System and method for determination of acoustic paths in a passenger compartment of a vehicle

Abstract

An acoustic path determination system in a passenger compartment (4) of a vehicle (1) provided with an audio system (10) having speakers (12) configured to reproduce sounds within the passenger compartment (4) is described, which provides: a generation stage (20), configured to generate within the passenger compartment (4), via the speakers (12), passenger-compartment audio signals; and a determination stage (22), configured to determine and adaptively update over time estimates of the acoustic paths within the passenger compartment (4), as a function of the detection and processing of the passenger-compartment audio signals. The passenger-compartment audio signals include signaling, alert or warning sounds, and / or "ESE" - Engine Sound Enhancement sounds and / or additional sounds designed to be present in the passenger compartment (4) during operation of the vehicle (1) and addressed to the user of the vehicle (1).

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This patent application claims priority from Italian patent application no. 102024000028194, filed on December 11, 2024, the entire disclosure of which is incorporated herein by reference.TECHNICAL FIELD

[0002] The present solution relates to a system and a method for determination of acoustic paths in the passenger compartment of a vehicle, in particular a motor vehicle.STATE OF THE ART

[0003] In a known manner, an optimal control of the audio system within the passenger compartment of a vehicle requires an adequate representation of the sound environment and in particular the determination of the acoustic paths which characterize it, in particular the paths between speakers, arranged in the passenger compartment and configured to emit sound signals, and the areas where the ears of the listener are located (typically near the headrests of the seats), at which sensors are installed, which are configured to detect the acoustic signals emitted by the speakers.

[0004] In particular, the use of active road noise cancellation (ARNC) techniques in modern motor vehicles is known, aimed at reducing noise in the passenger compartment mainly due to the rolling noise of the tyres of the motor vehicle and to aerodynamic noise.

[0005] Active noise cancellation techniques generally allow actively reducing acoustic noise by generating, via the speakers, waveforms inverted to those of noise (for example, with the same sound level and inverted phase), also called "antiphase" or "anti-noise" waveforms.

[0006] An active noise cancellation system generally uses one or more reference sensors (typically accelerometers, in the automotive field) to detect an external noise reference signal, generates an anti-noise waveform based on the noise reference signal and reproduces anti-noise waveforms through one or more speakers. These anti-noise waveforms interfere in a destructive manner with the original noise signals, thereby reducing the level of noise reaching the ear of a listener.

[0007] The aforesaid ARNC techniques for noise cancellation in the passenger compartment of a motor vehicle require the representation of acoustic paths, including: so-called primary paths, which represent the path of noise signals from the noise source towards the noise cancellation zones, generally located at the ears of the listener (near the headrest of the seat); and so-called secondary acoustic paths, which represent the path of anti-noise signals from the speakers that emit the same anti-noise signals towards the aforesaid noise cancellation zones.

[0008] Typically, in the algorithms used, a representation of the secondary paths (i.e., an estimate of the corresponding transfer function) is introduced, while the primary paths are determined indirectly.

[0009] Traditional ARNC algorithms are based on a fixed or static representation of the audio system and the acoustic paths, which therefore does not allow to follow any changes of the system over time (for example due to aging or degradation phenomena or even to different areas or methods of use of the vehicle), thus causing a degradation of the performance over time of the audio system and / or of the aforesaid noise cancellation algorithms.

[0010] Some solutions have been proposed, in particular in the field of consumer electronics, which allow carrying out an adaptive estimate of acoustic paths during the operation of the related systems (i.e., being able to adapt to changes over time); however, such solutions are generally expensive in terms of resources and can be invasive from the point of view of the user experience.

[0011] For example, an adaptive technique that has been proposed for noise cancellation involves performing an estimate of the acoustic paths, during the operation of the system, using a driving signal, in particular a random noise (or white noise), which is mixed into an input signal of the anti-noise speaker.

[0012] This approach can work with some precision, but the driving signal is an unwanted artefact that can be perceived by a listener, so much so that its use in certain application areas is impractical.OBJECT OF THE INVENTION

[0013] The object of the present solution is generally to provide a system for determination of acoustic paths in the passenger compartment of a vehicle, which can overcome or in any case limit the problems previously highlighted.

[0014] In accordance with the object indicated above, according to the present solution a system and a method are provided, as defined in the appended claims.BRIEF DESCRIPTION OF THE FIGURES

[0015] The present invention will now be described with reference to the accompanying drawings, which illustrate a non-limiting exemplary embodiment thereof, wherein: Figure 1 schematically shows a motor vehicle provided with an audio system, with examples of acoustic paths highlighted; Figure 2 is a schematic block diagram of a processing unit of the audio system; Figure 3 is a flowchart related to operations carried out by the processing unit of the audio system; Figures 4A-4B and 5A-5B show plots of quantities associated with the operation of the processing unit; Figure 6 is a schematic block diagram associated with a noise cancellation stage implemented by the processing unit; and Figure 7 is a schematic block diagram associated with an optimization stage of the audio system implemented by the processing unit. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0016] As will be described in detail in the following, an aspect of the present solution generally entails implementing a system for identifying or determining acoustic paths within a passenger compartment of a vehicle, configured to exploit, for such determination, sounds already reproduced by the audio system in the same passenger compartment. Such system is also able to adapt to temporal changes so as to preserve performance and robustness over time and can also be implemented on-line, i.e., during the operation of the audio system and / or associated noise cancellation algorithms, in a transparent manner for a user of the vehicle.

[0017] Figure 1 shows a vehicle, in particular a motor vehicle 1 (which can be indifferently of a traditional or thermal type, hybrid or electric type), provided with a body 2 resting on the ground by means of wheels 3, defining therein a passenger compartment 4 and comprising front and rear doors 5 that give access to the same passenger compartment 4 and a hatchback door 6 that gives access to a corresponding trunk.

[0018] Within the passenger compartment 4, the motor vehicle 1 comprises a pair of front seats 8, arranged at the front (with respect to the direction of travel) and designed to accommodate the driver of the motor vehicle 1 and a passenger; and rear seats 9, arranged at the rear (with respect to the same direction of travel).

