WO2017032946A1 - Method of measuring phrtf filters of a hearer, booth for implementing the method, and methods making it possible to culminate in the restitution of a personalized multichannel sound band - Google Patents

Abstract

The invention resides in the fine tuning of a method of measuring PHRTF ("Personalized Head Response Transfert Function") filters, of a hearer and its application in a device, nomadic or otherwise, allowing multichannel sound band restitution in a headset. The method of measurement is implemented in an acoustically treated and sound-proofed enclosed volume comprising at least 5 loudspeakers, broadcasting an acoustic signal, and all directed exactly towards the hearer's head which is fitted with an electro-acoustic transducer (of microphone type) by ear, and in that these microphones are used to record the parameters making it possible to calculate the PHRTF filters. The method is characterized in that it is purely and solely acoustic. The PHRTF filters are implemented and used in an application, either in a server, a terminal, a dongle or directly in a headset of the hearer by applying the convolution algorithm. The result is an individualized sound band that restores a 360° spatialization effect.

Description

 PHRTF filter measurement method of a listener, cabin for the implementation of the method, and methods for leading to the rendering of a personalized multichannel soundtrack Technical sector of the invention:

 The present invention relates to the technical field of measuring the acoustic behavior of an individual in a sound environment in order to integrate its unique morphological features into a sound processing method, particularly for nomadic personal listening, in particular to headphones.

Each individual is unique and perceives sounds in a modified way according to his morphological characteristics (shape of the head, shape of the flag of the ears, auditory canal, texture of the skin, nature of the hair, etc.). A sound will not be perceived identically by two different individuals. An individual placed in a sound field perceives in three dimensions the different sources of a sound scene with their information of position, sound level, extent, distance and displacement.

An individual therefore himself causes a certain number of propagation disturbances of the sound wave that he will receive according to his own morphological characteristics. It is these disturbances that make it possible to locate the source of emission, the source, the nature, and the associated object of a sound in space. Each individual therefore has, for each of his ears, a unique transfer function (that is to say a single filter) which defines the set of disturbances. This unique filter is called "HRTF" (for "Head Related Transfer Function").

To evaluate an individual's HRTF filters, a loudspeaker is moved angularly (azimuth angle and elevation angle) around the center of the head, with a measurement microphone inside each head. flag of both ears. The microphones measure the disturbances of the sound waves emitted by the loudspeaker in the different directions of propagation. The measurements made to obtain the HRTF filters of this individual. New techniques, including binaural listening (related to listening with two ears), provide additional sound information in relation to stereophony, including much more spatial perception information. Where the morphological peculiarities of individuals are of little importance in stereophony (if we send the same sound signals to several individuals, they will perceive only very slight changes because the stereophonic sound sends only certain information spatial, those which are frontal), the spatial rendering obtained thanks to the measurements of the HRTF filters is much more important, and this in an audible way, during a binaural listening).

To enjoy a better reproduction of a spatial sound field, it is necessary either to place the individual in the center of the sound field (so that he can identify where each different sound comes from) using a large number of speakers to recreate a 360 ° environment; or, through binaural listening, use HRTF filters that allow the speakers placed at the ears (usually a headset) to send modified sound waves that will give the individual that feeling of spatialization. Prior art:

For many years, home theater systems have been known to place loudspeakers in different parts of a room to create a certain spatial reproduction of the sound. These systems are obviously not nomadic (minimum two speakers, plus an amplifier). The generally adopted home theater systems are equipped with 6 loudspeakers that reproduce the sensation of a 360 ° sound field since in this configuration 2 HP are placed at the back. In more modern versions of home theater systems with 8, 10 or 12 speakers, the rendering is improved; and of course, the more loudspeakers are placed, the closer the rendering approaches to a real 360 ° rendering. The problem is obviously the cost, a 6 or 10 speaker home theater system is relatively expensive, and furthermore requires to be arranged in a room and therefore occupies a lot of room. These home-cinema devices are not nomadic any more. The general operation of a home theater system is to record different sound tracks which each will be sent back to the corresponding speaker taking into account the central listening position of the individual (commonly called "sweet spot").

Until now, headphone reproduction techniques have only been used on 2 stereo channels (sound reproduction aimed at recreating the illusion of a sound space) This is usually done using two channels (left and right) diffused by at least two transducers (speakers or earphones)).

The current new techniques of binaural listening, allow to bring additional sound information in relation to the stereophony by allowing to reproduce the sound fields diffused in particular by home-cinema systems, as regards the information of spatial perception and it takes significantly higher proportions with HRTF filters.

