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EP1251717A1 - Method and circuit for headphone listening of audio recording - Google Patents

Method and circuit for headphone listening of audio recording Download PDF

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Publication number
EP1251717A1
EP1251717A1 EP01810373A EP01810373A EP1251717A1 EP 1251717 A1 EP1251717 A1 EP 1251717A1 EP 01810373 A EP01810373 A EP 01810373A EP 01810373 A EP01810373 A EP 01810373A EP 1251717 A1 EP1251717 A1 EP 1251717A1
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EP
European Patent Office
Prior art keywords
signal
delayed
right channel
left channel
channel signal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Application number
EP01810373A
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German (de)
French (fr)
Inventor
Valentin Chareyron
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Yellowknife AVV
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Yellowknife AVV
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Filing date
Publication date
Application filed by Yellowknife AVV filed Critical Yellowknife AVV
Priority to EP01810373A priority Critical patent/EP1251717A1/en
Priority to US10/475,194 priority patent/US7254238B2/en
Priority to EP02708120A priority patent/EP1380188A1/en
Priority to PCT/CH2002/000192 priority patent/WO2002085067A1/en
Priority to JP2002582660A priority patent/JP2004527961A/en
Publication of EP1251717A1 publication Critical patent/EP1251717A1/en
Withdrawn legal-status Critical Current

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04S—STEREOPHONIC SYSTEMS 
    • H04S1/00—Two-channel systems
    • H04S1/002—Non-adaptive circuits, e.g. manually adjustable or static, for enhancing the sound image or the spatial distribution
    • H04S1/005—For headphones

Definitions

  • the present invention relates to electronic devices intended for the sound reproduction. It relates, more particularly, to a method and a circuit specially designed to adapt the signals of different channels delivered by an audio reproduction system under the specific conditions of listening to them through headphones.
  • the invention applies equally well to the processing of right channel signals and of the left channel of a stereophonic reproduction system than that of channel signals of a multi-channel system such as, for example, that the system known as "Surround".
  • Existing audio reproduction systems are designed for listening with one enclosure per channel adequately placed in a room.
  • the two speakers are ideally located at the base of an equilateral triangle whose listener occupies a vertex.
  • the two earphones are placed at the immediate vicinity of the listener's ears. His brain goes like this simply perceive the sound sources reproduced on a crossing line his head from ear to ear, completely ignoring an essential part of the audio reproduction system, namely the volume of air located between each pregnant and the listener. This therefore does not correspond to the listening conditions by speakers and does not allow the correct reproduction of the sound image.
  • the method of reproduction itself operates, in fact, two channels per channel, the channel direct, from the enclosure to the nearest ear, and the indirect route, from the speaker to the most distant ear (four-way stereo).
  • the sounds of the indirect channels have longer paths and are therefore perceived with a certain delay.
  • the path length difference is about 7 cm, which results in a phase shift of 206 ⁇ s.
  • the object of the present invention is to provide a method and a circuit which provide optimal listening conditions for hearing headphones.
  • the first delay is between 100 and 200 ⁇ s
  • the second delay between 500 and 700 ⁇ s.
  • the delayed signal intended for the channel left and the delayed signal for the right channel are filtered beforehand in a way that favors low frequencies at the expense of high ones.
  • the filtering action is zero at 0 Hz and total at 24 kHz.
  • the first attenuation is advantageously between 20 and 30%, and the second attenuation between 50 and 60%.
  • the first attenuation is advantageously between 5 and 15%, and the second attenuation between 65 and 75%.
  • an audio source has been represented diagrammatically stereophonic S, conventional type, with two outputs 10 and 12 deliver the signal of the left channel L and the signal of the right channel respectively R.
  • the circuit 14 is, in fact, a microprocessor. Consequently, it goes without saying that the L and R signals applied to its inputs are in the form digital. The description of the processing of these signals will therefore refer to operations, not electronic components. The numbers of reference of these operations will be assigned the letter L when it comes to left channel and the letter R when it is the right channel.
  • the first operations performed on the L and R signals are, on the one hand, at 20, their passage through a low-pass filter and, on the other hand, at 22, their 25% attenuation.
  • the filtering operation carried out in 20 aims to promote frequencies low at the expense of high. This action is not essential but it contributes to improving the desired effect. Typically, the action of the filter is zero at 0 Hz then it gradually increases to 24 kHz, frequency for which its action is total.
  • the two filtered signals then undergo, at 24, an attenuation of 55% then are delayed, in 26, by 146 ⁇ s. For a sampling frequency of 48 kHz, this delay corresponds to an offset of 7 signal samples.
  • Signal R-45d thus attenuated to 45% of its initial level and delayed by 146 ⁇ s, is then added, in 28L, to the L-75 signal attenuated to 75% of its level initial, but not delayed, to obtain an intermediate left channel signal composite L1.
  • the signal L-45d attenuated to 45% of its initial level and delayed by 146 ⁇ s, is added, at 28R, to signal R-75 attenuated to 75% of its original level, but not delayed, to obtain a signal composite intermediate channel R1.
  • the signal R1-30d thus attenuated to 30% of its initial level and delayed by 583 ⁇ s, is then added, in 36L, to the L1-90 signal attenuated to 90% of its level initial, but not delayed, to obtain a composite signal Lc which appears on the output 16 and constitutes the signal of the left channel intended for listening by helmet.
  • the signal L1-30d attenuated to 30% of its initial and delayed level of 583 ⁇ s, is added, in 36R, to signal R1-90 attenuated to 90% of its original level, but not delayed, to obtain a signal composite Rc which appears on the output 20 and constitutes the signal of the right channel intended for headphone listening.
  • the circuit according to the invention performs two treatments successive signals, i.e. the transformation of the starting signals L and R into signals L1 and R1 (stage 14a), then the transformation of these into Lc and Rc signals (stage 14b).
  • these two treatments will be designated respectively azimuth and outsourcing.
  • FIGS 2 and 3 respectively show the effect of azimuth and that of outsourcing.
  • These figures represent the head 40 of a helmet wearer whose headphones on the left and right are designated by the references 42L and 42R.
  • the azimuth processing of the L and R signals results, like the shows figure 2, to substitute, for the two physical sound sources that constitute the 42L and 42R headphones, two virtual sound sources 44L and 44R positioned in front of the helmet wearer's eyes, at the tops of the base of an equilateral triangle whose opposite side is substantially located between both ears.
  • the stereophonic image perceived by the listener develops over 60 °, which corresponds to the conditions, generally accepted as the most comfortable, listening through speakers.
  • the outsourcing processing of the L1 and R1 signals results, like the shows figure 3, to move away the two virtual sound sources 44L and 44R from the listener's front and replace them with sources 46L and 46R.
  • the sound sources are no longer simply in the ears of the wearer of the helmet, of which they then cross the head without succeeding in generating the image desired stereo, but they are moved in front of him, at a distance distance and at an angle that provide listening conditions satisfactory stereophonic.
  • the invention applies, in general, to any hearing with the headphones, that it is, in particular, listening to music or to better separate, in an airplane cockpit, the different sources of messages.
  • the invention can also find an interesting application in the speech therapy field by allowing customization of amplification of sound signals to compensate for certain deficiencies hearing.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Stereophonic System (AREA)

