Patent Description:
Standard loudspeakers are integrated into the vehicle and are coupled with an entertainment system in order to output music, telephone conversations etc..

The integration of the loudspeakers is a challenge for designers and, furthermore, due to limited space assigned to loudspeakers, their minimum volume impedes generating sound waves with low frequencies.

Therefore, ideas have been created to couple trim panels to electro-mechanical exciters for generating sound. Those exciters are inducing vibrations to the trim part, i.e. the panel, which replaces a loudspeaker membrane. An example for such an acoustic system is presented by <CIT>.

<CIT> discloses a programmable digital sound reproduction system comprising a controller, a plurality of active loudspeaker chassis connected to the controller for communication purposes, and at least one sensor for capturing data in order to determine temperature and/or moisture in the environment of the loudspeaker chassis to actively correct the sound information.

<CIT> shows a loudspeaker that dynamically adjusts output of its audio signal, for thermal and power mitigation, wherein the loudspeaker comprises a transducer with a voice coil and a thermal sensor is provided which measures a temperature of the voice coil of the transducer.

<CIT> discloses an audio playback device with a first temperature sensing circuit that is connected to a sound coil of the audio playback device.

Contrary to acoustic systems permanently installed in buildings, acoustic systems of vehicles are confronted by high temperature changes and high humidity changes in the seasons of the year, which has an influence on the quality and performance of the acoustic system and the sound created by the system.

Therefore, it is an object of the present invention to create an acoustic system with improved sound quality.

This object is achieved by an acoustic system comprising a trim part an exciter coupled to the trim part for inducing vibrations to the trim part so that the trim part emits sound, in particular sound which can be heard by humans, a sensor measuring humidity, and a control unit coupled to the exciter and the sensor measuring humidity, the control unit being configured so as to determine control signals for the exciter depending on the measured humidity, wherein the sensor for measuring humidity are arranged so as to measure humidity of the trim part and/or the exciter. Thus, the sensor or sensors are preferably arranged at or in or immediately adjacent to the trim part and/or the exciter. This allows the humidity to be measured directly at the point of sound generation. An indirect measurement would, for example, use a sensor distanced from the trim part in order to deduct from the measured humidity of the interior of the vehicle the humidity of the trim part which could be done by using test results stored in a look-up table.

The acoustic system according to the invention is equipped with a tuning system allowing to tune the sound depending on the actual humidity. Humidity does influence the sound created by the trim part as both the trim part and the exciter are sensible to humidity. Their characteristics, in particular their mechanical properties like stiffness, are significantly changing depending on humidity. The control unit receives data from at least one sensor and tunes the control signals for the exciter depending on humidity so that the acoustic system is insensitive, or at least less sensitive than without the control unit, to the changing environment and compensates sound imperfections based on changes in humidity.

The trim part may be a plate-shaped panel part having a rigidity. The trim part mainly extends two-dimensionally and can be flat or curved and preferably has a thickness of at least <NUM>.

The exciter may dynamically bend or deform the trim part or may only move the whole trim part.

If the sensor or sensors are arranged distanced from the trim part and/or the exciter, it will, however, be possible to determine the temperature and/or humidity of the trim part and/or the exciter by measuring methods which allow to deduce or estimate the temperature and/or humidity of the trim part and/or the exciter based on the sensed temperature/humidity at a distance therefrom. The temperature may for example be determined by an infrared camera.

In order to obtain highest sound quality, the sensor measuring temperature and/or the sensor measuring humidity are/is preferably coupled to the trim part and/or the exciter to directly sense their temperature/humidity.

The acoustic system according to the present invention may comprise a memory unit for storage of temperature and/or humidity dependent processing parameters. These parameters may be achieved by calibration tests. In those calibration tests, set reference signals are sent to the exciter at reference conditions, i.e. at a reference temperature and a reference humidity. The sound emitted by the trim part is sensed to determine a reference sound result. In a next step, the temperature and/or humidity are/is changed, and the sound emitted is sensed. The control signal is tuned such that the generated, emitted sound is close to or the same as the previous reference sound. The tuning parameters elaborated by the calibration are finally stored in a memory or, alternatively, an algorithm reflecting the tuning is stored in the memory.

There are several ways to tune the control signals for the exciter.

The control unit may comprise a processing unit configured to process an audio input signal with processing parameters. Those processing parameters may be provided by the memory unit mentioned above. The processing unit can be a digital signal processor (DSP).