[0019] The motor vehicle 1 further comprises an audio system 10, configured to reproduce sound signals within the passenger compartment 4, comprising for this purpose a plurality of speakers 12, having in a known manner different frequency contributions (for example mid-range speakers, tweeters, etc.), typically arranged at the doors 5; in the illustrated example, the audio system 10 further comprises a subwoofer, arranged at the trunk.

[0020] As schematically illustrated in the aforesaid Figure 1, the audio system 10 further comprises a digital processing unit 14 (microprocessor, microcontroller or the like), configured to drive the aforesaid speakers 12 to generate the sound signals to be reproduced in the passenger compartment 4.

[0021] In a possible implementation, such digital processing unit 14 may coincide with, or be part of, a control and management unit of an infotainment system of the motor vehicle 1, designed to control, in a known manner, the generation of digital audio-video (information and entertainment) content and also the activation, adjustment or monitoring of different functions of the motor vehicle 1 (for example the management of air conditioning or the control of data associated with the operation of the motor vehicle 1).

[0022] The digital processing unit 14 is also operatively coupled to a control unit (ECU - Electronic Control Unit) of the motor vehicle 1, not illustrated herein, designed to supervise the general operation of the same motor vehicle 1 (in a manner known per se, not described in detail herein).

[0023] The aforesaid audio system 10 further comprises: detection sensors 16, for example microphones, arranged within the passenger compartment 4 of the motor vehicle 1, configured to detect passenger-compartment signals emitted by the speakers 12; and reference sensors 18, for example accelerometers or microphones, arranged for example outside the passenger compartment 4, configured to detect reference signals, indicative of environmental noise, in particular rolling noise.

[0024] In a possible implementation, the detection sensors 16 are arranged at headrests of the front seats 8 (and possibly of the rear seats 9), so as to provide a detection in the proximity of the ears of the users of the motor vehicle 1 (at least of the driver).

[0025] The reference sensors 18 can instead be arranged at the wheels 3 of the motor vehicle 1, for example coupled to the hubs of the wheels 3, so as to provide a detection associated with environmental noise, for example associated with the rolling noise of the tyres or aerodynamic noise.

[0026] The aforesaid digital processing unit 14 is, among other features, configured to determine acoustic paths within the passenger compartment 4 of the motor vehicle 1 and corresponding frequency transfer functions.

[0027] In particular, by way of example, as is indeed shown in Figure 1, the aforesaid acoustic paths comprise: at least a first acoustic path, denoted with P p , which defines a transfer function between a respective reference sensor 18 (acting, in an ARNC noise cancellation algorithm, as a noise reference sensor) and a respective detection sensor 16 (acting, in an ARNC noise cancellation algorithm, as an error sensor), the aforesaid first acoustic path P p being in such case a so-called primary acoustic path; and at least a second acoustic path, denoted with P S , which defines a transfer function between a respective speaker 12 within the passenger compartment 4 and a respective detection sensor 16 (acting, as indicated, as an error sensor for the ARNC noise cancellation algorithm).

[0028] It should be noted in any case that the aforesaid acoustic paths may comprise other types of paths and / or other elements of the audio system 10 or in general of the motor vehicle 1.

[0029] For example, the digital processing unit 14 can be configured to determine an acoustic path between a respective speaker 12 and a respective detection sensor 16, for the determination of a corresponding frequency response function (FRF), to be used for example for the purposes of adjusting ("tuning") the audio system 10 of the motor vehicle 1.

[0030] In particular, the digital processing unit 14 can be configured to implement, on the basis of the signals provided by the detection and reference sensors 16, 18, noise cancellation algorithms, such as ARNC algorithms, and / or optimization algorithms of the audio system 10 (tuning, optimization or adjustment algorithms).

[0031] As shown in Figure 2, the aforesaid digital processing unit 14 comprises a generation stage 20, configured to generate within the passenger compartment 4 of the motor vehicle 1, via the speakers 12, passenger-compartment audio signals, such as for example signaling, alert or warning signals, ESE (Engine Sound Enhancement) signals, or additional sounds usually reproduced in the passenger compartment 4 during the normal operation of the motor vehicle 1 and having an informative content for a user.

[0032] In general, such audio signals can correspond to sounds that characterize the user experience, both as regards signals, alerts or warnings (so-called chimes and warning sounds) and as regards the driving experience (ESE signals). In a known manner, in a vehicle, chimes are sounds or acoustic signals that are emitted to attract the driver's attention to certain conditions or actions. These sounds are generally pleasant and non-invasive, and may indicate events such as lights turning on, doors opening, seat belts not being fastened, or other routine notifications that do not pose an immediate danger. In a vehicle, warning sounds are acoustic signals designed to warn the driver of potentially dangerous situations or malfunctions of the vehicle. These sounds are often louder and more insistent with respect to chimes, and can indicate problems such as low oil pressure, engine overheating, low tyre pressure, or other conditions that require immediate attention.

[0033] According to an aspect of the present solution, the digital processing unit 14 further comprises a determination stage 22, configured to determine acoustic paths within the passenger compartment 4 of the motor vehicle 1, as a function only of the aforesaid passenger-compartment audio signals, i.e. without requiring the generation of dedicated and specific (for such determination operation) additional audio signals, such as driving signals, white noise signals, etc.

[0034] In particular, such determination stage 22 can be configured to determine secondary acoustic paths and the digital processing unit 14 can further comprise a noise cancellation stage 24, configured to implement active noise cancellation algorithms (ARNC algorithms) based on the aforesaid secondary acoustic paths.

[0035] In addition, or alternatively, the determination stage 22 can be configured to determine frequency response functions (FRFs) and the digital processing unit 14 can further comprise an optimization stage 26, configured to implement algorithms for adjusting or optimizing the audio system 10 based on the aforesaid frequency response functions (in particular for the purpose of optimizing the audio reproduction by the on-board entertainment systems).

[0036] According to an aspect of the present solution, the aforesaid determination stage 22 is configured to determine the aforesaid acoustic paths adaptively, that is, adapting over time to possible changes associated with the audio system 10, for example due to aging or degradation phenomena or even to different conditions of use of the motor vehicle 1 (for example, to different conditions of occupancy of the passenger compartment 4).

