RNC active noise cancellation method requires the placement of different sensors, microphones, and speakers in various locations within the vehicle. The lengthy signal cabling and expensive A2B signal transmission chips increase signal latency and cost. Additionally, existing RNC active noise reduction algorithms are complex, requiring expensive, high-performance signal processing chips, but the noise reduction dB is limited, and the convergence time is too long. The result is a lot of effort for little gain.

[0052] This invention addresses these characteristics of automotive road noise by proposing a novel active road noise reduction (RNC) method. The aim is to overcome the various shortcomings of existing RNC methods, achieving better noise reduction, faster convergence, more stable performance, more targeted components, a more rational system layout, and lower overall cost.

[0053] Example 1

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

[0055] Specifically, the road noise source signal sensor 7 is installed at the bottom 41 of the car seat 4 inside the vehicle, or on the frame 5 below the car seat 4 inside the vehicle, for collecting road noise signals and feeding them back to the active noise cancellation signal processing controller. Further, in this embodiment, the road noise source signal sensor 7 is installed at the bottom 41 of the car seat 4. Moreover, the road noise source signal sensor 7 uses a noise-capturing microphone and / or a vibration sensor. In this embodiment, a noise-capturing microphone is used.

[0056] Specifically, the anti-phase low-frequency vibrator 8 is disposed 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 disposed at the middle 12 of the headrest 1. The active noise cancellation signal processing controller is connected to the anti-phase low-frequency vibrator 8 through a 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 disposed inside the headrest 1 or above the seat back near the headrest 1.

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

[0058] Specifically, a single error microphone is used, positioned on the headrest 1 of the car seat 4 near the ear. In this embodiment, a set of two error microphones, a left-ear error microphone 91 and a right-ear error microphone 92, are positioned opposite each other on the headrest 1 of the car seat 4 to acquire ambient noise near the passenger's ear canal on both sides of the headrest 1 and feed it back to the active noise cancellation signal processing controller. Furthermore, a noise control loop is formed by connecting the anti-phase low-frequency vibrator 8 and any one of the error microphones to the active noise cancellation signal processing controller.

[0059] Example 2

[0060] As shown in Figure 1, the present invention discloses an active road noise reduction car seat, including an active road noise reduction system installed in the car seat 4. The active road noise reduction system includes: an active noise reduction signal processing controller, and a road noise source signal sensor 7, an anti-phase noise cancellation speaker, an error microphone, and a power amplifier circuit connected to the active noise reduction signal processing controller.

[0061] Specifically, the road noise source signal sensor 7 is installed at the bottom 41 of the car seat 4 inside the car to collect road noise signals and feed them back to the active noise cancellation signal processing controller. In this embodiment, the road noise source signal sensor 7 is a noise capture microphone.

[0062] Specifically, the phase-reversing noise cancellation horn is located in the headrest 1. The active noise cancellation signal processing controller is connected to the phase-reversing noise cancellation horn via a power amplifier circuit to provide phase-reversed road noise signals. Further, the phase-reversing noise cancellation horn includes a pair of left-ear phase-reversing noise cancellation horns 82 and 83, respectively, positioned opposite each other on the headrest 1; or, the phase-reversing noise cancellation horn includes a left-ear phase-reversing noise cancellation horn 82 and 83, respectively, positioned inside the roof and above the headrest 1. Further, the phase-reversing noise cancellation horn employs a pair of low-delay bass left-ear phase-reversing noise cancellation horns 82 and 83, placed near the ears on the headrest 1 of the car seat 4. The right-ear phase-reversing noise cancellation horn 83, positioned near the right ear, outputs phase-reversed noise to create a noise-canceling quiet zone in the right ear; the other left-ear phase-reversing noise cancellation horn 82, positioned near the left ear, outputs phase-reversed noise to create a noise-canceling quiet zone in the left ear. Specifically, the placement of the phase-reversing noise cancellation horn can vary. It can be located at the top, middle, or bottom of the headrest 1, or at the top of the seat back adjacent to the headrest 1. It can even be located on the roof 6 above the seat (including the left side 61, the middle 62, and the right side 63 of the roof 6). When using a single anti-phase noise-canceling horn, it can be positioned at the middle 62 of the roof 6. When using a pair of left-ear anti-phase noise-canceling horns 82 and right-ear anti-phase noise-canceling horns 83, the left-ear anti-phase noise-canceling horns 82 and right-ear anti-phase noise-canceling horns 83 can be installed at the left side 61 and right side 63 of the roof 63, respectively. It can be located as close to the occupant's head as well as the location of the error microphone.

