Apparatus and method for driving loudspeakers of a sound system in a vehicle

Abstract

An apparatus and a method for driving loudspeakers of a sound system in a vehicle, the system having at least two loudspeakers of a basic system, and a plurality of loudspeakers of a focus system wherein each of the loudspeakers has a position in an environment. The apparatus includes a basic channel provider for providing basic system audio channels for driving the loudspeakers of the basic system and a focused source renderer for providing focus system audio channels to drive the loudspeakers of the focus system. The focused source renderer is configured to calculate a plurality of filter values for the loudspeakers of the focus system based on the positions of the loudspeakers of the focus system and based on a position of a focus point.

Claims

1. An apparatus for driving loudspeakers of a sound system in a vehicle, the sound system comprising at least two loudspeakers of a basic system, and a plurality of loudspeakers of a focus system, wherein each of the loudspeakers of the basic system and of the focus system has a position in an environment, and wherein the apparatus comprises: a basic channel provider for providing basic system audio channels (BSAC) for driving the loudspeakers of the basic system, a focused source renderer for providing focus system audio channels (FSAC) to drive the loudspeakers of the focus system, wherein the focused source renderer is configured to calculate a plurality of filter values for the loudspeakers of the focus system based on the positions of the loudspeakers of the focus system and based on a position of a focus point, wherein the focused source renderer is configured to generate at least three focus group audio channels (FGAC, FGAC-1 to FGAC-3) for at least some of the loudspeakers of the focus system based on the plurality of filter values and based on a focus audio base signal (FABS, FABS-1) to provide the focus system audio channels (FSAC), so that an audio output produced by the loudspeakers of the focus system, when being driven by the focus system audio channels (FSAC), allows for localizing the position of the focus point by a listener in the environment; wherein the focus audio base signal (FABS) only comprises first frequency portions of an audio effect signal (AES), wherein the first frequency portions only have frequencies which are higher than a first predetermined frequency value, and wherein at least some of the first frequency portions have frequencies which are higher than a second predetermined frequency value, wherein the second predetermined frequency value is higher than or equal to the first predetermined frequency value, wherein the focused source renderer is configured to generate the at least three focus group audio channels (FGAC, FGAC-1 to FGAC-3) based on the focus audio base signal (FABS, FABS-1) such that the focus group audio channels (FGAC, FGAC-1 to FGAC-3) only have frequencies which are higher than a predetermined frequency value, and wherein the basic channel provider is configured to generate the basic system audio channels (BSAC) based on a secondary effect signal (SES), wherein the secondary effect signal (SES) only comprises second frequency portions of the audio effect signal (AES), wherein the second frequency portions only have frequencies which are lower than or equal to the second predetermined frequency value, and wherein at least some of the second frequency portions have frequencies which are lower than or equal to the first predetermined frequency value.

2. The apparatus according to claim 1, wherein the basic system is a surround system comprising at least four loudspeakers, wherein the basic channel provider is a surround channel provider for providing surround system audio channels.

3. The apparatus according to claim 1, wherein the environment is a vehicle, wherein the focus point is positioned near an assumed and/or determined head position of a vehicle occupant in the vicinity of an upper end of a seat arranged in the vehicle.

4. The apparatus according to claim 3, wherein the sound bar is arranged inwardly in the edge of a roof of the vehicle or in a B-pillar of the vehicle.

5. The apparatus according to claim 3, wherein at least one directional microphone is directed to a seat so as to acquire speech of a vehicle occupant, wherein the acquired speech is comprised in the focus audio base signal (FABS) such that the speech acquired from one of the vehicle occupants is played back in at least one focus point near another one of the vehicle occupants.

6. The apparatus according to claim 5, wherein the directional microphone is adapted to be used for hands-free telephone communication.

7. The apparatus according to claim 6, wherein a plurality of directional microphones are arranged for acquiring speech from a plurality of vehicle occupants, wherein the focus system is controlled to position focus points near the assumed and/or determined head positions of the plurality of vehicle occupants.

8. The apparatus according to claim 3, wherein at least one head tracker unit is arranged for determining a head position of at least one of the vehicle occupants, wherein the apparatus is adapted to shift the focus point depending on the head position.