The advantage of binaural spatialized listening is that it can broadcast a sound field 360 ° (previously recorded) and retranscribe to at least two speakers using the HRTF filter measurement technique.

The major disadvantage of this technology is that it is standardized: the spatial sound rendering systems operate on the basis of a set of "standard" binaural filters, derived from an acoustic measurement on an artificial bust or one or more standard morphology users. As noted above, perceptual acoustic location indices are not at all general for all listeners but very specific and therefore unique for each individual, resulting in a number of location errors, including increased confusion. in back. Thus, sound rendering systems based on standard binaural filters are unreliable for a majority of listeners. As noted, another possibility for recreating spatialization is to measure an individual's unique HRTF filters and use these filters to process sound waves so that spatialization data can be reproduced from only two high speakers placed at the level of the ears. Thus, we take into account the unique sound deformation of each individual rather than a standard deformation.

The problem is that the method of measuring individual HRTF filters (for each ear) is extremely tedious and lasts several hours. The individual must remain stationary for this duration and must support a helmet equipped with electroacoustic transducers for each ear.

France Telecom Patent No. FR 03 02467 is known which makes it possible to simulate the unique HRTF filters of an individual by greatly limiting the immobilization time of the individual during the measurement. This patent comes out of the acoustic-acoustic approach by proposing a process that uses photos of the individual's head. After taking pictures, a software program will calculate the HRTF filter based on parameters embedded in the morphology analysis software. HRTF filters are not directly measured but estimated algorithmically from these photos. Subsequently, the information is transmitted to a server that will modify the multichannel data broadcast taking into account the HRTF filters to send them to at least two speakers. This solution has very important disadvantages:

 - not being faithful to acoustic reality (mathematical estimation from photos), and

 omitting certain characteristics that disturb the acoustic field (non-visible elements, shadows, nature of the hair, texture of the skin in particular).

The quality of the rendering absolutely can not equal the rendering of the acoustic - acoustic measurement. The measure is therefore at the expense of its quality. Home theater-type devices are also known which are capable of sending multichannel sound to a headset. The individual then has the impression of having a spatialized rendering in a helmet. These devices have the following drawbacks:

 - absolutely not nomadic: the headphones can only work properly near the home cinema installation that was used to measure the filters

HRTF.

 - no customization depending on the individual HRTF filter. Whoever uses the headset, the sound coming out of the headphones will be the same. In general, many systems process the sound before it is fixed on the media (CD, DVD, Blu-Ray, servers, etc.) on different 5.1, 7.1 or stereo channels and the listener can not act to adapt this its to its own auditory parameters. Technical problem posed:

 There is therefore a real need for a method of rapid realization of the HRTF filters unique for an individual that is performed only acoustically to be totally faithful to the reality of acoustic diffusion, as well as for a method for using these filters for nomadic devices (headsets), all to restore a 360 ° spatialization effect equivalent to that rendered by a speaker multicast system.

As indicated above, for a spatial reproduction, we currently use several channels (and therefore several speakers that are naturally unsuitable for a reproduction in headphones, so non-nomadic). For headphone reproduction it is therefore necessary to define and characterize the behavior of our ears subjected to auditory stimuli according to different directions called "360 °" since it is a configuration used with several loudspeakers (6.8 , 12 ...) to reproduce soundtracks of audiovisual content in these same formats (5.1.7.1, ...).

Summary of the invention The invention resides in obtaining customized HRTF filters for binaural synthesis of binaural-sounding headset sound, referred to herein as PHRTF (Personalized Head Response Response Function). .

This restitution is optimized and individualized taking into account the morphological characteristics of each individual.

The present invention also relates to a method of storing the filters in a persistent memory, online or local (in the terminal or directly in the headset)

The present invention also relates to a method of restitution in the helmet of the soundtrack adapted to the individual by calculating, in the helmet itself, the resulting soundtrack.

The invention relates to a method for measuring personalized PHRTF filters of a listener ("Personalized Head Response Transfer Function"), characterized in that it comprises the following steps:

 a step of diffusion of an acoustic signal by at least 5 loudspeakers all directed to the focal point of a closed volume treated acoustically and acoustically isolated from the sound environment outside said volume, said focal point being located at the center of said volume; closed volume;

 a step of simultaneous measurement for each ear of a head of a listener placed at said focal point of said closed volume of the frequency response resulting from the broadcast, using a microphone per ear; and

 a step of generating a set of personalized PHRTF filters for said listener by a digital system from said measurements; and or :

- said method is performed without taking a photograph of the head of the listener. According to a particular embodiment, each loudspeaker broadcasts a constant or frequently-weighted acoustic signal according to a continuous frequency sweep from 20000 Hz to at least 20 Hz and according to at least 5 angles defined by the position of the loudspeakers.

