Patent Description:
Moreover, the present invention is directed to a vehicle comprising such a sound generation assembly.

Additionally, the present invention relates to a method for operating a sound generation assembly for a vehicle.

The present invention further is directed to a data processing apparatus, a computer program, and a computer-readable storage medium.

Furthermore, the present invention relates to a use of a sound generation assembly.

Vehicles, such as bicycles, scooters, motorcycles, cars, trucks, building machines and buses, use different types of sound generation assemblies depending on the type of the vehicle and the use of the vehicle.

An electric car may for example use one sound generation assembly as a part of a signal-horn system. Another sound generation assembly may be used as a part of an alarm-horn system. A further sound generation assembly may be used as a part of an acoustic vehicle alerting system (AVAS). The same applies to electric trucks and electric buses.

Bicycles, scooters, and motorcycles may also comprise a signal-horn system.

Moreover, any one of the vehicles as mentioned above may comprise a sound generation assembly being configured to generate an acoustic user feedback. Such an acoustic user feedback may be used in connection with locking or unlocking the vehicle. This means that the vehicle is able to issue a sound when being locked or unlocked.

The fact that vehicles use different sound generation assemblies is due to very different requirements which have to be fulfilled by the different applications needing a sound generation assembly. For example, a sound generation assembly being used as a part of a signal-horn system needs to be able to generate a sound of a certain volume or intensity. The same may apply to a sound generation assembly being used as a part of an alarm-horn system. In contrast thereto, a sound generation assembly being used as a part of an acoustic vehicle alerting system (AVAS) or for generating an acoustic user feedback usually does not need to generate a very loud sound, i.e. a sound of a high volume or high intensity. However, especially in contrast to signal horn systems and alarm-horn systems, these systems need to be able to generate a sound of high quality which shall be perceived by a listener to be pleasant.

Moreover, <CIT> discloses a sound output device. <CIT> shows a piezoelectric speaker and electroacoustic transducer. <CIT> is directed to a high-quality sound speaker using a piezoelectric element. <CIT> discloses a terminal with a piezoelectric speaker system and method for operating thereof.

It is an objective of the present invention to simplify such arrangements of different sound generation assemblies. At the same time, the known functionalities shall not be impaired.

According to a first aspect, there is provided a sound generation assembly for a vehicle. The sound generation assembly comprises a first electroacoustic transducer comprising a piezo actuator and a second electroacoustic transducer comprising a non-metallic diaphragm and an electromagnetic actuator connected thereto. Moreover, the sound generation assembly comprises a control unit being electrically connected to the first electroacoustic transducer and to the second electroacoustic transducer. The control unit is configured to provide a first actuation signal to the first electroacoustic transducer and a second actuation signal to the second electroacoustic transducer. The first actuation signal and the second actuation signal are different and synchronized. The piezo actuator and, thus, the first electroacoustic transducer is able to produce a comparatively loud, but simple sound. This is due to the fact that a piezo actuator usually is tuned to a predefined frequency or frequency range. When doing so, the piezo actuator requires only a comparatively small amount of electric power. Thus, when comparing the comparatively loud sound, i.e. the sound of relatively high volume or intensity, to the consumption of electric power, the piezo actuator is highly efficient. The second electroacoustic transducer may comprise a standard loudspeaker. Consequently, the second electroacoustic transducer is able to generate a sound of high quality and high variety. However, when being compared to the sound being generated by the first electroacoustic transducer, the sound being generated by the second electroacoustic transducer is less loud, i.e. has a smaller volume or intensity. According to the present invention, the sound being generated by the first electroacoustic transducer and the sound being generated by the second electroacoustic transducer are synchronized. This means that the sound being generated by the first electroacoustic transducer and the sound being generated by the second electroacoustic transducer are acoustically combined such that a listener only perceives the combined sound. The combined sound may be of high quality and, at the same time, of high volume or high intensity. Thus, using the sound generation assembly of the present invention, a sound that is loud and simultaneously perceived to be pleasant may be generated.

Consequently, the sound generation assembly of the present invention may be used for different applications. For example, the sound generation assembly of the present invention may be used as a common sound generation assembly of at least two out of the group consisting of a signal-horn system, an alarm-horn system, an acoustic vehicle alerting system (AVAS) and an acoustic user feedback generation system. Thus, instead of a plurality of different sound generation assemblies, only one sound generation assembly of the present invention may be needed. Thus, compared to prior art solutions, the sound generation assembly of the present invention is compact and comprises a comparatively low amount of parts. This reduces system complexity.