9. The apparatus according to claim 3, wherein audio signals generated by at least one of a driver assistance system, an entertainment system, a navigation system and a telephone are comprised in the focus audio base signal (FABS, FABS-1) such that the audio signals are played back in at least one focus point near at least one of the vehicle occupants.

10. The apparatus according to claim 9, wherein the audio signal is alternated between a plurality of focus points in case of a warning so as to raise the vehicle occupant's awareness.

11. The apparatus according to claim 1, wherein the filter values are delay values (.sub.11 . . . .sub.1n).

12. The apparatus according to claim 1, wherein the focus system comprises one or more sound bars, each of the sound bars comprising at least three loudspeakers.

13. The apparatus according to claim 12, wherein at least two sound bars are arranged and controlled so as to position a respective focus point near either side of an assumed and/or determined head position of at least one of the vehicle occupants for providing stereo sound.

14. The apparatus according to claim 1, wherein the basic channel provider is configured to generate the basic system audio channels (BSAC) based on the focus audio base signal (FABS) and based on panning information for blending the focus audio base signal (FABS, FABS-1) between the basic system and the focus system, and wherein the focused source renderer is configured to generate the at least three focus group audio channels (FGAC, FGAS-1 to FGAS-3) based on the focus audio base signal (FABS, FABS-1) and based on the panning information for blending the focus audio base signal (FABS, FABS-1) between the basic system and the focus system.

15. The apparatus according to claim 1, wherein the focus system is a Wave Field Synthesis system.

16. The apparatus according to claim 1, wherein the focus system employs Higher Order Ambisonics.

17. The apparatus according to claim 1, wherein the plurality of the delay values (.sub.11 . . . .sub.1n) is a plurality of time delay values, and wherein the focused source renderer is adapted to generate each of the focus system audio channels (FSAC) by time shifting the focus audio base signal (FABS, FABS-1) by one of the time delays of the plurality of time delays.

18. The apparatus according to claim 1, wherein the plurality of the delay values (.sub.11 . . . .sub.1n) is a plurality of phase values, and wherein the focused source renderer is adapted to generate each of the focus system audio channels (FSAC) by adding one of the phase values of the plurality of phase values to each phase value of a frequency-domain representation of the focus audio base signal (FABS, FABS-1).

19. A sound system in a vehicle, comprising: a basic system comprising at least two loudspeakers, a focus system comprising a plurality of loudspeakers, a first amplifier module, a second amplifier module, and an apparatus according to claim 1, wherein the first amplifier module is arranged to receive the basic system audio channels (BSAC) provided by the basic channel provider of the apparatus, and wherein the first amplifier module is configured to drive the loudspeakers of the basic system based on the basic system audio channels (BSAC), and wherein the second amplifier module is arranged to receive the focus system audio channels (FSAC) provided by the focused source renderer of the apparatus, and wherein the second amplifier module is configured to drive the loudspeakers of the focus system based on the focus system audio channels (FSAC).

20. A method for driving loudspeakers of a sound system in a vehicle, the sound system comprising at least two loudspeakers of a basic system, and a plurality of loudspeakers of a focus system, wherein each of the loudspeakers of the basic system and of the focus system has a position in an environment, in particular a vehicle, and wherein the method comprises: providing basic system audio channels (BSAC) to drive the loudspeakers of the basic system, providing focus system audio channels (FSAC) to drive the loudspeakers of the focus system, calculating a plurality of filter values for the loudspeakers of the focus system based on the positions of the loudspeakers of the focus system and based on a position of a focus point, and generating at least three focus group audio channels (FGAC, FGAC-1 to FGAC-3) for at least some of the loudspeakers of the focus system based on the plurality of filter values and based on a focus audio base signal (FABS, FABS-1) to provide the focus system audio channels (FSAC), so that an audio output produced by the loudspeakers of the focus system, when being driven by the focus system audio channels (FSAC), allows localizing the position of the focus point by a listener in the environment; wherein the focus audio base signal (FABS) only comprises first frequency portions of an audio effect signal (AES), wherein the first frequency portions only have frequencies which are higher than a first predetermined frequency value, and wherein at least some of the first frequency portions have frequencies which are higher than a second predetermined frequency value, wherein the second predetermined frequency value is higher than or equal to the first predetermined frequency value, wherein the focused source renderer is configured to generate the at least three focus group audio channels (FGAC, FGAC-1 to FGAC-3) based on the focus audio base signal (FABS, FABS-1) such that the focus group audio channels (FGAC, FGAC-1 to FGAC-3) only have frequencies which are higher than a predetermined frequency value, and wherein the basic channel provider is configured to generate the basic system audio channels (BSAC) based on a secondary effect signal (SES), wherein the secondary effect signal (SES) only comprises second frequency portions of the audio effect signal (AES), wherein the second frequency portions only have frequencies which are lower than or equal to the second predetermined frequency value, and wherein at least some of the second frequency portions have frequencies which are lower than or equal to the first predetermined frequency value.

