Acoustic system for a car seat with headrest

Abstract

An acoustic system for a seat with a headrest in a motor vehicle comprises: a U-shaped shell (15) shaped to surround the headrest of the seat in a substantially horizontal plane; loudspeakers (21, 23), referred to as tweeters, adapted to generate and control sound in the frequency range of 900–20,000 Hz; and positioned at the apex of the arms of the U such that, when the system is in position on the seat, they are directed substantially forward, toward the ears of a passenger seated in the seat; and loudspeakers (22, 24, 25, 27, 29, 31), referred to as midrange loudspeakers, adapted to generate and control sound in the frequency range of 80–2,000 Hz and distributed around the outer perimeter of the shell. A plural acoustic system and a motor vehicle comprising the system are also described. Figure to be published with the abbreviation: Fig 7

Description

Title of the invention: Acoustic system for a seat with headrest in a motor vehicle technical field

[0001] The present invention relates to an acoustic system for a seat with headrest of a motor vehicle. State of the art

[0002] Many companies and researchers are interested in personalized listening zones (in English “Personal Sound Zone [PSZ]”) to offer specific sound spaces to each listener for different applications (transport, home audio, etc.).

[0003] The minimum requirement of a PSZ system is to be able to reproduce a specific acoustic field over a so-called bright zone (BZ) while minimizing the sound level in a different zone called a dark zone (DZ) without using headphones or insulating panels.

[0004] According to perceptual studies, a listener experiences a "sound bubble" effect if the difference in sound level between the two zones is at least 30 dB. This difference in level can be achieved for frequencies below 1 kHz using a device of a few loudspeakers equipped with suitable filters and installed in headrests.

[0005] Otherwise, to reproduce high frequency signals (>1 kHz), a tweeter type speaker is usually used which can be associated with a mid-range type speaker to be able to go down to 1 kHz (and even below).

[0006] Today, to favor one listening zone over another in a vehicle's interior, the aim is to place the loudspeaker(s) closer to the listeners in order to minimize the emitted sound level and take maximum advantage of the natural attenuation of sound as it propagates through the air. Consequently, numerous patents exist describing different arrangements / integrations of loudspeakers within a headrest.

[0007] There are also active noise control systems that allow a "counter-noise" to be sent, which reduces the perceived annoyance.

[0008] However, conventional headrest speaker solutions do not achieve this level of "isolation": only 15 to 20 dB is attainable across the entire audible spectrum (20 Hz–20 kHz). This is primarily due to the presence of reflective and diffracting surfaces. Furthermore, these solutions are not very robust and perform poorly at high frequencies in complex acoustic environments.

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[0013] As for active noise control techniques, they are more suited to frequencies <1 kHz, because beyond that, the wavelength being "small", sources need to be close to the ears and it is very difficult at frequencies >1 kHz to control a wide area; only spot checks could be considered which does not meet the need and does not allow to generate a "bubble". Therefore, there is a real need for an acoustic system for a car seat with a headrest that resolves all or part of the aforementioned drawbacks. Description of the invention To resolve one or more of the aforementioned drawbacks, according to a first embodiment, an acoustic system for a seat with a headrest in a motor vehicle comprises: • a U-shaped shell shaped to be able to surround the headrest of the seat in a substantially horizontal plane; • loudspeakers, known as tweeters, adapted to generate and control sound in the 900–20,000 Hz frequency band; and positioned at the top of the U-shaped arms so that, when the system is in the seat position, they are directed substantially forward and toward the ears of a passenger seated in the seat; and • speakers, known as midrange speakers, adapted to generate and control sound in the 80 - 2000 Hz frequency band and distributed around the outer perimeter of the shell. Thus, it is possible to create a sound bubble around the head of the seat occupant. Specific characteristics or embodiments, usable alone or in combination, are: • the shell has an inclined plane on the bottom of the U such that, when the system is in position on the seat, the plane is oriented towards the rear and upwards, said plane including at least one midrange speaker; • at least one midrange speaker is fixed to the outside of one arm of the U-shaped shell; • the midrange speaker fixed to the outside of a branch is angled forwards; • a midrange speaker is installed in the tips of the U's arms, next to the tweeters; • The tips of the arms of the U-shaped shell include a speaker grille; and / or • the shell includes, inside the U, an area for attaching the system to the headrest.