According to a particular embodiment, at each diffusion of an acoustic signal, the frequency response resulting from the diffusion perceived at the level of the microphones is measured simultaneously for each ear, and characterized by comparing the difference between the acoustic signal emitted by the loudspeakers and that received by the two microphones.

According to a particular embodiment, from the measurements, two PHRTF filters are generated per ear and by diffusion speaker, ie at least 10 PHRTF filters for at least 5 loudspeakers.

The invention also relates to a cabin for implementing the method according to the invention, characterized in that it encloses said closed volume in an acoustically and acoustically isolated manner with respect to the external environment and in that said cabin is substantially a rectangular parallelepiped whose height is greater than the width, and has walls allowing an attenuation level of the external sound environment between 40dB and 50dB.

According to a particular embodiment, a minimum of 5 loudspeakers are placed for acoustic measurements.

According to a particular embodiment, the cabin can be removable or fixed.

According to a particular embodiment, the cabin measures 2100x1800x2400 (hx 1 x L) (in mm).

The invention also relates to a method of transforming at least 5 sound signals from 5 loudspeakers to 2 listening loudspeakers using the PHRTF filters measured according to the method of the invention, characterized in that it uses a convolution algorithm.

According to a particular embodiment, the method comprises:

 an application step for each signal outside LFE and for each ear of the corresponding measured PHRTF filter;

 an injection step in each left and right final signal of the attenuated LFE signal of 13 dB, for each signal of each channel:

 - left binaural signal = (sum (convolution (channel i signal, left hrtf)) + (LFe-13dB signal));

 - right binaural signal = (sum (convolution (signal_channel_i, right hrtf)) + (Signal LFE-13dB)).

According to a particular embodiment, the PHRTF filters are combined with specific acoustic transformation filters that can be in particular acoustic characteristics of a concert hall, or predefined effects: opera, rock, classical, music, etc.

The invention also relates to a method of storing in a persistent memory, online or local (server, PC or other) PHRTF filters obtained according to the measurement method according to the invention, characterized in that the storage is carried out in a server, or alternatively in a generic memory in a terminal or in the mobile device, or in a dongle connected to the terminal, or in an SD card or micro-SD.

The invention also relates to a method of restitution in a nomadic device of the personalized soundtrack, modified by the transformation method according to the invention characterized in that the individualization of the original soundtrack is performed directly in the headset of the auditor.

The invention also relates to a method of restitution in a mobile device of the personalized soundtrack, modified by the transformation method according to the invention, characterized in that the individualisation of the original soundtrack is performed in a computer server before distribution of the multimedia content in a mobile terminal of the listener.

The invention also relates to a method of restitution in a nomadic device of the personalized soundtrack, modified by the transformation method according to the invention, characterized in that the individualisation of the band is original is performed in a mobile terminal of the auditor.

The invention also relates to a method of restitution in a nomadic device of the personalized soundtrack, modified by the transformation method according to the invention characterized in that the individualisation of the band is original is performed in a dongle connected to a device of the listener.

The invention also relates to a mobile device characterized in that it comprises at least two listening loudspeakers of a soundtrack and an electronic device allowing:

 storage of the PHRTF filters obtained according to the invention;

 - Transformation and other filters according to the invention via PHRTF filters of the sound signals from at least 5 speakers to 2 listening speakers; and

 - the return of the individualized soundtrack.

Mobile device according to claim 17, characterized in that it is a headset, in particular of the two-speaker type, one applied to each ear.

According to a particular embodiment, it is a virtual reality headset.

According to a particular embodiment, it is a device for the hearing impaired.

According to a particular embodiment, it is a telephone, a tablet computer, a laptop or other storage device for music, movies, video, which can be connected to a headset. Other features and advantages of the invention will become apparent in the description below and in the accompanying drawings, given as non-limiting examples:

 Figure 1 illustrates the arrangement of the speakers in an exemplary embodiment of the invention;

 Figure 2 illustrates the arrangement of the loudspeakers in another embodiment of the invention;

 Figure 3 illustrates the arrangement of the speakers in another embodiment of the invention;

 FIG. 4 illustrates the cabin in an exemplary embodiment of the invention; FIG. 5 illustrates the frequency representation of the PHRTF filters in an exemplary embodiment of the invention;

 FIG. 6 illustrates an example of temporal and frequency representation of the PHRTF filters;

 FIG. 7 illustrates an example of transformation of a multichannel soundtrack by PHRTF filters;

 FIG. 8 illustrates a rendering method according to an exemplary embodiment of the invention;

 Figure 9 illustrates a method of restitution according to another embodiment of the invention;

 Figure 10 illustrates a method of restitution according to another embodiment of the invention;

 Figure 11 illustrates a method of restitution according to another embodiment of the invention;

 Figure 12 illustrates a method of restitution according to another embodiment of the invention;

 Figure 13 illustrates a method of restitution according to another embodiment of the invention.