Description

(1) The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

(2) FIG. 1 is a schematic view of a sound system,

(3) FIG. 2 is a schematic view of a focus system, and

(4) FIG. 3 is a schematic view of a vehicle with the sound system.

(5) Corresponding parts are marked with the same reference symbols in all figures.

(6) FIG. 1 is a schematic view of a sound system 1, comprising: a basic system 2 comprising at least two loudspeakers 2.1, a focus system 3 comprising a plurality of at least three loudspeakers 3.1, a first amplifier module 4, a second amplifier module 5, and an apparatus 6 for driving the loudspeakers 2.1, 3.1 of the sound system 1.

(7) In an alternative embodiment, the basic system 2 may comprise only one or two loudspeakers depending on the system design. In particular, a basic system designed as stereo sound system may comprise at least two loudspeakers, wherein a basic system designed as a surround system may comprise three, four, five or more loudspeakers. Further, a simple design of a basic system comprises only one loudspeaker.

(8) Each of the loudspeakers 2.1, 3.1 of the basic system 2 and of the focus system 3 has a position in an environment. The apparatus 6 comprises: a basic channel provider 6.1 for providing basic system audio channels BSAC for driving the loudspeakers 2.1 of the basic system 2, a focused source renderer 6.2 for providing focus system audio channels FSAC to drive the loudspeakers 3.1 of the focus system 3.

(9) The focused source renderer 6.2 is configured to calculate a plurality of filter values, e.g. delay values .sub.XX, .sub.11 . . . .sub.1n for the loudspeakers 3.1 of the focus system 3 based on the positions of the loudspeakers 3.1 of the focus system 3 and based on an intended position of a focus point 8 in the environment 7, as illustrated in FIGS. 2 and 3. The focused source renderer 6.2 is configured to generate at least three focus group audio channels FGAC for at least some of the loudspeakers 3.1 of the focus system 3 based on the plurality of delay values .sub.XX, .sub.11 . . . .sub.1n and based on a focus audio base signal FABS to provide the focus system audio channels FSAC, so that an audio output produced by the loudspeakers 3.1 of the focus system 3, when being driven by the focus system audio channels FSAC, allows for localizing the position of the focus point 8 by a listener 9 in the environment 7.

(10) In an exemplary embodiment the focused source renderer 6.2 is configured to calculate the plurality of delay values .sub.XX, .sub.11 . . . .sub.1n as a first group of delay values as follows:

(11) The position of the focus point 8 is determined as a first position of a first focus point. The focus audio base signal FABS of the basic system 2 is determined as a first focus audio base signal, wherein the focused source renderer 6.2 is configured to generate the at least three focus group audio channels FGAC-1 as a first group of focus group audio channels.

(12) Further, the focused source renderer 6.2 is configured to calculate a second group of delay values for the loudspeakers 3.1 of the focus system 3 based on the positions of the loudspeakers 3.1 of the focus system 3 and based on a second position of a second focus point 8, wherein the focused source renderer 6.2 is furthermore configured to generate a second group of at least three focus group audio channels FGAC-2 for at least some of the loudspeakers 3.1 of the focus system 3 based on the plurality of delay values of the second group of delay values and based on a second focus audio base signal FABS-1.