[0014] In a second embodiment, a plural acoustic system for a row of seats comprises as many acoustic systems as above as there are seats in the row, the shells of said systems being joined together by at least one connecting piece.

[0015] In a particular embodiment, for a row of 3 seats, the plural acoustic system is such that the system associated with the middle seat is such that at least one midrange speaker is fixed on one arm of the U and is oriented towards the front.

[0016] In a third embodiment, a motor vehicle includes a system according to the first or second embodiment. Brief description of the figures

[0017] The invention will be better understood upon reading the following description, given solely by way of example, and with reference to the figures in the appendix in which: • [Fig.1] represents a front view of a row of seats comprising acoustic systems according to one embodiment; • [Fig.2] represents a top view of the row of seats in [Fig.1]; • [Fig. 3] represents a three-quarter rear perspective view of the row of seats of the [Fig.1]; • [Fig. 4] represents a three-quarter front perspective view of a system acoustics of the [Fig.l]; • [Fig.5] represents a three-quarter rear perspective view of an acoustic system of the [Fig.1]; • [Fig.6] represents a front view of an acoustic system from [Fig.1]; • [Fig. 7] represents a three-quarter front perspective view of the system acoustics of [Fig. 4] without the protective grilles; and • [Fig.8] represents a top view of a row of seats including acoustic systems according to another embodiment. Methods of implementation

[0018] The embodiments presented below refer to a motor vehicle, a car. However, those skilled in the art understand that they are also applicable to other types of vehicles such as vans, trucks, etc., and more generally any transport vehicle.

[0019] The terms "front", "rear", "top", "bottom", "transverse" are understood in relation to the vehicle and therefore, for equipment, in its intended position in the vehicle.

[0020] Figures 1, 2 and 3 represent two seats 1, 3 of a rear row of a motor vehicle (not shown). Each seat includes a headrest 5, 7.

[0021] According to a classic configuration, a rear board 9, also called a rear shelf, is fixed to the back of seats 1, 3, and delimits the top of the trunk.

[0022] Around each headrest is positioned an acoustic system 11, 13.

[0023] Figures 4, 5, 6 and 7 represent one of the acoustic systems 11, 13, for example system 11.

[0024] It comprises a U-shaped shell 15 in a substantially horizontal plane to surround the headrest 5.

[0025] The tops of the U's branches are closed by substantially vertical grilles 17, 19 which protect loudspeakers 21, 22, 23, 24.

[0026] The loudspeakers 21, 23, referred to as tweeters, are adapted to generate and control sound in the frequency range of 900–20,000 Hz. Due to their positioning, when the system is installed on the seat, they are directed substantially forward and toward the ears of a passenger seated in the seat. These small loudspeakers are arranged in a matrix to allow, through appropriate signal processing, the creation of an acoustic beam directed precisely toward the passenger's ears.

[0027] Speakers 22, 24, as well as speakers 25, 27, 29, 31, 33, are referred to as midrange speakers because they are suitable for generating and controlling sound in the frequency range of 80–2000 Hz. Speakers 25, 27, 29, 31, 33 are distributed around the outer perimeter of the housing 15.

[0028] In particular, the loudspeakers 27, 29, 31 are fixed on an inclined plane 35 formed in the bottom of the U of the shell 15, this inclined plane being oriented towards the rear and upwards.

[0029] The speakers 25, 33 are fixed on the outside of each arm of the U of the shell 15 and they are slightly oriented forwards.

[0030] Furthermore, the shell 15 includes, within the U-shape, an attachment zone 37 for the system to the headrest 5. The attachment zone has a substantially flat shape with at least one hole 39 adapted to allow the passage of a sliding rod for the headrest 5 and thus to modify the height of the headrest 5 without changing the position of the acoustic system. The shell 15 also includes a zone 41 adapted for fixing the system to the top of the seat back.

