Classifications

• • G—PHYSICS
  • G10—MUSICAL INSTRUMENTS; ACOUSTICS
  • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
  • G10K15/00—Acoustics not otherwise provided for
  • G10K15/02—Synthesis of acoustic waves

Definitions

• the invention relates to the field of processes for synthesizing a sound environment at the level of a vehicle.
• a sound environment signal is synthesized.
• This synthesized sound signal is intended to be rendered on an audio channel at the vehicle.
• the interest of this synthesized sound signal is to allow the generation of a sound environment that is controlled by driving parameters of the vehicle, to give the driver of the vehicle a feeling of increased realism in the color of the engine noise when the it is carried out inside the passenger compartment of the vehicle.
• the synthesized sound signal may be or may comprise a pre-existing motor noise of another vehicle than the driven vehicle, which is colored, that is to say modified, in particular by digital processing, to be made coherent with the driving of the driven vehicle. , and to improve the dynamic rendering of the driven vehicle.
• the synthesized sound signal may be or may comprise a novel signal that will be made consistent with the driving of the vehicle, by treatment there also advantageously digital.
• it can reconstruct a sound environment of a desired type, while maintaining consistent with the conduct adopted by the driver of the vehicle.
• a sound signal synthesis method in which an original sound signal is isolated, then pre-cut into blocks, and stored in the form of these pre-cut blocks, each pre-cut block being associated with a given combination of driving parameters.
• a major disadvantage of this method is the cutting even blocks.
• each block comprising a large number of sound samples, and the richness of the synthesis can be considered insufficient since many interesting signals remain inaccessible like all the concatenations between two consecutive portions of blocks, for example the last quarter of a block followed by the first two thirds of the next block.
• the invention proposes to achieve a better compromise between the richness of the possibilities of sound synthesis on the one hand and the simplicity of the system, both in terms of data management, storage memory size and computing power on the other hand.
• the invention proposes the original method of storing the whole sound signal as a function of time and constituting the blocks afterwards by sliding a window along the time axis.
• a method for synthesizing a sound environment at a vehicle comprising: a step of selecting an original sound signal stored as one or more characteristics in a function of time; a step of extracting several portions of said original sound signal from one or more driving parameters of the vehicle; a step of synthesis over time of a restitution sound signal from said parts of said original sound signal; characterized in that, in the extracting step, said portions of said sound signal of origin are extracted by application, on the original sound signal, a sliding time window whose positions on the time axis are based on the driving parameters or the vehicle respectively at different times of driving the vehicle.
• a sliding window means that between two possible contiguous positions of the window on the time axis there is at least partial, and preferably only partial, overlap between them corresponding parts of the original sound signal. Assuming that one can consider the block division of the method according to the prior art as a discrete windowing, the different blocks would then correspond to parts of the original sound signal that would be disjoined to each other. Even assuming that the different blocks are modified to correspond to parts of the original sound signal that overlap partially with each other, the number of blocks needed to cover the original sound signal would become sufficiently large to require more complex management and resources greater than the sliding window according to the invention.
• the partial overlap between two possible contiguous windows covers at least half the width of the window, so as to make the covering particularly significant.
• the partial overlap between two adjacent contiguous windows covers at least half the width of each of the two adjoining windows.
• the sliding pitch of the sliding window can go down to the width of a sample.
• the slip pitch of the sliding window could be practically continuous.
• the original sound signal is digital and each characteristic, depending on whether there is one or more, is stored in the form of a succession of samples over time.
• the parts extracted from the original sound signal succeed one another in time in the restitution sound signal, with or without overlap between the different portions of the original sound signal from which they are extracted, depending on the effect that one wishes to obtain.
• a certain covering is preferably used to guarantee the continuity of the sound signal restored to the ear.
• the synthesized sound environment will preferentially be restored at the level of the vehicle, that is to say inside the passenger compartment of the vehicle and or outside the vehicle around the vehicle.
• the invention may also be considered as covering a method of synthesizing a sound environment in a vehicle, comprising: a step of selecting an original sound signal stored in the form of one or more characteristics in function time ; a step of extracting several portions of said original sound signal from one or more driving parameters of the vehicle; a step of synthesizing a restitution sound signal from said parts of said original sound signal; characterized in that said portions of said original sound signal are extracted by a granular synthesis technique whose control parameters are representative of the evolution over time of the driving parameter (s) of the vehicle.