[0037] Furthermore, the determination stage 22 can be configured to determine the aforesaid acoustic paths on-line, i.e. in real time during the operation of the audio system 10 and of the aforesaid noise cancellation or optimization algorithms.

[0038] Such determination (in particular, the updating over time of the estimates of the acoustic paths) can be carried out at a lower processing rate with respect to the processing rate of the noise cancellation or audio optimization algorithm; or be carried out at preset time intervals, or even be carried out only if necessary (one-off), for example when a decrease in performance of the noise cancellation algorithm or of the audio reproduction algorithms is determined.

[0039] The determination of the acoustic paths can alternatively, or in addition, also be carried out off-line, i.e., in a separate time period with respect to the operation of the audio system 10, for example on the basis of audio signals previously stored during the operation of the same audio system 10.

[0040] In any case, the determination stage 22 is configured to use the aforesaid passenger-compartment audio signals to excite a frequency band of interest of the transfer functions involved in the noise cancellation or audio optimization applications, making it possible to determine the frequency response thereof.

[0041] In more detail, and with reference to Figure 3, the determination stage 22 can be configured firstly, step 30, to perform a preliminary (optional, but advantageous) operation of separation between groups of speakers 12 (woofers, mid-range, etc.) based on a different frequency content of the audio signals detected by the detection sensors 16.

[0042] Next, step 32, the determination stage 22 is configured to perform an operation of separation of the audio signals from the individual speakers 12 forming part of the same group, for example using beamforming techniques (similar to those typically already used in the motor vehicle 1 for Voice Recognition, VR, or Echo Cancelling and Noise Reduction, ECNR, content).

[0043] In particular, the determination stage 22 can implement algorithms comprising non-heuristic techniques (for example Deep Learning techniques) which, alongside beamforming, can improve the performance thereof, compensating for the effects of near-field reflections and propagation that can occur in the passenger compartment 4 (in this case, the use of a smaller number of sensors may also be required).

[0044] The possibility of carrying out off-line or reduced-rate processing may favour the use of beamforming algorithms or similar advanced processing algorithms.

[0045] Once the contributions of the individual speakers 12 have been separated, the determination stage 22 is configured to determine the individual frequency response functions between the speakers 12 and respective detection sensors 16, as indicated in step 34.

[0046] As shown in Figure 3, the aforesaid operations can then be repeated iteratively over time (at preset intervals or as needed), to adapt the estimate of the frequency response functions to changes of the audio system 10 and / or the environment related to the passenger compartment 4.

[0047] In this regard, Figure 4A shows a passenger-compartment audio signal, in the example having an impulse function, and Figure 4B shows a corresponding detection signal provided by a respective one of the detection sensors 16. In the trend of such detection signal, the impulsive contribution of the passenger-compartment audio signal with respect to a background noise can be recognized.

[0048] The determination stage 22 is configured to determine the aforesaid frequency response function FRF, shown by way of example in Figure 5A, as: H jω = Y jω X jω = fft y t fft s t where y(t) indicates the detection signal and s(t) indicates the passenger-compartment audio signal.

[0049] Figure 5B shows the corresponding impulse response: h t = ifft H jω

[0050] As indicated above, the determination stage 22 is thus able to adaptively determine the acoustic paths of interest within the passenger compartment 4 of the motor vehicle 1.

[0051] Figure 6 shows a possible implementation of the noise cancellation stage 24, designed to cooperate with the determination stage 22, in particular to exploit the adaptive determination of the acoustic paths thereof, in such case of the secondary acoustic paths for a noise cancellation algorithm.

[0052] In detail, in such Figure 6 a first transfer block 40 represents the transfer function of a primary acoustic path P(z), which models the transmission of the noise signal between the noise source and the noise cancellation zone, i.e. between a respective one of the reference sensors 18 and a respective one of the detection sensors 16 (in this case defined as an error sensor).

[0053] This first transfer block 40 schematically receives a noise reference signal x(n), provided by the aforesaid reference sensor 18, and outputs a primary disturbance signal d(n), which represents the disturbance to be cancelled at the noise cancellation zone.

[0054] A second transfer block 42 represents the transfer function of a secondary acoustic path S(z), which models the transmission of the audio signal between a respective speaker 12 and the aforesaid noise cancellation zone. In particular, such second transfer block 42 schematically receives a control signal c(n), which represents the driving signal provided to the aforesaid speaker 12, and outputs an anti-noise signal y(n).

[0055] A cancellation block 44 schematically receives at a first input the aforesaid primary disturbance signal d(n) and at a second input the anti-noise signal y(n), so as to output an error signal e(n), which is the result of a destructive interference between the primary disturbance d(n) and the anti-noise signal y(n) (in practice, such error signal is the signal measured by the aforesaid error sensor, which directly measures the result of this destructive interference).

[0056] In particular, the aforesaid noise cancellation stage 24 comprises: a control filter block 45, configured to receive at an input the noise reference signal x(n) and generate at an output the aforesaid control signal c(n); and an adaptation block 46, configured to suitably adapt the filtering action performed by the control filter block 45, for example modifying the weights, coefficients and / or transfer function thereof.

[0057] Such adaptation block 46 can for example operate by means of an LMS (Least Mean Squares) algorithm, or by means of a similar adaptive algorithm, and receives at an input the aforesaid error signal e(n) and also a filtered noise reference signal x'(n).

[0058] In particular, the noise cancellation stage 24 comprises an estimation block 47, which receives at an input the noise reference signal x(n) and outputs the filtered noise reference signal x'(n), implementing an estimate of the secondary acoustic path S'(z).

[0059] According to an aspect of the present solution, the aforesaid estimation block 47 is operatively coupled to the determination stage 22, so that the estimate of the secondary acoustic path S'(z) adapts its operation as a function of the determination of the acoustic paths by the same determination stage 22.

[0060] In other words, the determination stage 22 is configured to modify the estimate of the secondary acoustic path S'(z), based on the determined frequency response functions FRF, as discussed in detail above, in an adaptive manner.

