EP3739904B1 - Acoustic bending converter system and acoustic device - Google Patents

Description

technical field

Embodiments according to the invention relate to a micromechanical sound transducer.

background

• • WO 2012/095185 A1 / Bezeichnung: MIKROMECHANISCHES BAUELEMENT
• • WO 2016/202790 A2 / Bezeichnung: MEMS TRANSDUCER FOR INTERACTING WITH A VOLUME FLOW OF A FLUID AND METHOD FOR PRODUCING SAME
• • DE 10 2015 206 774 A1

The technical field of the present application can be traced back to the following three documents describing micromechanical devices:

• • WO 2012/095185 A1 / Description: MICROMECHANICAL COMPONENT
• • WO 2016/202790 A2 / Description: MEMS TRANSDUCER FOR INTERACTING WITH A VOLUME FLOW OF A FLUID AND METHOD FOR PRODUCING SAME
• • DE 10 2015 206 774 A1

Basically, these documents reveal the design of bending transducers and their specific possibilities and mechanisms for interacting with the environment. In particular, the above-mentioned documents relate to a novel MEMS (micro electromechanical system) actuator principle that is based on a silicon beam moving laterally in a plane, for example a substrate plane defined by a silicon disk or wafer. The silicon beam, which is connected to the substrate in a cavity, interacts with a volume flow. The novel MEMS described therein are defined as NED (Nanoscopic Electrostatic Drive).

Due to their size, these NEDs are particularly suitable for miniaturization - reducing the size of components while retaining the full range of functions - of everyday objects that have increased integration requirements. For example, ultra-mobile devices such as smartwatches or hearables are subject to very tight space design limits. With the above-mentioned NED, sound transducers can be realized that can meet these increased requirements, whereby both sound quantity and Sound quality can be significantly improved compared to conventional sound transducers. The integration requirements relate both to the adaptation to the existing installation space in general and to the system design together with several components.

In the document DE 10 2017 114 008 A1 a hearing aid or headphones is disclosed which is designed in such a way that its outer dimensions of the housing correspond to the inner dimensions of the ear canal. A MEMS-based sound transducer is arranged in the housing so that a front volume is formed in the direction of the eardrum and a rear volume in the direction of the earpiece, which are separated from each other by the MEMS-based sound transducer. This sound transducer is designed in its geometric dimensions in such a way that it does not restrict the geometric dimensions of the resonance volumes, but it is difficult to keep a frequency curve constant over a large frequency range. In addition, the sound transducer consists of bending transducers which are elastically suspended on one side and which extend over a cavity and whose edge area is spaced apart on a front side by a gap. The gap increases due to the curvature of the sound transducers. Furthermore, a sound shielding device is disclosed which is formed by the side walls, the so-called sound blocking walls of the cavity. These walls are arranged in such a way that they at least partially prevent lateral sound passage along the gap. The disadvantage is that the sound transducers are piezoelectric and are therefore subject to pre-curvature, so that the measures disclosed serve to minimize the inaccuracies resulting from this pre-curvature.

In the document DE 10 2017 108 594 A1 A loudspeaker unit for a portable device for generating sound waves in the audible range is disclosed, which is characterized by a small size and high performance. In addition to the electrodynamic loudspeaker, the loudspeaker unit includes a MEMS-based tweeter, with the frequency ranges of both loudspeakers overlapping. This makes the electrodynamic loudspeaker compact and optimized for low frequencies. The disadvantage, however, is that it requires a lot of space and has a high power consumption, since two different system technologies have to be operated.

From the document DE 196 124 81 A1 Furthermore, an arrangement of a sound transducer for hearing aids that is tilted relative to a longitudinal axis is known. The sound-generating membrane is a conductive foil that is arranged between two surface electrodes and whose vibrations generate sound in the audible wavelength spectrum. This foil is not arranged parallel to the eardrum, which minimizes unwanted resonances in the ear canal. However, no other functional elements can be monolithically integrated in this structure, which means that additional space is required outside the ear canal.

Another state-of-the-art solution can be found in the WO 2010/133782 A1 This describes a dipole device for generating a pair of acoustic waves, the waves having opposite pressures and radiating in opposite directions. The EP 3 279 622 A1 describes a device for analyzing an audio spectrum. For this purpose, a large number of resonators with different resonance frequencies are arranged on a substrate around a recess. The DE 10 2015 210919 A1 describes MEMS transducers for interacting with a volume flow of a fluid comprising a substrate having a cavity and an electromechanical transducer connected to the substrate in the cavity and an element deformable along a lateral direction of movement, wherein a deformation of the deformable element along the lateral direction of movement and the volume flow of the fluid are causally related. The EP 2 986 024 A1 describes an audio measuring device and a method for detecting frequency information. The device comprises a substrate with a cavity, a membrane covering the cavity and a plurality of resonators on the membrane. The WO 00/41432 A2 describes a hearing aid with a large microphone diaphragm. The diaphragm can be designed as a single element or as a diaphragm that is divided into a number of smaller active diaphragms.