• the sliding step of the time window is less than one tenth of the width of the time window, or one-tenth of the smallest width of the time window when this width is variable.
• the richness offered at the level of the possibilities of synthesis starting from the same original sound signal is much more important than with a precut of blocks according to the method of the prior art.
• the sliding step of the time window is less than one hundredth of the width of the window time.
• the richness offered at the level of the possibilities of synthesis starting from the same original sound signal is extremely greater than with a precut of blocks according to the method of the prior art.
• the time window instead of remaining stationary at a nominal position corresponding to the constant value of said one or more parameters of driving of the vehicle, moves around said nominal position.
• said displacement around said nominal position is less than half the width of the time window, or half the smallest width of the time window when this width is variable.
• said displacement around said nominal position is less than one tenth of the width of the time window.
• Relatively small relative displacement, relative to the size of the window is sufficient to avoid the phenomena of parasitic signals due to a looped playback with a stationary window, while modifying only relatively little of the sound content selected by the window.
• This small displacement causes an arbitrary modification of the sound content of the selected original sound signal part, but the effects, during the sound reproduction, of this arbitrary modification are thus minimized.
• the amplitude of said displacement of the time window around the nominal position covers several slip steps at least on one side of the nominal position.
• the width of the time window also depends on the evolution over time of the driving parameter (s) of the vehicle. Such dependence can be achieved through a jig-like template giving the width of the window to be used according to a driving parameter of the vehicle, for example depending on the speed of the vehicle.
• the width of the time window remains constant and the same for all a stored original sound signal.
• the shape of the time window is constant over time for the same original sound signal; it is not excluded to consider a time window whose shape would be variable and vary according to one or more driving parameters.
• the shape of the time window has the shape of a Gaussian at its edges which is flattened at its center. It may be for example a Hanning window, or a Hamming window or a Blackman window. This makes it possible to avoid a click phenomenon due to an abrupt sound triggering of the next extracted part of the original sound signal relative to the previous extracted part.
• the Gaussian flattened in its center also called quasi-Gaussian, allows to increase the duration of perception by the ear of the part extracted from the original sound signal, which otherwise could in some cases seem a little fleeting.
• At the level of the at least one driving parameter at least a parameter representative of the speed of movement of the vehicle and at least one of its derivatives as a function of time and of on the other hand, a parameter representing the depression of the accelerator pedal and / or at least one of its derivatives as a function of time.
• the engine speed is also an advantageous parameter to use.
• the representative parameters are available and read on the vehicle network which is advantageously a CAN network.
• these parameters are read every 10 ms.
• the refreshing time of the driving parameters used to extract the parts of the original sound signal is advantageously lower than the width of the window.
• the position on the time axis of the time window is a function of a single complex driving parameter which is the linear combination of several simple driving parameters.
• a simple driving parameter is a directly available driving parameter for the synthesis method according to the invention. This has the advantage of simplifying the step of extracting the parts of the original sound signal. Alternatively, one can also have a multidimensional mapping where each driving parameter represents a dimension. This alternative is still a little more complicated to manage at the extraction stage.
• the original sound signal is a non-tonal sound signal.
• a tonal signal is a signal essentially centered around a fundamental frequency and frequencies harmonics associated with this fundamental frequency.
• the tonal signals are interesting, but they do not offer the richness that the non-tonal signals which constitute the great majority of the existing or possible signals can offer.
• the frequency registration proposed by the method of the prior art requires the use of tonal signals, and therefore does not offer the possibility of using non-tonal signals. Because of its intrinsic richness, the sound signal of non-tonal origin is preferred, especially since its treatment is made possible by the method according to the invention.
• the original sound signal is selected or preselected in a library according to the location of the vehicle advantageously obtained by navigation system and or depending on the time of day and or depending on the season and or depending on the climate outside the vehicle. All this allows a maximum adaptation of the sound environment to what could be called the general environment of the vehicle environment, which makes the sound environment synthesized more consistent, for the driver of the vehicle, with the vehicle environment.
• the original sound signal can be loaded from a portable memory.
