Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04S—STEREOPHONIC SYSTEMS 
  • H04S1/00—Two-channel systems
  • H04S1/007—Two-channel systems in which the audio signals are in digital form
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04S—STEREOPHONIC SYSTEMS 
  • H04S7/00—Indicating arrangements; Control arrangements, e.g. balance control
  • H04S7/30—Control circuits for electronic adaptation of the sound field
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04S—STEREOPHONIC SYSTEMS 
  • H04S7/00—Indicating arrangements; Control arrangements, e.g. balance control
  • H04S7/30—Control circuits for electronic adaptation of the sound field
  • H04S7/302—Electronic adaptation of stereophonic sound system to listener position or orientation
  • H04S7/303—Tracking of listener position or orientation
  • H04S7/304—For headphones
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04S—STEREOPHONIC SYSTEMS 
  • H04S2400/00—Details of stereophonic systems covered by H04S but not provided for in its groups
  • H04S2400/11—Positioning of individual sound objects, e.g. moving airplane, within a sound field
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04S—STEREOPHONIC SYSTEMS 
  • H04S2420/00—Techniques used stereophonic systems covered by H04S but not provided for in its groups
  • H04S2420/01—Enhancing the perception of the sound image or of the spatial distribution using head related transfer functions [HRTF's] or equivalents thereof, e.g. interaural time difference [ITD] or interaural level difference [ILD]

Definitions

• the present invention relates to a spatialization system of sound sources with improved performance allowing in particular the production of a spatialization system compatible with modular avionic data processing equipment of IMA type (abbreviation of the English expression “Integrated Modular Avionics ”) also called EMTI (for Modular Information Processing Equipment).
• IMA modular avionic data processing equipment
• EMTI Modular Information Processing Equipment
• 3D sound is in the same approach as the helmet visual by allowing pilots to acquire information of spatial situation (position of team members, threats, ...) in its own reference point, by a different communication channel than visual following a natural modality.
• 3D sound enriches the transmitted signal with situation information, static or dynamic, in space. Its use, in addition to locating teammates or threats, can cover other applications such as multi-speaker intelligibility.
• the system described in the above-mentioned request includes in particular for each source to be spatialized, a binaural processor with two convolutional channels whose role is on the one hand to calculate by interpolation the head transfer functions (left / right) at the point in which the sound source will be placed, on the other hand to create the spatialized signal on two channels from the original monophonic signal.
• the aim of the present invention is to define a spatialization system with improved performance such that it is able to be integrated into an avionics modular information processing equipment (EMTI) which imposes constraints in particular on the number of processors and their type.
• EMTI avionics modular information processing equipment
• the invention proposes a spatialization system in which it is no longer necessary to make an interpolation calculation of the head transfer functions. It is then possible to carry out the convolution operations in order to create the spatialized signals to have only one single computer instead of the n binaural processors necessary in the system according to the prior art for spatializing n sources.
• the invention relates to a spatialization system of at least one sound source creating for each source two spatialized monophonic channels intended to be received by a listener, comprising
• a filter database comprising a set of head transfer functions specific to the auditor
• a data presentation processor receiving the information from each source and comprising in particular a module for calculating the relative positions of the sources with respect to the listener,
• said data presentation processor comprises a module selection of head transfer functions with variable resolution adapted to the relative position of the source with the listener.
• pilot head transfer function bases adapted to the precision required for a given piece of information to be spatialized (threat, position of a drone, etc.), combined with optimal use of the spatial information contained in each of the positions of these bases makes it possible to considerably reduce the number of operations to be carried out for spatialization without degrading performance.
• FIG. 1 a general diagram of a spatialization system according to the invention
• FIG. 2 a block diagram of an exemplary embodiment of the system according to the invention
• FIG. 4 a layout diagram of the system according to the invention in a modular avionics type equipment
• IMA IMA.
• the invention is described below with reference to an aircraft audio system, in particular a combat aircraft, but it is understood that it is not limited to such an application and that it can be implemented. used in other types of vehicles (land or sea) as well as in fixed installations.
• the user of this system is, in this case, the pilot of an airplane but there can be several users simultaneously, in particular if it is a civil transport airplane, devices specific to each user. then being provided in sufficient number.
• FIG. 1 represents a general diagram of a spatialization system of sound sources according to the invention, the role of which is to make a listener hear sound signals (tones, words, alarms, etc.) using a stereophonic headphones so that they are perceived by the listener as if they came from a particular point in space, this point being able to be the effective position of the sound source or an arbitrary position.
• sound signals tones, words, alarms, etc.
