EP2194734A1 - Method and system for sound spatialisation by dynamic movement of the source - Google Patents

Abstract

The method involves defining spatialized sound signals by a virtual origin position among a set of virtual origin positions (33-35) corresponding to information position, and applying an oscillatory movement (32) describing the set of virtual origin positions of the spatialized sound signal to the spatialized sound signal by performing an algorithmic-process. A sound intensity variation law is applied on the spatialized sound signal during the movement of the spatialized sound signal, where sound intensity ranges between a maximum level (40) and a minimum level (39). An independent claim is also included for a system for algorithmic-processing of signals for sound spatialization.

Description

The field of the invention relates to a method of algorithmic processing of signals for sound spatialization for improving the location of the original virtual positions of the sound signals. Subsequently, we will use the term sound spatialization or 3D sound. The invention applies in particular to spatialization systems compatible with an avionics modular information processing equipment type IMA (abbreviation of the English expression "Integrated Modular Avionics") still called EMTI (for Modular Treatment Equipment some information).

In the field of embedded aeronautics and in particular in the military field, the majority of reflections leads to the need for a head-up display, which can be a helmet worn by the head, associated with a very large format visualization presented in head down. This set should improve the perception of the global situation ("situation awareness") while reducing the burden of the pilot through a presentation of a real-time synthesis of information from multiple sources (sensors, database) .

3D sound is part of the same approach as the helmet visual by allowing pilots to acquire spatial situation information in their own landmark via a communication channel other than the visual, following a natural mode that is less loaded than the view. .

Typically in the context of military aeronautical applications, weapon aircraft include threat detection systems, such as enemy aircraft radar snapping or collision risk, associated with visualization systems inside the cockpit. These systems alert the pilot of threats in his environment by displaying a visualization combined with a sound signal. 3D sound techniques provide an indication of the location of the threat through the hearing input channel, which is not overloaded and intuitive. The pilot is thus informed of the threat by means of a spatialized sound in the direction corresponding to the information.

For embedded aeronautical applications, a sound spatialization system consists of a calculation system performing algorithmic processing on the sound signals. The size of the aircraft cockpits limits the integration of audio equipment and therefore the systems of multiple speaker networks and / or mobile loudspeakers allowing a spatialization without algorithmic processing are little used for the restitution of sounds 3D.

• les techniques de génération de signaux binauraux sont basées sur la différence de niveau sonore (ILD en langage anglo-saxon pour « Interaural Level Difference ») entre les récepteurs auditifs d'un individu et sur la différence temporelle de réception des signaux sonores (ITD pour Interaural Time difference ») entre ces mêmes récepteurs. La figure 1 illustre une série de courbes représentant les différences de niveau sonore en fonction des fréquences du son pour un auditeur selon la position des sources sonores. Pour un son A1 au devant de l'auditeur, la courbe c1 représente la courbe du son en fonction des fréquences. La courbe c2 correspond au son A2 et la courbe c3 correspond au son A3.
• les techniques complémentaires de génération de signaux monauraux font varier le spectre de l'onde sonore en fonction de sa position en lui appliquant la fonction de transfert anatomique de l'individu (HRTF, pour « Head Related Transfer Functions » en langage anglo-saxon). La fonction de transfert anatomique incorpore les effets de dispersion secondaire tels les oreilles externes, les épaules, la forme du crâne, etc... La prise en compte de la HRTF permet d'augmenter la sensibilité à l'élévation d'un son ainsi que la discrimination avant-arrière. A titre d'exemple, la figure 2 représente une série de courbes HRTF pour différentes positions de la source sonore. La courbe c11 représente la fonction HRTF pour le son localisé en A11. La courbe c12 représente la fonction HRTF pour le son localisé en A12. La courbe c13 représente la courbe HRTF pour le son localisé en A13.

