EP0842508B1 - Acoustic wave focusing method and device - Google Patents

Acoustic wave focusing method and device Download PDF

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Publication number
EP0842508B1
EP0842508B1 EP96925774A EP96925774A EP0842508B1 EP 0842508 B1 EP0842508 B1 EP 0842508B1 EP 96925774 A EP96925774 A EP 96925774A EP 96925774 A EP96925774 A EP 96925774A EP 0842508 B1 EP0842508 B1 EP 0842508B1
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Prior art keywords
sound
signal
acoustic
loudspeakers
space
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German (de)
French (fr)
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EP0842508A1 (en
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Mathias Fink
Jacques Lewiner
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POUR LES APPLICATIONS DU RETOURNEMENT TEMPOREL Ste
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    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/18—Methods or devices for transmitting, conducting or directing sound
    • G10K11/26—Sound-focusing or directing, e.g. scanning
    • G10K11/34—Sound-focusing or directing, e.g. scanning using electrical steering of transducer arrays, e.g. beam steering
    • G10K11/341—Circuits therefor
    • G10K11/346—Circuits therefor using phase variation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R27/00—Public address systems

Definitions

  • the present invention relates to methods and acoustic wave focusing devices.
  • the invention relates more particularly to a method for sounding a space disturbing the propagation of acoustic waves in order to transmit in this space information in the form of acoustic waves by means of a number n of loudspeakers, n being a natural integer at less equal to 1, this method comprising sound stages during which at least one acoustic signal S (t) carrying information is transmitted in at least one area, called “target area", which belongs to the space to be sounded , this transmission being carried out by causing acoustic signals s i (t) to be emitted by at least one subset of so-called "active" loudspeakers, which subset comprises at least one loudspeaker chosen from among the n loudspeakers mentioned above.
  • the object of the present invention is in particular to optimize the transmission of information inside such space.
  • this device also comprises means to select the target area within the space to sound.
  • the space to be sounded is a train station 101 equipped of a large number of n of speakers 102, n being a natural integer for example greater than 10.
  • speakers 102 are signaling audible, for example an information message for the attention travelers 103
  • the resulting sound waves reach travelers 103 with significant distortions which are due to the fact that these sound waves undergo multiple paths and therefore arrive so inconsistent in travelers' ears 103.
  • the information message, or any other sound signal from the speakers is often difficult for travelers to understand 103.
  • an acoustic "calibration" operation is first carried out on the station 101, by determining the impulse response h ij (t) between each loudspeaker i and each point j being part of a set of predetermined points 107 said to be "calibration" distributed inside the station 1.
  • the calibration points 107 are preferably located approximately at breast height, for example at a height between 1.50 m and 1.75 m above the ground, and they are distributed in the various parts of the station 101 which are frequented by travelers 103.
  • the impulse response h ij (t) corresponds to the acoustic signal received at point j when the loudspeaker i emits a short acoustic pulse (ideally a Dirac pulse) or vice versa to the acoustic signal received at the loudspeaker i when emits at point j a short acoustic pulse (the impulse response is the same in both directions of propagation).
  • impulse responses can therefore be measured relatively simply, preferably at night or at least at a time when station 101 is not receiving audience, having each speaker emit successively 102 a short acoustic pulse, and by measuring the acoustic signals received following this pulse at the various calibration points 107, using 108 microphones ( Figure 3) previously arranged at the points 107.
  • each speaker 102 receives successively from a computer 109 the impulse signal to be sent, the computer 109 being connected, for example by a connection in bus, to a plurality of digital-to-analog converters 110, each of these digital-to-analog converters being connected to a speaker 102 via an amplifier 111, and each of these converters digital-analog 110 being addressable and controlled independently by the computer 109, so that each speaker 102 can emit a signal independent of other speakers.
  • the various microphones 108 located at level of the calibration points 107 are each connected to a analog to digital converter 112 via an amplifier 113, the converters 112 can be for example addressable converters connected by bus to computer 109, so that the signals picked up by the microphones 108 can be memorized by the computer 109 for each calibration point 107.
  • the impulse responses h ij (t) thus memorized by the computer 109 are then time inverted by this computer, which finally stores the time inversions of the impulse responses h ij (-t).
  • the sound signal S (t) is broadcast at by means of the computer 109, which receives the signal S (t) by through at least one entry route 117 comprising for example a microphone 118 or another source sending the signal S (t) to the computer, an amplifier 119 and a analog-to-digital converter 120.
  • the computer 109 is also connected to a interface 121 comprising for example a keyboard and a screen which allows an operator to choose the target area 114, 115 in which he wishes to broadcast a message or other audible signal.
  • a interface 121 comprising for example a keyboard and a screen which allows an operator to choose the target area 114, 115 in which he wishes to broadcast a message or other audible signal.
  • this message S (t) is received by the computer 109 , which calculates the signals s i (t) to be transmitted by each speaker 102 and transmits these signals to the corresponding speakers 102 via digital-analog converters 110 and amplifiers 111.
  • the signals s i (t) emitted only by some of the loudspeakers of the station 101, called active speakers, for example the loudspeakers closest to the target area.
  • each active loudspeaker that is to say in general each loudspeaker of the station 101, emits an acoustic signal
  • the method according to the invention can also be used to send a message particularly clear and possibly particularly strong at a given individual 122 ( Figure 2) or to a given group of individuals.
  • it may be a service message intended for a particular employee, or a message deterrent to an individual committing a offense or recklessness.
  • the operator identifies the position of individual 122 or the group of individuals receiving the message, this identification can be carried out by vision direct or indirectly by viewing one or more control screens linked to one or more cameras monitoring.
  • the operator indicates the position of the individual 122 to the computer 109 via interface 121, after which the computer 109 automatically determines a target area 123 of size collapsed, containing individual 122 and at least one dot calibration 107, then the operator broadcasts to the individual 122 his dissuasive message.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Measurement Of Velocity Or Position Using Acoustic Or Ultrasonic Waves (AREA)
  • Circuit For Audible Band Transducer (AREA)
  • Surgical Instruments (AREA)
  • Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)