[0063] Specifically, the error microphones are positioned on or near the headrest 1 of the car seat 4 to acquire ambient noise in the vicinity of the headrest 1 and feed it back to the active noise cancellation signal processing controller. Further, the error microphones include at least one set of left-ear error microphone 91 and right-ear error microphone 92 positioned opposite each other on the headrest 1 of the car seat 4; alternatively, the left-ear error microphone 91 and right-ear error microphone 92 can also be positioned on the left side 21 and right side 23 of the shoulder rest 2 of the car seat 4, respectively. The left-ear error microphone 91 and right-ear error microphone 92 are used to acquire ambient noise near the passenger's ear canals on both sides of the headrest 1 and feed it back to the active noise cancellation signal processing controller; the left-ear anti-phase noise cancellation speaker 82 and the left-ear error microphone 91, and the right-ear anti-phase noise cancellation speaker 83 and the right-ear error microphone 92 are respectively connected to the active noise cancellation signal processing controller to form two independent noise control loops.

[0064] Example 3

[0065] As shown in Figure 5, the present invention discloses an active road noise reduction car seat, including an active road noise reduction system installed in the car seat 4. The active road noise reduction system includes: an active noise reduction signal processing controller, and a road noise source signal sensor 7, an anti-phase noise cancellation horn and an anti-phase low-frequency vibrator 8, an error microphone, and a power amplifier circuit connected to the active noise reduction signal processing controller.

[0066] Specifically, the road noise source signal sensor 7 is installed at the bottom 41 of the car seat 4 inside the vehicle to collect road noise signals and feed them back to the active noise cancellation signal processing controller. Furthermore, the road noise source signal sensor 7 employs a noise-capturing microphone and / or a vibration sensor. In this embodiment, the road noise source signal sensor 7 employs a noise-capturing microphone.

[0067] Specifically, the anti-phase noise cancellation horn and the anti-phase low-frequency vibrator 8 are disposed on or near the headrest 1 of the car seat 4 to provide anti-phase road noise signals. The anti-phase low-frequency vibrator 8 is disposed on the headrest 1. Specifically, the anti-phase low-frequency vibrator 8 is disposed inside the headrest 1, or above the seat back near the headrest 1. The anti-phase noise cancellation horn is disposed on the headrest 1 or inside the roof and above the headrest 1. Further, the anti-phase noise cancellation horn includes a pair of left-ear anti-phase noise cancellation horns 82 and right-ear anti-phase noise cancellation horns 83, disposed opposite each other on the left side 11 and right side 13 of the headrest 1; or, the anti-phase noise cancellation horn includes a left-ear anti-phase noise cancellation horn 82 and a right-ear anti-phase noise cancellation horn 83 disposed inside the roof and above the headrest 1. The active noise cancellation signal processing controller is connected to the left ear anti-phase noise cancellation speaker 82 and the right ear anti-phase noise cancellation speaker 83, as well as the anti-phase low-frequency vibrator 8, through several power amplifier circuits to provide anti-phase road noise signals. Further, three anti-phase sound-generating devices (left ear anti-phase noise cancellation speaker 82, right ear anti-phase noise cancellation speaker 83, and anti-phase low-frequency vibrator 8) are located on the left and right sides of the headrest 1, with an anti-phase low-frequency vibrator 8 in the middle. The anti-phase road noise signal is split into two signals by a frequency divider filter. One signal, a sub-bass signal below 100Hz, is driven by a low-frequency power amplifier to power the anti-phase low-frequency vibrator 8 located in the middle of the headrest 1. The other signal, a bass signal above 100Hz, is driven by a bass power amplifier to power the bass speaker on the left or right side of the headrest 1. In this embodiment, 100Hz is just one example; other similar frequencies are also possible. This invention provides three different embodiments, in which one, two, and three sound-generating devices are installed near the headrest 1, respectively. At least one of these sound-generating devices is a reverse-phase low-frequency vibrator 8.