Different algorithmic sound spatialization treatments are now used to simulate the positioning of sounds in the environment of an individual:

• the binaural signal generation techniques are based on the difference in sound level (ILD) between the auditory receivers of an individual and on the temporal difference of reception of the sound signals (ITD for Interaural Time difference ") between these same receivers. The figure 1 illustrates a series of curves representing the differences in sound level according to the frequencies of sound for a listener according to the position of the sound sources. For an A1 sound in front of the listener, the curve c1 represents the curve of the sound as a function of the frequencies. The curve c2 corresponds to the sound A2 and the curve c3 corresponds to the sound A3.
• the complementary monaural signal generation techniques vary the spectrum of the sound wave according to its position by applying the anatomical transfer function of the individual (HRTF, for "Head Related Transfer Functions" in English language) . The anatomical transfer function incorporates the effects of secondary dispersion such as the outer ears, the shoulders, the shape of the skull, etc. The consideration of the HRTF makes it possible to increase the sensitivity to the elevation of a sound as well. than front-back discrimination. For example, the figure 2 represents a series of HRTF curves for different positions of the sound source. The curve c11 represents the HRTF function for the sound located at A11. The curve c12 represents the HRTF function for the sound located at A12. The curve c13 represents the HRTF curve for the sound located at A13.

Those skilled in the art are familiar with these sound spatialization techniques, which are not the subject of the invention. However, for information, we can cite the books "Adaptative 3D sound systems" by John Garas, published by Kluwer Academic Publishers, and "Signals, Sound, and Sensation" by Bill Hartmann AIP Press editions describing the latest techniques.

The patent is also known WO 2004/006624 A1 describing an avionic 3D sound system using, to increase the detection of the position of the sound, the use of an HRTF database.

Current sound spatialization systems have limitations in localization performance and often the disadvantage of ambiguous sound source localization. In particular, the localization performance of a sound played in front of a listener of a sound played behind a listener, and in the same way, in elevation, remain variable from one individual to another and generally insufficient.

Scientific studies have shown the contribution of dynamic signals to elevation and fore-and-aft location. A dynamic signal is a sound signal that does not have a constant localization with respect to the individual. This work was inspired by some animals known for their hearing ability, including felines that move their auditory receivers to locate sound sources. To illustrate the different studies carried out on dynamic signals in humans, we can cite in particular H. Wallach with "The role of head movements and vestibular and visual eues in sound localization", J. Exp. Psychol. Flight. 27, 1940, pages. 339-368 , WR Thurlow and PS Runge with "Effects of induced head movements on localization of direct sound", The Journal of the Acoustical Society of America., Vol. 42, 1967, pages. 480-487 / 489-493 and S. Perrett and W. Noble with "The effect of head rotations on vertical plane sound localization", The Journal of the Acoustical Society of America., Vol. 102, 1997, pages. 2325-2332 .

The article, " Resolution of front-back ambiguity in spatial hearing by listener and source movement, by FL Wightman and DJ Kistler, published in The Journal of the Acoustical Society of America, Volume 105, Issue 5, pages. 2841-2853 in May 1999 , summarizes the work done over the last fifty years on the contribution of dynamic signals in the localization of sounds. This study shows empirically that the movement of the subject, head movement for example, reduces the confusion in forward and backward localization, that the multidirectional displacement of the source at the initiative of a subject forced to remain motionless reduces the confusion. forward and backward localization and the monodirectional continuous movement of the source by an action outside the subject, not controllable by the subject, does not significantly reduce the confusion in front-rear location.

However, in the field of aeronautics and especially for pilots, it is not always possible to move his head sufficiently because of the limited space of movement of cockpits and electronic systems integrated into the helmet. The pilot's task, requiring his full concentration on the systems and his field of vision, is also a factor of constraint to movements. The strong loading factors under acceleration also limit the movements of the pilot and in particular of his head.

The present invention aims to avoid ambiguities of location of a sound source.

More specifically, the invention relates to an algorithmic signal processing method for sound spatialization for associating sound signals with information to be located by a listener. The spatialized sound signals are defined by a virtual position of origin corresponding to the position of the information, the method is characterized in that , by algorithmic processing, a movement describing a series of virtual positions of said signal is applied to a spatialized sound signal. signal around the original virtual position of the information.

Preferably, the movement around the original virtual position of the information is of oscillatory type.

In a second calculation mode, the movement around the original virtual position of the information is of the Random type.