A further advantage of the sound generation assembly of the present invention lies in the fact that the second electroacoustic transducer, e.g. comprising a standard loudspeaker, is able to provide a variety of different sounds. Thus, even though it may be assumed that the first electroacoustic transducer is only able to provide one single type of sound, using the sound generation assembly of the present invention, different combined sounds may be provided by generating different sounds using the second electroacoustic transducer.

In the present context, the fact that the first actuation signal and the second actuation signal are synchronized means that the first actuation signal and the second actuation signal are provided in a timely coordinated manner. In an example, a signal element of the first actuation signal and a signal element of the second actuation signal corresponding to each other, i.e. being configured to generate sounds that shall be combined, may be generated at the same time. In another example, the signal element of the first actuation signal and the signal element of the second actuation signal may be generated with a predefined timely offset.

Beyond that, the fact that the first actuation signal and the second actuation signal are different means that the first actuation signal and the second actuation signal originate from different signal sources and/or the first actuation signal and the second actuation signal are of a different type. As has been explained before, the first actuation signal is configured to actuate a piezo actuator which is tuned to a specific frequency or a specific frequency range. Thus, the first actuation signal may be a periodic signal, e.g. a square wave signal. The second actuation signal is configured to actuate the second electroacoustic transducer which may comprise a standard loudspeaker. Consequently, the second actuation signal may be more complex than the first actuation signal. For example, an amplitude and/or a frequency of the second actuation signal may vary over a range which is broad as compared to a range of variation of an amplitude and/or a frequency of the first actuation signal. In a special case, the amplitude and/or the frequency of the first actuation signal is constant, i.e. does not vary.

According to an example, the control unit comprises a signal generator unit configured to generate the first actuation signal. Additionally, the control unit comprises a data storage unit configured to store an audio file, and a data processing unit being configured to generate the second actuation signal based on the audio file. As has been explained before, for a listener, the sound resulting from the first electroacoustic transducer being operated using the first actuation signal and the second electroacoustic transducer being operated by the second actuation signal is combined. Using the storage unit, an audio file of high quality may be provided in a simple and efficient manner. Thus, high acoustic quality may be ensured for the sound originating from the second electroacoustic transducer and the combined sound. Moreover, different audio files may be stored on the storage unit such that a certain variety of different sounds may be provided in a simple manner.

According to another example, the piezo actuator is mechanically and acoustically coupled to an acoustic horn. In this context, an acoustic horn is to be understood as a tapering guide for soundwaves. The acoustic horn is configured to provide a match between an acoustic impedance of the piezo actuator and free air of an environment. As a consequence, soundwaves are guided from the piezo actuator to the environment of the sound generation assembly in a highly efficient manner. In other words, the first electroacoustic transducer is able to provide a relatively loud sound, i.e. a sound of high volume or high intensity, while only consuming comparatively little electric power.

The first electroacoustic transducer is located in an acoustic nearfield of the second electroacoustic transducer. Additionally or alternatively, the second electroacoustic transducer is located in an acoustic nearfield of the first electroacoustic transducer. In this context, an acoustic near field is to be understood as a region around a source of acoustic waves being characterized by irregular changes between locations with constructive and destructive interference. In contrast thereto, an acoustic farfield is a region remote from the source of acoustic waves were interference effects are negligible. In simplified words, the first electroacoustic transducer is located close to the second electroacoustic transducer and/or the second electroacoustic transducer is located close to the first electroacoustic transducer. This has the effect that a sound originating from the first electroacoustic transducer and a sound originating from the second electroacoustic transducer are perceived by a listener as a combined sound only. In this context, it is assumed that the listener is located in the acoustic farfield of both the first electroacoustic transducer and the second electroacoustic transducer.

According to the present invention, the distance between a center of the first electroacoustic transducer and the center of the second electroacoustic transducer is <NUM> to <NUM>. Preferably, this distance is <NUM> to <NUM>.

In a further example, the first electroacoustic transducer and the second electroacoustic transducer are arranged in a common housing. Consequently, the sound generation assembly is structurally simple. This is especially the case when being compared to a solution in which each electroacoustic transducer has its own housing. Relatively few parts are used. Moreover, the common housing renders the sound generation assembly compact.

