Device and method for audio signal equalization for vehicles implementing a data communication bus

Abstract

A vehicle audio signal equalization device and method implementing a data communication bus comprises: - a memory (200) arranged to store speed filter datasets comprising triplets associating a speed value and a gain value associated with coefficients to define a speed masking filter, and functional filter datasets comprising triplets associating an engine speed or fan speed value and a gain value associated with coefficients to define an engine or fan masking filter, - a collector (210) arranged to receive at least two parameters accessible on the communication bus,which parameters designate the vehicle speed and at least one functional parameter chosen from the group comprising the vehicle engine speed and a ventilation data set, and - a computer (220) arranged to receive as input a sound margin value, as well as said at least two parameters accessible on the communication bus, to derive therefrom at least one speed filter data set and at least one functional filter data set and to combine them into a masking equalization filter to be applied to an audio signal. Fig.2,

Description

Title of the invention: Device and method for equalizing an audio signal for a vehicle using a data communication bus

[0001] The invention relates to the field of audio signal processing in a vehicle, and more particularly to the equalization of such an audio signal in an environment which may be noisy, in particular when the noise in question is likely to vary over time.

[0002] The effect of masking a first audio signal by a second audio signal is the process by which the hearing threshold for the first signal is raised by the presence of the second signal. In other words, spectral masking occurs in a given frequency band when the presence of the second signal does not allow the detection of the first signal of lower amplitude in the same frequency band.

[0003] In a car, this effect is generally created by the aerodynamic noise linked to the rolling of the car, as well as by the noise of the engine. In the presence of noise, the perception of the spectral balance of the music diffused in the passenger compartment of the car can then be altered because certain frequencies will be masked.

[0004] The perceived tonal balance depends on the difference between the broadcast sound level and the masking threshold. Since musical signals have a given dynamic range (difference between the highest and lowest amplitudes), for a given average level value in dB SPL (for "Sound Pressure Level" in English) close to the threshold, certain components of the signal will be perceived and others will be masked.

[0005] In order to avoid the masking phenomenon and to preserve the perceived tonal balance, it is necessary to increase certain frequencies of the broadcast audio signal beyond the masking threshold. Since acoustic insulation is not sufficient, signal processing techniques have been developed to produce masking filters to compensate for the masking phenomenon.

[0006] In the state of the art, two types of techniques are conventionally implemented. A first technique, called SDVC (for "Speed ​​Dependent Volume Control" in English), consists of adding a gain calculated from a speed table to increase the sound volume of the audio signal (i.e., the entire audio signal) above the masking threshold. A second technique, called SDEC (for "Speed ​​Dependent Equalization Control" in English), consists of applying a low-frequency shelf filter (or "low shelf filter" in English) whose parameters depend on the speed and the overall attenuation of the system.

[0007] These two techniques have the advantage of requiring little computing power, which is particularly crucial in an automotive environment, both from the point of view of cost and from the point of view of ease of integration.

[0008] However, the background noise in a car-type vehicle has several sources, among which we can cite as examples: - the configuration of the vehicle itself linked to its sound insulation, its aerodynamics, the type of tires, engine, etc.; - certain vehicle features that can modify the background noise such as the HVAC system (for "Heating, Ventilation and Air-Conditioning" in English, or heating, ventilation and air conditioning system), activation / deactivation of the thermal engine of hybrid cars, etc.; - rolling noise and aerodynamic noise which increases with the speed of the car; - the nature of the road surface, with coarse-grained tarmac roads or pavements being noisier than smooth tarmac roads; and - the environment, with open country roads being less noisy than tunnels. Rain and wind also increase background noise in the vehicle.

[0009] Background noise can generally be described as broadband noise with a 6 dB per octave decay in the high frequencies. However, depending on the noise sources listed above, this definition may not be sufficient to describe the masking phenomena encountered in practice. For example, in the presence of rain, high frequencies may also be masked. Similarly, depending on the nature of the vehicle and its speed, the frequency bands actually masked may change over time.

[0010] Faced with such variable masking effects, it can be observed that the SDVC function increases the level of the entire signal as the speed increases. However, the perception of the broadcast audio frequency signal is not linear around the masking threshold (for example, high frequencies may be better perceived than low frequencies). Thus, as the speed increases, the SDVC function increases the level of the entire signal while this is not necessarily necessary for all frequencies.

[0011] For its part, the SDEC function introduces some spectral processing to avoid the previous effect. By amplifying the signal with a low-frequency shelving filter, the SDEC function ensures that for a typical noise profile (i.e., exhibiting a 6 dB per octave rolloff in the high frequencies), the low frequencies are increased above the masking threshold and the perceived spectral balance is preserved. The assumption in this case is that the background noise profile depends only on the vehicle speed. But as described above, such a profile can change radically and unpredictable manner, for example with the road surface or the environment.