Technical solution The invention therefore lies in the development of a method for measuring PHRTF filters of a listener, characterized in that said method is implemented in a closed volume, acoustically processed and sound isolated from the external sound environment to said volume, and said closed volume comprises at least 5 loudspeakers (without subwoofer), diffusing an acoustic signal, all directed to the focal point or convergence point located at its center of gravity, at the exact location where the the head of the listener who is provided with an electro-acoustic transducer allowing the reception of acoustic signals (microphone type, or other recording apparatus) per ear, and in that one records and / or transfers from from these microphones, to a remote recorder such as a PC, or other digital system, the parameters for calculating the PHRTF filters, and characterized in that it is performed without taking a photograph of the head of the listener

The PHRTF individual filter measurement process is done in a specially designed cabin to be as acoustically coherent as possible. Only the sound deformation related to the individual must exist.

The enclosed volume is preferably a cabin which is substantially a rectangular parallelepiped whose height must be greater than the width so as to correspond to the characteristics defined according to the ITU R-BS775 1 and 2 standard (recommendations concerning the multichannel stereo sound system with or without associated image), and should also have an acoustic insulation to attenuate the sounds coming from the outside so as not to distort the measurement. The appropriate and commonly accepted minimum attenuation level should be between 40 dB and 50 dB.

By "cabin" is meant here a closed enclosure on all sides and whose function is to contain said closed volume and ensure sound insulation and acoustic treatment, which implies the choice of obvious materials for the skilled person. Of course other forms of cabins may be considered. This can be removable or fixed. In a completely preferred way, in the case of a demountable cabin it measures 2400x1800x2100 (in mm) in order to get closer to the standards defined in the document ITU R-BS775 1. To carry out measurements in the cabin, we place at least 5 speakers

(necessary for a 5.0 audio broadcast). Naturally, it is possible to provide more speakers if desired: 6 for broadcast in 6.0, 7 for broadcast in 7.0.

We do not place a subwoofer (dedicated to the reproduction of "serious effects"), because the wavelength of the low frequencies is too great to be relevant in the measurement of a PHRTF filter, and therefore unusable in a measuring cabin. The arrangement of the loudspeakers is according to the ITU R-BS775 1 standard as illustrated in Figures 1 to 3. In these schematic figures in top view, the listener (1) is placed in the center of the cabin and placed at least 5 loudspeakers (HP) at the periphery of a circle of about 2m radius. Three loudspeakers are positioned in front of the listener (substantially facing him): one strictly opposite him and one on each side positioned at an angle of about 30 °. The two rear speakers (relative to the listener) are positioned at an angle of about 120 ° to the speaker opposite the listener. In the versions shown in Figures 2 and 3, the positions of the 3 front speakers remain exactly the same. In version 6.0, a loudspeaker is added at 180 ° to the one opposite the listener (Figure 2). In version 7.0, the position of the loudspeakers is changed: two loudspeakers located at the back left respectively having an angle of about 100 ° and 140 ° with respect to the loudspeaker in front (1) of the listener; two loudspeakers located at the back right respectively having an angle of about 100 ° and 140 ° relative to the speaker in front (1) of the listener. The listener carries two microphones (one per ear) that are calibrated to perform accurate measurements.

According to a preferred embodiment of the cabin (6) (Figure 4), the cabin comprises an acoustic window (2) in front of the listener so that the operator (3) can be visible to the listener (1). An acoustic door (5) is located behind the listener (1), opposite the acoustic glass (2).

The measuring system (7) is located outside the cabin (6) and is placed close to the operator (3). The listener (1) carries microphones (8).

The walls inside the cabin are designed in such a way as to sufficiently mitigate reflections that interfere with the localization of the walls of the sounds coming from the loudspeakers. This also makes it possible to attenuate the "room effect" (or cocktail effect) and thus to avoid an excessive modification of the diffusion of the measurement signals.

The cabin is equipped with acoustics composed of acoustical materials placed in a manner that respects the rules of audio cabin design acoustics in accordance with the provisions indicated above. For example the first reflections will be attenuated by the placement of lateral and upper diffusers (suppress the fusion effect), as for the serious stationary frequencies in the angles which cause an increase the undesirable acoustic energy in these frequencies, they will be attenuated by absorbers positioned in the front, rear and upper lateral angles.