In an example, the control unit comprises a control unit housing and the first electroacoustic transducer is located in or on the control unit housing. Such a configuration only needs comparatively few parts and is compact. Additionally, in this configuration, a volume of the control unit housing may be used as a resonance volume being acoustically coupled to the first electroacoustic transducer. This enhances the acoustic quality of a sound being generated by the first electroacoustic transducer and may additionally lead to the fact that the loudness of a sound being generated by the first electroacoustic transducer may be increased.

In this context, a resonance frequency of the control unit housing may differ by +/-<NUM>% or less from an operational frequency of the first electroacoustic transducer. In other words, the resonance frequency of the control unit housing and the operational frequency of the first electroacoustic transducer are matched. Thus, the control unit housing fulfills an acoustic functionality in connection with the first electroacoustic transducer. This enhances the acoustic quality of a sound being generated by the first electroacoustic transducer and may additionally lead to the fact that the loudness of a sound being generated by the first electroacoustic transducer may be increased.

According to a second aspect, there is provided a vehicle comprising a sound generation assembly according to the invention. Thus, using the sound generation assembly, the vehicle is able to issue a sound of high quality and at the same time of high volume or high intensity. In other words, the sound is loud and perceived to be pleasant at the same time by a listener. In the vehicle, the sound generation assembly may be used for different applications requiring a comparatively loud sound, a sound of high quality or a comparatively loud sound being of high quality at the same time. For example, the sound generation assembly may be used as a sound generation assembly of a signal-horn system, an alarm-horn system, an acoustic vehicle alerting system (AVAS) or an acoustic user feedback generation system. It is noted that the sound generation assembly may as well be used as a common sound generation assembly of at least two of these systems. Thus, instead of a plurality of different sound generation assemblies, only one sound generation assembly of the present invention may be needed. Thus, compared to prior art solutions, the sound generation assembly of the present invention is compact and comprises a comparatively low amount of parts. This reduces system complexity of the vehicle.

The vehicle may be a bicycle, especially an electric bicycle, a scooter, a motorcycle, a car, a truck or a bus, in particular an electric car, an electric truck or an electric bus.

According to a third aspect, there is provided a method for operating a sound generation assembly for a vehicle. The sound generation assembly has a first electroacoustic transducer comprising a piezo actuator and a second electroacoustic transducer comprising a non-metallic diaphragm and an electromagnetic actuator connected thereto. The method comprises:.

Thus, using the method of the present invention, a sound of high quality and at the same time of high volume or high intensity may be generated. Such a sound is loud and may be perceived to be pleasant at the same time. Consequently, the generated sound may be used for different applications requiring a comparatively loud sound, a sound of high quality or a comparatively loud sound being of high quality at the same time. For example, the sound generation assembly may be used as a sound generation assembly of a signal-horn system, an alarm-horn system, an acoustic vehicle alerting system (AVAS) or an acoustic user feedback generation system. It is noted that the sound generation assembly may as well be used as a common sound generation assembly of at least two of these systems.

It is noted that the method of the present invention may be executed on a sound generation assembly of the present invention. In this context, the method is executed on the control unit, more precisely on a data processing unit of the control unit, of the sound generation assembly of the present invention.

In an example, the first actuation signal has a higher frequency than the second actuation signal. Thus, the first electroacoustic transducer may be used to generate a sound offer higher frequency than the second electroacoustic transducer. Consequently, a combined sound, i.e. the combination of the sound being produced by the first electroacoustic transducer and the second electroacoustic transducer, covers a comparatively large spectrum of frequencies. This is an indicator of high sound quality.

According to an example, the first actuation signal is configured to cause a sound of a higher volume than the second actuation signal. As has been mentioned before, the first electroacoustic transducer is able to provide a comparatively loud sound in an energy-efficient manner. Consequently a comparatively loud sound may be produced using comparatively little electric power.

According to a fourth aspect, there is provided a data processing apparatus comprising means for carrying out the method of the invention. Thus, using the data processing apparatus, a sound of high quality and at the same time of high volume or high intensity may be generated. Consequently, the generated sound may be used for different applications requiring a comparatively loud sound, a sound of high quality or a comparatively loud sound being of high quality at the same time. For example, the sound generation assembly may be used as a sound generation assembly of a signal-horn system, an alarm-horn system, an acoustic vehicle alerting system (AVAS) or an acoustic user feedback generation system. It is noted that the sound generation assembly may as well be used as a common sound generation assembly of at least two of these systems.