Abstract

A method for making public announcements in a space (101) using n speakers (102) after having determined the impulse response hij(t) between a plurality of calibration points j belonging to said space and each speaker i. To transmit an information-bearing acoustic signal S(t) through at least one target area (114, 115, 123) in the space in which announcements are to be made, each speaker i is made to transmit a signal (a), where j is an index representing calibration points in the target area.

Description

La présente invention est relative aux procédés et dispositifs de focalisation d'ondes acoustiques.The present invention relates to methods and acoustic wave focusing devices.

L'invention concerne plus particulièrement un procédé pour sonoriser un espace perturbant la propagation des ondes acoustiques afin de transmettre dans cet espace des informations sous forme d'ondes acoustiques au moyen d'un nombre n de haut-parleurs, n étant un entier naturel au moins égal à 1, ce procédé comportant des étapes de sonorisation au cours desquelles on transmet au moins un signal acoustique S(t) porteur d'informations dans au moins une zone, dite "zone cible", qui appartient à l'espace à sonoriser, cette transmission étant réalisée en faisant émettre des signaux acoustiques si(t) par au moins un sous-ensemble de haut-parleurs dits "actifs", lequel sous-ensemble comporte au moins un haut-parleur choisi parmi les n haut-parleurs susmentionnés.The invention relates more particularly to a method for sounding a space disturbing the propagation of acoustic waves in order to transmit in this space information in the form of acoustic waves by means of a number n of loudspeakers, n being a natural integer at less equal to 1, this method comprising sound stages during which at least one acoustic signal S (t) carrying information is transmitted in at least one area, called "target area", which belongs to the space to be sounded , this transmission being carried out by causing acoustic signals s i (t) to be emitted by at least one subset of so-called "active" loudspeakers, which subset comprises at least one loudspeaker chosen from among the n loudspeakers mentioned above.

On connaít de nombreux exemples d'espaces perturbant la propagation des ondes acoustiques. On peut citer, entre autres exemples :

  • les gares et aérogares, ou plus généralement les lieux publics dans lesquels des réflexions multiples des ondes sonores rendent difficilement compréhensibles les messages sonores diffusés à l'intention des usagers,
  • et les espaces dans lesquels seraient disposés au moins localement des milieux multidiffuseurs, c'est-à-dire des milieux dans lesquels sont dispersés ou répartis des éléments réfléchissant ou diffusant individuellement les ondes acoustiques, avec une absorption faible, de nature à provoquer un étalement d'au moins un ordre de grandeur de la durée d'une impulsion acoustique.
We know many examples of spaces disrupting the propagation of acoustic waves. We can cite, among other examples:
  • stations and terminals, or more generally public places in which multiple reflections of sound waves make it difficult to understand the sound messages broadcast to users,
  • and spaces in which multicast media would be arranged at least locally, that is to say media in which are dispersed or distributed elements individually reflecting or diffusing the acoustic waves, with a low absorption, such as to cause spreading at least an order of magnitude of the duration of an acoustic pulse.

La présente invention a notamment pour but d'optimiser la transmission d'informations à l'intérieur d'un tel espace.The object of the present invention is in particular to optimize the transmission of information inside such space.

A cet effet, selon l'invention, un procédé du genre en question est essentiellement caractérisé en ce qu'au cours de chaque étape de sonorisation, chaque haut-parleur actif i émet un signal

Figure 00020001
où :

  • hij(-t) représente l'inversion temporelle de la réponse impulsionnelle hij(t), préalablement déterminée et mémorisée, entre le haut-parleur i et un point j prédéterminé dit "de calibration" appartenant à la zone cible, la zone cible comprenant un nombre p de points de calibration, p étant un entier naturel au moins égal à 1, la réponse impulsionnelle hij(t) correspondant au signal acoustique reçu au point j lorsque le haut-parleur i émet une courte impulsion acoustique,
  • et les coefficient aj sont des coefficients de pondération prédéterminés.
To this end, according to the invention, a method of the type in question is essentially characterized in that during each sound stage, each active speaker i emits a signal
Figure 00020001
or :
  • h ij (-t) represents the temporal inversion of the impulse response h ij (t), previously determined and stored, between the speaker i and a predetermined point j called "calibration" belonging to the target area, the area target comprising a number p of calibration points, p being a natural integer at least equal to 1, the impulse response h ij (t) corresponding to the acoustic signal received at point j when the loudspeaker i emits a short acoustic pulse,
  • and the coefficients a j are predetermined weighting coefficients.