This allows a measurement of the individual "unmodified" PHRTF filter by the cabin itself. The cabin specified above can be replaced by a smaller cabin, encompassing only the head and shoulders of the listener. Its internal dimensions may be, for example, the following dimensions: 900 mm in length, 810 mm in width and 675 mm in height or multiple of these dimensions. It includes loudspeakers positioned similarly to the positions described for the large cabin and having similar settings. The actual volume is smaller than that of the cabin specified above. To compensate for this real volume loss, Wave Field Synthesis (WFS) technology is used to modify cabin acoustics to reproduce sound waves identical to those produced in the larger cabin model.

Once the listener is installed and the measuring microphones are positioned in his ear canals, the measurement can begin. Each loudspeaker broadcasts an acoustic signal of constant or frequently weighted level according to a continuous frequency sweep from 20,000 Hz to at least 20 Hz and following at least 5 different angles, of which at least 2 at the back of the individual (which correspond to the 5 positions of Figure 1).

At each diffusion, the frequency response resulting from the diffusion that is perceived at the level of the microphones is measured simultaneously for each ear. At least ten measurements (two per ear and per diffusion chamber) of acoustic disturbances are obtained directly on the individual.

From these measurements, the number of filters corresponding to the individual (two per ear and per diffusion chamber) is generated. In the case of 5 loudspeakers, 10 individual PHRTF filters will be obtained.

For each of the scattered signals, therefore, the difference between the transmitted signal (known) and the measured signal (perturbation) is obtained by a single and individual filter PHRTF which is the exact translation of the acoustic deformation produced by the individual in the space of diffusion.

FIG. 5 is an example of a frequency representation of the individual PHRTF filters for the left ear and for the right ear.

Figure 6 is an example of time and frequency representation of different individual PHRTF filters. The overall result of the entire measurement is a set of left and right filters depending on each speaker position, ie for a 5.0 signal, 10 individual PHRTF filters: lg, ld, 2g, 2d, 3g, 3d, 4g, 4d , 5g, 5g.

With convention:

 the left hp,

 2 = right hp,

 3 = central hp,

 4 = left rear hp,

 5 = right rear hp.

 Then g = fi lter for the left ear and fi lter for the right ear.

The reproduction of a 5.1 sound signal (6 discrete audio channels) therefore has 6 signals. It is therefore necessary to apply for each signal out of LFE ("low-frequency effects") and for each ear the corresponding measured PHRTF filter and reinject in each left and right final signal the signal of the LFE (attenuated by 10 dB in accordance with the recommendations of adjustment of home- to preserve a comfortable bass level in the final signal (attenuated by an additional 3 dB to maintain the overall equivalent level):

 For each signal of each channel:

 left binaural signal = (sum (convolution (channel i signal, left hrtf)) + (LFe-13db signal))

 right binaural signal = (sum (convolution (signal_channel_i, right hrtf)) + (Signal LFE-13db))

Once the set of PHRTF measurements for an individual is obtained, a convolution algorithm, known to those skilled in the art, is used to transform the at least 5 sound signals from the loudspeakers to two sound signals for both. headphones speakers. An example of the transformation is given in Figure 7, in the case of a configuration in 5.1 (6 separate audio channels and non-matrixed). The algorithm above thus allows to customize a multichannel soundtrack according to the specific morphological characteristics of each listener.

It is possible to combine the individual PHRTF filters with filters specific to a given concert hall, such as, for example, the Paris Opera (Bastille or Garnier) or the MET in New York. In case, the individual PHRTF filters of the listener are corrected by addition (positive or negative, with a degree of correction adaptable according to the influence that one wants to give to the acoustics of the desired room on the final soundtrack. It is also possible to combine the individual PHRTF filters with predefined effects such as those already present in conventional home cinema systems (for example: film, football, standard, opera, music ...). the same as that described above In both cases, the convolution algorithm remains the same, since it applies a unique set of individual PHRTF filters to the original soundtrack.

The present invention also relates to a method for storing PHRTF filters in a persistent memory, online or local (in the terminal or directly in the headset)

The PHRTF filters can be stored in a server containing a PHRTF filter database for, for example, the clients of an audiovisual content distribution service.

Alternatively, the storage of PHRTF filters can also be done in a generic memory in the terminal or in the headphones or in a dongle connected to the terminal, able to store these filters persistently but erasable and rewritable or any other semi-permanent storage memory (for example, a flash memory or a micro-SD card). This makes it possible to defer the generation of the personalized soundtrack at the listener level and thus to send to the listeners only the original soundtrack, which greatly simplifies the implementation on the server side.