According to a fifth aspect, there is provided a computer program comprising instructions which, when the computer program is executed by a computer, cause the computer to carry out the method of the invention. Thus, using the computer program, a sound of high quality and at the same time of high volume or high intensity may be generated. Consequently, the generated sound may be used for different applications requiring a comparatively loud sound, a sound of high quality or a comparatively loud sound being of high quality at the same time. For example, the sound generation assembly may be used as a sound generation assembly of a signal-horn system, an alarm-horn system, an acoustic vehicle alerting system (AVAS) or an acoustic user feedback generation system. It is noted that the sound generation assembly may as well be used as a common sound generation assembly of at least two of these systems.

According to a sixth aspect, there is provided a computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to carry out the method of the invention. Thus, using the computer-readable storage medium, a sound of high quality and at the same time of high volume or high intensity may be generated. Consequently, the generated sound may be used for different applications requiring a comparatively loud sound, a sound of high quality or a comparatively loud sound being of high quality at the same time. For example, the sound generation assembly may be used as a sound generation assembly of a signal-horn system, an alarm-horn system, an acoustic vehicle alerting system (AVAS) or an acoustic user feedback generation system. It is noted that the sound generation assembly may as well be used as a common sound generation assembly of at least two of these systems.

According to a seventh aspect, there is provided a use of the sound generation assembly of the invention as at least one of a signal-horn for a vehicle, an alarm-horn for a vehicle, a vehicle alerting sound generation assembly and a user feedback sound generation assembly for a vehicle. As has been explained before, the sound generation assembly of the present invention is able to provide a sound of high quality and at the same time of high volume or high intensity. Thus, a sound that is loud and perceived to be pleasant at the same time may be generated. Consequently, the generated sound may be used for different applications requiring a comparatively loud sound, a sound of high quality or a comparatively loud sound being of high quality at the same time. This is structurally simple and efficient.

These and other aspects of the present invention will become apparent from and elucidated with reference to the examples described hereinafter. Examples of the invention will be described in the following with reference to the following drawings.

The Figures are merely schematic representations and serve only to illustrate examples.

<FIG> shows four alternative vehicles <NUM>.

In <FIG>, the vehicle <NUM> is a bicycle which comprises a bicycle frame <NUM>. A sound generation assembly <NUM> is arranged in the bicycle frame <NUM>. Even though represented as a standard, purely human-powered bicycle, the bicycle can as well be an electric bicycle.

In <FIG>, the vehicle <NUM> is a motorcycle which comprises a motorcycle frame <NUM>. A sound generation assembly <NUM> is arranged in the motorcycle frame <NUM>.

In <FIG>, the vehicle <NUM> is a scooter which comprises a scooter frame <NUM>. A sound generation assembly <NUM> is arranged in the scooter frame <NUM>.

In <FIG>, the vehicle <NUM> is a car. A sound generation assembly <NUM> is arranged in the motor compartment <NUM> of the car.

<FIG> shows the sound generation assembly <NUM> of all of the exemplary vehicles <NUM> of <FIG> in more detail.

The sound generation assembly <NUM> comprises a first electroacoustic transducer <NUM>.

The first electroacoustic transducer <NUM> comprises a piezo actuator <NUM> and an acoustic horn <NUM>. The piezo actuator <NUM> and the acoustic horn <NUM> are mechanically and acoustically coupled.

This means that the piezo actuator <NUM> and the acoustic horn <NUM> are mechanically connected to one another. Furthermore, a sound being generated by the piezo actuator <NUM> may be transmitted to an environment <NUM> via the acoustic horn <NUM>.

The sound generation assembly <NUM> additionally comprises a second electroacoustic transducer <NUM>.

The second electroacoustic transducer <NUM> comprises a non-metallic diaphragm <NUM> and an electromagnetic actuator <NUM> being connected to the non-metallic diaphragm <NUM>.

Thus, the second electroacoustic transducer <NUM> may generate a sound and provide the sound to the environment <NUM> by moving the diaphragm <NUM> using the electromagnetic actuator <NUM>.

The sound generation assembly <NUM> also comprises a control unit <NUM>.

The control unit <NUM> comprises a data processing apparatus <NUM>.

The data processing apparatus <NUM> comprises a data processing unit <NUM> and a data storage unit <NUM>.

The data processing unit <NUM> is for example a microcontroller.

The data storage unit <NUM> comprises a computer-readable storage medium <NUM>.

The computer-readable storage medium <NUM> comprising instructions which, when executed by the data processing unit <NUM> or, more generally speaking a computer, cause the data processing unit <NUM> or computer to carry out a method for operating the sound generating assembly <NUM>.

