EP1403850A1 - Methods for producing and using a sound effects library representing the sound characteristics of a motor vehicle, devices therefor - Google Patents

Abstract

The sound generation system monitors (1,2) sounds generated by a vehicle, and applies a frequency shift to generate the sound of a high performance car operating under the same regime. These sounds are recorded digitally (7) and extracted by a controller (4) using the measured sound of the vehicle. The recorded sound is converted (8) to analog format and delivered to an audio amplifier (9).

Description

The invention relates to methods for developing and restoring a sound library representing acoustic characteristics of a motor vehicle in the form of sound sequences. It has applications in the automotive and leisure fields by simulating the sounds of an engine or other elements of an automobile. A device for implementation is also claimed.

The essence of the invention is to simulate inside the passenger compartment of a motor vehicle the sound of an engine and / or other members including in particular, the brakes, the exhaust, of another type of vehicle and preferably a prestigious or original vehicle. Thus, the driver on board his vehicle will have the impression of being inside a Ferrari® or any other type of vehicle that may interest him. In order to reinforce the subjective impression, the simulation is carried out according to the actual operating state of the engine. It can also be implemented on or in other types of vehicles than a car and, for example, a truck, a bus, a motorcycle.

Devices are known for simulating engine sounds in a car interior. In particular, US Pat. No. 6,356,185 discloses a digital device with a programmable filter as a function of the engine load. Also known from application WO 01/33543 are methods and devices for developing and using a sound library with the aim of generating sounds according to the conditions of use of the engine, a sound synthesis is implemented there.

The present invention provides an alternative to these known devices in which sounds are used which are processed before being recorded in the device. These sounds are chosen according to the operating conditions of the motor, in particular the frequency of rotation, this also allowing the activation or the putting on standby of the device.

In addition, in the invention, a specific processing of the recording sound makes it possible to reduce the amount of data to be stored in memory unlike the devices in which the sounds are recorded raw or with simple filtering. With the same amount of memory, more simulation possibilities are available. This treatment requires calculations upon return. However, these calculations are simplified and reduced compared to the methods implementing a synthesis.

The invention therefore relates to a method of developing a sound library representing the acoustic characteristics of sequences of sounds recorded from at least one reference motor vehicle, each sequence corresponding to operating conditions of the reference vehicle, the conditions of being defined by at least one operating parameter, the recorded sounds being intended to be reproduced later on a motor vehicle by selection as a function of the operating conditions of the motor vehicle on which the reproduction takes place, at least one of the parameters being the frequency of rotation of the motor.

• on enregistre sous forme de données numériques par numérisation à une fréquence d'échantillonnage Fe des séquences de sons correspondant à des paramètres de fonctionnement, lesdits paramètres de fonctionnement étant enregistrés parallèlement,
• on effectue une analyse fréquentielle de chacune desdites séquences afin de déterminer la fréquence fondamentale de chacune des séquences,
• on détermine une fréquence de référence F₀ à partir des fréquences fondamentales des séquences,
• on effectue une transposition fréquentielle sur chacune des séquences enregistrées afin qu'elles aient toutes la même fréquence fondamentale sensiblement égale à la fréquence de référence F₀ afin de former la sonothèque.

According to the invention of the process, during the development of the sound library:

• sequences of sounds corresponding to operating parameters are recorded in the form of digital data by digitization at a sampling frequency Fe, said operating parameters being recorded in parallel,
• a frequency analysis of each of said sequences is carried out in order to determine the fundamental frequency of each of the sequences,
• a reference frequency F ₀ is determined from the fundamental frequencies of the sequences,
• we carry out a frequency transposition on each of the recorded sequences so that they all have the same fundamental frequency substantially equal to the reference frequency F _{0 in} order to form the sound library.