[0012] For this reason, the Applicant has developed a masking equalization called NDEC (for "Noise Dependent EQ Control" in English), which consists of an equalization control based on noise captured by an acoustic sensor within the vehicle. This processing is based on an algorithm that analyzes the noise captured by a microphone to deduce the noise spectrum in real time and apply a compensation filter to the audio signal. It has the great advantage of being highly adaptable to different noises. However, it has many disadvantages, such as the need to use a microphone, very high consumption of computing and memory resources, and the need for dedicated processing for voice.

[0013] Currently, it is therefore necessary to make a choice between a simple masking equalization, but not very effective given the various noise sources, or an effective equalization, but extremely costly and complex to implement.

[0014] The invention improves the situation. To this end, it proposes an audio signal equalization device for a vehicle implementing a data communication bus comprising: - a memory arranged to store speed filter data sets comprising triplets associating a speed value and a gain value associated with coefficients for defining a speed masking filter, and functional filter data sets comprising triplets associating an engine speed value or a ventilation value and a gain value associated with coefficients for defining an engine or ventilation masking filter, - a collector arranged to receive at least two parameters accessible on the communication bus, which parameters designate the speed of the vehicle and at least one functional parameter chosen from the group comprising the engine speed of the vehicle and a ventilation data set, and - a calculator arranged to receive as input a sound margin value, as well as said at least two parameters accessible on the communication bus, to derive therefrom at least one speed filter data set and at least one functional filter data set and to combine them into a masking equalization filter to be applied to an audio signal.

[0015] This device is particularly advantageous because it makes it possible to implement equalization which is effective for the main sources of noise, with an implementation cost which remains reasonable, and which is based on an architecture present in all vehicles, without additional hardware.

[0016] According to various embodiments, the invention may have one or more of the following characteristics: - the calculator is arranged to determine a speed filter data set and a functional filter data set in the memory from the at least two parameters determined by the collector, to calculate a speed gain value from at least the gain value of the determined speed filter data set and the noise margin value and to derive a speed filter data set therefrom, and to determine a functional gain value from at least the gain value of the determined functional filter data set, the speed gain value and the noise margin value and to derive a functional filter data set therefrom, - the calculator is arranged to calculate the speed gain value by retaining the minimum between the gain value of the determined speed filter data set and the noise margin value,and to calculate the functional gain value by retaining the minimum between the gain value of the determined functional filter data set and the difference between the noise margin value and the speed gain value, , - the computer is arranged, in the presence of an engine speed functional parameter and a ventilation data set functional parameter, to determine a main functional filter data set and a second secondary functional filter data set from the engine speed functional parameter and the ventilation data set functional parameter, the gain value of the main functional filter data set being greater than the gain value of the secondary functional filter data set, to determine a first functional gain value from at least the gain value of the main functional filter data set, the speed gain value and the noise margin value and to derive therefrom a first functional filter data set, to determine a second functional gain value from at least the gain value of the secondary functional filter data set,from the first functional gain value, the speed gain value and the noise headroom value and derive therefrom a second functional filter data set, and to calculate a functional gain value and a functional filter data set from the first functional gain value, the second functional gain value, the first functional filter data set and the second functional filter data set, , - the calculator is arranged, when the speed parameter is lower than a chosen threshold, to determine a functional filter data set and a speed filter data set in the memory from the at least two parameters determined by the collector, to determine a functional gain value from at least the gain value of the determined functional filter data set and the noise margin value and to derive therefrom a functional filter data set from the functional gain value, and to determine a speed gain value from at least the gain value of the determined speed filter data set, the functional gain value and the noise margin value and to derive therefrom a filter data set speed from speed gain, - the calculator is arranged to calculate the functional gain value by retaining the minimum between the gain value of the determined functional filter data set and the noise margin value, and to calculate the speed gain value by retaining the minimum between the gain value of the determined speed filter data set and the difference between the noise margin value and the functional gain value, - the calculator is arranged, in the presence of an engine speed functional parameter and a ventilation data set functional parameter, to determine a main functional filter data set and a secondary functional filter data set from the engine speed functional parameter and the ventilation data set functional parameter, the gain value of the main functional filter data set being greater than the gain value of the secondary functional filter data set, to determine a first functional gain value from at least the gain value of the main functional filter data set and the noise margin value and to derive therefrom a first functional filter data set, to determine a second functional gain value from at least the gain value of the secondary functional filter data set,of the first functional gain value and the noise headroom value and derive therefrom a second functional filter data set, and to calculate a functional gain value and a functional filter data set from the first functional gain value, the second functional gain value, the first functional filter data set and the second functional filter data set, and, - the calculator is arranged to apply a high-pass filter to the masking equalization filter depending on the difference between the noise margin, the speed gain value and the functional gain value.

[0017] The invention also relates to a method for equalizing an audio signal for a vehicle implementing a data communication bus comprising: a) storing speed filter data sets comprising triplets associating a speed value and a gain value associated with coefficients for defining a speed masking filter, and functional filter data sets comprising triplets associating an engine speed value or a ventilation value and a gain value associated with coefficients for defining an engine or ventilation masking filter, (b) receiving at least two parameters accessible on the data communication bus, which parameters designate the vehicle speed and at least one functional parameter chosen from the group comprising the vehicle engine speed and a ventilation data set, and a noise margin value, and c) derive from the parameters of step b) and the sound margin value at least one set of speed filter data and at least one functional filter data set and to combine them into a masking equalization filter to be applied to an audio signal.

