EP2700069B1 - Generating sound for a rotating machine of a device - Google Patents

Description

The invention relates to a method for generating a sound of a rotating machine, such as the motor of a motor vehicle, a train, a helicopter, etc., and a method for generating a engine sound within a device like a motor vehicle. It also relates to a sound device generating a motor sound of a motor vehicle using such a method. Finally, it also relates to a motor vehicle equipped with such a sound device.

Advances in motor vehicles have significantly reduced the level of noise inside their cars. The occupants of the vehicle sometimes have the desire to associate a particular sound to the operation of their vehicle, and this reduction in the noise level of motor vehicles gives them the freedom to impose the sound of their choice.

The document FR2924260 proposes a solution for generating a synthetic sound inside the motor vehicle taking into account the engine speed and the position of the accelerator pedal. This synthesis of sound consists of a classical method of decomposing the sound of the real engine into different harmonics.

The document WO200225628 also describes a more complicated method of synthesizing a sound, which integrates a calculation of a phase associated with each harmonic of the sound, with the aim of seeking the most realistic reproduction of real sounds. The calculations used, however, are complex and incompatible with real-time use in a motor vehicle.

The document EP1705644 discloses a method of generating a rotating machine tone, comprising a step of determining frequencies and amplitudes of harmonics.

Thus, there is a need for a solution for generating a synthetic sound of a rotating machine such as a motor vehicle engine to achieve a more realistic and / or enjoyable and consistent with a real-time generation, in a manner coordinated with the actual operation of a motor vehicle engine for example.

For this purpose, the invention is based on a method of generating a rotating machine sound, comprising a step of determining the frequencies and amplitudes of n partials and / or harmonic relevant in the sound of a rotating machine, characterized in it includes a step of determining values and a step of calculating a synthesized sound of the rotating machine, composed from n partial and / or harmonic but whose frequency is wholly or partly offset values.

The invention is more precisely defined by the claims.

• La figure 1 représente un algorithme du procédé de génération d'un son de moteur selon un mode de réalisation de l'invention.
• Les figures 2a et 2b représentent des tableaux d'harmoniques et/ou partiels i pour respectivement deux types de moteurs différents selon un mode de réalisation de l'invention.
• La figure 3 représente un tableau de valeurs d'amplitudes en dB en fonction des harmoniques et/ou partiels et du régime moteur selon un mode de réalisation de l'invention.
• La figure 4 représente un tableau de valeurs d'un gain en fonction d'un souhait du conducteur selon un mode de réalisation de l'invention.
• La figure 5 représente un tableau de valeurs d'un gain en fonction de la vitesse du véhicule automobile selon un mode de réalisation de l'invention.

These objects, features and advantages of the present invention will be set forth in detail in the following description of a particular embodiment made in a non-limiting manner in relation to the appended figures among which:

• The figure 1 represents an algorithm of the method of generating a motor sound according to one embodiment of the invention.
• The Figures 2a and 2b represent harmonic and / or partial arrays for respectively two different types of motors according to one embodiment of the invention.
• The figure 3 represents a table of amplitude values in dB according to the harmonics and / or partial and the engine speed according to one embodiment of the invention.
• The figure 4 represents a table of values of a gain according to a wish of the driver according to one embodiment of the invention.
• The figure 5 represents a table of values of a gain as a function of the speed of the motor vehicle according to one embodiment of the invention.

According to one embodiment, the invention is based on a method for generating a sound of a particular motor of a motor vehicle, an algorithm according to one embodiment of which is shown in FIG. figure 1 . Alternatively, the same method can be used for generating a sound of any rotating machine or sound of an imaginary machine, which does not actually exist. It can be the rotating machine of any device, such as a helicopter, a plane, a train, etc.

The method first comprises an upstream phase, preparing parameters that will be used to generate the synthesis sound.

This upstream phase comprises a first step E1 for determining a fundamental frequency f ₀ (N) of the sound of the engine, then of n harmonics and / or partials i (i ₁ to i _n ) of the sound of this engine considered. The sound of the motor is represented by this fundamental frequency f ₀ (N), which depends in general on its operating speed N, that is to say on the crankshaft rotation frequency for a motor vehicle engine, then by the frequencies ixf ₀ (N), for all selected harmonic and / or partial values i. When i is an integer, we speaks of harmonic, while in other cases, it is a partial. For example, for a four-stroke engine, all selected partials are half-integers. Thus, this step E1 makes it possible to define the frequencies of n harmonic and / or partial relevant in the sound of the machine in question.