Grâce à ces dispositions, qui permettent une focalisation acoustique vers la zone cible, les informations transmises sous forme d'ondes acoustiques sont reçues de façon parfaitement claire dans la zone cible, et de façon beaucoup moins claire en dehors de la zone cible, ce qui ne présente aucun inconvénient et peut même constituer un avantage important dans la mesure où la zone cible est choisie de façon adaptée.Thanks to these provisions, which allow acoustic focus towards the target area, information transmitted as acoustic waves are received from perfectly clear in the target area, and so much less clear outside the target area, which does not has no drawbacks and can even be a significant advantage since the target area is chosen appropriately.

Dans des modes de réalisation préférés du premier aspect de l'invention, on peut éventuellement avoir recours en outre à l'une et/ou l'autre des dispositions suivantes :

  • les coefficients de pondération aj sont tous égaux à 1 ;
  • le sous-ensemble de haut-parleurs actifs comprend tous les haut-parleurs de l'espace à sonoriser ;
  • le nombre p de points de calibration de la zone cible est au moins égal à 2 ;
  • le nombre n de haut-parleurs est au moins égal à 2 ;
  • le signal S(t) correspond au moins en partie à un signal sonore choisi parmi les signaux représentatifs de la voix humaine et les signaux représentatifs de morceaux musicaux ;
  • l'espace à sonoriser est un lieu recevant du public, et les signaux S(t) correspondent au moins en partie à des messages d'information du public ;
  • au cours d'au moins certaines des étapes de sonorisation, on sonorise simultanément un nombre q de zones cibles, où q est un entier naturel au moins égal à 2, chaque haut-parleur actif i émettant alors la superposition de q signaux acoustiques
    Figure 00030001
    où k est un entier naturel compris entre 1 et q correspondant à chaque zone cible, Sk(t) représentant le signal acoustique porteur d'informations destiné à être diffusé dans la zone cible d'indice k : on utilise ainsi la propriété susmentionnée du procédé selon l'invention, selon laquelle chaque signal Sk(t) est parfaitement reçu dans la zone cible k, mais très mal reçu, ou pas reçu du tout, dans les autres zones cibles ;
  • la zone cible considérée dans au moins certaines des étapes de sonorisation est une zone la plus réduite possible comprenant au moins un point de calibration et dans laquelle se trouve au moins une personne destinataire d'un message vocal représenté par le signal S(t).
In preferred embodiments of the first aspect of the invention, it is possible optionally to have recourse to one and / or the other of the following arrangements:
  • the weighting coefficients a j are all equal to 1;
  • the subset of active speakers includes all the speakers in the space to be sounded;
  • the number p of calibration points of the target area is at least equal to 2;
  • the number n of speakers is at least equal to 2;
  • the signal S (t) corresponds at least in part to a sound signal chosen from the signals representative of the human voice and the signals representative of musical pieces;
  • the space to be sounded is a place receiving the public, and the signals S (t) correspond at least in part to messages of information to the public;
  • during at least some of the sound reinforcement steps, a sound q of target zones is simultaneously sounded, where q is a natural integer at least equal to 2, each active loudspeaker i then emitting the superposition of q acoustic signals
    Figure 00030001
    where k is a natural integer between 1 and q corresponding to each target area, S k (t) representing the acoustic signal carrying information intended to be broadcast in the target area of index k: the abovementioned property of the method according to the invention, according to which each signal S k (t) is perfectly received in the target area k, but very badly received, or not received at all, in the other target areas;
  • the target zone considered in at least some of the sound reinforcement steps is the smallest possible zone comprising at least one calibration point and in which there is at least one person receiving a voice message represented by the signal S (t).

Par ailleurs, le premier aspect de l'invention a également pour objet un dispositif pour la mise en oeuvre d'un procédé tel que défini ci-dessus, pour sonoriser un espace perturbant la propagation des ondes acoustiques, ce dispositif comportant :