Additionally, at least one audio file <NUM> is stored on the computer-readable storage medium <NUM>.

Moreover, on the computer-readable storage medium <NUM>, there is provided a computer program <NUM>.

Also the computer program <NUM> comprises instructions which, when the computer program <NUM> is executed by the data processing unit <NUM> or, more generally speaking, a computer, cause the computer or the data processing unit <NUM> to carry out the method for operating the sound generating assembly <NUM>.

Consequently, the data processing unit <NUM> and the data storage unit <NUM> form means <NUM> for carrying out the method for operating the sound generating assembly <NUM>.

The control unit <NUM> is electrically connected to the first electroacoustic transducer <NUM> and to the second electroacoustic transducer <NUM>.

Thereby, the control unit <NUM>, more precisely the data processing unit <NUM>, is configured to provide a first actuation signal S1 to the first electroacoustic transducer <NUM>.

It is understood that, to this end, also an information, e.g. an operational frequency, being stored on the data storage unit <NUM> may be used.

Consequently, the data processing unit <NUM> and the data storage unit <NUM> form a signal generator unit <NUM> configured to generate the first actuation signal S1. The first actuation signal S1 is for example a square wave signal of constant amplitude and frequency.

The control unit <NUM>, more precisely the data processing unit <NUM>, is also configured to provide a second actuation signal S2 to the second electroacoustic transducer <NUM>. The second actuation signal S2 is generated using the data processing unit <NUM>. The second actuation signal S2 is generated based on the audio file <NUM>. Thus, the second actuation signal S2 is a signal having a variable amplitude and variable frequency.

Due to the fact that the first electroacoustic transducer <NUM> comprises a piezo actuator <NUM> and the second electroacoustic transducer <NUM> comprises an electromagnetic actuator <NUM> for moving the non-metallic diaphragm <NUM>, the first actuation signal S1 and the second actuation signal S2 are of different types.

Moreover, the first actuation signal S1 and the second actuation signal S2 are synchronized as will be explained in more detail further below.

In the example shown in <FIG>, the first electroacoustic transducer <NUM>, the second electroacoustic transducer <NUM> and the control unit <NUM> are arranged in a common housing <NUM>.

In order not to hinder the sounds being produced by the first electroacoustic transducer <NUM> and the second electroacoustic transducer <NUM>, the common housing <NUM> has a grating adjacent to the first electroacoustic transducer <NUM> and the second electroacoustic transducer <NUM> respectively.

The first electroacoustic transducer <NUM> and the second electroacoustic transducer <NUM> are arranged such that the first electroacoustic transducer <NUM> is located in an acoustic nearfield of the second electroacoustic transducer <NUM>. At the same time, the second electroacoustic transducer <NUM> is located in an acoustic nearfield of the first electroacoustic transducer <NUM>.

In the present example, this means that a distance D between the center of the first electroacoustic transducer <NUM> and the center of the second electroacoustic transducer <NUM> is <NUM>.

Moreover, a resonance frequency of the common housing <NUM> is matched to an operational frequency of the first electroacoustic transducer <NUM>.

This means that the resonance frequency of the common housing <NUM> differs by +/-<NUM>% or less from an operational frequency of the first electroacoustic transducer <NUM>. Thus, the common housing <NUM> supports the acoustic functionality of the first electroacoustic transducer <NUM>.

From the perspective of the control unit <NUM>, the common housing <NUM> is a control unit housing <NUM>. Put otherwise, the first electroacoustic transducer <NUM> is located in the control unit housing <NUM> and a resonance frequency of the control unit housing <NUM> is matched to an operational frequency of the first electroacoustic transducer.

The sound generation assembly <NUM> may be operated using a method for operating a sound generation assembly <NUM> for a vehicle <NUM>.

According to the method, the first actuation signal S1 is provided to the first electroacoustic transducer <NUM>. As has been mentioned before, the first actuation signal S1 is a square wave signal of constant frequency and amplitude.

Moreover, the second actuation signal S2 is provided to the second electroacoustic transducer <NUM>.

As has also been explained before, the second actuation signal S2 is a complex signal of variable frequency and variable amplitude.

Thus, the second actuation signal S2 differs from the first actuation signal S1.

Moreover, the second actuation signal S2 and the first actuation signal S1 are synchronized. This means that the first actuation signal S1 and the second actuation signal S2 are provided in a timely coordinated manner.