The present invention also relates to a method of restitution in the helmet of the soundtrack adapted to the individual by calculating, in the helmet itself, the resulting soundtrack.

The processing, by application of the algorithm described above, three-dimensional sound data is done according to the different scenarios described below.

Disturbance measurement is used to adapt for each individual any single original soundtrack (in 1.0, 2.0, 4.0, 5.0, 5.1, 6.1, 7.1 and beyond). This adaptation is done in real time by keeping the electronic data as input, the same soundtrack for all users.

The present invention also relates to a method of restitution in the helmet of the soundtrack adapted to the individual by calculating, in the helmet itself, the resulting soundtrack.

There are several options for using individual PHRTF filters for application to headphones.

The preferred implementation mode developed according to the present invention is the individualization of the original soundtrack is performed directly in the headphone of the listener. See diagram shown in Figure 8. The computer server containing the original multimedia content distributes the same original content to all listeners. The terminal (nomadic or not) of the listener receives the original soundtrack from the server, possibly stores it locally and sends it to the listener's headset when he wants to access the content. The terminal does not change the original soundtrack.

The individual PHRTF filters are stored in the listener's headphones and it is this equipment that calculates, in real time, the personalized soundtrack, before broadcast in the speakers of the headphones. The individual PHRTF filters can be stored as in a terminal, in a fixed or removable permanent memory of the SD or micro-SD card type (re-writable or not) with a specific slot accessible from the outside by the listener. This slot allows you to customize the headset for each listener, by selecting the right PHRTF filters stored in the headset or by inserting the removable memory card containing the right filters.

The convolution is calculated in the helmet, which implies that the helmet has the ability to integrate the electronic device for this purpose. This imposes design constraints. For in-ear earpieces, the electronic device must integrate directly on the cable (like the currently existing remotes). This has the consequence that this method and system works with all headphones capable of directly receiving a digital signal (in this case a dematriate 5.1 digital audio signal).

Other possible modes of implementation are described below:

Variation 1: The individualization of the original soundtrack is performed in a computer server before distribution of the multimedia content in the terminal. See diagram shown in Figure 9.

In this mode, the individual PHRTF filters are stored in the computer server containing the original media content. The personalized soundtrack is produced in this server at the moment when the listener wishes to access the content for immediate listening ("streaming") or for storage in his terminal (PC or mobile device). The terminal (nomadic or not) receives the individualized soundtrack, stores it locally if necessary and sends it as it is, without further manipulation to the listener's headphones.

The convolution takes place in the server, the terminal receives a digital signal which is converted into analog in the reader and sent as is to the headphones. The headset therefore receives this analog signal (which represents the original soundtrack individualized for the listener), and there is no new constraint on the headphones. This has the consequence that this method and system work with all existing helmets.

Variant 2: The individualisation of the tape are original is performed in the mobile terminal of the listener. See diagram shown in Figure 10. In this version, the individual PHRTF filters are stored in the listener's terminal after a prior download procedure. Note that the same terminal can store several individual PHRTF filters corresponding to different listeners. The choice of the right PHRTF filters will then be done by a software offering this selection through an appropriate human-machine interface.

The computer server containing the original media content distributes the same original content to all listeners.

The terminal (nomadic or not) calculates the personalized soundtrack directly into the player when the listener wants to access the content, then sends the personalized soundtrack to the listener's headphones.

The convolution takes place in the terminal. As in version 1 above, the headset receives an analog signal (which represents the original soundtrack individualized for the listener), and there is no new constraint on the headset. This has the consequence that this method and system work with all existing helmets. Variation 3: The individualisation of the band are original is performed in a dongle connected to a nomadic equipment or not the listener. See diagram shown in Figure 11.

This variant is an alternative to variant 2. The computer server containing the original multimedia content distributes the same original content to all the listeners. The listener's terminal receives the original soundtrack from the server, and optionally stores it locally.

The individual PHRTF filters are stored in a "wireless" dongle that includes a connector (USB for example) that allows it to connect to an external port of the terminal, and paired or not with the listener's headphones. In the headset either via a wired connection (type an analog audio output) or via a wireless connection (type Bluetooth, or wi-fî).

The terminal (nomadic or not) sends to its external port, the original soundtrack, which is personalized in real time by the dongle "wireless", which sends the personalized soundtrack to the headphone of the listener. The "wireless" dongle contains both the individual PHRTF filters, the electronics needed to execute the convolution algorithm.