Abstract

The adaptation method for different channels (L,R) has left channel signals right channel added with a delay obtaining an intermediate signal (L1). Similarly for the right side channel (R1). A second step of adding the intermediate right side channel with a delay to the intermediate left hand channel signal producing a signal (Lc) and a corresponding right hand signal (Rc).

Description

La présente invention se rapporte aux dispositifs électroniques destinés à la reproduction de sons. Elle concerne, plus particulièrement, un procédé et un circuit spécialement conçus pour adapter les signaux des différents canaux délivrés par un système de reproduction audio aux conditions spécifiques de leur écoute au casque.The present invention relates to electronic devices intended for the sound reproduction. It relates, more particularly, to a method and a circuit specially designed to adapt the signals of different channels delivered by an audio reproduction system under the specific conditions of listening to them through headphones.

L'invention s'applique aussi bien au traitement des signaux de canal droit et de canal gauche d'un système de reproduction stéréophonique qu'à celui des signaux des canaux d'un système multi-canal tel, par exemple, que le système connu sous la désignation "Surround".The invention applies equally well to the processing of right channel signals and of the left channel of a stereophonic reproduction system than that of channel signals of a multi-channel system such as, for example, that the system known as "Surround".

Les systèmes existants de reproduction audio sont conçus pour une écoute avec une enceinte par canal disposée de manière adéquate dans un local. Dans le cas d'un système stéréophonique, les deux enceintes sont idéalement situées à la base d'un triangle équilatéral dont l'auditeur occupe un sommet.Existing audio reproduction systems are designed for listening with one enclosure per channel adequately placed in a room. In the case of a stereophonic system, the two speakers are ideally located at the base of an equilateral triangle whose listener occupies a vertex.

Or, lors d'une écoute au casque, les deux écouteurs sont disposés au voisinage immédiat des oreilles de l'auditeur. Son cerveau va ainsi simplement percevoir les sources sonores reproduites sur une ligne traversant sa tête d'une oreille à l'autre, en ignorant totalement un élément essentiel de la chaíne de reproduction audio, à savoir le volume d'air situé entre chaque enceinte et l'auditeur. Cela ne correspond donc pas aux conditions de l'écoute par enceintes et ne permet pas la reproduction correcte de l'image sonore.However, when listening to headphones, the two earphones are placed at the immediate vicinity of the listener's ears. His brain goes like this simply perceive the sound sources reproduced on a crossing line his head from ear to ear, completely ignoring an essential part of the audio reproduction system, namely the volume of air located between each pregnant and the listener. This therefore does not correspond to the listening conditions by speakers and does not allow the correct reproduction of the sound image.

En effet, si le support de transmission du signal implique bien un seul canal par canal à reproduire (deux canaux en stéréophonie), le procédé de reproduction lui-même exploite, en fait, deux voies par canal, soit la voie directe, de l'enceinte vers l'oreille la plus proche, et la voie indirecte, de l'enceinte vers l'oreille la plus éloignée (quatre voies en stéréophonie).Indeed, if the signal transmission medium does imply a single channel per channel to be reproduced (two channels in stereophony), the method of reproduction itself operates, in fact, two channels per channel, the channel direct, from the enclosure to the nearest ear, and the indirect route, from the speaker to the most distant ear (four-way stereo).