  • un nombre n de haut-parleurs répartis à l'intérieur dudit espace, n étant un entier naturel au moins égal à 1,
  • au moins une voie d'entrée pour recevoir un signal S(t) porteur d'informations à transmettre sous forme d'ondes acoustiques dans au moins une zone, dite zone cible, qui appartient à l'espace à sonoriser, cette transmission étant réalisée en faisant émettre des signaux acoustiques si(t) par au moins un sous-ensemble de haut-parleurs dits actifs, lequel sous-ensemble comporte au moins un haut-parleur choisi parmi les n haut-parleurs susmentionnés,
  • un système de traitement de signal pour déterminer chaque signal si(t) par la formule :
    Figure 00040001
    où :
    • hij(-t) représente l'inversion temporelle de la réponse impulsionnelle hij(t), préalablement déterminée et mémorisée, entre un haut-parleur actif i et un point j prédéterminé dit "de calibration" appartenant à la zone cible, la zone cible comprenant un nombre p de points de calibration, p étant un entier naturel au moins égal à 1, et la réponse impulsionnielle hij(t) correspondant au signal acoustique reçu au point j lorsque le haut-parleur i émet une courte impulsion acoustique,
    • et les coefficients aj sont des coefficients de pondération prédéterminés,
    le sytème de traitement de signal étant relié à la voie d'entrée pour recevoir le signal S(t) et aux différents haut-parleurs pour leur transmettre respectivement les signaux si(t).
Furthermore, the first aspect of the invention also relates to a device for implementing a method as defined above, for sounding a space disturbing the propagation of acoustic waves, this device comprising:
  • a number n of loudspeakers distributed inside said space, n being a natural integer at least equal to 1,
  • at least one input channel for receiving a signal S (t) carrying information to be transmitted in the form of acoustic waves in at least one zone, called the target zone, which belongs to the space to be sounded, this transmission being carried out by causing acoustic signals s i (t) to be emitted by at least one subset of so-called active loudspeakers, which subset comprises at least one loudspeaker chosen from among the n aforementioned loudspeakers,
  • a signal processing system for determining each signal s i (t) by the formula:
    Figure 00040001
    or :
    • h ij (-t) represents the temporal inversion of the impulse response h ij (t), previously determined and stored, between an active loudspeaker i and a predetermined point j called "calibration" belonging to the target area, the target area comprising a number p of calibration points, p being a natural integer at least equal to 1, and the impulse response h ij (t) corresponding to the acoustic signal received at point j when the loudspeaker i emits a short acoustic pulse ,
    • and the coefficients a j are predetermined weighting coefficients,
    the signal processing system being connected to the input channel to receive the signal S (t) and to the various loudspeakers to transmit the signals s i (t) to them respectively.

Avantageusement, ce dispositif comporte en outre des moyens pour sélectionner la zone cible au sein de l'espace à sonoriser.Advantageously, this device also comprises means to select the target area within the space to sound.

D'autres caractéristiques et avantages de l'invention apparaítront au cours de la description détaillée suivante d'une de ses formes de réalisation, donnée à titre d'exemple non limitatif, en regard des dessins joints.Other characteristics and advantages of the invention will appear during the detailed description following of one of its embodiments, given as non-limiting example, with reference to the accompanying drawings.

Sur les dessins :

  • la figure 1 est une vue en coupe d'une gare ferroviaire dans laquelle le procédé selon le premier aspect de l'invention peut être mis en oeuvre,
  • la figure 2 est une vue de dessus de la gare ferroviaire de la figure 1,
  • et la figure 3 est une vue schématique partielle montrant un exemple de dispositif de mise en oeuvre du procédé selon le premier aspect de l'invention.
In the drawings:
  • FIG. 1 is a sectional view of a railway station in which the method according to the first aspect of the invention can be implemented,
  • FIG. 2 is a top view of the railway station in FIG. 1,
  • and FIG. 3 is a partial schematic view showing an example of a device for implementing the method according to the first aspect of the invention.

Dans l'exemple représenté sur les figures 1 à 3, l'espace à sonoriser est une gare ferroviaire 101 équipée d'un grand nombre de n de haut-parleurs 102, n étant un entier naturel par exemple supérieur à 10.In the example shown in Figures 1 to 3, the space to be sounded is a train station 101 equipped of a large number of n of speakers 102, n being a natural integer for example greater than 10.

Lorsque les haut-parleurs 102 émettent un signal sonore, par exemple un message d'information à l'attention des voyageurs 103, les ondes sonores qui en résultent parviennent aux voyageurs 103 avec des distorsions importantes qui sont dues à ce que ces ondes sonores subissent des trajets multiples et arrivent par conséquent de façon incohérente aux oreilles des voyageurs 103.When speakers 102 are signaling audible, for example an information message for the attention travelers 103, the resulting sound waves reach travelers 103 with significant distortions which are due to the fact that these sound waves undergo multiple paths and therefore arrive so inconsistent in travelers' ears 103.

Les trajets multiples en question suivis par les ondes sonores sont dus à ce que :

  • d'une part chaque voyageur 103 reçoit des ondes sonores émises par plusieurs haut-parleurs 102, situés à des distances différentes les uns des autres par rapport à lui,
  • et d'autre part, les ondes sonores émises par chaque haut-parleur 102 arrivent aux voyageurs 103 non seulement selon un trajet direct, mais également selon de multiples trajets indirects après une ou plusieurs réflexions sur des obstacles tels que par exemples les quais 104, les murs 105 ou le toit 106 de la gare.
The multiple paths in question followed by the sound waves are due to the fact that:
  • on the one hand, each traveler 103 receives sound waves emitted by several loudspeakers 102, located at different distances from each other relative to him,
  • and on the other hand, the sound waves emitted by each loudspeaker 102 arrive at travelers 103 not only on a direct path, but also on multiple indirect paths after one or more reflections on obstacles such as for example the platforms 104, the walls 105 or the roof 106 of the station.