• avant enregistrement ou après enregistrement, on fait passer les sons à travers un filtre passe bande,
• le filtre passe bande est destiné, d'une part, à éliminer les composantes fréquentielles trop élevées par rapport à la fréquence d'échantillonnage pour numérisation, la fréquence de coupure de la partie passe bas correspondant sensiblement à la moitié ou moins de la fréquence d'échantillonnage, d'autre part, par la partie passe haut à éliminer les composantes fréquentielles trop basses ne pouvant être restituées par un moyen d'amplification et de restitution acoustique,
• l'état de fonctionnement est évalué par un ou plusieurs dès paramètres suivants :
  • démarreur enclenché ou non,
  • la position C de la pédale d'accélération,
  • la fréquence de rotation R du moteur,
  • la dépression à l'admission,
  • la vitesse enclenchée de la boite de vitesse,
  • la position de la pédale de frein,
  • l'accélération ou la décélération avant/arrière mesurée par un capteur,
  • la rotation du volant,
  • l'accélération ou la décélération latérale mesurée par un capteur,
• les sons sont choisis parmi les types sources suivants :
  • les sons du véhicule de référence en général,
  • les sons du moteur du véhicule de référence,
  • les sons de la transmission du véhicule de référence,
  • les sons de freinage du véhicule de référence,
  • les sons de roulement, notamment crissement des pneus, du véhicule, de référence
  • les sons d'échappement du véhicule de référence, un paramètre de type de son étant en outre enregistré,
• les sons de types sources différents ont une même fréquence de référence F₀ commune,
• on enregistre des sons provenant de plusieurs types de véhicules de référence, un paramètre de type de véhicule étant en outre enregistré,
• l'analyse fréquentielle est réalisée sur une courbe fréquentielle obtenue par une transformée de Fourier rapide (FFT) des sons numérisés enregistrés, la fréquence fondamentale correspondant au sommet principal de ladite courbe,
• en outre, on découpe chaque séquence en blocs, chaque bloc comportant Ne échantillons et étant d'une durée Te réduite par rapport à la durée totale de la séquence correspondante, Te = Ne / Fe, et on effectue l'analyse fréquentielle et la transposition sur chaque bloc de façon à ce que le procédé corresponde aux étapes suivantes :
  • on enregistre sous forme de données numériques à une fréquence d'échantillonnage Fe les séquences de sons correspondant à des paramètres de fonctionnement, lesdits paramètres de fonctionnement étant enregistrés parallèlement,
  • on découpe chaque séquence en n blocs séquentiels, chaque bloc comportant Ne échantillons pour une durée Te = Ne/Fe,
  • on effectue une analyse fréquentielle de chacun desdits blocs afin de déterminer la fréquence fondamentale de chacun des blocs,
  • on détermine une fréquence de référence F₀ à partir des fréquences fondamentales des blocs,
  • on effectue une transposition fréquentielle sur chacun des blocs enregistrées afin qu'ils aient tous la même fréquence fondamentale sensiblement égale à la fréquence de référence F₀,
• le nombre n de blocs pour une séquence est supérieur ou égal à 1 et préférentiellement compris entre 1 et 5,
• la fréquence de référence F₀ des blocs est commune aux blocs d'une séquence donnée, différentes séquences pouvant avoir pour leurs blocs respectifs des fréquences de référence F₀ différentes,
• de préférence, la fréquence de référence F₀ des blocs est commune à tous les blocs de toutes les séquences, différentes séquences ayant pour leurs blocs respectifs des fréquences de référence F₀ identiques,
• la fréquence de référence F₀ est calculée par une moyenne des fréquences fondamentales de chacune des séquences ou blocs respectivement,
• la fréquence de référence F₀ est calculée par prise du minimum des fréquences fondamentales de chacune des séquences ou blocs respectivement,
• la fréquence de référence F₀ est calculée par prise du maximum des fréquences fondamentales de chacune des séquences ou blocs respectivement,
• la fréquence d'échantillonnage est supérieure ou égale à 32KHZ et de préférence égale à 44,1KHz,
• on utilise une résolution de numérisation d'au moins 14bits et de préférence 16bits,
• on stocke la sonothèque dans une mémoire électronique du type circuit intégré.

In various embodiments of the invention of the method for developing a sound library, the following means used alone or in all their technically possible combinations are used:

• before recording or after recording, the sounds are passed through a bandpass filter,
• the band pass filter is intended, on the one hand, to eliminate the frequency components which are too high compared to the sampling frequency for digitization, the cut-off frequency of the low pass part corresponding substantially to half or less of the frequency d 'sampling, on the other hand, by the high pass part to eliminate the too low frequency components which cannot be restored by an acoustic amplification and restitution means,
• the operating state is evaluated by one or more of the following parameters:
  • starter engaged or not,
  • position C of the accelerator pedal,
  • the frequency of rotation R of the motor,
  • depression on admission,
  • the gearbox engaged speed,
  • the position of the brake pedal,
  • the forward / backward acceleration or deceleration measured by a sensor,
  • the rotation of the steering wheel,
  • lateral acceleration or deceleration measured by a sensor,
• the sounds are chosen from the following source types:
  • the sounds of the reference vehicle in general,
  • the sounds of the engine of the reference vehicle,
  • the transmission sounds of the reference vehicle,
  • the braking sounds of the reference vehicle,
  • rolling sounds, especially screeching tires, vehicle, reference
  • the exhaust sounds of the reference vehicle, a sound type parameter being also recorded,
• the sounds of different source types have the same common reference frequency F ₀ ,
• sounds from several types of reference vehicles are recorded, a vehicle type parameter also being recorded,
• the frequency analysis is carried out on a frequency curve obtained by a fast Fourier transform (FFT) of the digitized sounds recorded, the fundamental frequency corresponding to the main vertex of said curve,
• in addition, each sequence is cut into blocks, each block comprising Ne samples and being of a duration Te reduced compared to the total duration of the corresponding sequence, Te = Ne / Fe, and the frequency analysis and the transposition are carried out on each block so that the process corresponds to the following steps:
  • the sequences of sounds corresponding to operating parameters are recorded in the form of digital data at a sampling frequency Fe, said operating parameters being recorded in parallel,
  • each sequence is divided into n sequential blocks, each block comprising Ne samples for a duration Te = Ne / Fe,
  • a frequency analysis of each of said blocks is carried out in order to determine the fundamental frequency of each of the blocks,
  • a reference frequency F ₀ is determined from the fundamental frequencies of the blocks,
  • a frequency transposition is carried out on each of the recorded blocks so that they all have the same fundamental frequency substantially equal to the reference frequency F ₀ ,
• the number n of blocks for a sequence is greater than or equal to 1 and preferably between 1 and 5,
• the reference frequency F ₀ of the blocks is common to the blocks of a given sequence, different sequences possibly having different reference frequencies F ₀ for their respective blocks,
• preferably, the reference frequency F ₀ of the blocks is common to all the blocks of all the sequences, different sequences having for their respective blocks identical reference frequencies F ₀ ,
• the reference frequency F ₀ is calculated by an average of the fundamental frequencies of each of the sequences or blocks respectively,
• the reference frequency F ₀ is calculated by taking the minimum of the fundamental frequencies of each of the sequences or blocks respectively,
• the reference frequency F ₀ is calculated by taking the maximum of the fundamental frequencies of each of the sequences or blocks respectively,
• the sampling frequency is greater than or equal to 32KHZ and preferably equal to 44.1KHz,
• a scanning resolution of at least 14 bits and preferably 16 bits is used,
• the sound library is stored in an electronic memory of the integrated circuit type.