[0018] According to various embodiments, the invention may have one or more of the following features: - operation c) comprises cl) determining a speed filter data set and a functional filter data set from the at least two parameters determined by the collector, c2) calculating a speed gain value from at least the gain value of the determined speed filter data set and the noise margin value and deriving therefrom a speed filter data set, and c3) determining a functional gain value from at least the gain value of the determined functional filter data set, the speed gain value and the noise margin value and deriving therefrom a functional filter data set, - operation c2) comprises calculating the speed gain value by retaining the minimum between the gain value of the determined speed filter data set, the noise margin value, and operation c3) comprises calculating the functional gain value by retaining the minimum between the gain value of the determined functional filter data set, the difference between the noise margin value and the speed gain value, - when operation b) returns an engine speed functional parameter and a ventilation dataset functional parameter, operation c3) comprises c3a) determining a primary functional filter dataset and a second secondary functional filter dataset from the engine speed functional parameter and the ventilation dataset functional parameter, the gain value of the primary functional filter dataset being greater than the gain value of the secondary functional filter dataset, c3b) determining a first functional gain value from at least the gain value of the primary functional filter dataset, the speed gain value and the noise margin value and deriving therefrom a first functional filter dataset, c3c) determining a second functional gain value from at least the gain value of the secondary functional filter dataset,of the first functional gain value, the speed gain value and the noise margin value and deriving therefrom a second functional filter data set, and c3d) calculating a functional gain value and a functional filter data set from the first functional gain value, the second functional gain value, the first functional filter data set and the second functional filter data set, , - when the speed parameter of operation b) is less than a chosen threshold, operation c) comprises cl) determining a functional filter data set and a speed filter data set in the memory from the at least two parameters determined by the collector, c2) determining a functional gain value from at least the gain value of the determined functional filter data set and the noise margin value and deriving therefrom a functional filter data set from the functional gain value, and c3) determining a speed gain value from at least the gain value of the determined speed filter data set, the functional gain value and the noise margin value and deriving therefrom a speed filter data set from the speed gain, - operation cl) comprises calculating the functional gain value by retaining the minimum between the gain value of the determined functional filter data set, the noise margin value, and operation c2) comprises calculating the speed gain value by retaining the minimum between the gain value of the determined speed filter data set, the difference between the noise margin value and the functional gain value, - when operation b) returns an engine speed functional parameter and a ventilation dataset functional parameter, operation c2) comprises c2a) determining a primary functional filter dataset and a secondary functional filter dataset from the engine speed functional parameter and the ventilation dataset functional parameter, the gain value of the primary functional filter dataset being greater than the gain value of the secondary functional filter dataset, c2b) determining a first functional gain value from at least the gain value of the primary functional filter dataset and the noise margin value and deriving therefrom a first functional filter dataset, c2c) determining a second functional gain value from at least the gain value of the secondary functional filter dataset,of the first functional gain value and the noise margin value and deriving therefrom a second functional filter data set, and c2d) calculating a functional gain value and a functional filter data set from the first functional gain value, the second functional gain value, the first functional filter data set and the second functional filter data set, and , - the method further comprising the step d) applying a high-pass filter to the masking equalization filter as a function of the difference between the noise margin, the speed gain value and the functional gain value.

[0019] The invention also relates to a computer program comprising instructions for executing the method according to the invention, a data storage medium on which such a computer program is recorded and a computer system comprising a processor coupled to a memory, the memory having recorded such a computer program.

[0020] Other characteristics and advantages of the invention will appear more clearly upon reading from the following description, taken from examples given for illustrative and non-limiting purposes, taken from the drawings in which: - [Fig.l] represents a system for broadcasting an audio signal in a vehicle implementing the invention, - [Fig.2] represents an example of a device structure allowing the implementation of masking equalization in the system of [Fig.l], embodiment of the invention, - [Fig.3] represents a first embodiment of an equalization by the device of [Fig.2], - [Fig.4] represents a first example of implementation of the equalization of [Fig.3], - [Fig.5] represents a second example of implementation of the equalization of [Fig.3], - [Fig.6] represents a third example of implementation of the equalization of [Fig.3], and - [Fig.7] represents a second embodiment of an equalization by the device of [Fig.2].

[0021] The drawings and the description below contain, for the most part, elements of a certain character. They may therefore not only serve to better understand the present invention, but also contribute to its definition, if necessary.

[0022] This description is likely to involve elements that are subject to protection by copyright and / or copyright. The rights holder has no objection to the identical reproduction by anyone of this patent document or its description, as it appears in the official files. For the rest, he reserves his rights in full.