Il en résulte que le message d'information, ou tout autre signal sonore émis par les haut-parleurs, est souvent peu compréhensible pour les voyageurs 103.As a result, the information message, or any other sound signal from the speakers, is often difficult for travelers to understand 103.

Afin de pallier cet inconvénient, selon l'invention, on procède tout d'abord à une opération de "calibration" acoustique de la gare 101, en déterminant la réponse impulsionnelle hij(t) entre chaque haut-parleur i et chaque point j faisant partie d'un ensemble de points prédéterminés 107 dit "de calibration" répartis à l'intérieur de la gare 1. In order to overcome this drawback, according to the invention, an acoustic "calibration" operation is first carried out on the station 101, by determining the impulse response h ij (t) between each loudspeaker i and each point j being part of a set of predetermined points 107 said to be "calibration" distributed inside the station 1.

Les points de calibration 107 sont de préférence situés sensiblement à hauteur d'homme, par exemple à une hauteur comprise entre 1,50 m et 1,75 m au-dessus du sol, et ils sont répartis dans les diverses parties de la gare 101 qui sont fréquentées par les voyageurs 103.The calibration points 107 are preferably located approximately at breast height, for example at a height between 1.50 m and 1.75 m above the ground, and they are distributed in the various parts of the station 101 which are frequented by travelers 103.

La réponse impulsionnelle hij(t) correspond au signal acoustique reçu au point j lorsque le haut-parleur i émet une courte impulsion acoustique (idéalement une impulsion de Dirac) ou inversement au signal acoustique reçu au niveau du haut-parleur i lorsqu'on émet au niveau du point j une courte impulsion acoustique (la réponse impulsionnelle est la même dans les deux sens de propagation).The impulse response h ij (t) corresponds to the acoustic signal received at point j when the loudspeaker i emits a short acoustic pulse (ideally a Dirac pulse) or vice versa to the acoustic signal received at the loudspeaker i when emits at point j a short acoustic pulse (the impulse response is the same in both directions of propagation).

Ces réponses impulsionnelles peuvent donc être mesurées relativement simplement, de préférence de nuit ou tout au moins à un moment où la gare 101 ne reçoit pas de public, en faisant émettre successivement par chaque haut-parleur 102 une courte impulsion acoustique, et en mesurant les signaux acoustiques reçus à la suite de cette impulsion au niveau des différents points de calibration 107, au moyen de micros 108 (figure 3) préalablement disposés aux points de calibration 107.These impulse responses can therefore be measured relatively simply, preferably at night or at least at a time when station 101 is not receiving audience, having each speaker emit successively 102 a short acoustic pulse, and by measuring the acoustic signals received following this pulse at the various calibration points 107, using 108 microphones (Figure 3) previously arranged at the points 107.

Dans l'exemple particulier représenté sur la figure 3, chaque haut-parleur 102 reçoit successivement d'un calculateur 109 le signal impulsionnel à émettre, le calculateur 109 étant relié, par exemple par une liaison en bus, à une pluralité de convertisseurs numériques-analogiques 110, chacun de ces convertisseurs numériques-analogiques étant relié à un haut-parleur 102 par l'intermédiaire d'un amplificateur 111, et chacun de ces convertisseurs numériques-analogiques 110 étant adressable et commandé indépendamment par le calculateur 109, de façon que chaque haut-parleur 102 puisse émettre un signal indépendant des autres haut-parleurs.In the particular example shown in the figure 3, each speaker 102 receives successively from a computer 109 the impulse signal to be sent, the computer 109 being connected, for example by a connection in bus, to a plurality of digital-to-analog converters 110, each of these digital-to-analog converters being connected to a speaker 102 via an amplifier 111, and each of these converters digital-analog 110 being addressable and controlled independently by the computer 109, so that each speaker 102 can emit a signal independent of other speakers.

Par ailleurs, les différents micros 108 situés au niveau des points de calibration 107 sont reliés chacun à un convertisseur analogique-numérique 112 par l'intermédiaire d'un amplificateur 113, les convertisseurs 112 pouvant être par exemple des convertisseurs adressables reliés en bus au calculateur 109, de façon que les signaux captés par les micros 108 puissent être mémorisés par le calculateur 109 pour chaque point de calibration 107.In addition, the various microphones 108 located at level of the calibration points 107 are each connected to a analog to digital converter 112 via an amplifier 113, the converters 112 can be for example addressable converters connected by bus to computer 109, so that the signals picked up by the microphones 108 can be memorized by the computer 109 for each calibration point 107.

Les réponses impulsionnelles hij(t) ainsi mémorisées par le calculateur 109 sont ensuite inversées temporellement par ce calculateur, qui mémorise finalement les inversions temporelles des réponses impulsionnelles hij(-t).The impulse responses h ij (t) thus memorized by the computer 109 are then time inverted by this computer, which finally stores the time inversions of the impulse responses h ij (-t).

Une fois l'opération de calibration terminée, on démonte les différents micros 108 avec leurs convertisseurs 112 et leurs amplificateurs 113.Once the calibration operation is complete, we dismantle the different 108 microphones with their converters 112 and their amplifiers 113.