Known solutions do not require particularly dense packing of sound transducers, or use external assembly processes to add individual functions (e.g. electrical connection).

In view of this, there is a need for a concept that enables an increased packing density of the components compared to the state of the art in order to effectively and efficiently realize a high sound pressure.

An object of the invention is therefore to provide an acoustic bending transducer system with increased effectiveness and an acoustic device for improving sound conversion in a passage such as an ear canal.

This object is achieved by means of the subject matter in independent patent claim 1.

For example, a compact arrangement of a large number of bending transducers in a bending transducer system, which is designed as a sound transducer and which enables the integration of other system components in limited space, ensures high reproduction quality in an environment around the bending transducer system. The frequency response reproduced by the sound transducer, as it results from the combination of the transducer and the surrounding installation space, can be kept constant over a large frequency range, for example by orienting the volume flow at an angle in a passage, such as an ear canal. A variation can be less than 6 dB, for example.

The application describes a further development regarding an optimization of the arrangement of bending transducers with regard to space requirements, sound pressure level and Sound quality that can be provided by the NED in a specific environment - for example, in the ear canal of a human ear.

An acoustic bending transducer system is proposed with a large number of bending transducers which are designed such that deformable elements of the bending transducers oscillate coplanarly in a common flat layer, wherein the bending transducers have different resonance frequencies and different extensions of the deformable elements along a common longitudinal axis which is transverse to a direction of oscillation of the deformable elements. The bending transducers can be, for example, electrostatic bending actuators (NED actuators), piezoelectric actuators or thermomechanical actuators. The majority of bending transducers are designed for deflection in an oscillation plane. The bending transducers are arranged next to one another in the common flat layer or oscillation plane along a first axis and extend along a second axis which is transverse to the first axis. In order to fully utilize the spatial conditions within the same common flat layer, individual or multiple bending transducers can also be arranged at an angle to the majority of the bending transducers which are aligned parallel to one another.

A further aspect of the application relates to an acoustic device, e.g. a hearing aid with: an acoustic bending transducer system with at least one bending transducer that has at least one deformable element that is arranged in a cavity and an opening through which a fluidic volume flow interacting with a movement of the bending transducer in the cavity passes, and a housing that is adapted to be inserted into a passage, wherein the bending transducer system is held in the housing such that the fluidic volume flow can be aligned obliquely to a longitudinal axis of the passage in a state in which the housing is inserted into the passage. The acoustic device can be miniaturized and is therefore particularly suitable for installation in in-the-ear hearing aids (ITE) and hearables as well as smartwatches and other ultra-mobile devices.

Advantages and functionalities of the features of the acoustic bending transducer system as described above and below equally apply to an acoustic device provided therewith.

Further developments according to the invention are defined in the subclaims.

According to one embodiment, the bending transducer system has one or more cavities in which the bending transducers are arranged and one or more openings in the cavities through which a fluidic volume flow that interacts with a large number of bending transducers can pass. The openings in the cavities can be common openings of two or more cavities that communicate with each other via the fluidic volume flow. In addition, openings in the cavities of the bending transducer system allow communication between individual bending transducers or the bending transducer system with an environment that surrounds them.

According to one embodiment, the bending transducers are arranged in a space that is delimited by a first and a second substrate parallel to the common vibration plane, and walls between the substrates that divide the space along a longitudinal direction or a direction transverse to the longitudinal direction in the common vibration plane into cavities that are arranged between adjacent bending transducers. Thus, a cavity is delimited, for example, by the first substrate, the second substrate and two opposing walls of adjacent bending transducers. Since the plurality of bending transducers is designed to be deflected via their deformable elements in the common vibration plane of a layer, the bending transducers can each have a distance from the first substrate and the second substrate through which adjacent cavities can be fluidically coupled to one another. Due to the fluidic coupling of adjacent cavities, the plurality of bending transducers can exert a common force on a fluid located in the cavities, whereby a high sound level can be achieved with the micromechanical sound transducer.

Depending on the design, each bending transducer of the acoustic bending transducer system can comprise a deformable element that can be deformed electrostatically, piezoelectrically or thermomechanically. This provides a multitude of options for flexibly adapting the bending transducer system to desired requirements.

Furthermore, it is particularly advantageous if, in the acoustic bending transducer system, at least a first subset of at least one first bending transducer has a deformable element clamped on one side, and additionally or alternatively at least a second subset of at least one second bending transducer each has a deformable element clamped on both sides. Grouping individual subsets of specific bending transducers enables a practical use of the installation space and at the same time a targeted location of similar bending transducers to generate the desired frequencies or sound pressures. Because the deformable element of each bending transducer can be clamped on one or both sides, bending transducers can be realized with deformable elements with different mechanical properties and dimensions, which in turn are responsible for generating different frequencies and sound pressures. Furthermore, an installation space available in the same layer of the bending transducer system can be used particularly advantageously.