For example, Figures 2a and 2b illustrate stored harmonic and partial solutions for respectively a six-cylinder and a four-cylinder engine. As a remark, several solutions can be provided for the same engine, according to different desired renderings. For example, the table of the figure 3 represents a more complete choice for a six-cylinder engine. These two representation solutions of a six-cylinder engine ( Figures 2a and 3 ) are coherent with each other because they include a large number of harmonics and / or partials in common.

Then, the method comprises a second step E2 generating n any number ai, advantageously between [-0.2; 0,2]. Since these numbers may be arbitrary, they are defined for example by a random generation. However, any other method to define them may be appropriate since they are arbitrary.

According to an advantageous variant embodiment, the values of ai between [-0.1; 0,1].

According to an alternative embodiment, it may be chosen less than n values ai.

According to another embodiment, it will be ensured to obtain at least one non-zero value of ai.

Then, the method comprises a third step E3 of determining a data table of reference values of an amplitude k (i, N *) in dB as a function of the harmonics and / or partial determined in the first step and in function certain selected values of engine speed N *.

According to a first approach, this third step is performed empirically, by recording the actual noise of the engine and then decomposition. According to a second approach, this third step is carried out by a simple expertise, according to artistic criteria.

The method then comprises a fourth step E4 of determining a data table representing a gain G ₁ in dB, to take into account the intervention of the driver on the engine. In particular, it takes into account the position of the accelerator pedal, which represents an important desire of the driver in terms of the operation of the vehicle. For this, gain values G1 as a function of certain predefined values C * representing an action of a conductor are predefined and stored, as illustrated by way of example by the table of the figure 4 .

The method then comprises a fifth step E5 of determining a data table representing a second gain G ₂ in dB as a function of predefined speed values V * of the motor vehicle. The table presented in figure 5 presents the values retained for this gain as a function of V *, according to this embodiment. This gain reduces the volume of the sound when the speed increases, to reach a comfortable situation at high speed on the highway for example.

The method comprises a sixth step E6 of recording the values thus obtained in a memory. These stored data are represented by way of example by the table of the figure 3 .

Then, the method implements an iterative phase, which evolves with time. The values defined previously during the upstream phase then remain always constant, and the process is limited to the second iterative phase. Alternatively, it may be chosen to modify these values according to defined criteria.

The seventh step E7 comprises the calculation of a synthesized sound s (N, t) of the engine of the motor vehicle, for a time t and for the engine speed N, by the following formula: $$\mathrm{s}\left(\mathrm{NOT},\mathrm{t}\right)=\underset{\mathrm{i}=\mathrm{<figure-callout\; id="1"\; label="i"\; filenames="imgf0002.png"\; state="\{\{state\}\}">i</figure-callout>}\mathrm{1}}{\overset{\mathrm{in}}{\Sigma }}\mathrm{k}\left(\mathrm{i},\mathrm{NOT}\right)\times \mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="imgf0002.png"\; state="\{\{state\}\}">sin</figure-callout>}\left[\mathrm{2}\times \mathrm{\pi }\times \mathrm{t}\times \mathrm{f}\left(\left(\mathrm{i}+\mathrm{have}\right),\mathrm{NOT}\right)\right]$$

As a remark, this step therefore integrates the measurement or estimation of a regime N of the engine at time t. The amplitude value k (i, N) is obtained by extrapolation of the predefined values during the upstream phase and stored in the data table.

Thus, according to the embodiment of the invention, the frequency of each harmonic and / or partial i is slightly shifted by a random value, that is to say in the sense of any value. This calculation of the frequencies taken into account in this calculation of the sound makes it possible to arrive at a more realistic sound, without increasing the complexity of the computation, which is compatible with an implementation by modest computing devices while allowing a calculation in time. real.

According to an alternative embodiment, equation (1) is replaced by the following equation (2), in which a phase Φ (i) is added for each harmonic and / or partial, these phases Φ (i) being in advance calculated once and for all in any way, for example randomly, in the range] 0; 2 π [. $$\mathrm{s}\left(\mathrm{NOT},\mathrm{t}\right)=\underset{\mathrm{i}=\mathrm{i}\mathrm{1}}{\overset{\mathrm{in}}{\Sigma }}\mathrm{k}\left(\mathrm{i},\mathrm{NOT}\right)\times \mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="imgf0002.png"\; state="\{\{state\}\}">sin</figure-callout>}\left[\mathrm{2}\times \mathrm{\pi }\times \mathrm{t}\times \mathrm{f}\left(\left(\mathrm{i}+\mathrm{have}\right),\mathrm{NOT}\right)+\mathrm{\Phi }\left(\mathrm{i}\right)\right]$$

According to one embodiment, the frequency function f (i, N) is determined by f (i, N) = (N / 60) * i, so that in both equations (1) and (2) above , f ((i + ai), N) = (N / 60) x (i + ai),
where N / 60 represents the engine speed in rev / s.
As a remark, this realization amounts to considering as the fundamental frequency of the sound of the motor f ₀ (N) = N / 60.