Par la suite, à chaque fois qu'il est nécessaire de sonoriser une ou plusieurs zones cibles appartenant à la gare 101, par exemple une zone cible 114 correspondant à un quai 104 particulier et/ou une zone cible 115 correspondant à tout ou partie du hall 116 de la gare, on fait émettre par chaque haut-parleur i de la gare un signal sonore

Figure 00070001
où :

  • les indices j correspondent aux indices des points de calibration appartenant à la zone cible ou aux zones cibles considérées, chaque zone cible comprenant au moins un point de calibration 107 et de préférence plusieurs,
  • aj représente un coefficient de pondération prédéterminé qui peut éventuellement être utilisé pour privilégier certains points de calibration 107 correspondant à des zones particulièrement fréquentées par le public, ces coefficients de pondération pouvant être le plus souvent tous égaux entre eux et généralement tous égaux à 1,
  • S(t) correspond à un signal porteur d'informations, ce signal pouvant être un message d'informations destiné aux voyageurs, une musique d'ambiance, la retransmission d'un programme radiodiffusé, ou autre,
  • et le signe ⊗ représente le produit de convolution.
Thereafter, each time it is necessary to add sound to one or more target areas belonging to the station 101, for example a target area 114 corresponding to a particular platform 104 and / or a target area 115 corresponding to all or part of the hall 116 of the station, an audible signal is emitted by each loudspeaker i of the station
Figure 00070001
or :
  • the indices j correspond to the indices of the calibration points belonging to the target zone or to the target zones considered, each target zone comprising at least one calibration point 107 and preferably several,
  • a j represents a predetermined weighting coefficient which can optionally be used to favor certain calibration points 107 corresponding to areas particularly frequented by the public, these weighting coefficients can most often be all equal to each other and generally all equal to 1,
  • S (t) corresponds to an information-carrying signal, this signal possibly being an information message intended for travelers, background music, retransmission of a radio program, or the like,
  • and the sign ⊗ represents the convolution product.

On rappelle ici que le produit de convolution d'une fonction f(t) par une fonction g(t) vaut :

Figure 00080001
We recall here that the convolution product of a function f (t) by a function g (t) is worth:
Figure 00080001

La diffusion du signal sonore S(t) est réalisée au moyen du calculateur 109, qui reçoit le signal S(t) par l'intermédiaire d'au moins une voie d'entrée 117 comportant par exemple un micro 118 ou une autre source envoyant le signal S(t) vers le calculateur, un amplificateur 119 et un convertisseur analogique-numérique 120.The sound signal S (t) is broadcast at by means of the computer 109, which receives the signal S (t) by through at least one entry route 117 comprising for example a microphone 118 or another source sending the signal S (t) to the computer, an amplifier 119 and a analog-to-digital converter 120.

Le calculateur 109 est relié par ailleurs à une interface 121 comprenant par exemple un clavier et un écran qui permet à un opérateur de choisir la zone cible 114, 115 dans laquelle il souhaite diffuser un message ou autre signal sonore.The computer 109 is also connected to a interface 121 comprising for example a keyboard and a screen which allows an operator to choose the target area 114, 115 in which he wishes to broadcast a message or other audible signal.

Après avoir sélectionné la ou les zones cibles voulues au moyen de l'interface 121, l'opérateur peut alors par exemple parler dans le micro 118 pour diffuser un message dans cette zone cible : ce message S(t) est reçu par le calculateur 109, qui calcule les signaux si(t) à faire émettre par chaque haut-parleur 102 et transmet ces signaux aux haut-parleurs 102 correspondants par l'intermédiaire des convertisseurs numériques-analogiques 110 et des amplificateurs 111.After having selected the desired target area (s) by means of the interface 121, the operator can then for example speak into the microphone 118 to broadcast a message in this target area: this message S (t) is received by the computer 109 , which calculates the signals s i (t) to be transmitted by each speaker 102 and transmits these signals to the corresponding speakers 102 via digital-analog converters 110 and amplifiers 111.

Eventuellement, il serait possible de ne faire émettre les signaux si(t) que par certains des haut-parleurs de la gare 101, dits haut-parleurs actifs, par exemple les haut-parleurs les plus voisins de la zone cible.Optionally, it would be possible to have the signals s i (t) emitted only by some of the loudspeakers of the station 101, called active speakers, for example the loudspeakers closest to the target area.

Le cas échéant, il serait même possible de sonoriser simultanément plusieurs zones cibles en envoyant respectivement dans les différentes zones cibles des signaux acoustiques porteurs d'informations Sk(t) différents.If necessary, it would even be possible to simultaneously sound several target zones by sending respectively to the different target zones acoustic signals carrying information S k (t) different.

Dans ce cas, chaque haut-parleur actif, c'est-à-dire en général chaque haut-parleur de la gare 101, émet un signal acoustique

Figure 00090001
In this case, each active loudspeaker, that is to say in general each loudspeaker of the station 101, emits an acoustic signal
Figure 00090001

Le cas échéant, le procédé selon l'invention peut également être utilisé pour envoyer un message particulièrement clair et éventuellement particulièrement fort à un individu donné 122 (figure 2) ou à un groupe donné d'individus.Where appropriate, the method according to the invention can also be used to send a message particularly clear and possibly particularly strong at a given individual 122 (Figure 2) or to a given group of individuals.