This advantageously results in a larger vibration amplitude at higher frequencies in the case of cantilever-clamped bending transducers, since the cantilever-clamped bending transducers are characterized by an advantageous ratio of mass to length of the deformable element of the bending transducer.

In order to be able to reproduce different frequencies and/or generate different sound pressures, according to a particularly advantageous embodiment, the at least first subset of at least one first bending transducer has on average a higher resonance frequency than the at least second subset of at least one second bending transducer, or vice versa. Due to certain requirements for the installation space and with regard to the different frequencies and their sound pressures, the stiffness, mass, length and cross-sectional geometry of the deformable elements of the respective bending transducers can be adapted.

In order to be able to reproduce different frequencies and/or generate different sound pressures in a particularly simple and dedicated manner, the first subset of at least one first bending transducer has on average a shorter length than the second subset of at least one second bending transducer.

According to a particularly preferred embodiment, each bending transducer defines two opposing cavities, each cavity being accessible via at least one opening for the passage of the fluidic volume flow. It is thus possible to fluidically couple the individual cavities and thus specifically control the properties of the volume flow conveyed by the individual bending transducers, which particularly with regard to a build-up pressure or sound pressure of the volume flow may be desired.

To generate sound pressures in a frequency spectrum using the acoustic bending transducer system that are accessible to the human ear, it is recommended to provide deformable elements in the bending transducers that have a length that is greater than 100 µm. To enable a particularly compact design of miniaturized sound transducers, the deformable element of each bending transducer should have a length that is less than 4000 µm. To save space in installing the bending transducer system in an elongated shell, an external dimension of the bending transducer system along the common longitudinal axis lateral to the common flat layer is maximum and greater than an external dimension of the bending transducer system transverse to it.

In a particularly preferred embodiment, the external dimensions of the bending transducer system along the common longitudinal axis are between 750 µm and 2000 µm. In an even more preferred embodiment, the external dimensions of the bending transducer system along the common longitudinal axis are between 800 µm and 1200 µm. Bending transducer systems with the dimensions mentioned above can be installed in in-ear hearing aids in a space-saving manner, while ensuring sufficient hearing quality for the user.

In particularly advantageous embodiments, an outer surface of the bending transducer system describes an oval elongated along the common longitudinal axis, a rectangle elongated along the common longitudinal axis or a polygon elongated along the common longitudinal axis, coplanar to the common flat layer. Such elongated shapes allow the installation space in an elongated shell with a cylindrical or rectangular cross-section to be used particularly well. In addition, by selecting the outer surface or an outer contour of the bending transducer system appropriately, an inner cross-section of an elongated shell can be essentially completely occupied, for example an ear canal can be sealed.

According to an expedient embodiment, the bending transducers are divided into groups of one or more bending transducers, wherein in groups with several bending transducers, the several bending transducers are arranged along the common longitudinal axis are arranged one behind the other. In such an arrangement, the individual pressures of the volume flow caused by the respective deformable elements of the bending transducers would add up. Consequently, by advantageously staggering or grouping the bending transducers and their selective activation, not only a desired pressure or sound pressure of the volume flow released into the environment could be controlled in a targeted manner, but also different sound frequencies could be generated. For example, short bending transducers can be arranged in the area of the openings, since they are characterized by a comparatively high rigidity - relative to long bending transducers - which makes high resonance frequencies possible. If such bending transducers are arranged in the area of the openings that connect the cavities with the environment, resonances can be avoided and thus sound quality or hearing quality can be improved. In addition or alternatively, according to a further expedient embodiment, the bending transducers are divided into groups of one or more bending transducers, whereby in groups with several bending transducers, the several bending transducers are arranged next to one another in the common plane transverse to the common longitudinal axis. Analogous to the arrangement of several bending transducers one behind the other along the common longitudinal axis, a desired sound pressure and a location of the sound can also be controlled when arranging them next to each other transversely to the common longitudinal axis.

Advantageously, the fluidic volume flow - in the bending transducer system - of the acoustic device runs in the plane of the common flat layer of the bending transducer system. Due to the arbitrary design and orientation of the cavities and deformable elements of the individual bending transducers of the bending transducer system, a targeted course of the fluidic volume flow in the bending transducer system can be provided and thus controlled. The volume flow can thus be directed specifically to the place where its effect on its surroundings is optimal.