[0061] It should be noted, in this regard, that the performance of the cancellation algorithm strongly depends on such estimation block 47, since the more the estimate S' (z) accurately models the secondary acoustic path S(z), the better the performance of the algorithm. Advantageously, the determination stage 22 allows updating the estimation block 47, so as to maintain a good performance over time, operating transparently to the user, using sounds already normally reproduced by the audio system 10.

[0062] In particular, the operation of the noise cancellation stage 24 is transparent to the user without degradation of performance and without requiring an increase in the complexity of the control logic, also offering an increase in the versatility of the management of computational resources (it should be noted in such regard that the determination stage 22 operates independently and externally with respect to the actual control logic of the noise cancellation algorithm).

[0063] With reference to Figure 7, a possible implementation of the optimization stage 26, designed to cooperate with the determination stage 22, is now described, in particular to exploit the adaptive determination of the acoustic paths thereof within the passenger compartment 4 of the motor vehicle 1, in such case to implement optimization algorithms of the audio system 10 based on the corresponding frequency response functions.

[0064] Such optimization stage 26 generally comprises a reproduction control block 50, configured to control the reproduction of the audio signals via the various audio channels available within the passenger compartment 4 (and the associated speakers 12); and a routing block 52, configured to route the audio signals towards the aforesaid audio channels.

[0065] The optimization stage 26 further comprises an adjustment or tuning block 54 for adjusting the audio channels, coupled between the output of the routing block 52 and the aforesaid audio channels, here generally indicated with 56.

[0066] According to an aspect of the present solution, the aforesaid adjustment block 54 is operatively coupled to the determination stage 22, to adapt its operation as a function of the determination of the acoustic paths by the same determination stage 22.

[0067] In other words, the determination stage 22 is configured to modify the adjustment of the audio channels (for example an equalization thereof, in terms of amplitude and phase), on the basis of the frequency response functions FRF, which are determined as discussed above.

[0068] Advantageously, the operation of the optimization stage 26 allows to maintain over time the performance of the entertainment system by compensating for changes in the acoustic transfer functions, for example due to ageing of the components or changes in the acoustic response in the passenger compartment 4.

[0069] Furthermore, such optimization stage 26 allows optimizing the user experience for example on the basis of the number of occupants of the same passenger compartment 4, compensating for the related impact on the transfer functions.

[0070] Based on what has been discussed, the advantages that the present solution allows to achieve emerge in an evident manner.

[0071] In any case, it is again highlighted that such solution allows to increase the stability of the performance (for example for noise cancellation algorithms and for optimization algorithms of the entertainment system) in systems characterized by time-variant paths (due to degradation, ageing, influence of the occupants or other factors occurring in the passenger compartment).

[0072] The proposed solution, thanks to the use of audio signals already reproduced in the passenger compartment during the normal operation of the system, allows to implement an identification of the acoustic paths in a manner that is transparent to the user.

[0073] Furthermore, such solution involves a limited complication of the architecture and allows a high versatility of the management of computational resources, since the identification of acoustic paths is possible both on-line and off-line, and can also be carried out with variable update rates, at preset intervals or upon need.

[0074] Finally, it is clear that modifications and variations can be made to what has been described without thereby departing from the scope of the present invention, as defined by the appended claims.

[0075] It should be noted in particular that the described solution can be used in various types of applications, even different from the examples described in detail above, in general whenever the determination of acoustic paths within the passenger compartment of a vehicle (of any type) is required.

Examples

Embodiment Construction

[0016]As will be described in detail in the following, an aspect of the present solution generally entails implementing a system for identifying or determining acoustic paths within a passenger compartment of a vehicle, configured to exploit, for such determination, sounds already reproduced by the audio system in the same passenger compartment. Such system is also able to adapt to temporal changes so as to preserve performance and robustness over time and can also be implemented on-line, i.e., during the operation of the audio system and / or associated noise cancellation algorithms, in a transparent manner for a user of the vehicle.

[0017]Figure 1 shows a vehicle, in particular a motor vehicle 1 (which can be indifferently of a traditional or thermal type, hybrid or electric type), provided with a body 2 resting on the ground by means of wheels 3, defining therein a passenger compartment 4 and comprising front and rear doors 5 that give access to the same passenger compartment 4 and ...

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This patent application claims priority from Italian patent application no. 102024000028194, filed on December 11, 2024, the entire disclosure of which is incorporated herein by reference.TECHNICAL FIELD

[0002] The present solution relates to a system and a method for determination of acoustic paths in the passenger compartment of a vehicle, in particular a motor vehicle.STATE OF THE ART

[0003] In a known manner, an optimal control of the audio system within the passenger compartment of a vehicle requires an adequate representation of the sound environment and in particular the determination of the acoustic paths which characterize it, in particular the paths between speakers, arranged in the passenger compartment and configured to emit sound signals, and the areas where the ears of the listener are located (typically near the headrests of the seats), at which sensors are installed, which are configured to detect the acoustic signals emitted by the speakers.

[0004] In particular, the use of active road noise cancellation (ARNC) techniques in modern motor vehicles is known, aimed at reducing noise in the passenger compartment mainly due to the rolling noise of the tyres of the motor vehicle and to aerodynamic noise.

[0005] Active noise cancellation techniques generally allow actively reducing acoustic noise by generating, via the speakers, waveforms inverted to those of noise (for example, with the same sound level and inverted phase), also called "antiphase" or "anti-noise" waveforms.

[0006] An active noise cancellation system generally uses one or more reference sensors (typically accelerometers, in the automotive field) to detect an external noise reference signal, generates an anti-noise waveform based on the noise reference signal and reproduces anti-noise waveforms through one or more speakers. These anti-noise waveforms interfere in a destructive manner with the original noise signals, thereby reducing the level of noise reaching the ear of a listener.

[0007] The aforesaid ARNC techniques for noise cancellation in the passenger compartment of a motor vehicle require the representation of acoustic paths, including: so-called primary paths, which represent the path of noise signals from the noise source towards the noise cancellation zones, generally located at the ears of the listener (near the headrest of the seat); and so-called secondary acoustic paths, which represent the path of anti-noise signals from the speakers that emit the same anti-noise signals towards the aforesaid noise cancellation zones.

