METHOD AND SYSTEM FOR ESTIMATING ACTIVE NOISE CONTROL PERFORMANCE OF VEHICLES

A method of estimating active noise control performance of a vehicle includes performing ANC by reproducing an acoustic signal for reducing noise introduced from the outside to the inside of the vehicle through a speaker and receiving a residual signal remaining after noise reduction from a microphone, generating an estimation signal for a control signal for controlling output of the speaker such that the acoustic signal is reproduced during the ANC, generating an estimation signal for original noise before the ANC based on the residual signal and the estimation signal for the control signal, and estimating noise reduction performance based on the estimation signal for the original noise and the residual signal.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to Korean Patent Application No. 10-2023-0112996, filed on Aug. 28, 2023 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.

BACKGROUND

The present disclosure relates to an active noise control system for vehicles, and more specifically, to a method and system for estimating the active noise control performance of vehicles.

2. Description of the Related Art

Active noise control (ANC) systems attenuate unwanted noise using feedforward and feedback structures to adaptively remove unwanted noise within a listening environment, such as inside a vehicle cabin. ANC systems typically cancel or reduce unwanted noise by generating canceling sound waves for destructively interfering with unwanted audible noise. In canceling interference, noise and “anti-noise” which is approximately equal in magnitude but opposite in phase reduce a sound pressure level (SPL) at a certain location. In a vehicle cabin listening environment, potential sources of unwanted noise come from sounds radiated by the engine, interaction between the tires of the vehicle and a road surface on which the vehicle is traveling, and/or sound due to vibrations of other parts of the vehicle. Accordingly, unwanted noise varies depending on speed, road conditions and driving conditions of the vehicle.

An active noise control system for vehicles is always operated in the ON state after vehicle production, and it is impossible to measure a noise level with the active noise control system turned off, and thus the noise reduction performance of the active noise control system can be estimated.

Therefore, in this technical field, there is a need for a technique for estimating noise reduction performance without turning off the active noise control system of a vehicle even while the active noise control system is in the ON state.

SUMMARY

An object of the present disclosure is to estimate noise reduction performance without turning off an active noise control system for vehicles even while the system is in an ON state.

Another object of the present disclosure is to provide active noise control performance in real time.

Yet another object of the present disclosure is to monitor performance and stability deterioration due to long-term operation of the active noise control system.

Further another object of the present disclosure is to provide information by which a past operation history can be checked at the time of maintaining an active noise control system to aid in function development, improvement, and maintenance.

The object of the present disclosure is not limited to the object mentioned above, and other objects not mentioned will be clearly understood by those skilled in the art from the following description.

In accordance with an aspect of the present disclosure, the above and other objects can be accomplished by the provision of a method of estimating active noise control performance of a vehicle performed by an active noise control (ANC) system, the method includes performing ANC by reproducing an acoustic signal for reducing noise introduced from the outside to the inside of the vehicle through a speaker and receiving a residual signal remaining after noise reduction from a microphone, generating an estimation signal for a control signal for controlling output of the speaker such that the acoustic signal is reproduced during the ANC, generating an estimation signal for original noise before the ANC on the basis of the residual signal and the estimation signal for the control signal, and estimating noise reduction performance on the basis of the estimation signal for the original noise and the residual signal.

Here, the estimation signal for the original noise may be generated by summing the residual signal and the estimation signal for the control signal.

Here, the estimation signal for the control signal may be generated by a secondary path model filter on the basis of an output signal of an active filter.

Here, the output signal of the active filter may be generated by the active filter on the basis of a reference signal generated by an accelerometer, a reference signal filtered by the secondary path model filter, and a residual signal remaining after noise reduction.

Here, the noise reduction performance may be estimated using a value obtained by subtracting a sound pressure level of the residual noise from a sound pressure level of the estimation signal for the original noise.

In accordance with another aspect of the present disclosure, there is provided an active noise control system for a vehicle, including a processor configured to perform active noise control (ANC) by reproducing an acoustic signal for reducing noise introduced from the outside to the inside of the vehicle through a speaker and receive a residual signal remaining after noise reduction from a microphone, generate an estimation signal for a control signal for controlling output of the speaker such that the acoustic signal is reproduced during the ANC, generate an estimation signal for original noise before the ANC on the basis of the residual signal and the estimation signal for the control signal, and estimate noise reduction performance on the basis of the estimation signal for the original noise.

Here, the estimation signal for the original noise may be generated by summing the residual signal and the estimation signal for the control signal.

Here, the estimation signal for the control signal may be generated by a secondary path model filter on the basis of an output signal of an active filter.