This solution for improving the location of 3D sounds is particularly intended for listeners who are subject to movement and workloads. Naturally, a listener gives movement to his auditory receivers to better locate a sound. The invention allows the listener to remain motionless. Indeed, since the original virtual position is the spatialized position of the sound, the movement of the sound source around this position provides location information better than that of a continuous monodirectional movement.

For aeronautical applications, the spatialization system can also be coupled with a pilot's helmet position detection device. Advantageously, the movement is then correlated to the angle of difference between the listening direction of the listener and the original virtual position of said sound signal. The movement then varies according to the orientation of the pilot vis-à-vis the information to be detected which is associated with the sound signal.

Preferably, the amplitude of motion is correlated with the value of said deviation angle and the orientation of movement is also correlated with the orientation of the plane of said deviation angle. The pilot thus receives information indicating whether he is moving in the direction of the information to be acquired.

• l'intensité sonore est comprise entre un niveau maximal et un niveau minimal.
• le niveau est maximal lorsque le signal sonore correspond à la position virtuelle d'origine.
• le niveau est minimal pour les positions extrêmes du mouvement oscillatoire.

Moreover, during the movement of the spatialized signal, a law of variation of the sound intensity is also applied to the spatialized signal where:

• the loudness is between a maximum level and a minimum level.
• the level is maximum when the sound signal corresponds to the original virtual position.
• the level is minimal for the extreme positions of the oscillatory movement.

This spatialisation effect of the sound simulates a movement of the sound signal converging towards the original virtual position of the information. This dynamic effect improves sound detection.

The invention also relates to the algorithmic signal processing system for sound spatialization comprising a first sound spatialization calculation means for associating sound signals with information to be located by a listener. Said system is characterized in that it comprises a second path calculating means providing data enabling the first means spatialization calculus to apply motion to a spatialized sound signal around its original virtual position. This movement of the sound signal is preferably oscillatory.

The system also comprises a third means for calculating at least one law for varying the intensity of a sound signal to modify the intensity of the spatialized sound signal during the oscillatory movement.

Preferably, it also comprises a position data receiving means and the second trajectory calculation means calculates the difference in distance between the original virtual position of the sound source and the position supplied by the reception means and calculates a movement correlating with said distance difference.

In a first mode of implementation, the position data receiving means is connected to a helmet position detector carried by a listener.

In a second embodiment, the position data receiving means is connected to a camera detecting the positioning of the listener. This camera is not worn by the listener.

In an aeronautical application mode, the sound signals come from a sound database of the aircraft and said sound signals are associated with information of at least one avionic device.

A first avionic device is a display device.

A second avionics device is a navigation device.

A third avionics device is an alert device.

• La figure 3 représente le système de spatialisation pour un système informatique. L'exemple s'applique notamment à un système avionique.
• La figure 4 illustre une situation d'alerte dans un cockpit d'aéronef et une application du système de spatialisation du son.
• La figure 5 représente une application aéronautique du système de spatialisation et notamment l'oscillation d'un signal sonore autour d'une position virtuelle d'origine. Ce schéma illustre la variation du mouvement d'oscillation en fonction de la position du pilote vis-à-vis de la position virtuelle d'origine du signal sonore et la variation d'intensité du signal en fonction de la position virtuelle du signal sonore dans le mouvement oscillatoire.
• La figure 6 illustre la différence temporelle d'arrivée des sons au niveau des oreilles d'un auditeur selon la position des sons.
• La figure 7 représente l'effet simulé par la variation de l'intensité sonore sur le mouvement oscillatoire.

The invention will be better understood and other advantages will become apparent on reading the description which follows given by way of non-limiting example and by virtue of the appended figures among which:

• The figure 3 represents the spatialization system for a computer system. The example applies in particular to an avionics system.
• The figure 4 illustrates an alert situation in an aircraft cockpit and an application of the sound spatialization system.
• The figure 5 represents an aeronautical application of the spatialization system and in particular the oscillation of a sound signal around a virtual position of origin. This diagram illustrates the variation of the oscillation movement as a function of the position of the pilot vis-à-vis the original virtual position of the sound signal and the variation of intensity of the signal as a function of the virtual position of the sound signal in the oscillatory movement.
• The figure 6 illustrates the temporal difference of arrival of the sounds in the ears of a listener according to the position of the sounds.
• The figure 7 represents the effect simulated by the variation of the sound intensity on the oscillatory movement.