It is understood that the parallel recording of the parameters corresponding to the operating conditions is intended to subsequently allow the selection of sounds as a function of the operating conditions of the engine on which the restitution takes place. If this recording of the parameters can be continuous, preferably for the restitution, a minimum number of parameter values is associated with each sequence or block, in particular in the case of blocks, only one parameter value is stored for each parameter of the block defining the operating conditions, this in order to reduce the quantity of information associated with each sequence or block of sounds. For example, in memory, in a first set of stored data, the directory, we have for each sequence or block, the values of the parameters and addresses (physical or symbolic address: file name for example) of start and end of the sequence or block (you can also have the start address and the size), the other stored data sets, the sound files, corresponding to sequences or blocks of sounds. Thus, for the reproduction, the device determines the current operating condition, searches the directory for a correspondence which will enable it to determine the address of the sound data. In addition, data concerning the frequency transpositions and of scaling of the parameters are stored so that the rendering device can correctly calculate the conditions of restitution.

the sound sequences may correspond to changing operating conditions of the reference vehicle, for example a progressive depressing of the accelerator pedal so that the engine speed rises during the sequence. In such a case, the block cutting is intended to form blocks which, each in themselves, correspond to relatively stable conditions of the parameters, for example 1 ^st block at 1000 rpm, 2 ^nd block at 1100 rpm, 3 ^rd at 1200rpm, etc. We may have to keep only certain blocks depending on the definition step we want. The sequences can also correspond to stable operating conditions. In all cases, a block must correspond to substantially stable operating conditions.

The choice of the reference frequency F ₀ makes it possible to optimize the process according in particular to objectives of quality of reproduction.

The invention also relates to a method for restoring recorded sounds from a sound library according to any one of the preceding characteristics taken individually or in combination, by selection of recorded digital sounds whose fundamental frequency is substantially equal to the reference frequency F ₀ , as a function of operating conditions of a motor vehicle on which restitution takes place, the operating conditions being defined by operating parameters and at least one of the parameters being the frequency of rotation of said motor.

• on détermine une valeur théorique du paramètre de fonctionnement courant pour le véhicule de référence à partir de la mesure du paramètre de fonctionnement courant,
• on sélectionne les sons numérisés enregistrés dont le paramètre correspond à la valeur théorique,
• on calcule la fréquence fondamentale de restitution F_r des sons en fonction du paramètre de fonctionnement courant,
• on effectue un décalage fréquentiel des sons numérisés enregistrés sélectionnés afin qu'ils aient une fréquence fondamentale sensiblement égale à la fréquence fondamentale de restitution F_r, ledit décalage étant une interpolation ou décimation en fonction des valeurs respectives de la fréquence fondamentale de restitution F_r et de la fréquence de référence F₀,

et en ce que :

• on envoie l'ensemble des sons sélectionnés et décalés dans un moyen de conversion numérique analogique, d'amplification et de restitution acoustique.

According to the restitution process, the operating state of the motor vehicle is determined by measuring at least one current operating parameter and in that for each operating parameter considered:

• a theoretical value of the current operating parameter for the reference vehicle is determined from the measurement of the current operating parameter,
• we select the recorded digital sounds whose parameter corresponds to the theoretical value,
• the fundamental frequency of reproduction F _r of the sounds is calculated as a function of the current operating parameter,
• a frequency shift is performed of the selected recorded digital sounds so that they have a fundamental frequency substantially equal to the fundamental frequency of restitution F _r , said shift being an interpolation or decimation as a function of the respective values of the fundamental frequency of restitution F _r and of the reference frequency F ₀ ,

and in that :

• all the sounds selected and shifted are sent in a digital analog conversion, amplification and acoustic reproduction means.