Bien évidemment, les sons des voies indirectes ont des trajets plus longs et sont donc perçus avec un certain retard. Pour fixer les idées, dans le cas d'un signal stéréophonique, la différence de longueur de trajet est d'environ 7 cm, ce qui entraíne un déphasage de 206 µs.Obviously, the sounds of the indirect channels have longer paths and are therefore perceived with a certain delay. To fix the ideas, in the case of a stereophonic signal, the path length difference is about 7 cm, which results in a phase shift of 206 µs.

Voilà pourquoi, l'écoute au casque, qui ne tient pas compte des voies indirectes, prive le cerveau des informations dont il a besoin pour reconstituer l'image sonore.This is why listening to headphones, which does not take into account the channels indirect, deprives the brain of the information it needs to reconstruct the sound image.

La présente invention a pour but de fournir un procédé et un circuit qui apportent des conditions d'écoute optimales pour une audition au casque.The object of the present invention is to provide a method and a circuit which provide optimal listening conditions for hearing headphones.

De façon plus précise, l'invention concerne un procédé d'adaptation des signaux des différents canaux délivrés par un système de reproduction audio aux conditions spécifiques de leur écoute au casque, caractérisé en ce qu'il consiste:

  • à additionner à au moins un signal destiné au canal gauche au moins un signal destiné au canal droit retardé d'une première durée pour obtenir un signal de canal gauche intermédiaire et audit signal destiné au canal droit ledit signal destiné au canal gauche retardé de la même durée pour obtenir un signal de canal droit intermédiaire; puis
  • à additionner au signal de canal gauche intermédiaire le signal de canal droit intermédiaire retardé d'une deuxième durée, pour obtenir un signal de canal gauche adapté, et au signal de canal droit intermédiaire le signal de canal gauche intermédiaire retardé de la même durée, pour obtenir un signal de canal droit adapté.
More specifically, the invention relates to a method for adapting the signals of the different channels delivered by an audio reproduction system to the specific conditions of listening to them with headphones, characterized in that it consists:
  • adding to at least one signal intended for the left channel at least one signal intended for the right channel delayed by a first duration to obtain an intermediate left channel signal and to said signal intended for the right channel said signal intended for the left channel delayed by the same time to obtain an intermediate right channel signal; then
  • adding to the intermediate left channel signal the intermediate right channel signal delayed by a second duration, to obtain a suitable left channel signal, and to the intermediate right channel signal the intermediate left channel signal delayed by the same duration, for obtain a suitable right channel signal.

De façon avantageuse, lorsque le procédé s'applique à un système de reproduction stéréophonique délivrant seulement un signal de canal gauche et un signal de canal droit, le premier retard est compris entre 100 et 200 µs, et le deuxième retard entre 500 et 700 µs.Advantageously, when the method applies to a system of stereophonic reproduction delivering only a left channel signal and a right channel signal, the first delay is between 100 and 200 µs, and the second delay between 500 and 700 µs.

Selon un mode de réalisation préféré, le signal retardé destiné au canal gauche et le signal retardé destiné au canal droit sont préalablement filtrés d'une manière qui privilégie les fréquences basses au dépens des hautes. Typiquement, l'action de filtrage est nulle à 0 Hz et totale à 24 kHz. According to a preferred embodiment, the delayed signal intended for the channel left and the delayed signal for the right channel are filtered beforehand in a way that favors low frequencies at the expense of high ones. Typically, the filtering action is zero at 0 Hz and total at 24 kHz.

De préférence:

  • le signal destiné au canal gauche et le signal destiné au canal droit subissent préalablement une première atténuation; et
  • le signal retardé destiné au canal gauche et le signal retardé destiné au canal droit subissent préalablement une deuxième atténuation.
Preferably:
  • the signal intended for the left channel and the signal intended for the right channel undergo a first attenuation beforehand; and
  • the delayed signal intended for the left channel and the delayed signal intended for the right channel undergo a second attenuation beforehand.

Dans le cas d'un système de reproduction stéréophonique, la première atténuation est avantageusement comprise entre 20 et 30%, et la deuxième atténuation entre 50 et 60%.In the case of a stereophonic reproduction system, the first attenuation is advantageously between 20 and 30%, and the second attenuation between 50 and 60%.

De préférence, également:

  • le signal de canal gauche intermédiaire et le signal de canal droit intermédiaire subissent préalablement une première atténuation; et
  • le signal de canal gauche intermédiaire retardé et le signal de canal droit intermédiaire retardé subissent préalablement une deuxième atténuation.
Preferably also:
  • the intermediate left channel signal and the intermediate right channel signal are first attenuated; and
  • the delayed intermediate left channel signal and the delayed intermediate right channel signal undergo a second attenuation beforehand.