• a portable memory is a memory that is not on the vehicle. It is for example a USB key that brings into the vehicle its driver.
• the richness and flexibility of the choice with regard to the original sound signal are improved.
• the extraction step there is a step of modifying the spectral height of said parts extracted from said original sound signal.
• This type of filtering allows a fine adjustment of the rendered sound.
• the synthesis step there is a step of sound reproduction of the sound signal of restitution to inside the passenger compartment of the vehicle.
• This restitution step can also take place outside the vehicle, advantageously with a sound signal of different origin than that used for restitution inside the passenger compartment of the vehicle.
• This synthesized sound signal is intended to be rendered on an audio channel at the vehicle.
• the audio channel is preferably of the loudspeaker type, possibly preceded by an amplifier or an amplification chain.
• a vehicle includes a truck, a car, a motorcycle, a train, a bus, an airplane.
• a vehicle is preferably a motor vehicle, preferably terrestrial.
• a vehicle is preferably a car.
• FIG. 1 shows schematically an example of highlighting the sliding window used in the synthesis method according to the invention
• FIG. 2 diagrammatically represents an example of a block diagram of the progress of the synthesis method according to the invention
• FIG. 3 shows schematically another example of highlighting the sliding window used in the synthesis method according to the invention
• FIG. 4 schematically represents an exemplary template of the nominal position, as a function of the speed of the vehicle, of the sliding window used in the synthesis method according to the invention
• FIG. 5 shows schematically an example of template, depending on the depression of the accelerator pedal, the gain applied to the sliding window used in the synthesis method according to the invention
• FIG. 6 diagrammatically represents another example of a template of the nominal position, as a function of the speed of the vehicle, of the sliding window used in the synthesis method according to the invention
• - Figure 7 shows schematically another example of template, depending on the depression of the accelerator pedal, the gain applied to the sliding window used in the synthesis method according to the invention
• FIG. 8 diagrammatically represents an example of a template, as a function of the engine speed, of the gain applied to a harmonic of the fundamental frequency of a tonal signal used in the synthesis method according to the invention
• FIG. 9 schematically represents an example of a template, as a function of a linear combination of the speed of the vehicle and the depression of the accelerator pedal, of the overall gain applied to the set of a reconstituted tonal signal used. in the synthesis process according to the invention.
• FIG. 1 diagrammatically represents an example of highlighting of the sliding window used in the synthesis method according to the invention.
• An original sound signal sso2 is stored as a function of time t in a memory. On the ordinate, it is the acoustic pressure expressed in Pascals, which represents the amplitude of the original sound signal.
• the windows F1 to F5 actually represent five positions F1, F2, F3, F4 and F5 of the sliding window. It is the application of a window F1 to F5 to the sound signal of origin sso2, during the extraction step, which gives some of the parts extracted from the original sound signal which will be used to realize the synthesis of the sound signal of restitution.
• the parts extracted from the original sound signal that will be used to carry out the synthesis of the restitution sound signal are also called grains.
• the extraction step is like a step of applying several windows, that is to say applying several positions of the sliding window.
• the difference pg between the windows F1 and F2 represents the sliding pitch pg, that is to say the smallest difference that can be between two adjacent positions of the sliding window.
• the sliding step size pg can vary from a few samples, even possibly a significant number of samples, to advantageously a single sample to preserve a maximum richness in the possibilities offered to extract parts of the sound signal from the sample. origin sso2.
• the window F2 has a width d which will remain preferentially constant over time, but which could possibly vary according to one of the driving parameters of the vehicle, for example the speed of the vehicle.
• the window F2 is positioned at time ti on the time axis t.
• the sliding window must remain at the position of the instant ti several times, and in order to avoid parasitic phenomena resulting from a loop playback of the same portion of the original sound signal sso2, instead of using several times in the window F2, we can make small displacements of the window F2 around the position of the moment ti.
• One of these displacements of a length of translates the sliding window and one passes from the window F2 to the window F3.
• the sampling frequency of the original sound signal sso2 or sso1 being approximately 45 kHz, for example 44.100 Hz
• the slip pitch corresponding to the value of a sample is equal to about 23 ⁇ s
• the width of a window is about 100ms
• the length of the small displacements of a window around a nominal position intended to be repeated several times remains bounded by an interval of plus or minus 5ms around the p Nominal osition
• the spectral density which is the number of grains or parts extracted from the original sound signal is advantageously about 1 6 grains per second.