• on effectue un calcul de pondération sur les sons devant être restitués, la pondération dépendant des mesures des paramètres courants,
• la sélection des sons numérisés enregistrés comporte en outre une étape de calcul consistant à effectuer une combinaison pondérée de sons au cours de laquelle on associe des sons dont les paramètres sont voisins de la valeur théorique, (en pratique numériquement égaux ou proches)
• on calcule les coefficients de pondération,
• l'étape de calcul consiste à effectuer une combinaison pondérée de sons au cours de laquelle on associe des sons dont le paramètre est le plus proche inférieur ou égal à la valeur théorique avec des sons dont le paramètre est le plus proche supérieur ou égal à la valeur théorique,
• l'étape de calcul consiste à effectuer une interpolation pour la valeur théorique du paramètre à partir des sons enregistrés,
• on combine des sons de plusieurs types sources différents pour restitution,
• on utilise une sonothèque avec des sons numérisés enregistrés sous forme de séquences, les sons étant restitués par séquence, (ou bouclage de séquences)
• on utilise une sonothèque avec des sons numérisés enregistrés sous forme de séquences découpées en blocs, et pour chaque période de temps Te :
  • on détermine l'état de fonctionnement de l'engin à moteur par mesure d'au moins un paramètre de fonctionnement courant et en ce que pour chaque paramètre de fonctionnement considéré :
  • on détermine une valeur théorique du paramètre de fonctionnement courant pour le véhicule de référence à partir de la mesure du paramètre de fonctionnement courant,
  • on sélectionne et calcule une combinaison pondérée de n blocs dont les paramètres sont voisins de la valeur théorique par calcul d'un jeu de n coefficients de pondération associés aux n blocs sélectionnés puis pondération de chacun des n blocs par son coefficient de pondération obtenu et sommation des blocs pondérés,
  • on calcule la fréquence fondamentale de restitution F_r en fonction du paramètre de fonctionnement courant,
  • on effectue un décalage fréquentiel de la combinaison pondérée afin qu'elle ait une fréquence fondamentale sensiblement égale à la fréquence fondamentale de restitution F_r, ledit décalage étant une interpolation ou décimation en fonction des valeurs respectives de la fréquence fondamentale de restitution F_r et de la fréquence de référence F₀,

et en ce que :

• on envoie la combinaison décalée dans un moyen de conversion numérique analogique, d'amplification et de restitution acoustique,
• la fréquence d'échantillonnage est supérieure ou égale à 32KHZ et de préférence égale à 44,1 KHz,
• on utilise une résolution de numérisation d'au moins 14bits et de préférence 16bits,
• on stocke la sonothèque dans une mémoire électronique du type circuit intégré,
• on amplifie les sons restitués et le moyen restitution acoustique des sons est l'équipement en haut-parleurs de l'engin à moteur dans lequel a lieu la restitution,
• en outre par un moyen de mise en veille; on mesure la fréquence de rotation du moteur et lorsque ladite fréquence devient inférieure à un seuil prédéterminé, on coupe l'alimentation électrique des moyens destinés à la restitution, et lorsque la fréquence repasse au-dessus dudit seuil, on rétablit l'alimentation électrique,
• lorsque la durée de la restitution est supérieure à la durée des sons sélectionnés, on boucle ladite restitution en recommençant la restitution au début des sons sélectionnés. (on boucle donc une séquence ou un ou des blocs, avant ou après transposition, notamment selon la disponibilité en mémoire de stockage des sons sélectionnés transposés)

In various embodiments of the invention of the method for developing a sound library, the following means used alone or in all their technically possible combinations are used:

• a weighting calculation is performed on the sounds to be reproduced, the weighting depending on the measurements of the current parameters,
• the selection of recorded digital sounds also includes a calculation step consisting of carrying out a weighted combination of sounds during which sounds whose parameters are close to the theoretical value are associated (in practice numerically equal or close)
• we calculate the weighting coefficients,
• the calculation step consists in carrying out a weighted combination of sounds during which we associate sounds whose parameter is closest less than or equal to the theoretical value with sounds whose parameter is closest greater than or equal to the theoretical value,
• the calculation step consists in performing an interpolation for the theoretical value of the parameter from the recorded sounds,
• we combine sounds from several different source types for playback,
• we use a sound library with digitized sounds recorded in the form of sequences, the sounds being reproduced by sequence, (or looping of sequences)
• a sound library is used with digitized sounds recorded in the form of sequences cut into blocks, and for each time period Te:
  • the operating state of the motor vehicle is determined by measuring at least one parameter of current operation and in that for each operating parameter considered:
  • a theoretical value of the current operating parameter for the reference vehicle is determined from the measurement of the current operating parameter,
  • a weighted combination of n blocks is selected and calculated, the parameters of which are close to the theoretical value by calculating a set of n weighting coefficients associated with the n selected blocks then weighting of each of the n blocks by its weighting coefficient obtained and summation weighted blocks,
  • the fundamental restitution frequency F _r is calculated as a function of the current operating parameter,
  • a frequency shift of the weighted combination is carried out so that it has a fundamental frequency substantially equal to the fundamental frequency of restitution F _r , said shift being an interpolation or decimation as a function of the respective values of the fundamental frequency of restitution F _r and of the reference frequency F ₀ ,

and in that :