Dans le cas d'un système de reproduction stéréophonique, la première atténuation est avantageusement comprise entre 5 et 15%, et la deuxième atténuation entre 65 et 75%.In the case of a stereophonic reproduction system, the first attenuation is advantageously between 5 and 15%, and the second attenuation between 65 and 75%.

L'invention concerne aussi un circuit pour la mise en oeuvre du procédé défini ci-dessus, caractérisé en ce qu'il comporte:

  • des premiers moyens pour produire un signal intermédiaire de canal gauche résultant de l'addition d'au moins un signal destiné au canal gauche à au moins un signal destiné au canal droit retardé d'une première durée, et un signal intermédiaire de canal droit résultant de l'addition du signal destiné au canal droit au signal destiné au canal gauche retardé de la même durée, et
  • des deuxièmes moyens pour produire un signal de canal gauche adapté résultant de l'addition du signal intermédiaire de canal gauche au signal intermédiaire de canal droit retardé d'une deuxième durée et un signal de canal droit adapté résultant de l'addition du signal intermédiaire de canal droit au signal intermédiaire de canal gauche retardé de la même durée.
The invention also relates to a circuit for implementing the method defined above, characterized in that it comprises:
  • first means for producing an intermediate left channel signal resulting from the addition of at least one signal intended for the left channel to at least one signal intended for the right channel delayed by a first duration, and an intermediate right channel signal resulting adding the signal intended for the right channel to the signal intended for the left channel delayed by the same duration, and
  • second means for producing a suitable left channel signal resulting from the addition of the intermediate left channel signal to the intermediate right channel signal delayed by a second duration and a suitable right channel signal resulting from the addition of the intermediate signal right channel to the intermediate signal of left channel delayed by the same duration.

D'autres caractéristiques de l'invention ressortiront de la description qui va suivre, faite en regard des dessins annexés, sur lesquels:

  • la figure 1 représente un circuit selon l'invention, destiné à l'adaptation des signaux d'une source stéréophonique, et
  • les figures 2 et 3 servent à expliquer ses effets.
Other characteristics of the invention will emerge from the description which follows, given with reference to the appended drawings, in which:
  • FIG. 1 represents a circuit according to the invention, intended for the adaptation of the signals of a stereophonic source, and
  • Figures 2 and 3 are used to explain its effects.

Sur la figure 1, on a représenté schématiquement une source audio stéréophonique S, de type conventionnel, dont les deux sorties 10 et 12 délivrent respectivement le signal du canal gauche L et le signal du canal droit R.In FIG. 1, an audio source has been represented diagrammatically stereophonic S, conventional type, with two outputs 10 and 12 deliver the signal of the left channel L and the signal of the right channel respectively R.

Ces signaux sont appliqués aux deux entrées d'un circuit 14 à deux étages 14a et 14b, objet de la présente invention, qui a pour fonction de les traiter en vue de délivrer, sur ses sorties 16 et 18 respectives, des signaux de canal gauche Lc et de canal droit Rc optimisés en vue d'une écoute au casque.These signals are applied to the two inputs of a two-stage circuit 14 14a and 14b, object of the present invention, which has the function of treating them in view of delivering, on its respective outputs 16 and 18, channel signals left Lc and right channel Rc optimized for headphone listening.

Dans le mode de mise en oeuvre de l'invention décrit ici à titre d'exemple, le circuit 14 est, en fait, un microprocesseur. En conséquence, il va de soi que les signaux L et R appliqués sur ses entrées se présentent sous forme numérique. La description du traitement de ces signaux se référera donc à des opérations et non à des composants électroniques. Les numéros de référence de ces opérations seront affectés de la lettre L lorsqu'il s'agit du canal gauche et de la lettre R lorsqu'il s'agit du canal droit.In the embodiment of the invention described here by way of example, the circuit 14 is, in fact, a microprocessor. Consequently, it goes without saying that the L and R signals applied to its inputs are in the form digital. The description of the processing of these signals will therefore refer to operations, not electronic components. The numbers of reference of these operations will be assigned the letter L when it comes to left channel and the letter R when it is the right channel.

Les premières opérations effectuées sur les signaux L et R sont, d'une part, en 20, leur passage à travers un filtre passe-bas et, d'autre part, en 22, leur atténuation de 25%.The first operations performed on the L and R signals are, on the one hand, at 20, their passage through a low-pass filter and, on the other hand, at 22, their 25% attenuation.

L'opération de filtrage réalisée en 20 a pour but de favoriser les fréquences basses au dépens des hautes. Cette action n'est pas indispensable mais elle contribue à l'amélioration de l'effet recherché. Typiquement, l'action du filtre est nulle à 0 Hz puis elle augmente progressivement jusqu'à 24 kHz, fréquence pour laquelle son action est totale. The filtering operation carried out in 20 aims to promote frequencies low at the expense of high. This action is not essential but it contributes to improving the desired effect. Typically, the action of the filter is zero at 0 Hz then it gradually increases to 24 kHz, frequency for which its action is total.

Les deux signaux filtrés subissent ensuite, en 24, un atténuation de 55% puis sont retardés, en 26, de 146 µs. Pour une fréquence d'échantillonnage de 48 kHz, ce retard correspond à un décalage de 7 échantillons des signaux.The two filtered signals then undergo, at 24, an attenuation of 55% then are delayed, in 26, by 146 µs. For a sampling frequency of 48 kHz, this delay corresponds to an offset of 7 signal samples.