According to one further option of the present invention, an optional amplifier receiving an input signal from the processing unit provides an output control signal to the exciter which is different from the input signal.

One variant to tune the control signal comprises at least one digital phase and amplitude filter which is part of the control unit or defines the control unit and processes audio input signals to control signals for the exciter. Digital phase an amplitude filters are cost-effective devices for processing signals.

The control unit may include an audio input signal interface via which it receives audio signals from a head unit which can be the entertainment system of a vehicle.

The control system may be connected to a head unit to receive audio signals therefrom or may be part of the head unit.

The sensor measuring temperature and/or the sensor measuring humidity can be part of an exciter module comprising the exciter or can be arranged outside the exciter module. One example is to embed the sensor/sensors into the trim part in order to receive genuine data.

Further features and options of the present invention are presented in the following description together with the enclosed drawings. In the drawings,.

<FIG> shows a vehicle door having a side window <NUM> and a trim part <NUM> which is directly or indirectly attached to a metal frame <NUM> of the door. Trim part <NUM> defines the visible interior door panel or a part of the door panel and is a substantially plate-shaped part which can be made of plastics or composite material.

The visible side of the panel, that is the side facing the vehicle interior, may be covered by a decoration layer, for example a leather skin, a wood veneer, or a plastic film or coating.

An acoustic system <NUM> comprises trim part <NUM>, an electrically driven exciter <NUM> which is mechanically coupled to the rear side of the trim part either by being directly coupled to the trim part or by being indirectly coupled to the trim part via an intermediate mechanical bridge part.

Acoustic system <NUM> further comprises a control unit <NUM> which can be arranged outside the door, for example behind the instrument panel, and which is configured to determine and create control signals for exciter <NUM>.

A temperature sensor <NUM> and a humidity sensor <NUM> are arranged within or in contact with or adjacent to trim part <NUM> and, preferably, also close to exciter <NUM>. The sensors <NUM>, <NUM> are electrically coupled to control unit <NUM>.

<FIG> shows one embodiment of the acoustic system <NUM>.

Only to improve the overview, are sensors <NUM> and <NUM> depicted distanced from trim part <NUM>. In fact, both sensors <NUM>, <NUM> are arranged at, in or close to trim part <NUM> and/or exciter <NUM> as stated above. Furthermore, sensor <NUM> may be an infrared sensor so the sensor <NUM> can be arranged distanced from the trim part <NUM> which still allows to directly measure the temperature of the trim part <NUM>.

Control unit <NUM> may comprise a processing unit <NUM> in form of a digital signal processor which receives data from sensors <NUM>, <NUM>. Processing unit <NUM> may be electrically coupled to an exterior memory <NUM> or may have an embedded memory <NUM>.

Processing parameters for processing and tuning audio input signals to generate control signals for the exciter <NUM> depending on temperature and/or humidity, are stored in memory <NUM>.

Control unit <NUM> further comprises an audio input signal interface <NUM> receiving audio signals <NUM> from a head unit <NUM> which is also shown in <FIG>.

Head unit <NUM> may be the entertainment system or part of the entertainment system of the vehicle. Furthermore, interface <NUM> is able to receive clock data <NUM> allowing to synchronize signals and, at the end, sound emitted from trim part <NUM> with signals and sound emitted from other trim parts or conventional loudspeakers.

Processing unit <NUM> is electrically or optically coupled to an amplifier <NUM> being able to receive input control signals from processing unit <NUM> and to generate output control signals to exciter <NUM> to which amplifier <NUM> is directly connected.

Interface <NUM> may be connected to an outer unit for receiving software updates or, more general, information and software <NUM>. The connection to interface <NUM> can be achieved via cable or via air, i.e. wireless.

In the following, operation of the acoustic system <NUM> is explained.

Memory <NUM> contains processing parameters which are obtained during calibration of the system as explained above. Parameters may be stored in a lookup table in the memory. Alternatively or additionally, an arithmetic model could be stored in the memory <NUM> which allows tuning sound emitted by trim part <NUM> and to process signals.