• the offset combination is sent in a means of digital analog conversion, of acoustic amplification and restitution,
• the sampling frequency is greater than or equal to 32KHZ and preferably equal to 44.1 KHz,
• a scanning resolution of at least 14 bits and preferably 16 bits is used,
• the sound library is stored in an electronic memory of the integrated circuit type,
• the restored sounds are amplified and the acoustic sound reproduction means is the loudspeaker equipment of the motor vehicle in which the restitution takes place,
• further by a standby means; the frequency of rotation of the motor is measured and when said frequency becomes lower than a predetermined threshold, the electrical supply of the means intended for restitution is cut off, and when the frequency goes back above said threshold, the electrical supply is restored,
• when the duration of the restitution is greater than the duration of the selected sounds, said restitution is looped by recommencing restitution at the beginning of the selected sounds. (we therefore loop a sequence or one or more blocks, before or after transposition, in particular according to the availability in storage memory of the selected sounds transposed)

The sound library and the restitution can therefore be more or less extensive. In a minimal version, the sound library only includes sounds from a single source and a single type of vehicle, in this case the parameters intended to allow the selection of sounds may not include a source type parameter and / or vehicle types, only the operating parameters, for example engine speed (rotation frequency), then being used. In more advanced versions, several sounds of different source types can be recorded in a sound library with their corresponding source type parameters and the restitution can combine sequences / blocks of several source types. It is understood that in this case, it is preferable that the reference frequency F ₀ is the same for all the sequences / blocks of all the source types in order to simplify the restitution. In the most advanced version in which the sound library includes sounds coming from several types of vehicles, we understand that the restitution will only concern one type of vehicle particular, the sequences / blocks being selected according to the corresponding vehicle type parameter.

The present invention finally relates to a device for implementing the above methods and in particular for the reproduction from the sound library of digitized sounds recorded and transposed to a reference frequency F ₀ . The device comprises at least one computer means of the microprocessor, microcontroller or digital signal processing processor (DSP), program memory for execution according to the restitution method, sound memory comprising the sound library, interpolation means / decimation, said interpolation / decimation means preferably being software and at least one digital analog converter (DAC).

• le dispositif comporte en outre un moyen de mise en veille dont le fonctionnement est lié à la fréquence de rotation du moteur,
• la mise en veille correspond à une interruption de l'alimentation du dispositif de restitution, le moyen de mise en veille continuant à être alimenté,
• le moyen d'interruption est un relais électromagnétique commandé par le moyen de mise en veille, la position de repos, décollé, correspondant à l'interruption,
• la restitution est effectuée en stéréophonie, l'enregistrement étant lui-même stéréophonique, deux CAN étant employés.

In various embodiments of the invention of the device, the following means used alone or in all their technically possible combinations are used:

• the device also comprises a standby means, the operation of which is linked to the frequency of rotation of the motor,
• the standby corresponds to an interruption of the supply to the rendering device, the standby means continuing to be supplied,
• the interruption means is an electromagnetic relay controlled by the standby means, the rest position, lifted off, corresponding to the interruption,
• the restitution is carried out in stereophony, the recording being itself stereophonic, two CAN being employed.

Thus, the invention is characterized during the development of the sound library by a step of frequency transposition on the sounds recorded so that they all have the same fundamental frequency F ₀ . During playback the sounds are selected according to the current operation of the engine measured by one / several parameters then change of scale of the measurement to theoretical value of the parameter (s) (the scales of parameters not being the same between the recording vehicle and the engine with restitution engine). During the selection, a calculation can be made in order to refine the restitution (in particular weighted combination or interpolation). Finally, the selected sounds which are always at the fundamental frequency F ₀ must be offset frequently by an interpolation or decimation as a function of a fundamental restitution frequency F _r determined according to the measurements (or, rather, of the theoretical value of / parameters which is taken from it).

• La Figure 1 correspond à schéma bloc d'un dispositif pour la restitution d'une sonothèque,
• La Figure 2, un schéma électronique d'un moyen de mise en veille d'un dispositif de restitution,
• La Figure 3 représente un schéma fonctionnel de mise en oeuvre de l'invention.

The present invention will be better understood on reading the following of a nonlimiting exemplary embodiment where:

• Figure 1 corresponds to a block diagram of a device for restoring a sound library,
• FIG. 2, an electronic diagram of a means of putting a restitution device on standby,
• Figure 3 shows a functional diagram of implementation of the invention.