[0008] Typically, in the algorithms used, a representation of the secondary paths (i.e., an estimate of the corresponding transfer function) is introduced, while the primary paths are determined indirectly.

[0009] Traditional ARNC algorithms are based on a fixed or static representation of the audio system and the acoustic paths, which therefore does not allow to follow any changes of the system over time (for example due to aging or degradation phenomena or even to different areas or methods of use of the vehicle), thus causing a degradation of the performance over time of the audio system and / or of the aforesaid noise cancellation algorithms.

[0010] Some solutions have been proposed, in particular in the field of consumer electronics, which allow carrying out an adaptive estimate of acoustic paths during the operation of the related systems (i.e., being able to adapt to changes over time); however, such solutions are generally expensive in terms of resources and can be invasive from the point of view of the user experience.

[0011] For example, an adaptive technique that has been proposed for noise cancellation involves performing an estimate of the acoustic paths, during the operation of the system, using a driving signal, in particular a random noise (or white noise), which is mixed into an input signal of the anti-noise speaker.

[0012] This approach can work with some precision, but the driving signal is an unwanted artefact that can be perceived by a listener, so much so that its use in certain application areas is impractical.OBJECT OF THE INVENTION

[0013] The object of the present solution is generally to provide a system for determination of acoustic paths in the passenger compartment of a vehicle, which can overcome or in any case limit the problems previously highlighted.

[0014] In accordance with the object indicated above, according to the present solution a system and a method are provided, as defined in the appended claims.BRIEF DESCRIPTION OF THE FIGURES

[0015] The present invention will now be described with reference to the accompanying drawings, which illustrate a non-limiting exemplary embodiment thereof, wherein: Figure 1 schematically shows a motor vehicle provided with an audio system, with examples of acoustic paths highlighted; Figure 2 is a schematic block diagram of a processing unit of the audio system; Figure 3 is a flowchart related to operations carried out by the processing unit of the audio system; Figures 4A-4B and 5A-5B show plots of quantities associated with the operation of the processing unit; Figure 6 is a schematic block diagram associated with a noise cancellation stage implemented by the processing unit; and Figure 7 is a schematic block diagram associated with an optimization stage of the audio system implemented by the processing unit. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0016] As will be described in detail in the following, an aspect of the present solution generally entails implementing a system for identifying or determining acoustic paths within a passenger compartment of a vehicle, configured to exploit, for such determination, sounds already reproduced by the audio system in the same passenger compartment. Such system is also able to adapt to temporal changes so as to preserve performance and robustness over time and can also be implemented on-line, i.e., during the operation of the audio system and / or associated noise cancellation algorithms, in a transparent manner for a user of the vehicle.

[0017] Figure 1 shows a vehicle, in particular a motor vehicle 1 (which can be indifferently of a traditional or thermal type, hybrid or electric type), provided with a body 2 resting on the ground by means of wheels 3, defining therein a passenger compartment 4 and comprising front and rear doors 5 that give access to the same passenger compartment 4 and a hatchback door 6 that gives access to a corresponding trunk.

[0018] Within the passenger compartment 4, the motor vehicle 1 comprises a pair of front seats 8, arranged at the front (with respect to the direction of travel) and designed to accommodate the driver of the motor vehicle 1 and a passenger; and rear seats 9, arranged at the rear (with respect to the same direction of travel).

[0019] The motor vehicle 1 further comprises an audio system 10, configured to reproduce sound signals within the passenger compartment 4, comprising for this purpose a plurality of speakers 12, having in a known manner different frequency contributions (for example mid-range speakers, tweeters, etc.), typically arranged at the doors 5; in the illustrated example, the audio system 10 further comprises a subwoofer, arranged at the trunk.

[0020] As schematically illustrated in the aforesaid Figure 1, the audio system 10 further comprises a digital processing unit 14 (microprocessor, microcontroller or the like), configured to drive the aforesaid speakers 12 to generate the sound signals to be reproduced in the passenger compartment 4.

[0021] In a possible implementation, such digital processing unit 14 may coincide with, or be part of, a control and management unit of an infotainment system of the motor vehicle 1, designed to control, in a known manner, the generation of digital audio-video (information and entertainment) content and also the activation, adjustment or monitoring of different functions of the motor vehicle 1 (for example the management of air conditioning or the control of data associated with the operation of the motor vehicle 1).

[0022] The digital processing unit 14 is also operatively coupled to a control unit (ECU - Electronic Control Unit) of the motor vehicle 1, not illustrated herein, designed to supervise the general operation of the same motor vehicle 1 (in a manner known per se, not described in detail herein).

[0023] The aforesaid audio system 10 further comprises: detection sensors 16, for example microphones, arranged within the passenger compartment 4 of the motor vehicle 1, configured to detect passenger-compartment signals emitted by the speakers 12; and reference sensors 18, for example accelerometers or microphones, arranged for example outside the passenger compartment 4, configured to detect reference signals, indicative of environmental noise, in particular rolling noise.

[0024] In a possible implementation, the detection sensors 16 are arranged at headrests of the front seats 8 (and possibly of the rear seats 9), so as to provide a detection in the proximity of the ears of the users of the motor vehicle 1 (at least of the driver).

[0025] The reference sensors 18 can instead be arranged at the wheels 3 of the motor vehicle 1, for example coupled to the hubs of the wheels 3, so as to provide a detection associated with environmental noise, for example associated with the rolling noise of the tyres or aerodynamic noise.

[0026] The aforesaid digital processing unit 14 is, among other features, configured to determine acoustic paths within the passenger compartment 4 of the motor vehicle 1 and corresponding frequency transfer functions.

[0027] In particular, by way of example, as is indeed shown in Figure 1, the aforesaid acoustic paths comprise: at least a first acoustic path, denoted with P p , which defines a transfer function between a respective reference sensor 18 (acting, in an ARNC noise cancellation algorithm, as a noise reference sensor) and a respective detection sensor 16 (acting, in an ARNC noise cancellation algorithm, as an error sensor), the aforesaid first acoustic path P p being in such case a so-called primary acoustic path; and at least a second acoustic path, denoted with P S , which defines a transfer function between a respective speaker 12 within the passenger compartment 4 and a respective detection sensor 16 (acting, as indicated, as an error sensor for the ARNC noise cancellation algorithm).