[0023] [Fig.l] represents a broadcasting system 110 of an audio signal implemented implementing the invention in a broadcasting environment which takes the form of a vehicle 100. The vehicle is here represented in the form of a car, but the invention applies to any type of vehicle. As will appear below, the invention is based particularly on the fact that the vehicle 100 implements a data communication bus such as a CAN bus.

[0024] The broadcasting system 110 comprises several loudspeakers 112 as well as an equalization device 114 according to the invention. The equalization device 114 is configured to implement masking equalization according to any one of the embodiments described with [Fig. 3] or [Fig. 7]. [Fig. 2] represents a schematic example of the implementation of the device 114.

[0025] In various embodiments, the equalization device 114 is not integrated into the broadcasting system 110, but connected to it via a wired link (for example a USB or equivalent connection) or wirelessly (for example a Bluetooth, WiFi or equivalent connection) in order to exchange data, such as the broadcast audio signal and the equalized audio signal. The broadcast system 110 may comprise a single loudspeaker 112.

[0026] [Fig. 2] represents a schematic example of implementation of the equalization device 114. In the example described here, the equalization device 114 comprises a memory 200, a collector 210 and a calculator 220.

[0027] The memory 200 can be any type of data storage suitable for receiving digital data: hard disk, hard disk with flash memory, flash memory in any form, RAM, magnetic disk, locally distributed storage or in the cloud, etc. However, taking into account the automotive application of the invention, the memory 200 will more likely be a flash memory or a hard disk which can be accessed by the system 110, the collector 210 and the computer 220.

[0028] In the example described here, the memory 200 receives all the data relating to the device 114, i.e., the programs and software instantiating the collector 210 and the calculator 220, their parameters, the data received as input (if any), the intermediate gain and filter coefficient values, the data stored in buffer memory, as well as the masking filter data as output. The data calculated by the device can be stored on any type of memory similar to the memory 200, or on it. This data can be erased after the device has performed its tasks or retained.

[0029] The memory 200 receives speed filter data sets comprising triplets associating a speed value, a gain value, and speed masking filter coefficients, and functional filter data sets comprising triplets associating an engine speed value or a ventilation value, a gain value, and engine or ventilation masking filter coefficients. The coefficient sets allow the various filters to be implemented quickly and at low cost. The coefficient sets may be generic or specifically adapted to each vehicle. In the context of the invention, the latter option is preferred. In the examples described here, the masking filters implemented are biquadratic filters. Alternatively, these filters could be of another type such as recursive filters or finite impulse response filters made in the time domain.These filters can also be implemented in the frequency domain.

[0030] The memory 200 receives parameters as input data, as well as one or more sound margin data.

[0031] The parameters are used to define the characteristics of the masking noise phenomena that the device 114 aims to filter. These parameters are obtained by the collector 210 from a vehicle communication bus, for example the bus CAN. This implementation is particularly advantageous because the CAN bus circulates a lot of information that allows the status of the vehicle to be qualified, whether its speed, its engine speed or other functional information such as the parameters of the HVAC system (for example and without limitation, an operating indicator, a ventilation speed value and a ventilation power value. In the following, the speed represents a speed parameter, while the engine speed and the parameters of the HVAC system represent a functional parameter. The reason for this distinction is that the speed represents a fairly well-known source of noise, both through the coating and the aerodynamics and the rolling of the vehicle, and the masking filtering associated with it is fairly well-known. On the other hand, the masking filtering of noises related to the engine or the HVAC system is poorly controlled when one wishes to calculate it with a reasonable cost.This is why the SDEC method, for example, does not treat them.

[0032] The Applicant realized with surprise that, against all expectations, the CAN provides all the essential data to define functional noises such as engine noise or HVAC noise, which makes it possible to complete the SDEC filtering. As will be seen below, this distinction between various sources and their characterization allows differentiated processing that approaches the performance of the NDEC, but with a much lower cost and very great versatility of vehicle platforms, without a microphone being necessary. This simplicity, which relies on the pre-existing CAN (or another communication bus), also makes it possible to simplify the integration of the device 114 in the vehicle.

[0033] Thus, to save on computation costs, the speed, engine speed and HVAC system data ranges are discretized to associate with each a filter gain and filter coefficients stored in the memory 200. Thus, each triplet associating a speed value (respectively engine speed or HVAC system data), a gain and a set of filter coefficients defines a speed filter data set (respectively engine or ventilation). These filter data sets are manipulated by the computer 220 to calculate the masking equalization filter. Preferably, the filter data sets are customized for each vehicle family and are subject to adjustment prior to the implementation of the device 114.

[0034] The sound margin data can be of two types: attenuation on the one hand, linked to the desired sound volume for the audio signal, and a maximum gain desired for the device 114. In the following, the sound margin will represent the smaller of these two values. Alternatively, only one of these two values ​​can be considered, in which case the sound margin is either equal to the attenuation or equal to the maximum gain desired, depending on the intended case.