In Figure 1, which schematically represents a device usable to simulate the sound of an engine in a motor vehicle from a sound library, there is a controller 4, which can be a microcontroller, a microprocessor or a digital signal processor (DSP), connected by addressing and data buses to memories. A read only memory 6 for storing the operating program. The ROM also contains the sound library (digital samples and parameters) and any configuration data intended to establish a relationship between the parameters on recording and the current parameters, for example the range of frequency (speed) of the engine which may be different. between the registration car and the return car. The controller 4 is also associated with random access memory 7 and with a digital or analog converter 8 (DAC) mono or stereo (or more) as the case may be. An amplifier 9 is provided at the output of the DAC. A means of adjusting the sound level being able to be produced by software by logical shift operations of the digital data, no conventional means of potentiometer type adjustment has been shown

In the Figure two parameters for evaluating the operating state of the engine, the speed and the load, are considered. The load C of engine 2 is evaluated by the position of the accelerator. The engine R speed 1 (rotation frequency) is evaluated by the engine rotation speed (specific sensor). The corresponding signals 1 and 2 are sent to the controller 4 via a module 3 for shaping the signals. The signal shaping module 3 transforms the analog signal of the engine speed R into a filtered logic signal whose frequency reflects the state of the engine. The engine R speed 1 and the engine load C 2 are evaluated regularly over time and determine the selection of sounds from the sound library. In the case of sounds in sequences cut into blocks, in a simplified version, a block among all the blocks stored in the read-only memory is selected. In a more advanced version, a weighted combination of blocks is used for the restitution. Indeed, the sound library is physically limited and all the operating conditions of the reference vehicle could not be recorded. It is therefore necessary to use sounds corresponding to parameters close to the theoretical value which must be restored to produce sounds corresponding to current operation. For example, for a parameter which is the motor rotation frequency, the reference vehicle goes from 800rpm / min to 9000rpm, the engine of the motor vehicle on which the restitution takes place goes from 500 rpm to 4000rpm / min and it is therefore necessary, from a current measurement for example equal to 3000 revolutions / min, determine a theoretical value corresponding to that of the reference vehicle. For this, a conversion is carried out which gives a theoretical value at around 6658 revolutions / min. The sound library includes, for example, sequences / blocks at ... 5000, 5500, 6000, 6500, 7000 ... revolutions / min. A weighted combination of the sequences / blocks is then carried out at 6500 and 7000 revolutions / min. In the most advanced mode, an interpolation is made from the available sounds. After this step, the sounds are always at a reference frequency F ₀ and it is necessary to perform a frequency offset to correspond to the current operating mode. After these calculations, the data is sent to the digital-analog converter 8, the analog signals thus reconstituted being amplified and filtered by the amplifier 9 which includes a filter and sent to an acoustic reproduction means 10 of the loudspeaker type. Depending on the level of quality required, the available computing power and / or the memory capacity, the resolution of the converters can be chosen between 8 and 24 bits. Preferably 16 bits are used. The acquisition frequency is preferably 44100Hz. However, it is envisaged that the frequency of acquisition and restitution is lower and, for example, up to 8,000 Hz also depending on the level of quality required, the computing power and / or the memory capacity. Likewise, a stereophonic device or not is envisaged.

A standby device depending on the engine speed R allows the restitution device to be switched off when the engine of the vehicle in which the device is installed is stopped. When the engine speed R is zero, the restitution device is de-energized so that the electrical consumption of the system used is almost zero, that is to say reduced to the consumption of said standby device. A perfectly explicit electronic diagram alone is given in Figure 2 with a circuit integrated low-consumption CMOS of the stable mono flip-flop type, an input of which is connected to a clipping amplifier receiving a filtered signal (R1C1) corresponding to the motor rotation frequency. At each pulse of this signal the flip-flop is reset to zero. In the absence of reset, after a time defined by the components R6C3, a switchover occurs and the relay K1 is switched, which cuts the power supply to the playback device.

In other embodiments of the invention, the amplifier 9 can be omitted, the output of the digital-analog converter being connected to an existing sound device of the motor vehicle and for example to a car radio. In another less advanced form of the invention, the measurement of the load C of the engine 2 can be omitted, only the speed R of the engine 1 being measured or vice versa.

FIG. 3 represents a general functional diagram of the process of the invention which, for reasons of simplification, considers only a single sound source depending on a single parameter, the engine speed R. It is understood that the process which is there shown can be extended to any number of source types and parameters. In this same Figure, R is the engine speed, S the sound source, B ₁ ... B _n are n sound blocks (sounds digitized and transposed to the reference frequency F ₀ ), E ₁ ... E _n are the n sound samples corresponding to the blocks and C ₁ ... C _n are n weighting coefficients. The configuration table 11 corresponds to the set of weighting coefficients of the blocks of the sequences. For each operating state of the engine, a set of n weighting coefficients of the n blocks is calculated. Thus in the case where the operation of the engine is measured by the engine speed, the values of the weighting coefficients will be referenced as a function of the corresponding values of R. The values of these weighting coefficients C _i (i = 1 to n) selected in the configuration table 11 as a function of R are sent to an additive synthesis module 12 or they are associated with the samples E _i (i = 1 to n) of the corresponding sound blocks for weighting and the set of weighted blocks is added , allowing to obtain in the time domain a time evolution of fundamental frequency Fo. Thus, in this embodiment of Figure 3, from n selected blocks of unit duration Te, we obtain by weighting and addition the equivalent of a single block of duration Te.