The invention relates to sound spatialization systems and a method for improving the localization of a sound in the environment of a listener. The results obtained by empirical method shows that an individual more easily detects the origin of a sound when the sound is moving. The above works show better results in location tests with continuous moving sound. The essential characteristic of the spatialization process is to confer an oscillatory movement to a sound around its original virtual position.

The needs in the field of aeronautics, in particular for man-machine interfaces with regard to the cockpit, particularly favor the sound spatialization techniques to improve the interaction of the control systems with the crew. The complexity of these systems, the multiple functions for navigation, for security management and for maneuvers overwhelm the information pilot. This information may come from visualization systems, warning lights, interaction systems and also co-pilots and crews navigating for communications. 3D sound techniques provide an indication of the position of an information. Thus the pilot can better perceive his origin, his priority and the nature of the action to be given accordingly.

Within an aircraft cockpit, a sound spatialization system lies at the border between the avionics systems and the man-machine interface. The figure 3 schematizes a spatialization system in an aircraft cockpit and particularly in a weapons plane where the pilot wears a helmet incorporating a device 6 for detecting the position of the helmet. This The aircraft type includes a plurality of avionics systems 7, including collision-avoidance navigation systems 71 to avoid collisions, and systems for military operations such as target detection devices 72 and aircraft attack devices. target. Avionics systems may also include a meteorological device 73. These systems are most often coupled to visualization devices. The figure 3 does not represent all the avionics systems that can be associated with the spatial system. The skilled person knows the avionics architectures and is able to implement a sound spatialization system with any avionics device transmitting information to the pilot.

The figure 4 schematizes a particular situation showing the interest of a spatialized system with an anticollision system. The field of vision 24 of the pilot flying the aircraft is oriented to the left at a given instant. This driver has a speaker system 21 positioned inside the helmet at the level of his ears. The cockpit of the aircraft comprises several visualizations 21-23 and the pilot's field of vision is oriented towards the visualization 23. For example, an event such as a risk of collision with the ground detected by the anti-collision system alerts the pilot by displaying on visualization 21 the risk situation with the navigation data to be monitored and the flight instructions to be established. The system also issues audible alerts associated with the information on the screen. The spatialized sound associated with the alerts indicates to the pilot the location of the information to be taken into account and thus reduces his mental workload thanks to the audio stimulus given by the spatialization system. The reaction time of the driver is reduced.

A sound spatialization system 1 is generally associated with a sound reception device and a sound database system 81 storing prerecorded sounds, such as synthesized alert messages, signaling sounds, software application sounds. or sounds from internal communications systems as external to the aircraft. For example, the spatialization of audio communications gives additional information on the interlocutor with whom the pilot is in communication.

The sound reproduction system 5 includes the earphones inside the pilot's helmet and also includes the cockpit loudspeaker system. For the use of binaural sounds in the spatialization system, the sound reproduction system must be of stereophonic type for the application of the temporal difference effects of the signals between the loudspeakers.

The output of the spatialization module also comprises a signal processing device for adding additional effects on the spatialized signals, such as Tremolo effects or Doppler effect for example.

The sound spatialization calculating means 2 performs the algorithmic processing of the sounds to produce the monaural signals, realizing the modification of the sound intensity, the binaural signals, realizing the modification of the phase of the signals to simulate a time shift and the setting anatomical transfer functions (HRTF).

Binaural signals are used for the localization of sound sources in azimuth and require a stereophonic reproduction system. Among the binaural type signals, the calculation means establish an algorithmic processing for simulating a distance of the sound sources by modifying the sound level (ILD) and a temporal offset between the sounds (ITD).

Monaural signals are used for elevation location and to distinguish a sound source positioned in front of or behind the listener. Monaural signals do not require a stereophonic reproduction system. The spatialization system is connected to an HRTF database 82 storing the anatomical transfer functions of the known pilots. These transfer functions can be customized for each driver by an individual measurement. The database may also include several anatomical standard profiles in order to be correlated with a pilot at the first use of the system to detect the adapted profile. This manipulation is faster than the individual measurement.