[0028] It should be noted in any case that the aforesaid acoustic paths may comprise other types of paths and / or other elements of the audio system 10 or in general of the motor vehicle 1.

[0029] For example, the digital processing unit 14 can be configured to determine an acoustic path between a respective speaker 12 and a respective detection sensor 16, for the determination of a corresponding frequency response function (FRF), to be used for example for the purposes of adjusting ("tuning") the audio system 10 of the motor vehicle 1.

[0030] In particular, the digital processing unit 14 can be configured to implement, on the basis of the signals provided by the detection and reference sensors 16, 18, noise cancellation algorithms, such as ARNC algorithms, and / or optimization algorithms of the audio system 10 (tuning, optimization or adjustment algorithms).

[0031] As shown in Figure 2, the aforesaid digital processing unit 14 comprises a generation stage 20, configured to generate within the passenger compartment 4 of the motor vehicle 1, via the speakers 12, passenger-compartment audio signals, such as for example signaling, alert or warning signals, ESE (Engine Sound Enhancement) signals, or additional sounds usually reproduced in the passenger compartment 4 during the normal operation of the motor vehicle 1 and having an informative content for a user.

[0032] In general, such audio signals can correspond to sounds that characterize the user experience, both as regards signals, alerts or warnings (so-called chimes and warning sounds) and as regards the driving experience (ESE signals). In a known manner, in a vehicle, chimes are sounds or acoustic signals that are emitted to attract the driver's attention to certain conditions or actions. These sounds are generally pleasant and non-invasive, and may indicate events such as lights turning on, doors opening, seat belts not being fastened, or other routine notifications that do not pose an immediate danger. In a vehicle, warning sounds are acoustic signals designed to warn the driver of potentially dangerous situations or malfunctions of the vehicle. These sounds are often louder and more insistent with respect to chimes, and can indicate problems such as low oil pressure, engine overheating, low tyre pressure, or other conditions that require immediate attention.

[0033] According to an aspect of the present solution, the digital processing unit 14 further comprises a determination stage 22, configured to determine acoustic paths within the passenger compartment 4 of the motor vehicle 1, as a function only of the aforesaid passenger-compartment audio signals, i.e. without requiring the generation of dedicated and specific (for such determination operation) additional audio signals, such as driving signals, white noise signals, etc.

[0034] In particular, such determination stage 22 can be configured to determine secondary acoustic paths and the digital processing unit 14 can further comprise a noise cancellation stage 24, configured to implement active noise cancellation algorithms (ARNC algorithms) based on the aforesaid secondary acoustic paths.

[0035] In addition, or alternatively, the determination stage 22 can be configured to determine frequency response functions (FRFs) and the digital processing unit 14 can further comprise an optimization stage 26, configured to implement algorithms for adjusting or optimizing the audio system 10 based on the aforesaid frequency response functions (in particular for the purpose of optimizing the audio reproduction by the on-board entertainment systems).

[0036] According to an aspect of the present solution, the aforesaid determination stage 22 is configured to determine the aforesaid acoustic paths adaptively, that is, adapting over time to possible changes associated with the audio system 10, for example due to aging or degradation phenomena or even to different conditions of use of the motor vehicle 1 (for example, to different conditions of occupancy of the passenger compartment 4).

[0037] Furthermore, the determination stage 22 can be configured to determine the aforesaid acoustic paths on-line, i.e. in real time during the operation of the audio system 10 and of the aforesaid noise cancellation or optimization algorithms.

[0038] Such determination (in particular, the updating over time of the estimates of the acoustic paths) can be carried out at a lower processing rate with respect to the processing rate of the noise cancellation or audio optimization algorithm; or be carried out at preset time intervals, or even be carried out only if necessary (one-off), for example when a decrease in performance of the noise cancellation algorithm or of the audio reproduction algorithms is determined.

[0039] The determination of the acoustic paths can alternatively, or in addition, also be carried out off-line, i.e., in a separate time period with respect to the operation of the audio system 10, for example on the basis of audio signals previously stored during the operation of the same audio system 10.

[0040] In any case, the determination stage 22 is configured to use the aforesaid passenger-compartment audio signals to excite a frequency band of interest of the transfer functions involved in the noise cancellation or audio optimization applications, making it possible to determine the frequency response thereof.

[0041] In more detail, and with reference to Figure 3, the determination stage 22 can be configured firstly, step 30, to perform a preliminary (optional, but advantageous) operation of separation between groups of speakers 12 (woofers, mid-range, etc.) based on a different frequency content of the audio signals detected by the detection sensors 16.

[0042] Next, step 32, the determination stage 22 is configured to perform an operation of separation of the audio signals from the individual speakers 12 forming part of the same group, for example using beamforming techniques (similar to those typically already used in the motor vehicle 1 for Voice Recognition, VR, or Echo Cancelling and Noise Reduction, ECNR, content).

[0043] In particular, the determination stage 22 can implement algorithms comprising non-heuristic techniques (for example Deep Learning techniques) which, alongside beamforming, can improve the performance thereof, compensating for the effects of near-field reflections and propagation that can occur in the passenger compartment 4 (in this case, the use of a smaller number of sensors may also be required).

[0044] The possibility of carrying out off-line or reduced-rate processing may favour the use of beamforming algorithms or similar advanced processing algorithms.

[0045] Once the contributions of the individual speakers 12 have been separated, the determination stage 22 is configured to determine the individual frequency response functions between the speakers 12 and respective detection sensors 16, as indicated in step 34.

[0046] As shown in Figure 3, the aforesaid operations can then be repeated iteratively over time (at preset intervals or as needed), to adapt the estimate of the frequency response functions to changes of the audio system 10 and / or the environment related to the passenger compartment 4.