• FIG. 2 schematically represents an example of a block diagram of the progress of the synthesis method according to the invention.
• Several pc driving parameters are used to drive the extraction step. Among these parameters are used the RPM engine speed expressed in rotations per minute rpm, recess of the accelerator pedal EP expressed as a percentage%, the speed of the vehicle V expressed in kilometers per hour km / h.
• these different driving parameters are regularly refreshed, for example every 10ms per reading on the automobile network, for example of the CAN type. Indeed, the engine speed, the pedal depression and the vehicle speed are all available on the CAN automobile network.
• a part P2 of the system are stored original sound signals, for example the original sound signals sso1 and sso2, in separate memories. Respectively associated with the sound signals sso1 and sso2, are stored maps cs1 and cs2.
• the map cs1, associated with the original sound signal sso1 contains two elementary maps, cs11 and cs1 2.
• the elementary map cs11 represents a first mask of the nominal position, according to the speed of the vehicle, of the sliding window used.
• the elementary map cs1 1 makes it possible to associate the value of the vehicle speed with a nominal position, along the original sound signal sso1, with the sliding window.
• a gain is applied to obtain the part extracted from the original sound signal sso1 which will be used by the synthesis of the restitution sound signal.
• This gain is given by the elementary map cs1 2 thanks to the value of the depression of the accelerator pedal at said given measurement instant.
• the part extracted from the original sound signal sso1 is a grain of the sound signal of origin sso1.
• the cs2 map associated with the sound signal of origin sso2, also contains two elementary maps, cs21 and cs22.
• the elementary mapping cs21 represents a second gauge of the nominal position, different from the first template, depending on the speed of the vehicle, the sliding window used.
• the basic mapping cs22 represents a second template, different from the first template, depending on the depression of the accelerator pedal, the gain applied to the sliding window used.
• the elementary cartography cs22 could represent, if necessary, another template, according to one of the driving parameters or according to a linear combination of these driving parameters, of the modification of the height of the grain, corresponding to a spectral translation. of the part extracted from original sound signal. Of course, there may be more than two original sound signals stored.
• either one or the other, original sound signals sso1 and sso2 can be selected.
• the original sound signal or signals selected, sso1 and or sso2 the corresponding cartography or maps, cs1 and or cs2, are used to control the extraction step.
• it may be chosen or not to add a tonal signal to generate, or indeed even several tonal signals to generate.
• This tonal signal is generated using a mapping cs3 including two elementary maps cs31 and cs32.
• the elementary map cs31 represents, for different harmonics of a fundamental frequency, the curve of gain in dB as a function of the engine speed.
• the elementary map cs32 represents for the set constituted by the different harmonics of a fundamental frequency as well as by said fundamental frequency, the overall gain curve in dB (decibels) as a function of a linear combination of the vehicle speed and the pedal depression.
• a part P3 of the system are different DSP 1 and DSP2 processing respectively allowing a signal to be synthesized from the sets of parts extracted respectively from the original sound signals sso1 and sso2 by first extracting the parts extracted from the sound signals of origin using the maps stored in the P2 part of the system and then by concatenation of different grains or parts extracted from the original sound signal, possibly previously filtered.
• Another DSP3 processing makes it possible to calculate a tonal synthesis signal to be added to one or the other of the signals synthesized from the original sound signals sso1 and sso2. The calculation uses cs3 mapping to generate the tonal synthesis signal.
• a summator S makes it possible to sum the signals synthesized from the sound signals of origin sso1 and sso2 if these two signals have been synthesized and to keep the signals which have been synthesized if there has been only one .
• the summator S also makes it possible to add, to the signal synthesized from an original sound signal or, where appropriate, to the sum of the signals synthesized from the original sound signals sso1 and sso2, the tonal synthesis signal generated. by calculation if there is one.
• the sound reproduction signal is sent on an audio channel HP, for example an HP speaker, to be restored in the passenger compartment of the vehicle. Prior to sending it on the audio reproduction channel HP, and after its output from the summer S, the restitution sound signal may have been filtered and / or amplified.