[0035] The collector 210 and the calculator 220 directly or indirectly access the memory 200. They can be implemented in the form of appropriate computer code executed on one or more processors. By processors, it is meant any processor suitable for the calculations described below. Such a processor can be implemented in any known manner, in the form of a microprocessor for a personal computer, laptop, tablet or smartphone, a dedicated chip of the FPGA or SoC type, a computing resource on a grid or in the cloud, a cluster of graphics processing units (GPUs), a microcontroller, or any other form capable of providing the computing power necessary for the implementation described below. One or more of these elements can also be implemented in the form of specialized electronic circuits such as an ASIC. A combination of processor and electronic circuits can also be envisaged.Given the automotive context of the invention, the simplest possible processors will be preferred in order to optimize the cost of the device 114.

[0036] It will also appear that the collector 210 has the sole function of recovering the parameters and the noise margin to operate the computer 220. Alternatively, the collector 210 and the computer 220 could be merged, or on the contrary the computer 220 could be split into smaller units, provided that functionally the operation of the device 114 does not change.

[0037] [Fig. 3] represents a first embodiment of masking equalization implemented by the device of [Fig. 2]. In this embodiment, it is considered that the speed is the most important source of noise. For this reason, its processing is prioritized. Then, the noise associated with the functional parameter is processed, and this processing depends as will be seen on the processing of the speed noise. In the example represented in [Fig. 3], only one functional parameter is considered to be present. Alternatively, it would be possible to process several functional parameters, for example in the manner described with the second embodiment of masking equalization.

[0038] In an operation 300, the collector 210 recovers from the CAN bus the data necessary for processing by the computer 220, i.e. the vehicle speed V (speed parameter), one of the engine speed rpm and the HVAC ventilation data[]), and the sound margin HR. The speed V, the engine speed rpm and the HVAC ventilation data[] may be obtained by any data circulating on the CAN (or other vehicle communication bus), directly or indirectly.

[0039] Then the speed noise is processed in operations 310, 320 and 330. In operation 310, the computer 220 calls the memory 200 in order to retrieve the speed filter data set which corresponds to the speed V by means of a function Filt 1 () which receives the speed V as an argument. If the value of the speed V is not present in the speed filter data sets present in the memory 200, the function Filt 1 () can return the speed filter data set whose speed is closest to the speed V or a speed filter data set derived from an interpolation of one or more speed filter data sets. Then, in operation 320, a gain LSG is determined by means of a Min() function. The Min() function has the role of taking into account in the processing by the computer 220 the fact that the headroom is finite: it is not possible to apply any correction to the audio signal depending on its volume. In addition, if the audio signal played is very loud, beyond the risks of saturation of the loudspeakers 112, it may be considered useless to amplify the signal to filter the masking. Thus, in the example described here, the Min() function retains the lowest value between the gain value of the speed filter data set of operation 310 and the headroom.Finally, in operation 330, if operation 320 generated an LSG gain different from the gain of operation 310, a Filt2() function is executed in operation 330 to determine the velocity filter data set in memory 200 whose gain most closely matches the LSG gain. Again, the Filt2() function may return the velocity filter data set whose GV gain is closest to the LSG gain, or a velocity filter data set derived from an interpolation of one or more velocity filter data sets.

[0040] After operations 310 to 330, the computer 220 performs operations 340 to 360 to process the noise associated with the functional parameter. As mentioned above, the embodiment of [Fig.3] only processes a single functional parameter, whether it is the engine speed or ventilation data. Operation 340 is similar to operation 310 and executes the Filtl() function with the functional parameter considered to determine the functional filter data set that most closely matches it in memory 200. Then, in operation 350, a gain P is calculated to account for the noise headroom, similarly to operation 320. However, to account for the processing of operations 310 to 340, it is not the noise headroom that is compared to the gain of the functional filter data set of operation 340, but the noise headroom minus the speed gain GV of operation 330.Finally, in operation 360, the functional filter data set of operation 340 is reprocessed according to the functional gain P determined in operation 350, and the functional filter data set FP[] is returned.

[0041] Finally, in an operation 370, the computer 220 executes a function Comb() which combines the speed gain GV and the speed filter data set FV[] of the operation 330 with functional gain GP and the functional filter data set FP[] of the operation 360 to calculate the masking equalization filter MF.

[0042] In a preferred embodiment, the MF masking equalization filter is refined in an optional operation 380 by means of a high-pass filter in order to protect the loudspeakers 112 from excessive bass gain.

[0043] It appears that operations 310 and 340 can be performed in parallel. The following operations 350, on the other hand, depend on operations 320 and 330.