Those skilled in the art are familiar with the different signal processing techniques and algorithms developed by calculation means 2 for sound spatialization.

For the implementation of the invention, two functional means 3 and 4 complete the spatialization calculation means. The first means 3 has the function of calculating the trajectory of the oscillatory movement to be imparted to the spatialized sound. The oscillatory movement has a trajectory that can vary in elevation and azimuth with respect to the listener. The oscillatory trajectory is in an angular range whose apex of the angle is centered on the listener. For an aircraft cockpit application comprising a position detector 6 of the pilot's helmet, the calculation means 3 determines an angle of difference between the orientation of the pilot's gaze, indirectly by the position of the helmet, and the virtual position. origin of the sound signal. The figure 5 schematizes the application of the invention for calculating the trajectory of the oscillatory movement. The drawing on the left represents the case where the orientation of the pilot is such that the direction of his field of vision 42 is strongly decorrelated with the direction 43 of his field of vision if it was oriented towards the position of origin of the signal sound. The deviation angle 31 is calculated by the calculation means 3. This deviation angle can be in a plane varying in azimuth and in elevation as a function of the orientation 42 of the pilot's field of view. The calculation means 3 also calculates the trajectory of the oscillatory movement 32 as a function of this angle of variation 31.

The trajectory of the oscillatory movement 32, or 41 on the drawing of the right of the figure 5 , is a function of the angle of difference 31, or 36. The coordinates of the original virtual position 33 are defined by an azimuth coordinate a1 and an elevation coordinate e1. Preferably, the trajectory of the oscillatory movement 32 is bidirectional and continuous, thus achieving an oscillatory movement back and forth along an arc of a circle connected to the angular bearings 44 and 45. However, the trajectory calculation means can define a trajectory that can be oval or other shape. The scan speed of this path is also configurable. It is preferably greater than the speed of movement of the head with a latency of less than 70 ms to preserve the natural sound.

• Si l'écart angulaire 31 est supérieur à 45°, la position angulaire par rapport au regard du pilote varie de 15°.
• Si l'écart angulaire 31 est compris entre 45° et 20°, la position angulaire par rapport au regard du pilote varie de 10°.
• S l'écart angulaire 31 est compris entre 20° et 10°, la position angulaire par rapport au regard du pilote varie de 5°.
• Si l'écart angulaire 31 est compris entre 10° et 0°, la position angulaire par rapport au regard du pilote varie de 2°.
• Lorsque l'écart angulaire 31 est égal à 0°, la source sonore ne bouge plus.

The law defining the path of displacement depends on angular steps that can be defined, by way of non-limiting example, as follows:

• If the angular difference 31 is greater than 45 °, the angular position relative to the pilot's view varies by 15 °.
• If the angular difference 31 is between 45 ° and 20 °, the angular position relative to the pilot's view varies by 10 °.
• S angular deviation 31 is between 20 ° and 10 °, the angular position relative to the pilot's view varies by 5 °.
• If the angular difference 31 is between 10 ° and 0 °, the angular position relative to the pilot's view varies by 2 °.
• When the angular difference 31 is equal to 0 °, the sound source no longer moves.

When the trajectory of the oscillatory movement is determined by the angular steps, the spatialization process calculates, by the calculation means 2, the trajectory of the oscillatory movement 32 around the virtual position 33. The calculated angles are used by the calculation functions of FIG. monaural and binaural signals to determine the trajectory 32 around the original virtual position 33. This trajectory 32 comprises a series of several virtual positions delimited by two extreme positions 34 and 35. These two extreme positions are located according to the coordinates of the position of origin 33 added with angular bearings in azimuth 44 and elevation 45. The signals ITD and ILD depend on the angles in azimuth and elevation.

où a_i est l'amplitude de la i^ème harmonique, f_i sa fréquence et Φ _i sa phase à l'origine To understand the operation of the spatialization module 3, it is necessary to first define the sound signals. In an aeronautical sound spatialization application, a sound signal is defined as a vibration perceived by the human ear, described in the form of a sound wave and which can be represented in the time and frequency domain (spectrum of the wave). Mathematically, a sound signal is defined by the formula (1): $$S\left(t\right)={\displaystyle \underset{i}{\Sigma }}{\mathrm{at}}_i\cdot \mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">cos</figure-callout>}\left(2\pi \cdot f_i\cdot t+{\mathrm{\Phi }}_i\right)=f\left(t\right)$$

where a _i is the amplitude of the i ^th harmonic, f _i its frequency and Φ _i its phase at the origin