[0068] Specifically, the error microphones are positioned on or near the headrest 1 of the car seat 4 to acquire ambient noise in the vicinity of the headrest 1 and feed it back to the active noise cancellation signal processing controller. The error microphones include at least one set of left-ear error microphone 91 and right-ear error microphone 92 positioned opposite each other on the headrest 1 of the car seat 4; or, the left-ear error microphone 91 and right-ear error microphone 92 can also be positioned on the left side 21 and right side 23 of the shoulder rest 2 of the car seat 4, respectively. The left-ear error microphone 91 and right-ear error microphone 92 are used to acquire ambient noise near the passenger's ear canals on both sides of the headrest 1 and feed it back to the active noise cancellation signal processing controller; the left-ear anti-phase noise cancellation speaker 82 and the left-ear error microphone 91, and the right-ear anti-phase noise cancellation speaker 83 and the right-ear error microphone 92 are respectively connected to the active noise cancellation signal processing controller to form two independent noise control loops.

[0069] Furthermore, a pair of left-ear error microphones 91 and right-ear error microphones 92 are placed near the ears on the headrest 1. The right-ear error microphone 92 is placed near the right ear to pick up residual noise in the right ear area after noise cancellation, while the left-ear error microphone 91 is placed near the left ear to pick up residual noise in the left ear area after noise cancellation. The specific positions of the error microphones can vary, but they are all in the same area as the noise-canceling speaker. The error microphones can be located at the top, middle, or bottom of the headrest 1, or at the top of the seat back adjacent to the headrest 1. They can even be located on the roof above the seat, as long as they are close to the occupant's head. The relative position of the error microphones and the noise-canceling speaker can be above the noise-canceling speaker, below the noise-canceling speaker, or side by side with the noise-canceling speaker. The optimal position for the error microphones is as close to the occupant's ears as possible. The two error microphones are distributed near the left and right ears respectively. The error microphones of this invention can also be a single microphone. Unlike the separate error microphones for the left and right ears, a single error microphone only needs to be close to the head to pick up residual noise after noise cancellation in the head area. The error microphone, like the inverting noise cancellation speaker or vibrator, is located near the head of the seat, within a similar noise cancellation area. The signal processing method for the error microphone is also similar to that of the road noise acquisition microphone.

[0070] Each seat features two sets of noise-canceling speakers and error microphones, sharing a single road noise source signal. This creates two localized noise-canceling quiet zones around each ear, resulting in more precise noise cancellation. Because the noise-canceling speakers do not reuse the car's existing speakers but are installed independently in the headrest 1, it allows for optimized performance selection. Furthermore, due to their proximity to the occupant's head, a high-power amplifier is unnecessary. Active noise cancellation operates locally, minimizing the risk of interference and coupling, which could lead to feedback or other unstable conditions. The speakers and error microphones, which output inverted sound waves, are located near the head, facilitating the creation of a localized noise-canceling quiet bubble around the driver's or passenger's head. This avoids the challenges of active noise cancellation in large spaces and reduces the implementation complexity of active road noise cancellation systems. The entire active noise cancellation system can be independently placed within the car seat 4, eliminating complex long wiring within the vehicle, reducing the need for expensive A2B audio communication chips, and lowering costs while increasing flexibility.

[0071] Example 4

[0072] A noise reduction method for an active road noise cancellation car seat, implemented using an active road noise cancellation car seat as described in Example 1, includes the following steps:

[0073] Step 1: The active noise reduction signal processing controller of the active road noise reduction system sends a command to acquire road noise. 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.

[0074] Step 2: The active noise reduction signal processing controller sends the predicted inverted road noise signal to the inverted noise reduction speaker and / or the inverted low-frequency vibrator 8, and collects real-time noise information through the error microphone. Through the hybrid feedback adaptive active noise reduction algorithm, active road noise reduction control is achieved by suppressing road noise through the inverted noise generated by the secondary channel, thereby achieving noise reduction.