(13) Furthermore, the focused source renderer 6.2 is configured to generate a third group of at least three focus group audio channels FGAC-3 for at least some of the loudspeakers 3.1 of the focus system 3, wherein each of the focus group audio channels FGAC-3 of the third group of focus group audio channels FGAC-3 is a combination of one focus group audio channel of the first group of focus group audio channels FGAC-1 and one focus group audio channel of the second group of focus group audio channels FGAC-2.

(14) At last, the focused source renderer 6.2 is adapted to provide the focus group audio channels FGAC-3 of the third group of focus group audio channels FGAC-3 as the focus system audio channels FSAC to drive the loudspeakers 3.1 of the focus system 3.

(15) The basic system 2 may be a surround system comprising at least four loudspeakers 2.1, wherein the basic channel provider 6.1 is a surround channel provider for providing basic system audio channels BSAC being surround system audio channels.

(16) In an exemplary embodiment of the invention illustrated in FIG. 3 the environment 7 is a vehicle 10, in particular the interior of the vehicle 10. In this embodiment the focus point 8 is positioned near an assumed and/or determined head position of the listener 9 being a vehicle occupant in the vicinity of an upper end of a seat 11 arranged in the vehicle 10.

(17) In this embodiment the focus system 3 comprises one or more sound bars 3.2, each of the sound bars 3.2 comprising at least three loudspeakers 3.1 in a single enclosure. The sound bars 3.2 are arranged inwardly in the edge 12 of a roof of the vehicle 10. In an alternative embodiment the sound bars 3.2 may be arranged in a B-pillar 13 of the vehicle 10.

(18) Preferably the sound bars 3.2 are arranged laterally from the occupants 9 in the front seats 11. It may be advisable also to arrange sound bars 3.2 laterally from the occupants 9 in the back seats 11.

(19) A directional microphone 14 is directed to each seat 11 so as to acquire speech S of a vehicle occupant 9 sitting in the respective seat 11. The acquired speech S is comprised in the focus audio base signal FABS such that the speech S acquired from one of the vehicle occupants 9 is played back in at least one focus point 8 near another one of the vehicle occupants 9.

(20) The focused source renderer 6.2 may be fed with position data for the focus point 8 or focus points 8 by a control unit (not illustrated), e.g. a board computer of the vehicle 10. The different sound sources 14, 16, 17, 18, 19 may be assigned different focus points 8 and 8. A head tracker unit 15 may be arranged for determining a head position of the vehicle occupants 9. The head tracker unit 15 may feed the head position directly to the focussed source renderer 6.2 as in FIG. 1, so that the focus points 8 are determined by the focussed source renderer 6.2 depending on the head position. Likewise, the head tracker unit 15 may feed the head position to the control unit, e.g. the board computer (not illustrated) so that the focus points 8 are determined by this control unit and then forwarded to the focussed source renderer 6.2. The apparatus 6 is adapted to shift the focus point 8 depending on the head position acquired by the head tracker 15.

(21) In an exemplary embodiment the focus system 3 may be a Wave Field Synthesis system and/or employ Higher Order Ambisonics.

(22) In one embodiment the plurality of the delay values .sub.XX, .sub.11 . . . .sub.1n is a plurality of time delay values, and wherein the focused source renderer 6.2 is adapted to generate each of the focus group audio channels FGAC by time shifting the focus audio base signal FABS by one of the time delays of the plurality of time delays. The focus system audio channels FSAC sent to the focus system 3 are determined by combining, e.g. adding, the signals of the focus group audio channels FGAC, FGAC-1 to FGAC-3 corresponding to the same loudspeaker 3.1.

(23) In an alternative or additional embodiment the plurality of the delay values .sub.XX, .sub.11 . . . .sub.1n, is a plurality of phase values, and wherein the focused source renderer 6.2 is adapted to generate each of the focus group audio channels FGAC, FGAC-1 to FGAC-3 by adding one of the phase values of the plurality of phase values to each phase value of a frequency-domain representation of the focus audio base signal FABS.