[0047] In this regard, Figure 4A shows a passenger-compartment audio signal, in the example having an impulse function, and Figure 4B shows a corresponding detection signal provided by a respective one of the detection sensors 16. In the trend of such detection signal, the impulsive contribution of the passenger-compartment audio signal with respect to a background noise can be recognized.

[0048] The determination stage 22 is configured to determine the aforesaid frequency response function FRF, shown by way of example in Figure 5A, as: H jω = Y jω X jω = fft y t fft s t where y(t) indicates the detection signal and s(t) indicates the passenger-compartment audio signal.

[0049] Figure 5B shows the corresponding impulse response: h t = ifft H jω

[0050] As indicated above, the determination stage 22 is thus able to adaptively determine the acoustic paths of interest within the passenger compartment 4 of the motor vehicle 1.

[0051] Figure 6 shows a possible implementation of the noise cancellation stage 24, designed to cooperate with the determination stage 22, in particular to exploit the adaptive determination of the acoustic paths thereof, in such case of the secondary acoustic paths for a noise cancellation algorithm.

[0052] In detail, in such Figure 6 a first transfer block 40 represents the transfer function of a primary acoustic path P(z), which models the transmission of the noise signal between the noise source and the noise cancellation zone, i.e. between a respective one of the reference sensors 18 and a respective one of the detection sensors 16 (in this case defined as an error sensor).

[0053] This first transfer block 40 schematically receives a noise reference signal x(n), provided by the aforesaid reference sensor 18, and outputs a primary disturbance signal d(n), which represents the disturbance to be cancelled at the noise cancellation zone.

[0054] A second transfer block 42 represents the transfer function of a secondary acoustic path S(z), which models the transmission of the audio signal between a respective speaker 12 and the aforesaid noise cancellation zone. In particular, such second transfer block 42 schematically receives a control signal c(n), which represents the driving signal provided to the aforesaid speaker 12, and outputs an anti-noise signal y(n).

[0055] A cancellation block 44 schematically receives at a first input the aforesaid primary disturbance signal d(n) and at a second input the anti-noise signal y(n), so as to output an error signal e(n), which is the result of a destructive interference between the primary disturbance d(n) and the anti-noise signal y(n) (in practice, such error signal is the signal measured by the aforesaid error sensor, which directly measures the result of this destructive interference).

[0056] In particular, the aforesaid noise cancellation stage 24 comprises: a control filter block 45, configured to receive at an input the noise reference signal x(n) and generate at an output the aforesaid control signal c(n); and an adaptation block 46, configured to suitably adapt the filtering action performed by the control filter block 45, for example modifying the weights, coefficients and / or transfer function thereof.

[0057] Such adaptation block 46 can for example operate by means of an LMS (Least Mean Squares) algorithm, or by means of a similar adaptive algorithm, and receives at an input the aforesaid error signal e(n) and also a filtered noise reference signal x'(n).

[0058] In particular, the noise cancellation stage 24 comprises an estimation block 47, which receives at an input the noise reference signal x(n) and outputs the filtered noise reference signal x'(n), implementing an estimate of the secondary acoustic path S'(z).

[0059] According to an aspect of the present solution, the aforesaid estimation block 47 is operatively coupled to the determination stage 22, so that the estimate of the secondary acoustic path S'(z) adapts its operation as a function of the determination of the acoustic paths by the same determination stage 22.

[0060] In other words, the determination stage 22 is configured to modify the estimate of the secondary acoustic path S'(z), based on the determined frequency response functions FRF, as discussed in detail above, in an adaptive manner.

[0061] It should be noted, in this regard, that the performance of the cancellation algorithm strongly depends on such estimation block 47, since the more the estimate S' (z) accurately models the secondary acoustic path S(z), the better the performance of the algorithm. Advantageously, the determination stage 22 allows updating the estimation block 47, so as to maintain a good performance over time, operating transparently to the user, using sounds already normally reproduced by the audio system 10.

[0062] In particular, the operation of the noise cancellation stage 24 is transparent to the user without degradation of performance and without requiring an increase in the complexity of the control logic, also offering an increase in the versatility of the management of computational resources (it should be noted in such regard that the determination stage 22 operates independently and externally with respect to the actual control logic of the noise cancellation algorithm).

[0063] With reference to Figure 7, a possible implementation of the optimization stage 26, designed to cooperate with the determination stage 22, is now described, in particular to exploit the adaptive determination of the acoustic paths thereof within the passenger compartment 4 of the motor vehicle 1, in such case to implement optimization algorithms of the audio system 10 based on the corresponding frequency response functions.

[0064] Such optimization stage 26 generally comprises a reproduction control block 50, configured to control the reproduction of the audio signals via the various audio channels available within the passenger compartment 4 (and the associated speakers 12); and a routing block 52, configured to route the audio signals towards the aforesaid audio channels.

[0065] The optimization stage 26 further comprises an adjustment or tuning block 54 for adjusting the audio channels, coupled between the output of the routing block 52 and the aforesaid audio channels, here generally indicated with 56.

[0066] According to an aspect of the present solution, the aforesaid adjustment block 54 is operatively coupled to the determination stage 22, to adapt its operation as a function of the determination of the acoustic paths by the same determination stage 22.

[0067] In other words, the determination stage 22 is configured to modify the adjustment of the audio channels (for example an equalization thereof, in terms of amplitude and phase), on the basis of the frequency response functions FRF, which are determined as discussed above.

[0068] Advantageously, the operation of the optimization stage 26 allows to maintain over time the performance of the entertainment system by compensating for changes in the acoustic transfer functions, for example due to ageing of the components or changes in the acoustic response in the passenger compartment 4.

[0069] Furthermore, such optimization stage 26 allows optimizing the user experience for example on the basis of the number of occupants of the same passenger compartment 4, compensating for the related impact on the transfer functions.

[0070] Based on what has been discussed, the advantages that the present solution allows to achieve emerge in an evident manner.

[0071] In any case, it is again highlighted that such solution allows to increase the stability of the performance (for example for noise cancellation algorithms and for optimization algorithms of the entertainment system) in systems characterized by time-variant paths (due to degradation, ageing, influence of the occupants or other factors occurring in the passenger compartment).