Le signal R-45d, ainsi atténué à 45% de son niveau initial et retardé de 146 µs, est alors additionné, en 28L, au signal L-75 atténué à 75% de son niveau initial, mais non retardé, pour obtenir un signal de canal gauche intermédiaire composite L1.Signal R-45d, thus attenuated to 45% of its initial level and delayed by 146 µs, is then added, in 28L, to the L-75 signal attenuated to 75% of its level initial, but not delayed, to obtain an intermediate left channel signal composite L1.

En parallèle et de manière identique, le signal L-45d, atténué à 45% de son niveau initial et retardé de 146 µs, est additionné, en 28R, au signal R-75 atténué à 75% de son niveau initial, mais non retardé, pour obtenir un signal de canal droit intermédiaire composite R1.In parallel and in an identical manner, the signal L-45d, attenuated to 45% of its initial level and delayed by 146 µs, is added, at 28R, to signal R-75 attenuated to 75% of its original level, but not delayed, to obtain a signal composite intermediate channel R1.

Les opérations 22 à 28 qui viennent d'être décrites sont effectuées dans l'étage 14a.The operations 22 to 28 which have just been described are carried out in the floor 14a.

Les opérations suivantes sont, pour les signaux L1 et R1, d'une part, en 30, une atténuation de 10% et, d'autre part, en 32, une atténuation de 70% suivie, en 34, d'un retard de 583 µs. Pour la fréquence d'échantillonnage, précédemment mentionnée, de 48 kHz, ce retard correspond à un décalage de 28 échantillons des signaux.The following operations are, for the signals L1 and R1, on the one hand, at 30, an attenuation of 10% and, on the other hand, in 32, an attenuation of 70% followed, in 34, a delay of 583 µs. For the sampling frequency, previously mentioned, 48 kHz, this delay corresponds to an offset of 28 signal samples.

Le signal R1-30d, ainsi atténué à 30% de son niveau initial et retardé de 583 µs, est alors additionné, en 36L, au signal L1-90 atténué à 90% de son niveau initial, mais non retardé, pour obtenir un signal composite Lc qui apparaít sur la sortie 16 et constitue le signal du canal gauche destiné à l'écoute par casque.The signal R1-30d, thus attenuated to 30% of its initial level and delayed by 583 µs, is then added, in 36L, to the L1-90 signal attenuated to 90% of its level initial, but not delayed, to obtain a composite signal Lc which appears on the output 16 and constitutes the signal of the left channel intended for listening by helmet.

En parallèle et de manière identique, le signal L1-30d, atténué à 30% de son niveau initial et retardé de 583 µs, est additionné, en 36R, au signal R1-90 atténué à 90% de son niveau initial, mais non retardé, pour obtenir un signal composite Rc qui apparaít sur la sortie 20 et constitue le signal du canal droit destiné à l'écoute par casque.In parallel and in an identical manner, the signal L1-30d, attenuated to 30% of its initial and delayed level of 583 µs, is added, in 36R, to signal R1-90 attenuated to 90% of its original level, but not delayed, to obtain a signal composite Rc which appears on the output 20 and constitutes the signal of the right channel intended for headphone listening.

Les opérations 30 à 36 sont effectuées dans l'étage 14b. Operations 30 to 36 are carried out in stage 14b.

Il apparaít ainsi que le circuit selon l'invention procède à deux traitements successifs des signaux, soit la transformation des signaux de départ L et R en signaux L1 et R1 (étage 14a), puis la transformation de ces derniers en signaux Lc et Rc (étage 14b). Dans la suite de la description, ces deux traitements seront désignés respectivement azimutage et externalisation.It thus appears that the circuit according to the invention performs two treatments successive signals, i.e. the transformation of the starting signals L and R into signals L1 and R1 (stage 14a), then the transformation of these into Lc and Rc signals (stage 14b). In the following description, these two treatments will be designated respectively azimuth and outsourcing.

On se référera maintenant aux figures 2 et 3 qui montrent respectivement l'effet de l'azimutage et celui de l'externalisation. Ces figures représentent la tête 40 d'un porteur de casque dont les écouteurs de gauche et de droite sont désignés par les références 42L et 42R.We will now refer to Figures 2 and 3 which respectively show the effect of azimuth and that of outsourcing. These figures represent the head 40 of a helmet wearer whose headphones on the left and right are designated by the references 42L and 42R.

On rappellera qu'au terme du traitement d'azimutage (étage 14a):

  • le signal L1 résulte de l'addition du signal L atténué de 25% au signal R atténué de 55% et retardé de 146 µs;
  • le signal R1 résulte de l'addition du signal R atténué de 25% au signal L atténué de 55% et retardé de 146 µs.
It will be recalled that at the end of the azimuth treatment (stage 14a):
  • signal L1 results from the addition of signal L attenuated by 25% to signal R attenuated by 55% and delayed by 146 µs;
  • signal R1 results from the addition of signal R attenuated by 25% to signal L attenuated by 55% and delayed by 146 µs.