[0044] It therefore appears that, by successive key, the masking equalization filter is constructed taking into account the available sound margin. In order to further lower the costs of the invention, the calculations of the coefficients of the filters can be carried out by storing all-pass type filter data sets which are modified according to the gain determined at certain stages. For example, the filter data set of operation 360 can be determined from the following operations: - gainLin = Transformation of the functional gain value (in dB) into linear gain according to the formula gainLin=10A(P / 20); - bO = 0.5 * ((1 + gainLin) + b0_ap * (1 - gainLin)); - bl= 0.5 * ((1 + gainLin) * al_ap + bl_ap * (1 - gainLin)); - b2 = 0.5 * ((1 + gainLin) * a2_ap + (1 - gainLin)); - al = al_ap; and - a2= a2_ap. where ai and bi are the coefficients of the functional filter dataset FP[] and ai_ap and bi_ap are the coefficients of the all-pass filter dataset.

[0045] [Fig.4] shows an example of a masking equalization filter produced when the noise margin is greater than the sum of the speed gain and the functional gain.

[0046] This example is based on the following data: a speed of 70km / h corresponding to a speed filter data set having a gain of 3.3dB, a noise margin of 13dB, and an engine noise fundamental frequency value of 120Hz determined from the rpm value of 3600 as the product of the engine speed (rpm) times the number of cylinders divided by 120 (other formulas could be used) corresponding to a speed filter data set having a gain of 5dB.

[0047] The Min() function of operation 320 returns a speed gain of 3.3dB, which means that the speed filter data set of operation 310 is unchanged. Then, the functional gain is determined by comparing the gain of 5dB to the value 13-3.3 or 9.7dB, which means that, again, the functional filter data set of operation 340 is unchanged. By the nature of engine noise, the coefficients of the engine filter data set will be related to the harmonics of the fundamental frequency of the engine noise which is the frequency of 120Hz explained above.

[0048] Finally, the final gain is calculated by subtracting the speed gain and the functional gain from the noise margin, i.e. 13-3.3-5=4.7dB which is used as a reference value by the high-pass filter of operation 380.

[0049] [Fig.5] shows an example of a masking equalization filter produced when the noise margin is lower than the gain of the speed filter data set associated with the vehicle speed.

[0050] This example is based on the following data: a speed of 105km / h corresponding to a speed filter data set having a gain of 4dB, a noise margin of 3.1 dB, and a value of the fundamental frequency of the engine noise of 120Hz corresponding to a speed filter data set having a gain of 5dB.

[0051] The Min() function of operation 320 returns a speed gain of 3.1 dB, which means that the speed filter data set of operation 310 must be modified in operation 330. Unfortunately, operation 330 returns a speed filter data set whose speed gain is 3.1 dB. Therefore, the functional gain does not have to be calculated because operation 350 will necessarily return OdB (3.1-3.1). The same is true for the high-pass filter. In this case, there is no functional filter applied (the 0th order filter is applied).

[0052] [Fig.6] represents a third example which concerns the case where the noise margin is greater than the gain of the speed filter dataset associated with the vehicle speed, but less than the added speed gain of the gain of the functional filter dataset associated with the functional parameter.

[0053] This example is based on the following data: a speed of 105km / h corresponding to a speed filter data set having a gain of 4dB, a noise margin of 3dB, and a value of the fundamental frequency of the engine noise of 120Hz corresponding to a speed filter data set having a gain of 5dB.

[0054] The Min() function of operation 320 returns a speed gain of 3dB, which means that the speed filter data set of operation 310 must be modified in operation 330. In this example, operation 330 returns a speed filter data set whose speed gain is 2dB. Therefore, the functional gain will be calculated as follows: Min(5;3-2)=ldB. The functional filter is determined accordingly in operation 360, and the 0th order high pass filter is applied because the 3dB noise margin is equal to the sum of the speed gain (2dB) and the functional gain (IdB).

[0055] These examples are arbitrary but allow us to see how taking into account the sound margin significantly modifies the definition of the masking equalization filter.

[0056] [Fig.7] shows an alternative embodiment which takes into account a subtlety and explains the treatment of the case where a speed functional parameter and a ventilation data functional parameter are present.

[0057] In this embodiment, operations similar to those of [Fig. 3] have numerical references whose last two digits are identical to those of the operations of [Fig. 3]. Only the differences will be described.

[0058] The main difference of this embodiment is that it takes into account a speed threshold to prioritize the processing of speed noise in relation to functional noise. As shown in [Fig.3], from the noise margin, each processing begins the remaining margin to process the remaining noise.

[0059] When the speed is high, aerodynamic noise is very important and must be prioritized over functional noise. On the other hand, at low speed, for example below 50 km / h, it may be interesting to reverse the treatment.

[0060] Thus, in an operation 705, the speed V is compared to a threshold Vm. If this comparison indicates a high speed, then the processing described with [Fig.3] is executed (with the addition of the processing of the two functional parameters described below) in an operation 709.

[0061] Otherwise, the functional noise will be processed as a priority. In the embodiment described here, two distinct functional noises are processed: engine noise and ventilation noise. To know which one to process as a priority, a function Filt3() is executed in an operation 710 similar to operation 310 to retrieve the engine filter data set corresponding to the functional parameter rpm and the ventilation filter data set corresponding to the functional parameter HVAC ventilation data[]. These two sets are classified according to the gain associated with them, and in an operation 720 and an operation 722, a first functional gain PG1 and its set of coefficients is determined similarly to operation 320, and a second functional gain PG2 and its set of coefficients is determined taking into account the first functional gain PG1 in operations 724 and 726.Finally, in an operation 730, the functional gain coefficients PG1 and PG2 and their corresponding coefficient sets are combined in an operation 730. Thus, it appears that the hierarchical processing by erosion of the sound margin is replicated on the functional parameters of a distinct nature.