(24) Audio signals generated by at least one of a driver assistance system 16, an entertainment system 17, a navigation system 18, and a telephone 19 are comprised in the focus audio base signal FABS such that the audio signals are played back in at least one focus point 8 near at least one of the vehicle occupants 9.

(25) In the embodiment illustrated in FIG. 3 two sound bars 3.2 of the focus system 3 as one part of the whole sound system 1 are shown. Furthermore, the loudspeakers 2.1 of the basic system 2 are shown as another part of the whole sound system 1. The two sound bars 3.2 are arranged and controlled so as to position a respective focus point 8 near either side of an assumed and/or determined head position of at least one of the vehicle occupants 9 for providing stereo sound. This may be used to play back stereo sound from the entertainment system 17 or for systematically positioning specific audio signals at one ear and other specific audio signals at the other ear of the vehicle occupant 9. The level of awareness of the occupant 9, in particular the driver may thus be raised.

(26) Due to the described combination of the basic system 2 and the focus system 3 according to the invention, in particular according to the embodiments of FIGS. 1 and 2 signal components may be played through both parts of the sound system 1, e.g. through the sound bars 3.2 as well as trough the loudspeakers 2.1. In particular, e.g. signals with lower frequencies may be played through the basic system 2 and signals with higher frequencies may be played through the focus system 3.

(27) Furthermore, the basic channel provider 6.1 is configured to generate the basic system audio channels BSAC based on the secondary effect signal SES and based on panning information for blending the focus audio base signal FABS, FABS-1 between the basic system 2 and the focus system 3, wherein the focus audio base signal FABS, FABS-1 includes a direction signal. On the other hand, the focused source renderer 6.2 is configured to generate the at least three focus group audio channels FGAC, FGAC-1 to FGAC-3 based on the focus audio base signal FABS, FABS-1 and based on the panning information for blending the focus audio base signal FABS, FABS-1 between the basic system 2 and the focus system 3.

(28) For the blending of the focus audio base signal FABS, FABS-1 between the basic system 2 and the focus system 3 panning factors are determined depending on the panning information according to a panning law.

(29) In an exemplary embodiment the audio signal is alternated between the focus points 8, 8 to the left and to the right of the head position in case of a warning so as to raise the occupant's 9 awareness for the warning.

(30) The directional microphone 14 may be adapted to be used for hands-free telephone communication.

(31) The focused source renderer 6.2 may use an algorithm to calculate filter coefficients for generating a plurality of loudspeaker signals which provide a sound field reproducing focused energy at at least one configurable point, e.g. the focus point 8 in the environment 7, e.g. in the vehicle 10. The filter defined by the coefficients is applied to the audio signal of an auditory event to create an output signal for one loudspeaker 3.1 of the sound bar 3.2. A separate filter for each loudspeaker 3.1 is generated and applied to the audio signal of the auditory event. The superposition of the loudspeaker signals will create a sound field in the environment 7, e.g. in the vehicle 10 so that the audio energy in that sound field will be higher at the point where the auditory event should be localized compared to the sound energy in the surrounding area of that spot. If the source is positioned closely to the listener 9, e.g. the occupant, he will get the impression as if the sound source really is positioned at that point.

(32) In a preferred embodiment of the invention, a WFS based algorithm for creating focused sources is used to calculate the filter coefficients. The inputs of the algorithm are: the audio signal to be positioned in the vehicle 10 (=focus audio base signal FABS), the number of loudspeakers 3.1 in the sound bar 3.2, the positions of these loudspeakers 3.1 in the environment 7, the position of the focus point 8 in relation to the listener, e.g. the occupant 9, and the position of the listener 9 relative to the sound bar 3.2.

(33) The signal to be reproduced at the focus point 8 is delayed by .sub.1X (.sub.11 . . . .sub.1n) for each loudspeaker 3.1 so that the total delay (.sub.1n+.sub.2n) including the time .sub.2x (.sub.21 . . . .sub.2n) corresponding to the distance from the loudspeaker 3.1 to the focus point 8 is the same for all loudspeakers 3.1. The same calculation is performed for the other focus point 8, wherein the delay .sub.2x (.sub.21 . . . .sub.2n) then corresponds to the distance from the loudspeaker 3.1 to the focus point 8.