[0075] Furthermore, a road noise source signal sensor 7 located at the bottom 41 of the car seat 4 acquires road noise signals from the vicinity of the car chassis and splits them into two paths. One path generates an anti-noise signal with the opposite phase to the road noise signal on the right side of the head through a right-side inverting filter. This anti-noise signal is then emitted by a noise-canceling speaker on the right side of the headrest 1, canceling out the road noise transmitted through the air to the right side of the head, thus creating a noise-canceling quiet area near the occupant's right ear. Simultaneously, an error microphone near the right ear picks up the residual noise after denoising and feeds it back into an adaptive active noise reduction algorithm, automatically adjusting the coefficients of the inverting noise reduction filter to minimize the residual noise after denoising. The basic active noise reduction algorithm can employ the FxLMS adaptive hybrid feedback active noise reduction method, or other algorithms such as the FxAP affine projection active noise reduction algorithm or corresponding algorithms in the frequency domain. Simultaneously, 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 inverting filter. This anti-phase sound wave is then emitted by the noise-canceling speaker on the left side of the seat headrest 1, canceling out the road noise transmitted through the air to the left side of the head, creating a noise-canceling quiet zone near the occupant's left ear. 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, which automatically adjusts the coefficient of the inverting noise cancellation filter to minimize the residual noise after noise cancellation.

[0076] Furthermore, the active noise cancellation algorithm includes a hybrid feedback active noise cancellation method, comprising feedforward active noise cancellation and feedback active noise cancellation. The digital signal processor and / or analog signal processor in the active noise cancellation signal processing controller, along with a linear filtering circuit, map the noise signal to the actual generated noise frequency response. Then, an inverted noise cancellation horn and / or an inverted low-frequency vibrator drive the output of an inverted noise signal to cancel the acoustic vibrations of road noise. It uses a noise-capturing microphone and / or vibration sensor under the seat to monitor road noise signals, while simultaneously using another error microphone to continuously monitor the error signal of the noise cancellation effect. These two signals are used to adaptively adjust the active noise cancellation filtering circuit to achieve the best noise cancellation effect.

[0077] In the feedforward active noise cancellation method, a noise-capturing microphone and / or vibration sensor are installed at the bottom of the car seat 4. A digital signal processor and / or analog signal processor in the active noise cancellation signal processing controller, along with a linear filtering circuit, maps the noise signal acquired by the noise-capturing microphone and / or vibration sensor to a noise frequency response. The active noise cancellation signal processing controller then drives an inverted noise signal, which is then emitted through an inverted noise-canceling speaker and / or an inverted low-frequency vibrator 8 located on or around the headrest 1 of the car seat 4, to cancel out the road noise's acoustic vibrations. Furthermore, the linear filtering circuit is automatically adjusted to ensure that this mapping is correctly applied for maximum noise cancellation. The advantage of the feedforward active noise cancellation method is that because there is a temporal causal relationship between the noise source signal and the noise signal, it can simulate the linear system of the noise transmission path, thus achieving better active noise cancellation. However, without adaptive automatic adjustment, changes and disturbances in the acoustic path can easily lead to a deterioration in the noise reduction effect.

[0078] In the feedback active noise cancellation method, which is the opposite of the feedforward active noise cancellation method, the error microphone is placed on or around the headrest 1 to extract the vehicle noise caused by road noise. The feedback active noise cancellation method uses a digital signal processor and / or analog signal processor in the active noise cancellation signal processing controller, along with a linear filter circuit, to drive the inverted noise signal through an inverted noise cancellation horn and / or an inverted low-frequency vibrator 8 to cancel the sound wave vibration of the vehicle road noise. Furthermore, the distance between the error microphone and the noise cancellation horn is very short, resulting in less processing time in the feedback design. The feedback active noise cancellation method is most effective at eliminating low-frequency road noise with longer wavelengths. Because of the delay in the feedback path, the bandwidth for effective noise cancellation is limited, and it can only eliminate low-frequency noise with longer wavelengths.

[0079] Since both the road noise source signal sampling microphone and the error sampling microphone of this invention are located inside the car cabin, in the same space, the anti-phase sound wave emitted by the noise-canceling speaker may be conducted to the road noise sampling microphone under the seat, causing signal coupling. Therefore, the road noise signal collected in this way may be "impure," leading to system instability or even howling. Traditional RNC methods, on the other hand, do not have this signal crosstalk problem because the road noise signal is collected by an accelerometer outside the cabin. To solve this problem, this invention adopts improvements in both acoustics and algorithms to reduce the impact of acoustic signal coupling on the active noise cancellation effect. In terms of acoustic device arrangement, the noise-canceling speaker and the error microphone are placed in a very close space, near the headrest 1. This reduces the power of the anti-phase noise emitted by the noise-canceling speaker, and because the road noise sampling microphone is located under the seat, far from the noise-canceling speaker, the chance of the sound pressure emitted by the noise-canceling speaker feeding back to the road noise microphone is minimal.