Note that the "wireless" dongle can also connect to any digital 5.1 audio broadcast source (unregistered).

The server and the terminal have no information about the customization of the original soundtrack and therefore make no difference between a listener (and his headphones) that uses the individual PHRTF filters and a listener who uses the original soundtrack. The system for broadcasting the original soundtracks does not require any modification or adaptation and can therefore be used in a completely transparent manner for "standard" users and users using the method described here. The convolution takes place in the "wireless" dongle and sends to the headphones an analog signal either by wire connection or by "wireless" connection, which contains the original individual soundtrack for the listener. This version therefore works for "wireless" headphones able to connect according to "wireless" standards, but also those that have dual wireless and "wireless" connectivity. This has the consequence that this method and system work with all existing "wireless" headsets.

Variant 4: This variant is an application to video games and virtual reality, which use specific headphones (covering the eyes to show the space of the game or the environment of the VR application). In this case, the soundtrack can come from a local source to the terminal that receives information from online servers in the event that the virtual world is shared with other players or users. The sound is or can be a real-time "reconstructed" sound based on the actions taken by users (for example, gunshot sounds when a player is shooting). The convolution algorithm applies to the reconstituted sound, by applying the HRTF filter of the user wearing the helmet. The customization can be done in the terminal (PC, game console), as described in variant 2 and in Figure 9, or in the headset itself, as described in Figure 8.

Variant 5:

 The individualization of the original soundtrack is performed in hearing aids connected to a terminal that reads multimedia content (smartphone, tablet, TV, decoder, etc.), replacing the audio headset. The connection is often, but not necessarily, wireless. The sound reproduction method related to this variant is illustrated in Figure 12.

In this variant, the individual PHRTF filters are stored in the listener's prostheses after a prior loading procedure.

They are applied to the incoming sound by the same convolution algorithm as in the other terminals listed in this document. Convolution is applied before the usual auditory correction for the prosthesis user. Variant 6: This variant is similar to variants 2 and 5 above: the filters are stored in the terminal, and the customization is also done in the terminal. The personalized sound is sent to the hearing aids that broadcast it as is, without additional operation. The sound reproduction method related to this variant is illustrated in Figure 13.

Variant 7: This variant aims to eliminate the need for prior measurement and therefore the need for the measuring cabin. Instead of the PHRTF filter of the listener, the terminal embeds a certain number of filters measured on other people whose morphologies differ and cover, a priori, a broad spectrum of human morphologies. In this variant, the software application present in the terminal allows the user to choose the filter that best corresponds to his listening. This choice can be definitive and permanent, or not, that is to say that the user can choose other filters later. Of course, it is also possible to include the listener's personal filter later, once the measurement has been completed.

Naturally, the present invention is not limited to the embodiment described above by way of example; but it extends to other variants, depending on the number of speakers for the reproduction of the number of audio streams generated, without limitation (5.0, 5.1, 5.2, 7.1, 10.2, 11.1, Atmos ...). The present invention is compatible with all mono, stereo, quadraphonic broadcast formats.

The present invention also relates to the adaptation of one sound diffusion format to another - such as mp3 "surround" or HEAAC ("High-Effiency Advanced Audio Coding"), which can not be broadcast in a headset. The method according to the present invention is capable of transforming the soundtracks from each of these formats (to the extent that they are decoded beforehand) to make them broadcastable to the headphones and this in a completely personalized manner.

The present invention is not limited to the distribution system of the multimedia content including the soundtrack. The invention is completely compatible with CD, Blu-Ray, streaming or internet distribution formats. satellite or cable or "Video on Demand" (VOD), "Near Video on Demand" (NVOD) or Television on Demand.

The present invention is also completely compatible with compression algorithms used for storage or broadcasting of multimedia content.

The present invention is also compatible with all content protection technologies, DRM system or conditional access (such as Viacces, Nagra, Irdeto, Conax or NDS / Cisco)

The process works with all existing helmets in versions 1, 2 and 3.

The nomadic device comprising the electronic device is chosen from the non-exhaustive list of: telephones, tablet computers, laptops, or other device for storing music, films, video, games, audiovisual or multimedia contents.

It also adapts to the 3 types of existing helmets: closed, semi-open, in-ear and headband.

The invention also covers all the embodiments and all the applications which will be directly accessible to the person skilled in the art upon reading the present application, and of his own knowledge.