Les deux valeurs de gains G₁(C) et G₂(V) sont obtenues par extrapolation des valeurs mémorisées dans les tableaux de valeurs définis lors de la phase amont.An eighth step E8 of the method consists in considering the gains G1 and G2 to finally obtain the retained sound S (N, t): $$\mathrm{S}\left(\mathrm{NOT},\mathrm{t}\right)={\mathrm{<figure-callout\; id="1"\; label="BOY\; WUT"\; filenames="imgf0002.png"\; state="\{\{state\}\}">BOY\; WUT</figure-callout>}}_{\mathrm{1}}\left(\mathrm{VS}\right)\times {\mathrm{BOY\; WUT}}_{\mathrm{2}}\left(\mathrm{V}\right)\times \mathrm{s}\left(\mathrm{NOT},\mathrm{t}\right)$$

The two gain values G ₁ (C) and G ₂ (V) are obtained by extrapolation of the values stored in the tables of values defined during the upstream phase.

Steps E7 and E8 are repeated in time, according to a certain time step dt predefined. At each instant t, the method comprises a step E9 for broadcasting the calculated sound.

The sound generation method described above can naturally undergo variations without departing from the scope of the invention. In particular, the use of gains G ₁ and / or G ₂ remains optional. In addition, the amplitude values k (i, N) can be defined differently.

The method described above is implemented in a sound generation device of a motor, comprising at least one computer, which implements the steps of the method described above and which is connected to a sound diffusion device, which comprises an amplifier coupled to one or more speakers. The computer is further connected to a memory, comprising the various data mentioned above, useful for the implementation of the method.

The sound generation method of a motor vehicle engine can be implemented in different applications.

First, it can be implemented on board a motor vehicle. For this, the engine sound generation device is advantageously connected to a communication network on board the motor vehicle, by which it retrieves the values of the data representative of the engine speed, the position of the accelerator pedal, the vehicle speed, and possibly any vehicle actuator or other driver control and / or other quantities representative of the condition or operation of the vehicle, such as hybrid, thermal, electrical, LPG, etc., the motorization of the vehicle and / or the torque experienced by the engine to deal with deceleration, etc. The sound diffuser can be connected to the onboard speakers of the vehicle, also provided for broadcasting radio for example. Thus, the engine generating device is adapted to emit an engine sound inside the cabin, perfectly correlated with the real sound of the engine.

In this application, the steps E7 and E8 are repeated very quickly, in a very small time step, so as to be able to better follow the engine variations, to obtain a synthesis sound correlated best with the actual operation of the engine. These steps E7, E8 use a measurement of the engine speed N transmitted periodically to the calculator of the sound generator for the application of equations (1) or (2) of step E7. As a variant, this transmitted value of the engine speed N can be modified by the computer, according to an interpolation of the last values retained, in order to obtain a value of the engine speed varying according to a smaller period, in order to better follow the variations of the engine. The same approach applies to other data taken into account, such as the position of the accelerator pedal.

Alternatively, the device for generating its engine is used in a motor vehicle simulator, so as to reproduce the sound of a motor as realistic as possible.

Alternatively, the engine generating device is used to simply create a sound file from data from a predefined driving profile of a motor vehicle, including data of the engine speed, the support on the accelerator pedal, etc. In the latter case, the application of the principle of sound generation is no longer in a real-time constraint.

Thus, the solution described above allows the generation of a sound associated with any rotating machine, which can be implemented for real-time or not, with devices of the digital and / or analog type.