A frequency shift (transposition) is then operated, calculated according to the operating state of the motor. If the operating state of the motor requires a sound reproduction of a fundamental frequency greater than Fo, the previously obtained sound sequence is decimated, in the opposite case, it is interpolated.

We will now describe the method for calculating the weighting coefficients. For each of the blocks of the sound library are determined a lower limit restitution frequency (minimum frequency transposition), an upper limit restitution frequency (maximum frequency transposition) as well as, between these two limits, a range (or a value) of frequencies of maximum coefficient refund (C _i = 100%). In the case where the frequency of restitution calculated according to the operating conditions of the motor vehicle is lower than the lower limit or is higher than the upper limit, the calculated coefficient is zero (C _i = 0) and between these two limits, outside the range with maximum coefficient (C _i = 100%), the coefficient is calculated by linear extrapolation. Thus in the case of an example with three blocks, we consider the following table in which each box of the table has a (or a range of) frequency and its associated coefficient in percentage (except in the case where another box allows deduct the value as for block 1 x min frequency where we deduct 100% for any frequency less than 1000Hz. frequency min frequency range max frequency block 1 - less than 1000Hz / 100% 2000Hz / 0% block 3 1000Hz / 0% 2000Hz / 100% 3000Hz / 0% block 3 2000Hz / 0% greater than 3000Hz / 100% -

$$\text{bloc 2 : Ci= (1600 - 1000) / (20M - 1000) = 60 \%}$$

$$\text{bloc 3 : Ci (fréquence inférieure à 2000 Hz) = 0 \%}$$

For a restitution frequency having a value calculated at 1600 Hz, we have: $$\text{block 1: Ci = (2000 - 1600) / (2000 - 1000) = 40\%}$$

$$\text{block 2: Ci = (1600 - 1000) / (20M - 1000) = 60\%}$$

$$\text{block 3: Ci (frequency less than 2000 Hz) = 0\%}$$

$$\text{bloc 2 : Ci (fréquence supérieure à 2000 Hz) = 0 \%}$$

$$\text{bloc 3 : Ci (fréquence supérieure à 3000Hz) = 100 \%}$$

For a restitution frequency calculated at 4000 Hz, we have: $$\text{block 1: Ci (frequency greater than 2000 Hz) = 0\%}$$

$$\text{block 2: Ci (frequency greater than 2000 Hz) = 0\%}$$

$$\text{block 3: Ci (frequency higher than 3000Hz) = 100\%}$$

Depending on the blocks available and / or selected, combinations of blocks may be more complex than in this example.

In the time domain, the sampling is done in a manner compatible with that used for the creation of the configuration table, which is identical: the same sampling frequency Fe is used during creation and during restitution / simulation.

During the implementation of the methods of the invention, the restitution is preferably carried out by using a temporary storage memory area (buffer or "buffer") of the first in, first out type and / or by using a double buffer system so that the calculations can be done during the sound reproduction by the digital to analog converter 10 without the latter having to wait data and therefore without risk of interruption of the restitution.

Claims (15)