Il peut s'agir par exemple d'un message de service destiné à un employé particulier, ou encore d'un message dissuasif destiné à un individu en train de commettre une infraction ou une imprudence.For example, it may be a service message intended for a particular employee, or a message deterrent to an individual committing a offense or recklessness.

Pour cela, l'opérateur repère la position de l'individu 122 ou du groupe d'individus destinataire du message, ce repérage pouvant être effectué par vision directe ou encore indirectement en visionnant un ou plusieurs écrans de contrôle reliés à une ou plusieurs caméras de surveillance.For this, the operator identifies the position of individual 122 or the group of individuals receiving the message, this identification can be carried out by vision direct or indirectly by viewing one or more control screens linked to one or more cameras monitoring.

Ce repérage étant effectué, l'opérateur indique la position de l'individu 122 au calculateur 109 par l'intermédiaire de l'interface 121, après quoi le calculateur 109 détermine automatiquement une zone cible 123 de taille réduite, contenant l'individu 122 et au moins un point de calibration 107, puis l'opérateur diffuse vers l'individu 122 son message dissuasif.This location being carried out, the operator indicates the position of the individual 122 to the computer 109 via interface 121, after which the computer 109 automatically determines a target area 123 of size collapsed, containing individual 122 and at least one dot calibration 107, then the operator broadcasts to the individual 122 his dissuasive message.

Comme il va de soi, et comme il résulte d'ailleurs de ce qui précède, le premier aspect de l'invention n'est pas limitée à l'exemple de réalisation particulier qui vient d'être décrit ; elle en embrasse au contraire toutes les variantes, notamment celles dans lesquelles :

  • l'espace à sonoriser serait autre qu'une gare ferroviaire, par exemple un aérogare, une station de métro, une gare routière, une piscine, un stade, une plage, un musée (auquel cas les zones cibles peuvent correspondre à des zones situées au voisinage des différentes oeuvres d'art dans une même salle, ces zones cibles pouvant éventuellement être matérialisées par des lignes tracées au sol ou similaires, et des commentaires sonores différents pouvant éventuellement être diffusés simultanément respectivement dans ces différentes zones cibles), un espace appartenant à un parc d'attractions (auquel cas le fait de pouvoir faire entendre des sons uniquement dans certaines zones particulières de cet espace peut être utilisé notamment à titre de jeu), les salles de spectacles, et de façon plus générale, tout lieu recevant du public ou encore tout lieu privé perturbant la propagation des ondes acoustiques par des réflexions ou diffusions multiples,
  • l'invention serait utilisée pour écouter un programme sonore de haute fidélité, la zone cible correspondant alors à un espace où doit se placer l'auditeur pour écouter le programme sonore en question,
  • le nombre n de haut-parleurs serait inférieur à 10, par exemple égal à 1 (notamment lorsque l'espace à sonoriser comporte de multiples obstacles réverbérant particulièrement bien les ondes acoustiques), ou égal à 2,
  • le signal S(t) ne serait pas un signal acoustique compréhensible par l'oreille humaine, mais un signal codé destiné à être reçu et décodé par un dispositif de réception automatique,
  • le signal acoustique S(t) ne serait pas sonore, mais ultrasonore ou infrasonore,
  • et les réponses impulsionnelles hij(t) seraient déterminées autrement qu'en faisant émettre des signaux acoustiques impulsionnels, par exemple en faisant émettre successivement aux différents haut-parleurs 102 un signal acoustique modulé de façon prédéterminée, ou encore en faisant émettre aux haut-parleurs 102 des suites de signaux acoustiques prédéterminés, d'où l'on peut déduire la réponse impulsionnelle hij(t) par des méthodes de calcul connues en soi, explicitées par exemple dans la demande de brevet français n° 96 05102 du 23 avril 1996 pour le calcul des réponses impulsionnelles dans le domaine des ondes radio.
As is obvious, and as it follows from the above, the first aspect of the invention is not limited to the particular embodiment which has just been described; on the contrary, it embraces all variants, in particular those in which:
  • the space to be sounded would be other than a train station, for example a terminal, a metro station, a bus station, a swimming pool, a stadium, a beach, a museum (in which case the target areas may correspond to areas located in the vicinity of the different works of art in the same room, these target zones possibly being able to be materialized by lines drawn on the ground or the like, and different sound comments possibly being broadcast simultaneously respectively in these different target zones), a space belonging at an amusement park (in which case being able to hear sounds only in certain specific areas of this space can be used in particular as a game), concert halls, and more generally, any place receiving public or any private place disturbing the propagation of acoustic waves by multiple reflections or diffusions,
  • the invention would be used to listen to a high fidelity sound program, the target area then corresponding to a space where the listener must be placed to listen to the sound program in question,
  • the number n of loudspeakers would be less than 10, for example equal to 1 (in particular when the space to be publicized comprises multiple obstacles reverberating particularly well the acoustic waves), or equal to 2,
  • the signal S (t) would not be an acoustic signal understandable by the human ear, but a coded signal intended to be received and decoded by an automatic reception device,
  • the acoustic signal S (t) would not be audible, but ultrasonic or infrasonic,
  • and the impulse responses h ij (t) would be determined otherwise than by causing impulse acoustic signals to be emitted, for example by successively emitting to the different speakers 102 a predetermined modulated acoustic signal, or by having the loudspeakers emit speakers 102 of sequences of predetermined acoustic signals, from which the impulse response h ij (t) can be deduced by calculation methods known per se, explained for example in French patent application No. 96 05102 of April 23 1996 for the calculation of impulse responses in the field of radio waves.