Claims (15)

1. A method for generating a rotating machine sound, comprising a step (E1) of determining the frequencies and amplitudes of n relevant partials and/or harmonics (i) in the sonority of a rotating machine, characterized in that it comprises a step (E2) of determining values (ai) and a step of calculating (E7-E8) a synthetic sound of the rotating machine, made up of the n partials and/or harmonics (i) but whose frequency is all or partly shifted by the values (ai).
2. The method for generating a rotating machine sound as claimed in claim 1, characterized in that it comprises a step (E2) of determining random values (ai) and a step of calculating (E7-E8) a synthetic sound of the rotating machine, from the frequencies determined by the partials and/or harmonics (i) all or partly shifted by the random values (ai).
3. The method for generating a rotating machine sound as claimed in claim 1 or 2, characterized in that the step of calculating a synthetic sound s(N,t) (E7) comprises a calculation defined by the equation: $$\mathrm{s}\left(\mathrm{N},\mathrm{t}\right)={\displaystyle \sum _{\mathrm{i}=\mathrm{i}\mathrm{1}}^{\mathrm{in}}}\mathrm{k}\left(\mathrm{i},\mathrm{N}\right)\times \sin \left[\mathrm{2}\times \mathrm{\pi }\times \mathrm{t}\times \mathrm{f}\left(\left(\mathrm{i}+\mathrm{ai}\right),\mathrm{N}\right)\right]$$

   

   in which N is the speed of the rotating machine, t the time, k(i, N) an amplitude in dB, f(i+ai) the frequency associated with the harmonic/partial (i) shifted by the value (ai).
4. The method for generating a rotating machine sound as claimed in claim 1 or 2, characterized in that the step of calculating a synthetic sound s(N,t) (E7) comprises a calculation defined by the equation: $$\mathrm{s}\left(\mathrm{N},\mathrm{t}\right)={\displaystyle \sum _{\mathrm{i}=\mathrm{i}\mathrm{1}}^{\mathrm{in}}}\mathrm{k}\left(\mathrm{i},\mathrm{N}\right)\times \sin \left[\mathrm{2}\times \mathrm{\pi }\times \mathrm{t}\times \mathrm{f}\left(\left(\mathrm{i}+\mathrm{ai}\right),\mathrm{N}\right)+\mathrm{\Phi }\left(\mathrm{i}\right)\right]$$

   

   in which N is the speed of the rotating machine, t the time, k(i, N) an amplitude in dB, f(i+ai) the frequency associated with the harmonic/partial (i) shifted by the value (ai), Φ(i) any phase associated with the harmonic/partial (i), as randomly chosen between] 0 ; 2 π [.
5. The method for generating a rotating machine sound as claimed in one of the preceding claims, characterized in that the frequency f((i+ai), N) of each harmonic and/or partial (i) is defined by the equation f((i+ai), N) = (N/60) x (i + ai),
   in which N/60 represents the speed of the rotating machine in revolution/s.
6. The method for generating a rotating machine sound as claimed in one of the preceding claims, characterized in that the values (ai) are contained within the range [-0.2 ; 0.2].
7. The method for generating a rotating machine sound as claimed in the preceding claim, characterized in that the values (ai) are contained within the range [-0.1 ; 0.1].
8. The method for generating a rotating machine sound as claimed in the preceding claim, characterized in that it comprises determining n random values (ai), including at least one non-zero value.
9. The method for generating a rotating machine sound as claimed in one of the preceding claims, characterized in that the n relevant partials and/or harmonics (i) in the sonority of the rotating machine are determined empirically, by a simulator, and/or stored (E6).
10. The method for generating a rotating machine sound as claimed in one of the preceding claims, characterized in that it comprises a step of determining a gain G₁ that is a function of a driver command, such as the position of the accelerator pedal, and/or of a gain G₂ as a function of the speed of the vehicle, reference values of these gains being stored, and a step of calculating (E8) the synthetic sound by its multiplication by this gain or these gains.
11. The method for generating a rotating machine sound as claimed in one of the preceding claims, characterized in that it is carried out on board an appliance, in that it comprises an iteration of the step of calculating (E7-E8) a synthetic sound of the rotating machine, and a step of periodically transmitting the speed N and the position of an actuator of the appliance.
12. The method for generating a rotating machine sound as claimed in the preceding claim, characterized in that the appliance is a motor vehicle, rail car or aircraft, and in that the rotating machine is the engine of the appliance.
13. A device for generating a rotating machine sound, characterized in that it comprises at least one memory and one computer, which implements the method for generating a rotating machine sound as claimed in one of the preceding claims.
14. A motor vehicle, characterized in that it comprises a device for generating a rotating machine sound as claimed in the preceding claim.
15. A motor vehicle simulator, characterized in that it comprises a device for generating a rotating machine sound as claimed in claim 13.

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