Here, the output signal of the active filter may be generated by the active filter on the basis of a reference signal generated by an accelerometer, a reference signal filtered by the secondary path model filter, and a residual signal remaining after noise reduction.

Here, the noise reduction performance may be estimated using a value obtained by subtracting a sound pressure level of the residual noise from a sound pressure level of the estimation signal for the original noise.

DETAILED DESCRIPTION

The present disclosure will be described in detail with reference to the attached drawings as follows. Here, repeated descriptions, and detailed description of known functions and configurations that may unnecessarily obscure the gist of the present disclosure will be omitted. Embodiments of the present disclosure are provided to more completely explain the present disclosure to those skilled in the art. Accordingly, the shapes and sizes of elements in the drawings may be exaggerated for clearer explanation.

Hereinafter, preferred embodiments according to the present disclosure will be described in detail with reference to the attached drawings.

FIG.1shows an example of a typical active noise control (ANC) system.

Referring toFIG.1, a typical ANC system includes an accelerometer110, a primary path filter120, a processor130, a secondary path filter140, a comparator150, and a microphone160.

The accelerometer110detects vehicle body vibration y from a road surface, generates a reference signal x, and transmits the generated reference signal x to the processor130.

The primary path filter120transmits the vehicle body vibration y to the microphone160in the form of original noise d before control.

The processor130calculates an adaptive algorithm by Filtered Least Mean Square (FxLMS) based on the reference signal x generated by the accelerometer110, outputs a signal, and performs signal processing in a digital domain such as filtering a secondary path model.

Here, the processor130may be a digital signal processor (DSP).

A secondary path model filter131estimates a transfer function for a secondary path of the secondary path filter140and generates a filtered reference signal î on the basis of the reference signal x.

The controller133transmits the estimated reference signal x received from the secondary path model filter131and residual noise received from the microphone160to an active filter135.

The active filter135generates an active filter output signal u on the basis of the reference signal x received from the accelerometer110, the filtered reference signal î generated by the secondary path model filter133, and controlled residual noise e received from the microphone160.

Here, an FxLMS filter coefficient may be updated in real time by the active filter135.

The secondary path filter140generates a speaker output control signal y on the basis of the output signal u from the active filter135.

Here, the output control signal y generated by the secondary path filter140is a sound wave with the same magnitude and opposite phase as the original noise d before control and may be a signal for reducing the original noise d before control.

The comparator150transmits the controlled residual noise e obtained by subtracting the speaker output control signal y from the secondary path filter140from the original noise d before control from the primary path filter120to the microphone160.

The microphone160detects the controlled residual noise e and transmits the same to the processor230.

Meanwhile, in the ANC system as shown inFIG.1, merely the controlled residual noise e obtained by canceling the speaker output control signal y by the residual noise d before control can be measured, and the original noise d before control cannot be measured. However, the noise removal performance of the active noise control system can be estimated using a value obtained by subtracting the sound pressure level of the controlled residual noise e from the sound pressure level of the original noise d before control. Therefore, in situations in which the original noise d before control is unknown, the noise removal performance of the active noise control system cannot be estimated.

Hereinafter, an active noise control system according to an embodiment of the present disclosure which can estimate the noise removal performance of the active noise control system by estimating the original noise d before control even in a state in which the active noise control system is turned on will be described.

FIG.2shows an ANC system according to an embodiment of the present disclosure.

Referring toFIG.2, the ANC system according to the present embodiment includes an accelerometer210, a primary path filter220, a processor230, a secondary path filter240, a summer250, and a microphone260.

The accelerometer210detects vehicle body vibration γ from a road surface, generates a reference signal x, and transmits the generated reference signal x to the processor230.

The primary path filter220transmits the vehicle body vibration γ to the microphone260in the form of original noise d before control.

The processor230calculates an adaptive algorithm by Filtered Least Mean Square (FxLMS) on the basis of the reference signal x generated by the accelerometer210, outputs a signal, and performs signal processing in a digital domain such as filtering a secondary path model.

A first secondary path model filter231estimates a transfer function for a secondary path of the secondary path filter240and generates a filtered reference signal {circumflex over (x)} on the basis of the reference signal x.

The controller233transmits the estimated reference signal {circumflex over (x)} received from the secondary path model filter231and residual noise received from the microphone260to an active filter235.

The active filter235generates an active filter output signal u on the basis of the reference signal x received from the accelerometer210, the filtered reference signal {circumflex over (x)} generated by the secondary path model filter233, and residual noise e after control received from the microphone260.

Here, a filtered least mean square (FxLMS) filter coefficient may be updated in real time by the active filter235.

A second secondary path model filter236estimates a transfer function for the secondary path of the secondary path filter240and generates an estimation signal ŷ for a speaker output control signal y on the basis of the output signal u.