Calculation of interaural time delay (ITD):

où θ est l'angle azimutal, a le rayon de la tête, environ 8.75 cm, et C la célérité du son, 344 m/s. Ainsi 3a/c = 763 µs environ.
La figure 6 représente le diagramme temporel du son pour chaque oreille pour différentes positions de la source sonore. La source sonore A21 représente une première position où la source sonore est du côté de l'oreille gauche de l'auditeur et la source sonore A22 représente une deuxième position où la source sonore est du côté de l'oreille droite de l'auditeur. La source sonore A21 est plus proche de l'auditeur que la source A22 ne l'est.
Ainsi, si S ₁(t) = f(t) où f est la fonction définie dans la formule (1), alors S ₂(t) = f(t + Δt) (formule (2)) avec S1 le signal reçu sur l'oreille gauche et S2 le signal reçu sur l'oreille droite.
Sur la ligne temporelle de S1(t), on représente à la fois le son SA21 de la source sonore lorsqu'elle est en position A21 et à la fois le son SA22 lorsqu'elle est en position A22. On représente de même pour la ligne S2(t).
Le son SA21 arrive plus tôt à l'oreille gauche que l'oreille droite car le son est positionné du côté de l'oreille gauche.
Le son SA22 arrive plus tôt à l'oreille droite que l'oreille gauche car le son A22 est positionné du côté de l'oreille droite.
Sur une même échelle temporelle, le son SA21 arrive avant le son SA22 car la source sonore A21 est plus proche de l'auditeur que la source A22 ne l'est.The ITD signals include a phase change to simulate a different azimuth position by a time shift of the signal between the ears of a listener. A phase difference ΔΦ corresponds to an interaural time shift (ITD) of Δ t = ΔΦ / (2π f ) for a sound of frequency f.
If we equate the head with a sphere and consider sufficiently long waveforms, the interaural time delay is equal to $\mathrm{\Delta }t=\frac{3\mathrm{at}}{\mathrm{vs}}\mathrm{.}\sin \theta \mathrm{.}$

where θ is the azimuthal angle, has the radius of the head, about 8.75 cm, and C the velocity of the sound, 344 m / s. Thus 3a / c = approximately 763 μs.
The figure 6 represents the timing diagram of the sound for each ear for different positions of the sound source. The sound source A21 represents a first position where the sound source is on the left ear side of the listener and the sound source A22 represents a second position where the sound source is on the side of the right ear of the listener. The sound source A21 is closer to the listener than the source A22 is.
Thus, if S ₁ (t) = f (t) where f is the function defined in the formula (1), then S ₂ (t) = f (t + Δ t) (formula (2)) with S1 the signal received on the left ear and S2 the signal received on the right ear.
On the time line of S1 (t), we represent both the sound SA21 of the sound source when it is in position A21 and both the sound SA22 when it is in position A22. The same is true for the line S2 (t).
The SA21 sound arrives earlier in the left ear than the right ear because the sound is positioned on the side of the left ear.
The SA22 sound arrives earlier in the right ear than the left ear because the A22 sound is positioned on the side of the right ear.
On the same time scale, the sound SA21 arrives before the sound SA22 because the sound source A21 is closer to the listener than the source A22 is.