Le traitement d'azimutage des signaux L et R a pour résultat, comme le montre la figure 2, de substituer, aux deux sources sonores physiques que constituent les écouteurs 42L et 42R, deux sources sonores virtuelles 44L et 44R positionnées devant les yeux du porteur du casque, aux sommets de la base d'un triangle équilatéral dont le côté opposé est sensiblement situé entre les deux oreilles.The azimuth processing of the L and R signals results, like the shows figure 2, to substitute, for the two physical sound sources that constitute the 42L and 42R headphones, two virtual sound sources 44L and 44R positioned in front of the helmet wearer's eyes, at the tops of the base of an equilateral triangle whose opposite side is substantially located between both ears.

Ainsi, l'image stéréophonique perçue par l'auditeur se développe sur 60°, ce qui correspond aux conditions, généralement admises comme les plus confortables, d'une écoute par enceintes.Thus, the stereophonic image perceived by the listener develops over 60 °, which which corresponds to the conditions, generally accepted as the most comfortable, listening through speakers.

Toutefois, comme il apparaít sur la figure 2, les sources virtuelles 44L et 44R restent encore très proche du front du porteur du casque, ce qui ne lui apporte pas un confort d'écoute optimal.However, as it appears in Figure 2, the virtual sources 44L and 44R still remain very close to the helmet wearer's forehead, which does not not optimal listening comfort.

Le traitement d'externalisation des signaux L1 et R1, qui viennent de subir le traitement d'azimutage, a justement pour but de corriger cet effet.The outsourcing processing of the L1 and R1 signals, which have just undergone the azimuth treatment, precisely aims to correct this effect.

On rappellera ici qu'au terme du traitement d'externalisation:

  • le signal Lc résulte de l'addition du signal L1 atténué de 10% au signal R1 atténué de 70% et retardé de 583 µs;
  • le signal Rc résulte de l'addition du signal R1 atténué de 10% au signal L1 atténué de 70% et retardé de 583 µs.
It will be recalled here that at the end of the outsourcing processing:
  • signal Lc results from the addition of signal L1 attenuated by 10% to signal R1 attenuated by 70% and delayed by 583 µs;
  • the signal Rc results from the addition of the signal R1 attenuated by 10% to the signal L1 attenuated by 70% and delayed by 583 µs.

Le traitement d'externalisation des signaux L1 et R1 a pour résultat, comme le montre la figure 3, d'éloigner les deux sources sonores virtuelles 44L et 44R du front de l'auditeur et de les remplacer par des sources 46L et 46R.The outsourcing processing of the L1 and R1 signals results, like the shows figure 3, to move away the two virtual sound sources 44L and 44R from the listener's front and replace them with sources 46L and 46R.

De nombreux essais ont montré que le décalage de 583 µs imposé aux signaux L1 et D1 correspond à des conditions d'écoute optimale en positionnant les sources virtuelles 46L et 46R à une distance du sommet du triangle équilatéral trois fois supérieure environ à celle qu'elles occupaient. Selon les sensibilités des auditeurs, un effet identique peut être obtenu avec un décalage grossièrement compris entre 500 et 700 µs, qui offre donc la plus grande externalisation possible avec le plus grand nombre d'enregistrements.Numerous tests have shown that the offset of 583 µs imposed on signals L1 and D1 correspond to optimal listening conditions in positioning the virtual sources 46L and 46R at a distance from the top of the equilateral triangle about three times larger than the one they occupied. According to the sensitivities of the listeners, an identical effect can be obtained with an offset roughly between 500 and 700 µs, which therefore offers the most large outsourcing possible with the largest number of records.

Pour ce qui concerne le décalage imposé aux signaux L et D lors du traitement d'azimutage, étant donné que l'externalisation donne la sensation d'élargir d'environ trois fois la base stéréo, il a paru logique d'adopter un déphasage produisant un angle environ trois fois plus petit que lorsqu'il n'y a pas d'externalisation. Les essais effectués ont montré que la valeur de 146 µs permet, compte tenu de l'externalisation, de fournir une image stéréo sur environ 60° avec le plus grand nombre d'enregistrements. Bien entendu, selon les sensibilités des auditeurs, un effet identique peut être obtenu avec un décalage grossièrement compris entre 100 et 200 µs.Regarding the offset imposed on the L and D signals during the azimuth treatment, since outsourcing gives the sensation to expand the stereo base by about three times, it seemed logical to adopt a phase shift producing an angle approximately three times smaller than when there is no outsourcing. The tests carried out have shown that the value of 146 µs allows, given the outsourcing, to provide a stereo image on approximately 60 ° with the greatest number of records. Of course, according to the sensibilities of the listeners, an identical effect can be obtained with an offset roughly between 100 and 200 µs.