• FIG. 1 represents a general diagram of a spatialization system of sound sources according to the invention, the role of which is to make a listener hear sound signals (tones, words, alarms, etc.) using a stereophonic headphones so that they are perceived by the listener as if they came from a particular point in space, this point being able to be the effective position of the sound source or an arbitrary position.
• the detection of a missile by a countermeasure device may generate a sound the origin of which seems to come from the origin of the attack, allowing the pilot to react more quickly.
• the system according to the invention mainly comprises a processor CPU1 for presenting data and a calculation unit CPU2 generating the monophonic spatialized channels.
• the data presentation processor CPU1 notably comprises a module 101 for calculating the relative positions of the sources with respect to the listener, that is to say in the listener's head reference. These positions are for example calculated from information received by an attitude detector 11 from the listener's head and by a module 12 for determining the position of the source to be restored (this module can include an inertial unit, a tracking device such as a goniometer, a radar, etc.).
• the processor CPU1 is connected to a “filter” database 13 comprising a set of head transfer functions (HRTF) specific to the listener.
• HRTF head transfer functions
• the head transfer functions are for example acquired during an earlier learning phase. They are specific to the inter-aural delay of the listener (delay in the arrival of sound between the two ears), of the physiognomic characteristics of each listener. It is these transfer functions that give the listener the feeling of spatialization.
• the computing unit CPU2 generates the monophonic channels G and D spatialized by convolution of each monophonic sound signal characteristic of the source to be spatialized and contained in the “sounds” database 14 with head transfer functions from said database 13 estimated at the position of the source in the head reference.
• the calculation unit comprises as many processors as there are sound sources to be spatialized. Indeed, it is necessary in these systems to carry out a spatial interpolation of the head transfer functions in order to know the transfer functions at the point at which the source will be placed.
• This architecture requires multiplying the number of processors in the computing unit, which is incompatible with a modular spatialization system for integration into modular avionics information processing equipment.
• the spatialization system according to the invention has a specific algorithmic architecture which makes it possible in particular to reduce the number of processors of the computing unit.
• the applicant has shown that the computing unit CPU2 can then be produced by means of a programmable component of the EPLD type (abbreviation of “Programmable electronics by logic gates”).
• the data presentation processor of the system according to the invention comprises a module 102 for selecting head transfer functions with a variable resolution adapted to the relative position of the source with the listener (or position of the source in the head reference). Thanks to this selection module, it is no longer necessary to carry out interpolation calculations to estimate the transfer functions at the location where the sound source must be located. It is therefore possible to considerably simplify the architecture of the calculation unit, an exemplary embodiment of which will be described later.
• the selection module operating a selection of the resolution of the transfer functions as a function of the relative position of the sound source with respect to the listener, it is possible to work with a database 13 of the head transfer functions comprising a large number of functions distributed regularly throughout the space, knowing that only a part of these will be selected to perform the convolution calculations.
• the applicant worked with a database in which the transfer functions are collected with a step of 7 ° in azimuth, from 0 to 360 °, and with a step of 10 ° in elevation, from -70 ° to + 90 °.
• the applicant has shown that, thanks to the resolution selection module 102 of the system according to the invention, it is possible to limit the number of coefficients of each head transfer function used to 40 (compared to 128 or 256 in most systems of the prior art) without degrading the sound spatialization results, which further reduces the computing power necessary for the spatialization function.
• the calculation unit CPU2 can thus be reduced to a component of the EPLD type for example, even when several sources have to be spatialized, which makes it possible to dispense with the protocols of dialogue between the different binaural processors necessary for processing the spatialization of several sound sources in prior art systems.
• FIG. 2 represents a functional diagram of an exemplary embodiment of the system according to the invention.
• the spatialization system comprises a data presentation processor CPU1 receiving the information from each source and a calculation unit CPU2 of the spatialized right and left monophonic channels.
• the processor CPU1 notably comprises the module 101 for calculating the relative position of a sound source in the listener's head reference frame, this module receiving in real time information on the head attitude (listener position) and on the position of the source to be restored, as described above.
• the module 102 for selecting in resolution the HRTF transfer functions contained in the database 13 makes it possible to select, for each source to be spatialized, as a function of the relative position of the source, the transfer functions which will be used for the generation of spatialized sounds.
• a sound selection module 103 connected to the sound database 14 makes it possible to select the monophonic signal from the database which will be sent to the computing unit CPU2 to be convoluted to the functions adapted left and right head transfer.
• the sound selection module 103 operates a hierarchy between the sound sources to be spatialized. Depending on system events and the choice of platform management logic, a choice of concomitant sounds to be spatialized will be made. All of the information used to define this spatial presentation priority logic travels on the EMTI broadband bus.