Control unit <NUM> receives audio signals <NUM> from the head unit <NUM> via interface <NUM>. Those audio signals are transmitted to processing unit <NUM> which also receives data from sensors <NUM> and <NUM>. If the temperature and/or the humidity are different from temperature and/or humidity in the reference conditions for calibration, or if the temperature and/or the humidity values actually sensed are different from those reference values by a predefined, fixed amount, i.e. <NUM> or <NUM>% humidity, so that the acoustic sound emitted by trim part <NUM> would be significantly different from the sound delivered at reference conditions, processing unit <NUM> uses the parameters stored in memory <NUM> to trim and, thus, process the input signals received from interface <NUM> to control signals sent to amplifier <NUM>.

The control signals from processing unit <NUM> define an audio input signal for amplifier <NUM> which amends these signals in order to provide an audio output signal to exciter <NUM> which, finally, controls or leads to an actuation of exciter <NUM> and defines the control signal for exciter <NUM>.

Due to the coupling of exciter <NUM> to trim part <NUM>, vibrations are induced to trim part <NUM> so as to generate and emit sound which can be heard by humans.

The trim part <NUM> may be an interior panel, for example a door panel, an instrument panel or a ceiling panel or a part of such panel. An advantage of a vibrating trim part <NUM> that is only a part of a larger panel is that the acoustic behavior of the acoustic system can be better optimized or adapted to user preferences. The trim part <NUM> may be configured such that it can be removed and replaced easily.

The emitted sound usually is between <NUM> to <NUM><NUM>.

It is to be emphasized that all or some of the mentioned parts of control unit <NUM> can be embedded in one unit or can be separated and only connected by signal lines or wireless connections.

In the embodiment according to <FIG>, control unit <NUM> comprises numerous digital phase and amplitude filters <NUM>, <NUM>, <NUM> which do amend/process audio signals <NUM> received from the head unit depending on values for temperature and/or humidity received from sensors <NUM> and <NUM>. The control signals finally delivered by filters <NUM>, <NUM>, <NUM> are the control signals for exciter <NUM>.

A combination of the embodiments according to <FIG> and <FIG>, not shown in the figures, may comprise a memory <NUM> according to <FIG> which contains filters <NUM>, <NUM> and <NUM>. Thus, lookup tables etc. are not required in this embodiment and are replaced by filters.

<FIG> and <FIG> show embodiments in which audio signals are generated or emitted by head unit <NUM> which is distanced or separated from control unit <NUM>. However, it is possible to combine control unit <NUM> and head unit <NUM> or to embed control unit <NUM> into head unit <NUM> as shown in <FIG> and <FIG>.

The <FIG> embodiment is characterized by a head unit <NUM> which contains memory <NUM>, processing unit <NUM> and amplifier <NUM> as explained with respect to <FIG>.

Temperature and humidity sensors <NUM> and <NUM>, respectively, are, as an option only, part of an exciter module <NUM> which comprises exciter <NUM>. Exciter module <NUM> can be a device which may have an own housing.

Again, sensors <NUM> and <NUM> can each or both be arranged close to both exciter <NUM> and trim part <NUM> or can be arranged immediately adjacent to a trim part <NUM> or partly or fully embedded into trim part <NUM>.

It is to be emphasized that the present invention is not limited to one temperature and one humidity sensor <NUM> and <NUM>, respectively. Rather, additional sensors <NUM> and <NUM> may directly or indirectly measure the temperature and/or the humidity of trim part <NUM>, exciter <NUM> or, if required, the environment, more particular the vehicle interior.

Operation of the acoustic system according to <FIG> corresponds to the system according to <FIG> apart from the fact that the audio signals received by processing unit <NUM> are generated and processed within head unit <NUM> as processing unit <NUM> defines part of head unit <NUM>.

The embodiment according to <FIG> substantially corresponds to the embodiment according to <FIG> apart from temperature sensor <NUM> and humidity sensor <NUM> being arranged outside exciter module <NUM>.

Again, both sensors or one of both sensors <NUM>, <NUM> can be arranged close to or partly or fully within trim part <NUM>, respectively.

Claim 1:
An acoustic system, comprising a trim part (<NUM>), an exciter (<NUM>) coupled to the trim part (<NUM>) for inducing vibrations to the trim part (<NUM>) so that the trim part (<NUM>) emits sound, a sensor (<NUM>) measuring humidity, and a control unit (<NUM>) coupled to the exciter (<NUM>) and to the sensor (<NUM>) measuring humidity, the control unit (<NUM>) being configured so as to determine control signals for the exciter (<NUM>) depending on the measured humidity, wherein the sensor (<NUM>) for measuring humidity is arranged so as to measure humidity of the trim part (<NUM>) and/or the exciter (<NUM>).