Ainsi, grâce aux traitements successifs d'azimutage et d'externalisation, les sources sonores ne sont plus simplement dans les oreilles du porteur du casque, dont elles traversent alors la tête sans parvenir à générer l'image stéréophonique désirée, mais elles se trouvent déplacées devant lui, à une distance et sous un angle qui lui apportent des conditions d'écoute stéréophonique satisfaisante. Thus, thanks to the successive azimuth and outsourcing treatments, the sound sources are no longer simply in the ears of the wearer of the helmet, of which they then cross the head without succeeding in generating the image desired stereo, but they are moved in front of him, at a distance distance and at an angle that provide listening conditions satisfactory stereophonic.

La présente description a été faite en se référant à des atténuations des signaux qui, dans le cas d'une audition stéréophonique, permettent de préserver un certain équilibre à la sortie. Il va de soi que ces valeurs ont été données seulement à titre d'exemple et qu'elles peuvent être modifiées par l'auditeur selon sa sensibilité. Il en est de même pour les valeurs de décalage des signaux qui déterminent l'angle optimum des émissions sonores des deux sources virtuelles. Une modification de ces valeurs par le porteur du casque lui permet de créer les conditions d'écoute qui lui conviennent le mieux.The present description has been made with reference to attenuations of the signals which, in the case of stereophonic hearing, make it possible to maintain a certain balance at the exit. It goes without saying that these values were given only by way of example and that they can be modified by the auditor according to his sensitivity. The same is true for offset values signals which determine the optimum angle of the noise emissions of the two virtual sources. Modification of these values by the helmet wearer allows him to create the listening conditions that suit him best.

Comme déjà mentionné, l'invention ne se limite pas à l'adaptation, pour l'écoute au casque, des signaux délivrés par un système stéréophonique (un signal de canal gauche et un signal de canal droit). Elle est aussi utilisable pour traiter les signaux des différents canaux d'un système multi-canal. Dans ce cas, il suffit simplement, après avoir choisi les canaux qui iront sur l'oreille de gauche et ceux qui iront sur l'oreille de droite, d'effectuer, dans l'étage 16a:

  • l'addition, aux signaux destinés à l'oreille gauche, des signaux destinés à l'oreille droite retardés, et
  • l'addition, aux signaux destinés à l'oreille droite, des signaux destinés à l'oreille gauche retardés.
As already mentioned, the invention is not limited to adapting, for listening to the headphones, the signals delivered by a stereophonic system (a left channel signal and a right channel signal). It can also be used to process the signals of the different channels of a multi-channel system. In this case, it suffices simply, after having chosen the channels which will go on the left ear and those which will go on the right ear, to carry out, in the stage 16a:
  • adding delayed ear signals to the signals intended for the left ear, and
  • adding delayed ear signals to the right ear signals.

On notera, pour terminer, que l'invention s'applique, de manière générale, à toute audition au casque, qu'il s'agisse, notamment, de l'écoute de musique ou de mieux dissocier, dans un cockpit d'avion, les différentes sources de messages. L'invention peut aussi trouver une application intéressante dans le domaine de l'orthophonie en permettant une personnalisation de l'amplification des signaux sonores afin de compenser certaines déficiences auditives.Finally, it should be noted that the invention applies, in general, to any hearing with the headphones, that it is, in particular, listening to music or to better separate, in an airplane cockpit, the different sources of messages. The invention can also find an interesting application in the speech therapy field by allowing customization of amplification of sound signals to compensate for certain deficiencies hearing.

Claims (9)