et $\mathrm{\Delta }T=\frac{3a}{c}\mathrm{.}\mathit{sin}\left(\mathrm{\theta }+\mathit{P}\mathit{a}\mathit{l}\mathit{i}\mathit{e}\mathit{r}\mathit{a}\mathit{n}\mathit{g}\mathit{u}\mathit{l}\mathit{a}\mathit{i}\mathit{r}\mathit{e}\right),$

sin(θ + Palier angudaire), où θ est l'angle azimutal a1 sur la figure 5. Les valeurs d'angle évoluant dans la plage de palier angulaire sont utilisées pour le calcul des différentes positions virtuelles constituant la trajectoire 32. Ces valeurs sont injectées dans la formule 2. Les différentes valeurs d'angle comprises dans la plage de palier angulaire définissent les différentes positions virtuelles composant la trajectoire du signal sonore. Les sons doivent avoir une périodicité idéalement inférieure à 70 ms, afin d'éviter les effets artificiels de traînée lorsque l'on tourne la tête. De la même façon, l'empreinte sonore globale doit idéalement durer 250 ms au minimum.For the calculation of the trajectory 32 of the oscillatory movement around the original virtual position 33 and in the case where the head is likened to a sphere and where we consider sufficiently long waveforms, for calculation ITD signals, the interaural time delay for an azimuth θ given varies between $\mathrm{\Delta }t=\frac{3\mathrm{at}}{\mathrm{vs}}\mathrm{.}\sin \theta$

and $\mathrm{\Delta }T=\frac{3\mathrm{at}}{\mathrm{vs}}\mathrm{.}\mathit{sin}\left(\mathrm{\theta }+\mathit{P}\mathit{at}\mathit{l}\mathit{i}\mathit{e}\mathit{r}\mathit{at}\mathit{not}\mathit{boy\; Wut}\mathit{u}\mathit{l}\mathit{at}\mathit{i}\mathit{r}\mathit{e}\right),$

sin (θ + angular step ), where θ is the azimuth angle a1 on the figure 5 . The angle values evolving in the angular bearing range are used for the calculation of the different virtual positions constituting the trajectory 32. These values are injected into the formula 2. The various angle values included in the angular bearing range define the different virtual positions composing the trajectory of the sound signal. The sounds should have a periodicity ideally less than 70 ms, to avoid the artificial effects of drag when one turns the head. In the same way, the overall sound footprint should ideally last at least 250 ms.

Calculation of ILD signals:

The loudness is different between the left ear and the right ear of a listener. The difference in sound level is variable at an angle between the two ears.

The difference in sound level between the two ears varies between the ILD curve associated with the original virtual position 33 of the sound signal and the ILD curve associated with the extreme position of the sound signal on the trajectory of movement. The sound shift varies according to the angular bearings 44 and 45 (azimuth and elevation). The figure 1 illustrates for example a law of loudness that can be applied to sounds.

The value of the angular bearings 44 and 45 varies depending on the orientation of the pilot. The law regulating the bearings mentioned above shows that the more the listener moves towards the original position of the sound signal and the lower the value of the angular bearings, until the bearings are canceled for a direction substantially equal to the direction of rotation. the virtual position of origin. The position detection device 6 transmits the position coordinates to the calculation means 3 and according to these coordinates the angular bearings 44 and 45 will decrease or increase. The diagram on the right of the figure 3 corresponds to a situation where the orientation of the pilot approaches the original virtual position 33 of the sound signal. The angle of variation 36 is reduced and therefore the new trajectory 41 calculated by the calculation module 2 is of smaller amplitude, delimited by the two positions 36 and 37.

The values of the HRTFs are always used from the predetermination made for each subject and described previously.

In addition to the ILDs, the invention also includes, for each subject, calculation means 4 for processing the sound signal at the output of the calculation means 2 for spatializing the sound. This module 4 realizes a variation of the sound intensity of a sound signal according to the positions of the sound on the oscillatory movement.

Preferably, a law of regulation of linear sound is applied to a spatialized sound performing the oscillatory movement so that the intensity 39 of the sound signal is reduced by a predefined number of dB when the position of the sound signal is located at a position extreme of the oscillatory movement, these positions corresponding, on the figure 3 at positions 34 and 35 of the oscillatory movement 32, and the intensity 40 of the sound signal is maximum when the position of the sound signal is located at the original virtual position 33 of the sound signal. A linear regression law can for example determine the intermediate positions having an intermediate level of sound intensity between the maximum intensity and the decreased intensity.

• de simuler un éloignement par rapport à la position du signal sonore lorsque les positions du signal sonore durant le mouvement oscillatoire se rapprochent d'une position extrême du mouvement oscillatoire
• de simuler un rapprochement du signal sonore lorsque les positions du signal durant le mouvement oscillatoire se rapprochent de la position virtuelle d'origine du son spatialisé.