• the sound selection module 103 is for example connected to a configuration and parameterization 104 in which personalization criteria specific to the auditor are recorded.
• the data concerning the choice of the HRTF transfer functions as well as the sounds to be spatialized are sent to the computing unit CPU2 by means of a communication link 15. They are temporarily stored in a filtering memory and digital sounds 201.
• the part of the memory containing the digital sounds called "earcons" (name assigned to the sounds used as alarms or alerts and having a strong significant value) is for example loaded at initialization. It contains the samples of audio signals previously digitized in the sound database 14.
• the spatialization of one or more of these signals will be activated or suspended. As long as the activation persists, the signal concerned is read in a loop.
• the convolution calculations are performed by a computer 202, for example a component of the EPLD type which generates the spatialized sounds as has been described previously.
• a processor interface 203 constitutes a memory used for the filtering operations. It is composed of buffer registers for sounds, HRTF filters, as well as coefficients used for other functions such as soft switching and the simulation of atmospheric absorption which will be described later.
• earcons or audible alarms
• radios directly UHF / VHF
• FIG. 3 represents the diagram of a calculation unit of a spatialization system according to the example of FIG. 2.
• the spatialization system comprises an audio input / output conditioning module 16 which recovers the monophonic left and right spatialized channels at the output in order to format them before sending them to the listener.
• audio input / output conditioning module 16 which recovers the monophonic left and right spatialized channels at the output in order to format them before sending them to the listener.
• live communications if “live” communications must be spatialized, these communications are shaped by the conditioning module with a view to their spatialization by the computer 202 of the computing unit.
• live source By default, a sound coming from a so-called live source will always have priority over the sounds to be spatialized.
• the processor interface 203 which constitutes a short term memory for all the parameters used.
• the computer 202 constitutes the heart of the calculation unit. In the example in FIG. 3, it includes a module 204 for activating and selecting sources, performing the mixing function between the live inputs and the earcons type sounds.
• the computer 202 can perform the calculation functions for the n sources to be spatialized.
• the n sources In the example in Figure 3, four sound sources can be spatialized.
• It includes a double spatialization module 205, which receives the adapted transfer functions and performs the convolution with the monophonic signal to be spatialized. This convolution is carried out in time space by using the shifting capacities of the FIR filters (finite impulse response filters) associated with the inter-aural delays.
• FIR filters finite impulse response filters
• the soft switching module includes a soft switching module 206, connected to a calculation parametering register 207 optimizing the choice of transition parameters as a function of the speed of movement of the source and of the listener's head.
• the soft switching module allows a transition, without audible switching noise, when switching from one pair of filters to the next.
• This function is performed by double linear weighting ramp. It involves a double convolution: each sample of each output channel results from the weighted sum of two samples, each being obtained by convolution of the input signal with a spatialization filter, element of the HRTF base. At a given instant, there are therefore in input memory two pairs of spatialization filters per channel to be processed.
• a module 208 for simulating atmospheric absorption includes a module 208 for simulating atmospheric absorption.
• This function is for example performed by a linear filtering with 30 coefficients and a gain, realized on each channel (left, right) of each channel, after spatialization processing. This function allows the auditor to perceive the depth effect necessary for his operational decision.
• dynamic weighting modules 209 and summation 210 are provided for performing the weighted sum of the channels of each channel to provide a single stereophonic signal compatible with the output dynamics. The only constraint associated with this stereophonic reproduction is linked to the bandwidth necessary for sound spatialization (typically 20 kHz).
• FIG. 4 diagrams the hardware architecture of an avionics modular equipment 40 for processing information of the EMTI type. It includes a broadband bus 41 to which all the equipment functions are connected, including in particular the sound spatialization system according to the invention 42 as described above, the other man machine interface functions 43 such as by example voice control, head-up symbology management, helmet display, etc., and a system management card 44 which functions as an interface with the other equipment of the aircraft.
• the sound spatialization system 42 according to the invention is connected to the high speed bus via the data presentation processor CPUL II also comprises the calculation unit CPU2, as described above and formed for example of a component EPLD, compatible with the technical requirements of EMTI (number and type of operations, memory space, coding of audio samples, digital bit rate).

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Acoustics & Sound (AREA)
• Signal Processing (AREA)
• Multimedia (AREA)
• Stereophonic System (AREA)
• Measurement Of Velocity Or Position Using Acoustic Or Ultrasonic Waves (AREA)
• Holo Graphy (AREA)
• Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)

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• 2002
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