Here, the second secondary path model filter236is a filter integrated with the first secondary path model filter231and can perform the functions of the first secondary path model filter231and the second secondary path model filter236simultaneously.

A summer237sums the estimation signal ŷ for the control signal generated by the second secondary path model filter236and the residual noise e after control received from the microphone260to generate an estimation signal {circumflex over (d)} for the original noise before control.

Here, the estimation signal for the original noise before control may be estimated as a value close to the original noise before control, as represented by mathematical expression 1 below.

In mathematical expression 1, {circumflex over (d)} represents the estimation signal for the original noise before control, e represents controlled residual noise, y represents a control signal for controlling speaker output, and ŷ represents the estimation signal for the control signal for controlling the speaker output.

A storage unit238stores the controlled residual noise e or the estimation signal {circumflex over (d)} for the original noise before control.

Here, the storage unit238may be various types of volatile or non-volatile storage media.

The secondary path filter240generates a speaker output control signal y on the basis of the output signal u of the active filter235.

Here, the output control signal y generated by the secondary path filter240is a sound wave with the same magnitude and opposite phase to the original noise d before control and may be a signal for reducing the original noise d before control.

The comparator250transmits controlled residual noise e obtained by subtracting the speaker output control signal y from the secondary path filter240from the original noise d before control from the primary path filter220to the microphone260.

The microphone260detects the controlled residual noise e and transmits the same to the processor230.

FIG.3shows an active noise control system300according to another embodiment of the present disclosure.

Referring toFIG.3, the active noise control system100according to the present embodiment includes a processor310, a microphone330, a speaker350, an input/output interface370, and a memory390.

The processor310includes a control signal estimator313, an original noise estimator315, and a noise reduction performance estimator317.

The control signal estimator313performs ANC by outputting an acoustic signal for reducing noise introduced from outside the vehicle to the inside through a speaker, and generates an estimation signal for a control signal for controlling output of the speaker such that the acoustic signal is output at the time of performing ANC.

Here, the estimation signal for the control signal may be generated by a secondary path model filter on the basis of the output signal u of the active filter.

Here, the secondary path model filter may be generated by estimating a transfer function for the secondary path of the secondary path filter.

Here, the output signal u of the active filter may be generated on the basis of the reference signal x received from the accelerometer, the filtered reference signal {circumflex over (x)} generated by the secondary path model filter233, and the controlled residual noise after control e received from the microphone.

The original noise estimator315receives a residual signal remaining after noise reduction from the microphone330, receives the estimation signal for the control signal for controlling speaker output from the control signal estimator313, and generates an estimation signal for the original noise on the basis of the residual signal and the estimate signal for the control signal.

Here, the estimation signal for the original noise generated by the original noise estimator315may be transmitted to the memory390for storage.

The noise reduction performance estimator317estimates noise reduction performance on the basis of the estimation signal for the original noise.

Here, the noise reduction performance may be estimated using a value obtained by subtracting the sound pressure level of the controlled residual noise e from the sound pressure level of the estimation signal d for the original noise before control.

Here, the noise reduction performance estimator317transmits the noise reduction performance estimation result to the input/output interface370such that the noise reduction performance estimation result can be provided to an occupant inside the vehicle through the input/output interface370.

Additionally, the noise reduction performance estimation result generated by the noise reduction performance estimator317may be transmitted to the memory390for storage.

At least one microphone330is disposed inside the vehicle to detect external noise generated due to interaction between the tires of the vehicle and a road surface.

Here, the microphone330may be provided, for example, in a headrest of a seat, and may be disposed in an automobile headliner or various places to detect noise outside the vehicle.

The speaker350reproduces an anti-noise signal for signals received by the microphone330, generated by the processor310.

The input/output interface370provides noise reduction performance estimated by the noise reduction performance estimator317to an occupant inside the vehicle.

For example, the input/output interface370provides noise reduction performance estimation results to the occupant inside the vehicle through a display screen as shown inFIG.4.

The memory390may be various types of volatile or non-volatile storage media. Here, the memory390stores at least one of an estimation signal for a control signal for controlling speaker output, an estimation signal for original noise, noise reduction performance estimation results, or a combination thereof.

FIG.5is a flowchart showing an active noise control (ANC) method according to an embodiment of the present disclosure. The active noise control method according to the present embodiment can be performed by the processor310ofFIG.3.

Referring toFIG.5, the processor310performs active noise control (ANC) by reproducing an acoustic signal for reducing noise introduced from the outside of the vehicle to the inside through a speaker, and receives a residual signal remaining after noise reduction from the microphone at S510.