[0080] Furthermore, the active noise reduction algorithm also includes: a VAD module for speech detection; when the occupant in car seat 4 speaks, the speech signal detected by the nearby error microphone is much greater than the speech signal detected by the noise capture microphone at the bottom of car seat 4; 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 the occupant is detected speaking, the hybrid feedback adaptive active noise reduction algorithm process is stopped. At this time, the response function of the feedforward signal of the feedforward active noise reduction method is temporarily fixed and stops updating until the occupant stops speaking, and then the hybrid feedback adaptive active noise reduction algorithm process resumes updating.

[0081] Specifically, in this embodiment, the hybrid feedback adaptive active noise cancellation algorithm employs the following algorithm: the Filter-x Least Mean Square (FxLMS) adaptive algorithm. The Filter-x Least Mean Square (FxLMS) adaptive algorithm includes the following steps: a reference signal x(n) is picked up by a road noise reference sensor; a filter-x signal x'(n) is generated through a secondary path model; the reference signal x(n) generates a secondary signal y(n) through an adaptive filter W(n) to drive a noise cancellation speaker; the inverse noise response generated by the noise cancellation speaker is superimposed on the primary road noise field d(n) after passing through a secondary path h(n) in space; the error signal e(n) is obtained through an error microphone as the system's feedback input; the LMS algorithm performs iterative calculations, continuously adjusting the adaptive filter W(n), thereby continuously reducing the mean square error until the adaptive process converges. However, this is not the only limitation; 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 used in this invention adds a VAD (Voice over Action) speech detection module. When a passenger speaks, the adaptive filter coefficients are paused from being updated, so that the noise reduction effect is not disturbed by the speech.

[0082] Working principle:

[0083] This invention comprises several parts: a road noise sensor unit, one or more anti-phase noise-canceling speakers, one or more error microphones, an active noise cancellation (ANC) circuit, and a noise-canceling speaker driver amplifier circuit. The active road noise reduction method of this invention differs from previous distributed active road noise cancellation (RNC) methods. The entire active road noise reduction system of this invention is independently and completely installed in or near the car seat 4. It eliminates the need for complex in-vehicle wiring and long-distance signal transmission. This active noise reduction system includes a road noise source signal sensor 7 located at the bottom of the car seat, an anti-phase noise-canceling speaker located near the headrest 1 of the car seat 4, an error microphone located at the ear of the headrest 1 of the car seat 4, and circuits such as an active noise cancellation signal processing controller and a speaker amplifier. This controller circuit is often located at the bottom of the car seat along with the road noise sensor.

[0084] Microphones or sensors located under the car seat pick up road noise. This signal is processed by an active road noise cancellation system to generate an inverse road noise signal, which is then played through a noise-canceling speaker near headrest 1, canceling out the road noise transmitted to the head through the air. Residual noise in the noise-canceling area near headrest 1 is picked up by an error microphone placed near headrest 1. This error signal is passed to an adaptive algorithm, which automatically adjusts the parameters of the active noise cancellation system to adjust the inverse noise cancellation pressure played by the noise-canceling speaker, minimizing the signal detected by the error microphone. This active road noise cancellation system creates a limited, locally quiet noise-canceling area at the head position of the person in the car seat 4, significantly reducing the road noise heard by the person in the seat.

[0085] This invention abandons the accelerometer sensor and uses a road noise microphone as the road noise source signal sensor, placing it inside the car cabin near the chassis, in a location that is not easily touched or exposed to air conditioning vents. This way, it collects road noise signals transmitted into the vehicle cabin, rather than vibrations from outside the vehicle or its structure. The collected road noise signal has a higher correlation with the road noise heard by the occupants. Therefore, the area under the seat is an ideal location for placing the sensor to collect road noise. Furthermore, because the road noise signal acquisition microphone is closer to the chassis and farther from the horn behind the occupants' heads, it is less susceptible to interference from the horn's inverted signal, reducing the likelihood of howling and instability caused by signal coupling. Therefore, collecting road noise signals under the seat is a suitable location. After the road noise signal is collected, it undergoes preprocessing with a DC blocking circuit and a low-pass filter. The typical bandwidth of the resulting road noise signal is between 5Hz and 500Hz. This is the main energy frequency band of the road noise signal. The area under the seat is also a good location to place the active noise cancellation circuit board and power amplifier. The noise cancellation circuit and the road noise microphone or sensor can be integrated into a single box.