(34) By adding the output signals of multiple audio renderers, the focused signals of several auditory events are reproduced using the same sound bar 3.2. This allows for using more than one focused auditory event to be placed near the listener 9 at a time. The game, film or other audio source might render as many events as processing power and bandwidth of the transmission channel to the renderers allows.

(35) Because of the nature of focused sound effects, a high number of loudspeakers 3.1 may be needed to create a strongly audible focus effect that is experienced very clearly by the listener 9. To integrate a sound bar 3.2 for the playback of focused sources into a vehicle scenario, the space needed for the sound bar 3.2 needs to be as small as possible to increase acceptance by possible customers of such an audio solution. Therefore, the loudspeaker drivers or amplifiers 5 need to be as small as possible to optimize the space needed. Since a small loudspeaker driver 5 usually is not able to reproduce low frequency components with sufficient sound pressure level, the sound bar 3.2 may need additional support from the basic system 2, e.g. a surround setup or a stereo system, for lower frequencies. An extension of the invention splits the signal of a focused auditory event into a high frequency and a low frequency component. The cross-over frequency between these components may differ depending on the size and quality of the used loudspeaker drivers 5 in the sound bar 3.2. The low frequency components are played through the basic system 2, e.g. a surround setup or stereo system, while the high frequency components are played as a focus effect through the focus system 3.

(36) The focus audio base signal FABS preferably only comprises first frequency portions of an audio effect signal AES, wherein the first frequency portions only have frequencies which are higher than a first predetermined frequency value, and wherein at least some of the first frequency portions have frequencies which are higher than a second predetermined frequency value. The second predetermined frequency value is higher than or equal to the first predetermined frequency value, wherein the focused source renderer 6.2 is configured to generate the at least three focus group audio channels FGAC based on the focus audio base signal FABS such that the focus group audio channels FGAC only have frequencies which are higher than a predetermined frequency value. The basic channel provider 6.1 is configured to generate the basic system audio channels BSAC based on a secondary effect signal SES, wherein the secondary effect signal SES only comprises second frequency portions of the audio effect signal AES, wherein the second frequency portions only have frequencies which are lower than or equal to the second predetermined frequency value, and wherein at least some of the second frequency portions have frequencies which are lower than or equal to the first predetermined frequency value. The secondary effect signal SES and at least parts of the focus audio base signal FABS may be obtained from the audio effect signal AES by a filter 20.

(37) FIG. 2 illustrates the basic idea of driving the loudspeakers 3.1 to create a focus effect. The basic idea for creating a focus effect is, that each of the delays .sub.11 . . . .sub.1n of a loudspeaker signal plus the time .sub.2x a sound wave, emitted by the loudspeaker 3.1, needs to reach the focus point 8 should be equal for all loudspeakers 3.1. This may be described by the equation:
.sub.11+.sub.21=.sub.12+.sub.22=.sub.13+.sub.23= . . . =.sub.1n+.sub.2n

(38) In this case, it is ensured that the greatest possible constructive superposition of all sound waves of all loudspeakers 3.1 happens in the focus point 8 for all frequency ranges.

LIST OF REFERENCES

(39) 1 sound system 2 basic system 2.1 loudspeaker of the basic system 3 focus system 3.1 loudspeaker of the focus system 3.2 sound bar 4 first amplifier module 5 second amplifier module 6 apparatus for driving loudspeakers 6.1 basic channel provider 6.2 focused source renderer 7 environment 8, 8 focus point 9 listener, e.g. vehicle occupant 10 vehicle 11 seat 12 edge of a roof 13 B-pillar 14 directional microphone 15 head tracker unit 16 driver assistance system 17 entertainment system 18 navigation system 19 telephone 20 filter AES audio effect signal BSAC basic system audio channels .sub.11 . . . .sub.2n delay values FABS, FABS-1 focus audio base signal FGAC, FGAC-1 to FGAC-3 focus group audio channels FSAC focus system audio channels S speech SES secondary effect signal