Procédé d'adaptation des signaux des différents canaux (L, R) délivrés par un système de reproduction audio (10) aux conditions spécifiques de leur écoute au casque, caractérisé en ce qu'il consiste: à additionner à au moins un signal destiné au canal gauche (L) au moins un signal destiné au canal droit (R) retardé d'une première durée pour obtenir un signal de canal gauche intermédiaire (L1), et audit signal destiné au canal droit (R) ledit signal destiné au canal gauche (L) retardé de la même durée pour obtenir un signal de canal droit intermédiaire (R1); puis à additionner au signal de canal gauche intermédiaire (L1) le signal de canal droit intermédiaire (R1) retardé d'une deuxième durée, pour obtenir un signal de canal gauche adapté au casque (Lc), et au signal de canal droit intermédiaire (R1) le signal de canal gauche intermédiaire (L1) retardé de la même durée, pour obtenir un signal de canal droit adapté au casque (Rc). Method for adapting the signals of the different channels (L, R) delivered by an audio reproduction system (10) to the specific conditions of listening to them with headphones, characterized in that it consists: adding to at least one signal intended for the left channel (L) at least one signal intended for the right channel (R) delayed by a first duration to obtain an intermediate left channel signal (L1), and to said signal intended for the right channel (R) said signal for the left channel (L) delayed by the same time to obtain an intermediate right channel signal (R1); then adding to the intermediate left channel signal (L1) the intermediate right channel signal (R1) delayed by a second duration, to obtain a left channel signal suitable for headphones (Lc), and to the intermediate right channel signal (R1 ) the intermediate left channel signal (L1) delayed by the same duration, to obtain a right channel signal suitable for headphones (Rc). Procédé selon la revendication 1, caractérisé en ce que, dans le cas d'un système de reproduction stéréophonique délivrant un signal de canal gauche (L) et un signal de canal droit (R), le premier retard est compris entre 100 et 200 µs, et le deuxième retard entre 500 et 700 µs.Method according to Claim 1, characterized in that , in the case of a stereophonic reproduction system delivering a left channel signal (L) and a right channel signal (R), the first delay is between 100 and 200 µs , and the second delay between 500 and 700 µs. Procédé selon la revendication 1, caractérisé en ce que ledit signal retardé destiné au canal gauche et ledit signal retardé destiné au canal droit sont préalablement filtrés d'une manière qui privilégie les fréquences basses au dépens des hautes.Method according to claim 1, characterized in that said delayed signal intended for the left channel and said delayed signal intended for the right channel are previously filtered in a manner which favors low frequencies at the expense of high ones. Procédé selon la revendication 3, caractérisé en ce que l'action de filtrage est nulle à 0 Hz et totale à 24 kHz.Method according to claim 3, characterized in that the filtering action is zero at 0 Hz and total at 24 kHz. Procédé selon la revendication 1, caractérisé en ce que: ledit signal destiné au canal gauche et ledit signal destiné au canal droit subissent préalablement une première atténuation; et ledit signal retardé destiné au canal gauche et ledit signal retardé destiné au canal droit subissent préalablement une deuxième atténuation. Method according to claim 1, characterized in that : said signal intended for the left channel and said signal intended for the right channel undergo a first attenuation beforehand; and said delayed signal intended for the left channel and said delayed signal intended for the right channel undergo a second attenuation beforehand. Procédé selon la revendication 5, caractérisé en ce que, dans le cas d'un système de reproduction stéréophonique, la première atténuation est comprise entre 20 et 30%, et la deuxième atténuation entre 50 et 60%.Method according to claim 5, characterized in that , in the case of a stereophonic reproduction system, the first attenuation is between 20 and 30%, and the second attenuation between 50 and 60%. Procédé selon la revendication 1, caractérisé en ce que: le signal de canal gauche intermédiaire et le signal de canal droit intermédiaire subissent préalablement une première atténuation; et le signal de canal gauche intermédiaire retardé et le signal de canal droit intermédiaire retardé subissent préalablement une deuxième atténuation. Method according to claim 1, characterized in that : the intermediate left channel signal and the intermediate right channel signal are first attenuated; and the delayed intermediate left channel signal and the delayed intermediate right channel signal undergo a second attenuation beforehand. Procédé selon la revendication 7, caractérisé en ce que, dans le cas d'un système de reproduction stéréophonique, la première atténuation est comprise entre 5 et 15%, et la deuxième atténuation entre 65 et 75%.Method according to claim 7, characterized in that , in the case of a stereophonic reproduction system, the first attenuation is between 5 and 15%, and the second attenuation between 65 and 75%. Circuit pour la mise en oeuvre du procédé selon l'une des revendications 1 à 8, caractérisé en ce qu'il comporte: des premiers moyens (14a) pour produire un signal intermédiaire de canal gauche (L1) résultant de l'addition d'au moins un signal destiné au canal gauche (L) à au moins un signal destiné au canal droit (R) retardé d'une première durée, et un signal intermédiaire de canal droit (R1) résultant de l'addition dudit signal destiné au canal droit (R) audit signal destiné au canal gauche (L) retardé de la même durée, et des deuxièmes moyens (14b) pour produire un signal de canal gauche adapté au casque (Lc) résultant de l'addition du signal intermédiaire de canal gauche (L1) au signal intermédiaire de canal droit (R1) retardé d'une deuxième durée, et un signal de canal droit adapté au casque (Rc) résultant de l'addition du signal intermédiaire de canal droit (R1) au signal intermédiaire de canal gauche (L1) retardé de la même durée. Circuit for implementing the method according to one of Claims 1 to 8, characterized in that it comprises: first means (14a) for producing an intermediate left channel signal (L1) resulting from the addition of at least one signal for the left channel (L) to at least one signal for the right channel (R) delayed by a first duration, and an intermediate right channel signal (R1) resulting from the addition of said signal intended for the right channel (R) to said signal intended for the left channel (L) delayed by the same duration, and second means (14b) for producing a left channel signal suitable for headphones (Lc) resulting from the addition of the intermediate left channel signal (L1) to the intermediate right channel signal (R1) delayed by a second duration, and a right channel signal adapted to the helmet (Rc) resulting from the addition of the intermediate right channel signal (R1) to the intermediate left channel signal (L1) delayed by the same duration.
EP01810373A 2001-04-17 2001-04-17 Method and circuit for headphone listening of audio recording Withdrawn EP1251717A1 (en)

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EP01810373A EP1251717A1 (en) 2001-04-17 2001-04-17 Method and circuit for headphone listening of audio recording
US10/475,194 US7254238B2 (en) 2001-04-17 2002-04-05 Method and circuit for headset listening of an audio recording
EP02708120A EP1380188A1 (en) 2001-04-17 2002-04-05 Method and circuit for headset listening of an audio recording
PCT/CH2002/000192 WO2002085067A1 (en) 2001-04-17 2002-04-05 Method and circuit for headset listening of an audio recording
JP2002582660A JP2004527961A (en) 2001-04-17 2002-04-05 Method and circuit for listening to sound recording media with a headset

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