[0086] Road noise sources are collected from inside the vehicle near the chassis, where road noise enters the cabin. This signal has a high correlation with the road noise heard by occupants, resulting in good noise cancellation. Traditional RNC (Rear Noise Cancellation) methods, however, collect road noise from mechanical vibrations above the wheels outside the vehicle. This noise has a low correlation with cabin noise, which is the main reason for its poor noise cancellation performance. Because noise cancellation is performed in the localized space above the occupants' heads, it is easier to create a more effective localized noise cancellation area. However, due to the large interior space of a vehicle, it is difficult to actively cancel noise at all points within a large space using anti-phase sound sources. Furthermore, the sound field of active noise cancellation speakers is difficult to control in a large space. Therefore, using active noise cancellation in a large space is a less efficient approach.

[0087] Furthermore, the road noise active noise reduction car seat and its noise reduction method of this application are not only applicable to automobiles, but also to situations where the main noise source is the noise from the wheel rails under the vehicle, such as trains and high-speed trains.

[0088] Based on the preferred embodiments of the present invention, and through the above description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A road noise active noise reduction car seat, characterized by, The system includes an active road noise reduction system installed in a car seat. The active road noise reduction system includes: an active noise reduction signal processing controller, and a road noise source signal sensor, an anti-phase noise cancellation horn and / or an anti-phase 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 installed at the bottom of the car seat or on the frame below the car seat to collect road noise signals and feed them back to the active noise cancellation signal processing controller. An anti-phase noise cancellation horn is installed on or near the headrest of the car seat to provide an anti-phase road noise signal; and / or, an anti-phase low-frequency vibrator is installed on or near the headrest, and the active noise cancellation signal processing controller is connected to the anti-phase noise cancellation horn and / or the anti-phase low-frequency vibrator through the power amplifier circuit to provide an anti-phase road noise signal. The error microphone is positioned on or near the headrest of the car seat to acquire ambient noise in the vicinity of the headrest and feed it back to the active noise cancellation signal processing controller.

2. The road noise active noise cancellation vehicle seat of claim 1, wherein: The anti-phase low-frequency vibrator is disposed inside the headrest or above the seat back near the headrest; or, the anti-phase low-frequency vibrator is disposed inside the roof and above the headrest.

3. The road noise active noise reducing car seat of claim 1, wherein: The road noise source signal sensor uses a noise capture microphone and / or a vibration sensor.

4. The road noise active noise reducing car seat of claim 1, wherein: The phase-reversing noise cancellation speaker includes a pair of phase-reversing noise cancellation speakers for the left and right ears, which are positioned opposite each other on the headrest. Alternatively, the anti-phase noise cancellation horn includes a left-ear anti-phase noise cancellation horn and a right-ear anti-phase noise cancellation horn installed inside the roof and above the headrest; Alternatively, the anti-phase noise cancellation speaker includes a left-ear anti-phase noise cancellation speaker and a right-ear anti-phase noise cancellation speaker located above the seat back and near the headrest.

5. The road noise active noise reducing car seat of claim 4, wherein: The error microphone is positioned on the headrest of the car seat near the ear; or, the error microphone is positioned above the back of the car seat and near the headrest; or, the error microphone is positioned inside the roof and above the headrest. The anti-phase low-frequency vibrator and error microphone are connected to the active noise cancellation signal processing controller to form a noise control loop.

6. The active road noise reduction car seat according to claim 4, characterized in that: The error microphone includes a set of left and right ear error microphones positioned opposite each other on the headrest of the car seat, used to acquire ambient noise near the passenger's ear canals on both sides of the headrest and feed it back to the active noise cancellation signal processing controller; or, the error microphone includes a set of left and right ear error microphones positioned opposite each other above the back of the car seat and near the headrest, used to acquire ambient noise near the passenger's ear canals on both sides of the headrest and feed it back to the active noise cancellation signal processing controller; or, the error microphone includes a set of left and right ear error microphones positioned opposite each other inside the roof and above the headrest, used to acquire ambient noise near the passenger's ear canals on both sides of the headrest and feed it back to the active noise cancellation signal processing controller. The left ear anti-phase noise cancellation speaker and left ear error microphone, as well as the right ear anti-phase noise cancellation speaker and right ear error microphone, are respectively connected to the active noise cancellation signal processing controller to form two independent noise control loops.