[0062] Next, in operations 740, 750, and 760, the speed gain and speed filter data set are determined similarly to operations 340 through 360 (except that "functional" and "speed" have reversed roles), then the masking equalization filter is calculated in an operation 770, and an optional operation 780 applies the high-pass filter.

[0063] In the above, the filter data sets are formed by triplets that associate an index value (speed, engine rpm or ventilation data) and a gain value associated with coefficients that together define a masking filter. However, the gain value / coefficients pair could be re presented by coefficients alone, the gain value being implicitly contained in the standard of the coefficients.

[0064] In view of the above, the Applicant has therefore developed a processing which makes it possible to take into account various types of noise, to recover the information concerning them in a direct available source (the communication bus) and to calculate a masking equalization filter with a very low computational cost. This was unpredictable starting from the SDEC, as evidenced by the NDEC patent application filed by the Applicant under number FR2211921.

Claims

Claims

1. Audio signal equalization device for a vehicle implementing a data communication bus comprising: - a memory (200) arranged to store speed filter data sets comprising triplets associating a speed value and a gain value associated with coefficients for defining a speed masking filter, and functional filter data sets comprising triplets associating an engine speed value or a ventilation value and a gain value associated with coefficients for defining an engine or ventilation masking filter, - a collector (210) arranged to receive at least two parameters accessible on the communication bus, which parameters designate the speed of the vehicle and at least one functional parameter chosen from the group comprising the engine speed of the vehicle and a ventilation data set,and - a calculator (220) arranged to receive as input a sound margin value, as well as said at least two parameters accessible on the communication bus, to derive therefrom at least one speed filter data set and at least one functional filter data set and to combine them into a masking equalization filter to be applied to an audio signal.,

2. Device according to claim 1, wherein the calculator (220) is arranged: - to determine a speed filter data set and a functional filter data set in the memory (200) from the at least two parameters determined by the collector (210), - to calculate a speed gain value from at least the gain value of the determined speed filter data set and the noise margin value and to derive a speed filter data set therefrom, and - to determine a functional gain value from at least the gain value of the determined functional filter data set, the speed gain value and the noise margin value and to derive a functional filter data set therefrom.

3. Device according to claim 2, in which the calculator (220) is arranged to calculate the speed gain value by retaining the minimum between the gain value of the determined speed filter data set and the noise margin value, and to calculate the functional gain value by retaining the minimum between the gain value of the determined functional filter data set and the difference between the noise margin value and the speed gain value.

4. Device according to claim 2 or 3, wherein the computer (220) is arranged, in the presence of an engine speed functional parameter and a ventilation data set functional parameter: - to determine a main functional filter data set and a second secondary functional filter data set from the engine speed functional parameter and the ventilation data set functional parameter, the gain value of the main functional filter data set being greater than the gain value of the secondary functional filter data set, - to determine a first functional gain value from at least the gain value of the main functional filter data set, the speed gain value and the noise margin value and to derive therefrom a first functional filter data set,- to determine a second functional gain value from at least the gain value of the secondary functional filter data set, the first functional gain value, the speed gain value and the noise margin value and derive therefrom a second functional filter data set, and, - to calculate a functional gain value and a functional filter data set from the first functional gain value, the second functional gain value, the first functional filter data set and the second functional filter data set.

5. Device according to claim 1, wherein, the calculator (220) is arranged, when the speed parameter is lower than a chosen threshold: - to determine a functional filter data set and a speed filter data set in the memory (200) from the at least two parameters determined by the collector (210), - to determine a functional gain value from at least the gain value of the determined functional filter data set and the noise margin value and to derive therefrom a functional filter data set from the functional gain value, and - to determine a speed gain value from at least the gain value of the determined speed filter data set, the functional gain value and the noise margin value and to derive therefrom a functional filter data set from the functional gain value, derive a speed filter dataset from the speed gain.

6. Device according to claim 5, wherein the calculator (220) is arranged to calculate the functional gain value by retaining the minimum between the gain value of the determined functional filter data set and the noise margin value, and to calculate the speed gain value by retaining the minimum between the gain value of the determined speed filter data set and the difference between the noise margin value and the functional gain value.