This has the effect that a sound being generated by the first electroacoustic transducer <NUM> and a sound being generated by the second electroacoustic transducer <NUM> are generated in a timely coordinated manner.

As a consequence thereof, a listener <NUM> which is represented in <FIG> by an ear only, only hears a combination of the sound being generated by the first electroacoustic transducer <NUM> and a sound being generated by the second electroacoustic transducer <NUM>.

Since in the present example, the first actuation signal S1 has a higher frequency than the second actuation signal S2 and the first actuation signal S1 is configured to cause a sound of a higher volume than the second actuation signal S2, the combined sound comprises a comparatively broad spectrum of frequencies and is a high-volume sound.

In other words, the combined sound is loud and of high quality at the same time.

<FIG> shows another example of the sound generation assembly <NUM>. In the following, only the differences with respect to the sound generation assembly <NUM> of <FIG> will be explained.

In the example of <FIG>, the first electroacoustic transducer <NUM> and the control unit <NUM> are arranged in a common housing which is designated a control unit housing <NUM>. In other words, the first electroacoustic transducer <NUM> is arranged in the control unit housing <NUM>.

The second electroacoustic transducer <NUM> is arranged in a transducer housing <NUM> which is separate from the control unit housing <NUM>.

This has the advantage that a volume of the transducer housing <NUM> which has an effect on the acoustic characteristics of the second electroacoustic transducer <NUM> may be chosen independently from a volume of the control unit housing <NUM>.

It is emphasized that also in the example of <FIG>, the distance D between a center of the first electroacoustic transducer <NUM> and the center of the second electroacoustic transducer <NUM> is <NUM> as in the example of <FIG>.

Also the sound generation assembly <NUM> of <FIG> may be operated using a method for operating a sound generation assembly <NUM>. Reference is made to the explanations provided in connection with the example of <FIG>.

In both of the above examples, the sound generation assembly <NUM> may be used to produce a sound of high volume or high intensity and high quality. Consequently, the sound generation assembly <NUM> may be used as at least one of a signal-horn for a vehicle, an alarm-horn for a vehicle, a vehicle alerting sound generation assembly and a user feedback sound generation assembly for a vehicle.

For example, if the vehicle <NUM> is a bicycle as shown in <FIG>, more precisely an electric bicycle, or if the vehicle <NUM> is a scooter as shown in <FIG> the sound generation assembly <NUM> may be used as a common sound generation assembly of an alarm-horn and a user feedback sound generation assembly. The user feedback sound generation assembly may for example issue a confirmation sound if the bicycle or the scooter is locked or unlocked. Moreover, the user feedback sound generation assembly may be used for a find-my-bike functionality or a find-my-scooter functionality.

In another example, the vehicle <NUM> may be a motorcycle as shown in <FIG> or a car as shown in <FIG>. The motorcycle may be an electric motorcycle and the car may be an electric car.

In this example the sound generation assembly <NUM> may be used as a common sound generation assembly of an alarm-horn of an anti-theft system, a signal horn and a vehicle alerting sound generation assembly (AVAS).

Other variations to the disclosed examples can be understood and effected by those skilled in the art in practicing the claimed disclosure, from the study of the drawings, the disclosure, and the appended claims.

Claim 1:
A sound generation assembly (<NUM>) for a vehicle (<NUM>), comprising
a first electroacoustic transducer (<NUM>) comprising a piezo actuator (<NUM>),
a second electroacoustic transducer (<NUM>) comprising a non-metallic diaphragm (<NUM>) and an electromagnetic actuator (<NUM>) connected thereto, and
a control unit (<NUM>) being electrically connected to the first electroacoustic transducer (<NUM>) and to the second electroacoustic transducer (<NUM>),
characterized in that the control unit (<NUM>) is configured to provide a first actuation signal (S1) to the first electroacoustic transducer (<NUM>) and a second actuation signal (S2) to the second electroacoustic transducer (<NUM>), the first actuation signal (S1) and the second actuation signal (S2) being different and synchronized, wherein the first actuation signal (S1) and the second actuation signal (S2) are different in that the first actuation signal (S1) and the second actuation signal (S2) originate from different signal sources, and wherein a distance between a center of the first electroacoustic transducer (<NUM>) and a center of the second electroacoustic transducer (<NUM>) is <NUM> to <NUM>, such that a sound originating from the first electroacoustic transducer (<NUM>) and a sound originating from the second electroacoustic transducer (<NUM>) are perceived by a listener as a combined sound only.