7. A noise reduction method of a road noise active noise reduction car seat, characterized by: The active road noise reduction car seat according to any one of claims 1-6 is implemented by comprising the following steps: Step 1: The active noise cancellation signal processing controller of the active road noise cancellation system sends a command to acquire road noise. The road noise source signal sensor located at the bottom of the car seat picks up the signal and feeds it back to the active noise cancellation signal processing controller. The active noise cancellation signal processing controller generates a predicted inverse road noise signal through the feedforward active noise cancellation algorithm in the active noise cancellation algorithm. Step 2: The active noise cancellation signal processing controller predicts the inverted road noise signal and sends it to the inverted noise cancellation speaker and / or inverted low-frequency vibrator through the power amplifier circuit. It also collects real-time noise information through the error microphone and realizes active road noise control by using the inverted noise generated by the secondary channel to suppress road noise and achieve noise reduction.

8. The noise reduction method of a road noise active noise reduction vehicle seat according to claim 7, characterized in that: The active noise reduction algorithm includes: feedforward active noise reduction method, feedback active noise reduction method, or hybrid feedback active noise reduction method; The feedforward active noise cancellation method includes: a noise capture microphone and / or vibration sensor are installed at the bottom of the car seat; the noise signal acquired by the noise capture microphone and / or vibration sensor is mapped to the noise frequency response by a digital signal processor and / or analog signal processor and a linear filter circuit in the active noise cancellation signal processing controller; and the inverted road noise signal is driven by an inverted noise cancellation speaker and / or inverted low-frequency vibrator on or around the headrest of the car seat to cancel the sound wave vibration of the car road noise. Alternatively, the feedback active noise cancellation method includes: placing an error microphone on or around the headrest to extract vehicle noise caused by road noise; the feedback active noise cancellation method uses a digital signal processor and / or analog signal processor in the active noise cancellation signal processing controller and a linear filter circuit to drive the inverted noise signal through an inverted noise cancellation speaker and / or an inverted low-frequency vibrator to cancel the sound wave vibration of vehicle road noise. Alternatively, the hybrid feedback active noise cancellation method employs a combination of feedforward active noise cancellation and feedback active noise cancellation. The digital signal processor and / or analog signal processor in the active noise cancellation signal processing controller, along with the linear filter circuit, maps the noise signal to the actual generated noise frequency response. Then, an inverted noise cancellation horn and / or an inverted low-frequency vibrator drive the playback of an inverted noise signal to cancel out the acoustic vibration of the vehicle road noise. A noise-capturing microphone and / or vibration sensor under the seat are used to monitor the road noise signal, while another error microphone continuously monitors the error signal of the noise cancellation effect. These two signals are used to adaptively adjust the active noise cancellation filter circuit.

9. The noise reduction method of a road noise active noise reduction vehicle seat according to claim 8, characterized in that: The active noise reduction algorithm also includes: a VAD module for speech detection; when an occupant in the car seat speaks, the speech signal detected by the nearby error microphone is much greater 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 from the noise capture microphone and the error microphone; when the occupant is detected speaking, the adaptive process of the hybrid feedback adaptive active noise reduction algorithm is stopped, and at this time the response function of the feedforward signal of the feedforward active noise reduction method is temporarily fixed and stops updating until the occupant stops speaking, and then the adaptive process of the hybrid feedback adaptive active noise reduction algorithm resumes updating.

10. The noise reduction method of a road noise active noise reduction vehicle seat according to claim 9, characterized in that: The hybrid feedback adaptive active noise cancellation algorithm includes: a filter-x least mean square root adaptive algorithm, comprising the following steps: A reference signal x(n) is picked up by a road noise reference sensor. A filter-x signal x'(n) is generated by a secondary path model. The reference signal x(n) is passed through an adaptive filter W(n) to generate a secondary signal y(n) which drives a noise-canceling speaker. The inverse noise response generated by the noise-canceling speaker is superimposed on the primary road noise field d(n) after passing through a secondary path h(n) in space. The error signal e(n) is obtained by an error microphone and used 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 is continuously reduced, and the adaptive process converges.

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