For example, the processor310generates a sound wave with the same magnitude and opposite phase to the noise outside the vehicle to be transmitted to an occupant inside the vehicle and reproduces the sound wave through the speaker250to reduce the noise outside the vehicle.

Here, the processor310may reduce the noise outside the vehicle using an actual secondary path S(s) which is an electrical and acoustic path between the speaker350and the microphone330and a secondary path model algorithm using a secondary path model § which is a digital filter obtained by measuring the actual secondary path by a DSP and modeling the same into a transfer function.

Additionally, the processor310generates an estimation signal for a control signal for controlling output of the speaker such that the acoustic signal is reproduced during the ANC at S520.

Here, the estimation signal for the control signal may be generated by a secondary path model filter on the basis of the output signal of the active filter.

Here, the output signal of the active filter may be generated by the active filter on the basis of a reference signal generated by the accelerometer, a reference signal filtered by the secondary path model filter, and the residual signal remaining after noise reduction.

Additionally, the processor310generates an estimation signal for the original noise before the ANC on the basis of the residual signal and the estimation signal for the control signal at S530.

Here, the estimation signal for the original noise may be generated by summing the residual signal and the estimation signal for the control signal.

Additionally, the processor310estimates noise reduction performance on the basis of the estimation signal for the original noise at S540.

Here, the noise reduction performance may be estimated using a value obtained by subtracting the sound pressure level of the controlled residual noise e from the sound pressure level of the estimation signal d for the original noise before control.

Additionally, the processor310provides noise reduction performance estimation results to the occupant inside the vehicle at S550.

Here, the processor310transmits the noise reduction performance estimation results to the input/output interface370and can provide the noise reduction performance estimation results to the occupant inside the vehicle through the input/output interface370.

FIG.6shows a computer system according to an embodiment of the present disclosure.

Referring toFIG.6, embodiments of the present disclosure may be implemented in a computer system such as a computer-readable recording medium. As shown inFIG.6, the computer system600includes a processor610, an input/output interface630, and a memory650.

The processor610implements the active noise control performance estimation method for vehicles proposed in this specification. Specifically, the processor610implements all operations of the processor310in the active noise control system300described in the embodiment of the present disclosure and performs all operations of the active noise control performance estimation method according toFIG.5.

For example, the processor610performs ANC by reproducing an acoustic signal for reducing noise introduced from the outside of the vehicle to the inside through a speaker, receives a residual signal remaining after noise reduction from the microphone, generates an estimation signal for a control signal for controlling output of the speaker such that the acoustic signal is reproduced during the ANC, generates an estimation signal for original noise before ANC on the basis of the residual signal and the estimation signal for the control signal, and estimates noise reduction performance on the basis of the estimation signal for the original noise.

Here, the estimation signal for the original noise may be generated by summing the residual signal and the estimation signal for the control signal.

Here, the estimation signal for the control signal may be generated by a secondary path model filter on the basis of the output signal of an active filter.

Here, the output signal of the active filter may be generated by the active filter on the basis of a reference signal generated by an accelerometer, a reference signal filtered by the secondary path model filter, and a residual signal remaining after noise reduction.

Here, the noise reduction performance may be estimated using a value obtained by subtracting the sound pressure level of the residual noise from the sound pressure level of the estimation signal for the original noise.

The input/output interface630is connected to the processor610and directly obtains information or provides information to a user. For example, the input/output interface630provides noise reduction performance estimation results to an occupant inside the vehicle.

The memory650may be various types of volatile or non-volatile storage media. Here, the memory650stores at least one of an estimation signal for a control signal for controlling speaker output, an estimation signal for original noise, noise reduction performance estimation results, or a combination thereof.

According to the above-described embodiments of the present disclosure, it is possible to estimate noise reduction performance in real time and store a performance history without turning off an active noise control system even while the system is in an ON state and without affecting usability.

Furthermore, it is possible to provide the effects of an active noise control function to customers using objective numerical values.

Furthermore, it is possible to monitor performance and stability deterioration due to long-term operation of the active noise control system.

Furthermore, it is possible to check information by which a past operation history can be checked at the time of maintaining an active noise control system to aid in function development, improvement, and maintenance.

The above-described present disclosure may be implemented as computer-readable code on a program-recorded medium. Computer-readable media includes all types of recording devices that store data that can be read by a computer system. Examples of computer-readable media include a hard disk drive (HDD), a solid state drive (SSD), a silicon disk drive (SDD), a ROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, an optical data storage device, and the like.

Accordingly, the above detailed description should not be construed as restrictive in all respects and should be considered illustrative. The scope of the present disclosure should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the present disclosure are included in the scope of the present disclosure.