[0031] The operation of systems 11, 13 is as follows.

[0032] As an acoustic system, the shell is multi-compartmentalized to serve as an enclosure for the different loudspeakers. Each loudspeaker has its own compartment to prevent acoustic interactions between loudspeakers via the shell.

[0033] The arrangement of the midrange speakers 22, 24, 25, 27, 29, 31, 33 is such that it allows both the production of a direct field towards the occupant's ears and the processing of waves re-emitted by the various reflective surfaces (from an acoustic point of view) of a car interior. Hence their distribution all around the occupant's head. It should be noted that it is desirable to have at least 1 speaker on the rear panel to process the waves reflected by the rear window.

[0034] For the tweeters, the wavelengths being shorter, the sound is more directional and the absorption of the passenger compartment is greater, so the speakers are oriented towards the ears of the occupant.

[0035] The selection of frequency ranges for the speakers, particularly for the midrange speakers, allows for the use of smaller speakers. This advantageously facilitates integration into the seats without modification and keeps the acoustic system compact around the headrest. It also allows the speakers to be positioned in the near field, which promotes natural contrast due to the proximity of the sound sources in the bright area and strong geometric attenuation in the dark area.

[0036] The invention has been illustrated and described in detail in the drawings and the preceding description. This description is to be considered illustrative and given by way of example and not as limiting the invention to this single description. Numerous embodiments are possible.

[0037] For a row of 3 seats, [Fig. 8], it is thus possible to have a single-piece, multi-seat acoustic system by joining the acoustic systems of each seat with one or more connecting pieces. For example, the shells can be integrated into a single mold. For the middle seat 81, the midrange side speakers 83, 85 (corresponding to reference numerals 25, 33 in the embodiment described above) are positioned so as to be oriented forwards.

[0038] It is also possible to have an embodiment in which the headrest and the acoustic system are joined.

Claims

Demands

1. Acoustic system (11, 13) for a motor vehicle seat (1, 3) with a headrest (5, 7) comprising: • a U-shaped shell (15) shaped to surround the headrest of the seat in a substantially horizontal plane; • loudspeakers (21, 23), referred to as tweeters, adapted to generate and control sound in the frequency band 900 - 20,000 Hz; and positioned at the top of the arms of the U such that, when the system is in position on the seat, they are directed substantially forward and towards the ears of a passenger seated in the seat; and • speakers (22, 24, 25, 27, 29, 31, 33), known as midrange speakers, adapted to generate and control sound in the 80 - 2000 Hz frequency band and distributed around the outer perimeter of the shell.

2. System according to claim 1, wherein the shell has an inclined plane (35) on the bottom of the U such that, when the system is in position on the seat, the plane is oriented towards the rear and upwards, said plane comprising at least one midrange speaker (27, 29, 31).

3. System according to claim 1 or 2, wherein at least one midrange speaker (25, 33) is fixed to the outside of one arm of the U of the shell.

4. System according to claim 3, wherein the midrange speaker fixed to the outside of a branch is inclined forward.

5. System according to claim 1, 2, 3 or 4, wherein a midrange speaker (22, 24) is installed in the tips of the U arms, next to the tweeters (21, 23).

6. System according to any one of the preceding claims, wherein the apexes of the arms of the U of the shell comprise a protective grille (17, 19) for the loudspeakers.

7. System according to any one of the preceding claims, wherein the shell includes, inside the U, an attachment zone (37) of the system to the headrest.

8. Plural acoustic system for a row of seats comprising as many acoustic systems according to any one of claims 1 to 7 as there are seats in the row, the shells of said systems being joined together by at least one connecting piece.

9. Plural acoustic system according to claim 8 for a row of 3 seats, and such that the system associated with the middle seat is such that at least one midrange speaker is fixed on one arm of the U and is oriented forwards.

10. Motor vehicle comprising an acoustic system according to any one of the preceding claims.

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