• FIG. 3 diagrammatically represents another example of highlighting the sliding window used in the synthesis method according to the invention.
• the windows F6, F7, F8 and F9 represent four windows of width d which one applies successively to the original sound signal sso 1 different from the original sound signal sso2 of FIG.
• the four windows F6 to F9 there is from one window to the next a covering i important to ensure good continuity when restoring the synthesized restitution sound signal.
• Four parts extracted from the sound signal of origin sso 1 are obtained which will be concatenated with one another to give a sequence, for example, of acceleration of the synthesized restitution sound signal, in particular if the original sound signal sso 1 corresponds to a noise. recorded whose amplitude increases.
• the concatenation itself can be a concatenation so simple, each part extracted one after the other, or a more complex concatenation, where one begins to replay the next extracted part while one replay the previous extracted part even before it is finished.
• This overlap in the concatenation of the extracted parts to replay the extracted parts is preferential. Indeed, preferentially, after the synthesis step, there is a step of sound restitution of the restitution sound signal in the course of which said contiguous extracted portions partially overlap. Thus, the continuity of the replayed sound is well assured.
• FIG. 4 schematically represents an example of a template of the nominal position, as a function of the speed of the vehicle, of the sliding window used in the synthesis method according to the invention.
• This template establishes a correspondence between the speed of the driven vehicle and the time sequence of the original sound signal used. This correspondence is made according to a sound effect research. Each desired sound effect corresponds to a different plot of the curve representing the template. If the driven vehicle slows down from the vehicle speed vi + n to the vehicle speed vi, the sliding window will move, from right to left on the time axis, from the nominal position corresponding to the time t i + n of the sound signal of origin sso1 at the nominal position corresponding to the instant ti of the original sound signal sso1.
• the sliding window will move, from left to right on the time axis, from the nominal position corresponding to the instant ti of the audible signal.
• origin sso1 at the nominal position corresponding to the instant ti + n of the original sound signal sso1.
• a value of the vehicle speed is determined and the corresponding nominal position value is read on the ordinate.
• FIG. 5 schematically represents an example of a template, as a function of the depression of the accelerator pedal, of the gain applied to the sliding window used in the synthesis method according to the invention.
• the gain curve depends on the desired sound effect. In general, an increase in the pedal depression increases the gain and the overall sound volume, while a relaxation of the pedal depression decreases the gain and the overall sound volume.
• FIG. 6 diagrammatically represents another example of a template of the nominal position, as a function of the speed of the vehicle, of the sliding window used in the synthesis method according to the invention. The operation of Figure 6 is similar to that of Figure 4.
• FIG. 7 diagrammatically represents another example of a template, as a function of the depression of the accelerator pedal, of the gain applied to the sliding window used in the synthesis method according to the invention. The operation of Figure 7 is similar to that of Figure 5.
• FIG. 8 schematically represents an example of a template, as a function of the engine speed, of the gain applied to a given harmonic h of the fundamental frequency of a tonal signal used in the synthesis method according to the invention.
• a curve like that shown in Figure 8 exists for both the fundamental frequency (if present) and for each of the fundamental frequency harmonics that are used (which may be used without the fundamental frequency).
• only one curve has been shown for reasons of clarity.
• FIG. 9 schematically represents an example of a jig, as a function of a linear combination of the speed of the vehicle and of the depression of the accelerator pedal, of the overall gain applied to the whole of a reconstituted tonal signal used in FIG. the synthesis method according to the invention.
• the linear combination of the driving parameters represented on the abscissa is calculated.
• curves giving values in ordinate as a function of values on the abscissa are represented and is reading on the y-axis because it clearly explains the process.

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• Health & Medical Sciences (AREA)
• Audiology, Speech & Language Pathology (AREA)
• General Health & Medical Sciences (AREA)
• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Acoustics & Sound (AREA)
• Multimedia (AREA)
• Fittings On The Vehicle Exterior For Carrying Loads, And Devices For Holding Or Mounting Articles (AREA)
• Soundproofing, Sound Blocking, And Sound Damping (AREA)

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• 2009
  • 2009-06-16 FR FR0954007A patent/FR2946786B1/fr active Active
• 2010
  • 2010-06-03 EP EP10734787A patent/EP2443627A2/de not_active Withdrawn
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