Method for developing a sound library representing the acoustic characteristics of sequences of sounds recorded from at least one reference motor vehicle, each sequence corresponding to operating conditions of the reference vehicle, the operating conditions being defined by at least an operating parameter, the recorded sounds being intended to be reproduced later on a motor vehicle by selection as a function of the operating conditions of the motor vehicle on which the reproduction takes place, at least one of the parameters being the frequency of rotation motor, characterized in that , during the development of the sound library - sequences of sounds corresponding to operating parameters are recorded in the form of digital data by digitization at a sampling frequency Fe, said operating parameters being recorded in parallel, a frequency analysis of each of said sequences is carried out in order to determine the fundamental frequency of each of the sequences, - a reference frequency F ₀ is determined from the fundamental frequencies of the sequences, - a frequency transposition is carried out on each of the recorded sequences so that they all have the same fundamental frequency substantially equal to the reference frequency F _{0 in} order to form the sound library. Method according to claim 1, characterized in that the operating state is evaluated by one or more of the following parameters: - starter engaged or not, - position C of the accelerator pedal, - the frequency of rotation R of the motor, - depression on admission, - the engaged gear of the gearbox, - the position of the brake pedal, - the forward / reverse acceleration or deceleration measured by a sensor, - the rotation of the steering wheel, - lateral acceleration or deceleration measured by a sensor. Method according to claim 1 or 2, characterized in that the sounds are chosen from the following source types: - the sounds of the reference vehicle in general, - the sounds of the engine of the reference vehicle, - the transmission sounds of the reference vehicle, - the braking sounds of the reference vehicle, - rolling sounds, especially screeching tires, vehicle, reference - the exhaust sounds of the reference vehicle, a sound type parameter being further recorded. Method according to any one of the preceding claims, characterized in that , in addition, each sequence is divided into sequential blocks, each block comprising Ne samples and being of a duration Te reduced compared to the total duration of the corresponding sequence, Te = Ne / Fe, and the frequency analysis and the transposition are carried out on each block so that the process corresponds to the following steps: the sequences of sounds corresponding to operating parameters are recorded in the form of digital data at a sampling frequency Fe, said operating parameters being recorded in parallel, - each sequence is divided into n sequential blocks, each block comprising Ne samples for a duration Te = Ne / Fe, a frequency analysis of each of said blocks is carried out in order to determine the fundamental frequency of each of the blocks, - a reference frequency F ₀ is determined from the fundamental frequencies of the blocks, a frequency transposition is carried out on each of the blocks recorded so that they all have the same fundamental frequency substantially equal to the reference frequency F ₀ . Method according to any one of the preceding claims, characterized in that the reference frequency F ₀ is calculated by an average of the fundamental frequencies of each of the sequences or blocks respectively and in that , preferably, the reference frequency F ₀ of the blocks is common to all the blocks of all the sequences, different sequences having for their respective blocks identical reference frequencies F ₀ . Method according to any one of the preceding claims, characterized in that the sampling frequency Fe is greater than or equal to 32KHZ and preferably equal to 44.1 KHz, and a scanning resolution of at least 14 bits and of preferably 16bits. Method according to any one of the preceding claims, characterized in that the sound library is stored in an electronic memory of the integrated circuit type. Method for restoring recorded sounds by selecting digitized sounds recorded as a function of operating conditions of a motor vehicle on which restitution takes place, the operating conditions being defined by operating parameters and at least one of the parameters being the frequency of rotation of said motor, characterized in that the sounds are in a sound library developed according to any one of the preceding claims, the digitized sounds having a fundamental frequency substantially equal to the reference frequency F ₀ , and in which the operating state of the motor vehicle is determined by measuring at least one current operating parameter and in that for each operating parameter considered: - a theoretical value of the current operating parameter for the reference vehicle is determined from the measurement of the current operating parameter, - we select the recorded digital sounds whose parameter corresponds to the theoretical value, - the fundamental frequency of restitution F _r of the sounds is calculated as a function of the current operating parameter, a frequency shift is performed of the selected recorded digital sounds so that they have a fundamental frequency substantially equal to the fundamental frequency of restitution F _r , said shift being an interpolation or decimation as a function of the respective values of the fundamental frequency of restitution F _r and the reference frequency F ₀ , and in that the set of selected and offset sounds is sent in a means of digital analog conversion, amplification and acoustic reproduction. Method according to Claim 8, characterized in that a weighting calculation is carried out on the sounds to be reproduced, the weighting depending on the measurements of the current parameters. Method according to claim 8 or 9, characterized in that when the duration of the restitution is greater than the duration of the selected sounds, said restitution is looped by restarting the restitution at the start of the selected sounds. Method according to claim 8, 9 or 10, characterized in that the selection of the recorded digital sounds also comprises a calculation step consisting in carrying out a weighted combination of sounds during which combines sounds whose parameters are close to the theoretical value. Method according to any one of Claims 8 to 11, characterized in that a sound library is used with digitized sounds recorded in the form of sequences cut into blocks, and for each time period Te: the operating state of the motor vehicle is determined by measuring at least one current operating parameter and in that for each operating parameter considered: - a theoretical value of the current operating parameter for the reference vehicle is determined from the measurement of the current operating parameter, a weighted combination of n blocks is selected and calculated, the parameters of which are close to the theoretical value by calculation of a set of n weighting coefficients associated with the n selected blocks and then weighting of each of the n blocks by its weighting coefficient obtained and summation of the weighted blocks, - the fundamental restitution frequency F _r is calculated as a function of the current operating parameter, a frequency shift of the weighted combination is carried out so that it has a fundamental frequency substantially equal to the fundamental frequency of restitution F _r , said shift being an interpolation or decimation as a function of the respective values of the fundamental frequency of restitution F _r and of the reference frequency F ₀ , and in that the offset combination is sent in a digital analog conversion, amplification and acoustic reproduction means. Method according to any one of Claims 8 to 12, characterized in that , in addition, by means of standby, the frequency of rotation of the motor is measured and when said frequency becomes lower than a predetermined threshold, the electrical supply of the means intended for restitution is cut, and when the frequency returns above said threshold, the electrical supply is restored. Restitution device for implementing a method of restoring a sound library, characterized in that the method is according to any one of claims 8 to 13 and that the sounds of the sound library being digitized recorded and transposed to a reference frequency F ₀ , the device comprising at least one computer means of the microprocessor, microcontroller or digital signal processing processor (DSP), of the program memory for execution according to the restitution process, of the sound memory comprising the sound library , interpolation / decimation means, said interpolation / decimation means preferably being software, and at least one digital analog converter (DAC). Device according to Claim 14, characterized in that it further comprises a standby means, the operation of which is linked to the frequency of rotation of the motor, the standby corresponding to an interruption in the supply of the rendering device. proper, the standby means continuing to be supplied.

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