As represented by figure 7 , the sound processing module allows:

• to simulate a distance from the position of the sound signal when the positions of the sound signal during the oscillatory movement approach an extreme position of the oscillatory movement
• to simulate an approximation of the sound signal when the positions of the signal during the oscillatory movement are close to the original virtual position of the spatialized sound.

The intensity of the sound signal is indeed less strong for a signal far from its actual position. For the listener, this variation in intensity simulates a distance 51 between the listener and an extreme position of the high oscillatory movement. While for the original virtual position, the simulated distance 52 is small. The change in intensity simulates a spatial convergence of the oscillatory movement towards the original position. The law of variation of the sound intensity can be independent of the angular difference between the pilot's gaze and the direction of the sound source. The variation can also be random, ie not continuous between the original position and the extremes.

Preferably, the duration of a sound is greater than 250 ms. Ideally, the duration should even be greater than 5 s to take full advantage of the associated dynamic signals.

Any type of sound reproduction system may be used: a system comprising a loudspeaker, a system comprising several loudspeakers, a system of cartilaginous transducers, a plug system with or without wires, etc.

The sound spatialization method applies to any type of application whose needs require the location of a sound. It is particularly intended for applications associating sound with information to be taken into account by an auditor. It applies to the field of aeronautics for the human-machine interaction of avionics systems with the pilot, for simulator applications immersing an individual (virtual reality system for example or airplane simulator) and also in the automotive field for systems to alert the driver of a hazard and provide an indication of the origin of the hazard.

Claims (14)

A method of algorithmic signal processing for sound spatialization for associating sound signals with information to be located by a listener, the spatialized sound signals being defined by an original virtual position (33) corresponding to the position of the information, characterized in that, by algorithmic processing, a motion (32) describing a succession of virtual positions (33-35) of said signal around the virtual origin position of the information (33) is applied to a spatialized sound signal. ) and in that during the movement of the spatialized signal, a law of variation of the sound intensity is applied to the spatialized signal, the sound intensity being between a maximum level (40) and a minimum level (39), the level being at a maximum when the sound signal corresponds to the original virtual position (33) and the level being minimal for the extreme positions (34 and 35) of the movement (32). Method according to Claim 1, characterized in that the movement around the original virtual position of the information is of the oscillating type. Method according to claim 1, characterized in that the movement around the original virtual position of the information is of the Random type. Method according to any one of the preceding claims, characterized in that the movement is correlated with the angle of divergence (31) between the direction (42) of the listener's gaze and the virtual position of origin (33) said sound signal. Method according to claim 4, characterized in that the amplitude of the oscillatory movement is correlated with the value of said deviation angle (31). Method according to claim 5, characterized in that the orientation of the oscillatory movement (32) is correlated with the orientation of the plane of said deviation angle. An algorithmic signal processing system for sound spatialization comprising a first calculation means (2) for sound spatialization for associating sound signals with information to be located by a listener, the spatialized sound signals being defined by a virtual position of origin corresponding to the position of an item of information, said system being characterized in that comprises second trajectory calculating means (3) providing data enabling the first spatialization calculating means (2) to apply a movement to a spatialized sound signal around its original virtual position and in that it comprises third calculation means (4) of at least one law for varying the intensity of a sound signal to modify the intensity of the spatialized sound signal during the oscillatory movement. System according to Claim 7, characterized in that it comprises a position data receiving means and in that the second trajectory calculation means (3) calculates the difference angle between the virtual position of origin of the the sound source and the position provided by the receiving means and calculates an oscillatory movement correlating with said distance difference. System according to claim 8, characterized in that the position data receiving means is connected to a helmet position detector (6) carried by a listener. System according to claim 9, characterized in that the position data receiving means is connected to a camera not worn by the listener detecting the positioning of the listener. System according to claim 10, characterized in that the sound signals come from a sound database of an aircraft and in that said sound signals are associated with information of at least one avionic device (71-73) . System according to claim 11, characterized in that a first avionic device is a display device. System according to claim 12, characterized in that a second avionic device is a navigation device. System according to Claim 13, characterized in that a third avionic device is an alert device.

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