Claims (11)

  1. Process for sound-sweeping a space (101) which disturbs the propagation of acoustic waves, so as to transmit in this space information in the form of acoustic waves by means of a number n of loudspeakers (102), n being a natural integer at least equal to 1, this process including sound-sweeping steps in the course of which at least one acoustic signal S(t) carrying information is transmitted in at least one zone (114, 115, 123), termed a "target zone", which belongs to the space to be sound-swept (101), this transmission being carried out by having acoustic signals si(t) emitted by at least one subset of so-called "active" loudspeakers (102), which subset includes at least one loudspeaker chosen from among the n abovementioned loudspeakers, characterized in that in the course of each sound-sweeping step, each active loudspeaker i emits a signal
    Figure 00190001
    where:
    hij(-t) represents the temporal inversion of the impulse response hij(t), previously determined and stored, between loudspeaker i and a predetermined so-called "calibration" point j (107) belonging to the target zone (114, 115, 123), the target zone comprising a number p of calibration points, p being a natural integer at least equal to 1, the impulse response hij(t) corresponding to the acoustic signal received at the point j when loudspeaker i emits a short acoustic pulse,
    and the coefficients aj are predetermined weighting coefficients.
  2. Process according to Claim 1, in which the weighting coefficients aj are all equal to 1.
  3. Process according to either one of Claims 1 and 2, in which the subset of active loudspeakers (102) comprises all the loudspeakers of the space to be sound-swept (101).
  4. Process according to either one of Claims 1 and 2, in which the number p of calibration points (107) of the target zone (114, 115) is at least equal to 2.
  5. Process according to any one of the preceding claims, in which the number n of loudspeakers (102) is at least equal to 2.
  6. Process according to any one of the preceding claims, in which the signal S(t) corresponds at least in part to a sound signal chosen from among the signals representative of the human voice and the signals representative of musical snatches.
  7. Process according to Claim 5, in which the space to be sound-swept (101) is a place which receives the public, and the signals S(t) correspond at least in part to public information messages.
  8. Process according to Claim 6, in which, in the course of at least certain of the sound-sweeping steps, a number q of target zones (114, 115, 123) is simultaneously sound-swept, where q is a natural integer at least equal to 2, each active loudspeaker i then emitting the superposition of q acoustic signals
    Figure 00200001
    where k is a natural integer lying between 1 and q corresponding to each target zone, Sk(t) representing the information-carrying acoustic signal intended to be broadcast in the target zone of index k.
  9. Process according to any one of the preceding claims, in which the target zone (123) considered in at least certain of the sound-sweeping steps is as restricted a zone as possible comprising at least one calibration point (107) and in which there is at least one person (122) who is the destination of a voice message represented by the signal S(t).
  10. Device for implementing a process according to any one of the preceding claims, for sound-sweeping a space (101) which disturbs the propagation of acoustic waves, this device including:
    a number n of loudspeakers (102) distributed inside the said space, n being a natural integer at least equal to 1,
    at least one input pathway (117) for receiving a signal S(t) carrying information to be transmitted in the form of acoustic waves in at least one zone (114, 115, 123), termed the target zone, which belongs to the space to be sound-swept, this transmission being carried out by having acoustic signals si(t) emitted by at least one subset of so-called active loudspeakers (102), which subset includes at least one loudspeaker chosen from among the n abovementioned loudspeakers,
    a signal processing system (109) for determining each signal s h / i(t) via the formula:
    Figure 00210001
    where:
    hij(-t) represents the temporal inversion of the impulse response hij(t), previously determined and stored, between an active loudspeaker i and a predetermined so-called "calibration" point j belonging to the target zone, the target zone (114, 115, 123) comprising a number p of calibration points (107), p being a natural integer at least equal to 1, and the impulse response hij(t) corresponding to the acoustic signal received at the point j when loudspeaker i emits a short acoustic pulse,
    and the coefficients aj are predetermined weighting coefficients,
    the signal processing system (109) being linked to the input pathway so as to receive the signal S(t) and to the various loudspeakers (102) so as to transmit respectively thereto the signals si(t).
  11. Device according to Claim 10, furthermore including means (121) for selecting the target zone within the space to be sound-swept.
EP96925774A 1995-07-13 1996-07-11 Acoustic wave focusing method and device Expired - Lifetime EP0842508B1 (en)

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