Claims

A method for measuring personalized PHRTF filters of a listener ("Personalized Head Response Transfer Function"), characterized in that it comprises the following steps:  a step of diffusion of an acoustic signal by at least 5 loudspeakers all directed to the focal point of a closed volume treated acoustically and acoustically isolated from the sound environment outside said volume, said focal point being located at the center of said volume; closed volume;  a step of simultaneous measurement for each ear of a head of a listener placed at said focal point of said closed volume of the frequency response resulting from the broadcast, using a microphone per ear; and  a step of generating a set of personalized PHRTF filters for said listener by a digital system from said measurements; and or :  - said method is performed without taking a photograph of the head of the listener. Method according to Claim 1, characterized in that each loudspeaker transmits a constant or frequently-weighted acoustic signal according to a continuous frequency sweep from 20000 Hz to at least 20 Hz and according to at least 5 angles defined by the position of the loudspeakers. . Method according to any one of claims 1 and 2, characterized in that, at each diffusion of an acoustic signal, the frequency response resulting from the diffusion perceived at the level of the microphones is measured simultaneously for each ear, and characterized in what we compare the difference between the acoustic signal emitted by the loudspeakers and that received by the two microphones. Process according to any one of Claims 1 to 3, characterized in that, from the measurements, two PHRTF filters per ear and diffusion loudspeaker are generated, ie at least 10 PHRTF filters for at least 5 loudspeakers. Cabin for implementing the method according to any one of claims 1 to 4, characterized in that it encloses said closed volume acoustically and acoustically isolated manner with respect to the external environment and in that said cabin is substantially a rectangular parallelepiped whose height is greater than the width, and has walls for an attenuation level of the external sound environment between 40dB and 50dB. Cabin according to claim 5, characterized in that a minimum of 5 loudspeakers are placed for acoustic measurements. Cabin according to claim 5 or 6, characterized in that it can be dismountable or fixed. Cabin according to any one of claims 5 to 7, characterized in that it measures 2100x1800x2400 (hx 1 x L) (in mm). A method of transforming at least 5 sound signals from 5 loudspeakers to 2 listening loudspeakers using the PHRTF filters measured according to the method according to any one of claims 1 to 4, characterized in that uses a convolution algorithm. 10. The method of transformation according to claim 9 characterized in that it comprises: an application step for each signal outside LFE and for each ear of the corresponding measured PHRTF filter; an injection step in each left and right final signal of the attenuated LFE signal of 13 dB, for each signal of each channel:  - left binaural signal = (sum (convolution (channel signal i, hrtf_left)) + (LFe-13dB signal));  - right binaural signal = (sum (convolution (signal_canal_i, hrtf right)) + (LFE-13dB signal)). 11. A method of transformation according to claim 9 or 10, characterized in that PHRTF filters are combined with specific acoustic transformation filters that can be including acoustic characteristics of a concert hall, or predefined effects: opera, rock , classic, music, etc 12. A method of storing in a persistent memory, online or local (server, PC or other) PHRTF filters obtained according to the measuring method according to claims 1 to 4, characterized in that the storage is performed in a server, or alternatively in a generic memory in a terminal or in the mobile device, or in a dongle connected to the terminal, or in an SD or micro-SD card. 13. Method for restitution in a nomadic device of the personalized soundtrack, modified by the transformation method according to one of claims 9 to 11 characterized in that the individualization of the original soundtrack is performed directly in the headset of the 'auditor. 14. Method of restitution in a nomadic device of the personalized soundtrack, modified by the method of transformation of claims 9 to 11 characterized in that the individualization of the original soundtrack is performed in a computer server before distribution of the multimedia content in a mobile terminal of the listener. 15. Method of restitution in a nomadic device of the personalized soundtrack, modified by the process of transformation of the claims 9 at 11 characterized in that the individualization of the tape are original is performed in a mobile terminal of the listener. 16. Method of restitution in a nomadic device of the personalized soundtrack, modified by the method of transformation of claims 9 to 11 characterized in that the individualization of the tape is original is performed in a dongle connected to a device of the auditor. 17. Nomadic device characterized in that it comprises at least two listening loudspeakers of a soundtrack and an electronic device allowing: storage of the PHRTF filters obtained according to any one of claims 1 to 4;  the transformation and other filters according to claims 9 to 11 via the PHRTF filters of the sound signals coming from at least 5 loudspeakers to 2 listening loudspeakers; and  - the return of the individualized soundtrack. 18. Mobile device according to claim 17, characterized in that it is a headset, including two speakers, one applied to each ear. 19. Mobile device according to claim 18, characterized in that it is a virtual reality helmet. 20. Mobile device according to claim 18, characterized in that it is a device for the hearing impaired. 21. mobile device according to claim 17 characterized in that it is a telephone, a tablet computer, a laptop or other device for storing music, movies, video, which can be connected to a helmet.