7. Device according to claim 5 or 6, wherein the computer (220) is arranged, in the presence of an engine speed functional parameter and a ventilation data set functional parameter: - to determine a main functional filter data set and a secondary functional filter data set from the engine speed functional parameter and the ventilation data set functional parameter, the gain value of the main functional filter data set being greater than the gain value of the secondary functional filter data set, - to determine a first functional gain value from at least the gain value of the main functional filter data set and the noise margin value and to derive a first functional filter data set therefrom,- to determine a second functional gain value from at least the gain value of the secondary functional filter data set, the first functional gain value and the noise headroom value and derive therefrom a second functional filter data set, and - to calculate a functional gain value and a functional filter data set from the first functional gain value, the second functional gain value, the first functional filter data set and the second functional filter data set.,

8. Device according to one of the preceding claims, in which the calculator (220) is arranged to apply a high-pass filter to the masking equalization filter as a function of the difference between the noise margin, the speed gain value and the functional gain value.

9. A method of equalizing an audio signal for a vehicle implementing a data communication bus comprising: a) storing speed filter data sets comprising triplets associating a speed value and a gain value associated with coefficients for defining a speed masking filter, and functional filter data sets comprising triplets associating an engine speed value or a ventilation value and a gain value associated with coefficients for defining an engine or ventilation masking filter, b) receiving at least two parameters accessible on the data communication bus, which parameters designate the vehicle speed and at least one functional parameter chosen from the group comprising the vehicle engine speed and a ventilation data set, and a noise margin value, and c) deriving from the parameters of step b) and the noise margin value at least one speed filter data set and at least one functional filter data set and to combine them into a masking equalization filter to be applied to an audio signal.

10. The audio signal equalization method of claim 9, wherein operation c) comprises cl) determining a speed filter data set and a functional filter data set from the at least two parameters determined by the collector (210), c2) calculating a speed gain value from at least the gain value of the determined speed filter data set and the noise margin value and deriving therefrom a speed filter data set, and c3) determining a functional gain value from at least the gain value of the determined functional filter data set, the speed gain value and the noise margin value and deriving therefrom a functional filter data set.

11. A method of equalizing an audio signal according to claim 10, wherein operation c2) comprises calculating the speed gain value by retaining the minimum between the gain value of the determined speed filter data set, the noise margin value, and operation c3) comprises calculating the functional gain value by retaining the minimum between the gain value of the determined functional filter data set, the difference between the noise margin value and the speed gain value.

12. A method of audio signal equalization according to claim 10 or 11, wherein when operation b) returns an engine speed functional parameter and a ventilation data set functional parameter, operation c3) comprises: c3a) determining a primary functional filter data set and a second secondary functional filter data set from the engine speed functional parameter and the ventilation data set functional parameter, the gain value of the primary functional filter data set being greater than the gain value of the secondary functional filter data set, c3b) determining a first functional gain value from at least the gain value of the main functional filter data set, the speed gain value and the noise margin value and deriving therefrom a first functional filter data set, c3c) determining a second functional gain value from at least the gain value of the secondary functional filter data set, the first functional gain value, the speed gain value and the noise margin value and deriving therefrom a second functional filter data set, and c3d) calculating a functional gain value and a functional filter data set from the first functional gain value, the second functional gain value, the first functional filter data set and the second functional filter data set.

13. A method of equalizing an audio signal according to claim 9, wherein, when the speed parameter of operation b) is less than a chosen threshold, operation c) comprises: cl) determining a functional filter data set and a speed filter data set in the memory (200) from the at least two parameters determined by the collector (210), c2) determining a functional gain value from at least the gain value of the determined functional filter data set and the noise margin value and deriving a functional filter data set from the functional gain value, and c3) determining a speed gain value from at least the gain value of the determined speed filter data set, the functional gain value and the noise margin value and deriving a speed filter data set from the speed gain.

14. A method of equalizing an audio signal according to claim 13, wherein operation c1) comprises calculating the functional gain value by retaining the minimum between the gain value of the determined functional filter data set and the noise margin value, and operation c2) comprises calculating the speed gain value by retaining the minimum between the gain value of the determined speed filter data set, the difference between the noise margin value and the functional gain value.

15. An audio signal equalization method according to claim 13 or 14, wherein when operation b) returns an engine speed functional parameter and a ventilation data set functional parameter, operation c2) comprises: c2a) determining a primary functional filter data set and a secondary functional filter data set from the engine speed functional parameter and the ventilation data set functional parameter, the gain value of the primary functional filter data set being greater than the gain value of the secondary functional filter data set, c2b) determining a first functional gain value from at least the gain value of the primary functional filter data set and the noise margin value and deriving therefrom a first functional filter data set,c2c) determining a second functional gain value from at least the gain value of the secondary functional filter data set, the first functional gain value and the noise margin value and deriving therefrom a second functional filter data set, and c2d) calculating a functional gain value and a functional filter data set from the first functional gain value, the second functional gain value, the first functional filter data set and the second functional filter data set.,

16. A method of equalizing an audio signal according to one of claims 9 to 15, further comprising the step d) applying a high-pass filter to the masking equalization filter as a function of the difference between the noise margin, the speed gain value and the functional gain value.

17. A computer-implemented computer program comprising instructions for executing the method according to one of claims 9 to 1 A.

18. 10. Data storage medium on which the computer program according to claim 17 is recorded.

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