[0072] The proposed solution, thanks to the use of audio signals already reproduced in the passenger compartment during the normal operation of the system, allows to implement an identification of the acoustic paths in a manner that is transparent to the user.

[0073] Furthermore, such solution involves a limited complication of the architecture and allows a high versatility of the management of computational resources, since the identification of acoustic paths is possible both on-line and off-line, and can also be carried out with variable update rates, at preset intervals or upon need.

[0074] Finally, it is clear that modifications and variations can be made to what has been described without thereby departing from the scope of the present invention, as defined by the appended claims.

[0075] It should be noted in particular that the described solution can be used in various types of applications, even different from the examples described in detail above, in general whenever the determination of acoustic paths within the passenger compartment of a vehicle (of any type) is required.

Examples

Embodiment Construction

[0016]As will be described in detail in the following, an aspect of the present solution generally entails implementing a system for identifying or determining acoustic paths within a passenger compartment of a vehicle, configured to exploit, for such determination, sounds already reproduced by the audio system in the same passenger compartment. Such system is also able to adapt to temporal changes so as to preserve performance and robustness over time and can also be implemented on-line, i.e., during the operation of the audio system and / or associated noise cancellation algorithms, in a transparent manner for a user of the vehicle.

[0017]Figure 1 shows a vehicle, in particular a motor vehicle 1 (which can be indifferently of a traditional or thermal type, hybrid or electric type), provided with a body 2 resting on the ground by means of wheels 3, defining therein a passenger compartment 4 and comprising front and rear doors 5 that give access to the same passenger compartment 4 and ...

Claims

1. An acoustic path determination system in a passenger compartment (4) of a vehicle (1) provided with an audio system (10) having speakers (12) configured to reproduce sounds within the passenger compartment (4), comprising: a generation stage (20), configured to generate within the passenger compartment (4), via the speakers (12), passenger-compartment audio signals related to a user experience in the vehicle (1); and a determination stage (22), configured to determine and adaptively update over time estimates of said acoustic paths within the passenger compartment (4), as a function of the detection and processing of said passenger-compartment audio signals.

2. The system according to claim 1, wherein said passenger-compartment audio signals include signaling or alert or warning sounds and / or "ESE" - Engine Sound Enhancement sounds and / or additional sounds designed to be present in the passenger compartment (4) during operation of the vehicle (1) and addressed to the user of the vehicle (1).

3. The system according to claim 1 or 2, wherein said determination stage (22) is configured to generate said passenger-compartment audio signals to excite a frequency band of interest to determine frequency response functions associated with said acoustic paths and to process said detected passenger-compartment audio signals to determine said frequency response functions.

4. The system according to any one of the preceding claims, further comprising a noise cancellation stage (24) configured to implement active noise cancellation algorithms based on the determination of secondary acoustic paths within said passenger compartment (4); wherein said determination stage (22) is configured to determine and adaptively update over time estimates of said secondary acoustic paths.

5. The system according to claim 4, wherein said noise cancellation stage (24) comprises an estimation block (47), configured to receive at an input a noise reference signal (x(n)) and to output a filtered noise reference signal (x'(n)), implementing an estimate of a secondary acoustic path (S'(z)); wherein said estimation block (47) is operatively coupled to the determination stage (22), such that said estimate of the secondary acoustic path (S'(z)) is a function of the determination of the acoustic paths by said determination stage (22).

6. The system according to claim 5, wherein said noise cancellation stage (24) further comprises: a control block (45), configured to receive at an input said noise reference signal (x(n)) and generate at an output a control signal (c(n)) configured to drive at least one of said speakers (12) so as to generate an anti-noise signal (y(n)) designed to cancel a primary disturbance signal d(n), representing a signal to be cancelled at a noise cancellation zone within said passenger compartment (4), originating an error signal (e(n)); and an adaptation block (46), configured to adapt the filtering action performed by the control block (45) as a function of said filtered noise reference signal (x'(n)) and said error signal (e(n)).

7. The system according to any one of the preceding claims, further comprising an optimization stage (26) configured to implement adjustment algorithms of the audio system (10) based on frequency response functions (FRFs) within said passenger compartment (4); wherein said determination stage (22) is configured to determine and update over time the estimates of said acoustic paths for determining said frequency response functions (FRFs).

8. The system according to any one of the preceding claims, wherein said determination stage (22) is configured to determine said acoustic paths by adapting over time to changes associated with the audio system (10), due to aging and / or degradation phenomena and / or changed conditions of the passenger compartment (4) or of use of the vehicle (1).

9. The system according to any one of the preceding claims, wherein said determination stage (22) is configured to determine said acoustic paths on-line, during the operation of the audio system (10).

10. The system according to claim 9, wherein said determination stage (22) is configured to determine said acoustic paths with an updating rate lower than a processing rate associated with the operation of said audio system (10).

11. The system according to any one of the preceding claims, further comprising detection sensors (16), arranged within the passenger compartment (4), configured to detect the passenger-compartment audio signals emitted by the speakers (12); wherein said determination stage (22) is operatively coupled to said detection sensors (16) and said acoustic paths are determined between respective ones of said speakers (12) and respective ones of said detection sensors (16).

12. An audio system (10) for reproducing sounds within a passenger compartment (4) of a vehicle (1), comprising the system according to any one of the preceding claims.

13. A vehicle (1), comprising the audio system (10) according to claim 12.

14. An acoustic path determination method in a passenger compartment (4) of a vehicle (1) provided with an audio system (10) having speakers (12) configured to reproduce sounds within the passenger compartment (4), comprising: generating within the passenger compartment (4), via the speakers (12), passenger-compartment audio signals; and determining and adaptively updating over time estimates of said acoustic paths within the passenger compartment (4), as a function of the detection and processing of said passenger-compartment audio signals.

15. The method according to claim 14, wherein said passenger-compartment audio signals include signaling, alert or warning sounds, and / or "ESE" - Engine Sound Enhancement sounds and / or additional sounds designed to be present in the passenger compartment (4) during operation of the vehicle (1) and addressed to the user of the vehicle (1).

Images