In order to achieve a particularly advantageous interaction with the environment of the acoustic device, the bending transducer system is held in the housing in such a way that the fluidic volume flow of the acoustic device passes through the openings of the bending transducer system at an angle of between 5° and 80°, between 10° and 40°, or between 15° and 30° inclined to the longitudinal axis of the passage. By arranging the bending transducers relative to the longitudinal axis of the passage, the deformable elements are guided in relation to their orientation, for example in the direction of the eardrum of a human ear in an anti-parallel manner so that resonances in the ear canal are minimized. In addition, a higher packing density of the bending transducers can be achieved and higher sound pressures - related to a cross-sectional area of the canal - can be achieved, creating a larger acoustically active surface of the acoustic device.

In order to be able to use the acoustic device particularly efficiently, the acoustic bending transducer system can receive and/or emit an acoustic signal via the fluid volume flow passing through the openings. This enables the acoustic bending transducer system to work simultaneously as a receiver and/or transmitter of acoustic signals, which in turn significantly increases the flexibility in using the acoustic device. The transmission or reception of acoustic signals can take place alternately or continuously.

According to an advantageous embodiment, the acoustic device further comprises: a control unit for controlling the individual bending transducers of the bending transducer system and a power supply source for operating the acoustic device. Due to the diverse possibilities for miniaturizing the acoustic bending transducer system, additional components can also be accommodated in a space-saving manner despite the small dimensions of the acoustic device. This contributes significantly to increasing the wearing comfort and user-friendliness of the acoustic device.

In order to achieve a particularly high level of flexibility when using the acoustic device, two or more acoustic bending transducer systems can be held in the housing, with the common flat layer of the same aligned parallel to one another. This means that, for example, acoustic devices can be arranged or manufactured in the form of a substrate stack, which makes it possible to implement highly complex structures while keeping manufacturing costs relatively low. In addition, acoustic devices can also be easily customized in this way. Finally, by stacking several acoustic bending transducer systems, a higher sound pressure can be generated and/or a larger displayable frequency range can be covered.

The acoustic device can advantageously be constructed monolithically from several layers, or from substrates of different materials, which are are connected or bonded to one another in a common layer. This can be done, for example, in the form of an arrangement of a cover wafer above or a handling wafer below a common device wafer.

In order to provide a particularly space-saving and compact form of the acoustic device, the control unit and/or the energy supply source is arranged in the common flat layer of a bending transducer system. The control unit is of course set up for: fluid-dynamic damping, signal processing, wireless communication, voltage transformation. It can contain sensors, software, data storage, etc., which are arranged individually or together in the same acoustic device, or alternatively are provided separately from the acoustic device.

character description

Fig. 1

zeigt in einer perspektivischen Darstellung ein Biegewandlersystem gemäß einem Ausführungsbeispiel der vorliegenden Erfindung;

Fig. 2

zeigt in einer perspektivischen Darstellung das Ausführungsbeispiel aus Fig. 1 mit Substratebenen;

Fig. 3

zeigt in einer perspektivischen Darstellung ein Biegewandlersystem gemäß einem weiteren Ausführungsbeispiel der vorliegenden Erfindung;

Fig. 4

zeigt in einer perspektivischen Darstellung das Ausführungsbeispiel aus Fig. 3 mit Substratebenen;

Fig. 5

zeigt in einer Schnittdarstellung den Gehörgang, das Trommelfell und die Ohrmuschel eines menschlichen Ohres;

Fig. 6a

zeigt in einer perspektivischen Darstellung Elemente eines Biegewandlers gemäß einem Ausführungsbeispiel der vorliegenden Erfindung bei einem Anregungszustand;

Fig. 6b

zeigt in einer perspektivischen Darstellung Elemente des Biegewandlers aus Fig. 6a gemäß einem Ausführungsbeispiel der vorliegenden Erfindung bei einem weiteren Anregungszustand;

Fig. 7

zeigt eine Querschnittsansicht des Biegewandlers gemäß der Ausführungsform aus Fig. 6a entlang der Schnittebene A;

Fig. 8

zeigt in einer perspektivischen Darstellung ein Biegewandlersystem gemäß einem weiteren vorteilhaften Ausführungsbeispiel der vorliegenden Erfindung;

Fig. 9

zeigt eine Querschnittsansicht eines Biegewandlers gemäß einem weiteren vorteilhaften Ausführungsbeispiel der vorliegenden Erfindung.

Embodiments according to the present invention are explained in more detail below with reference to the accompanying figures. With regard to the schematic figures shown, it is pointed out that the functional blocks shown are to be understood both as elements or features of the device according to the invention and as corresponding method steps of the method according to the invention, and corresponding method steps of the method according to the invention can also be derived therefrom. They show:

Fig. 1

shows a perspective view of a bending transducer system according to an embodiment of the present invention;

Fig. 2

shows in a perspective view the embodiment from Fig. 1 with substrate levels;

Fig. 3

shows a perspective view of a bending transducer system according to a further embodiment of the present invention;

Fig. 4

shows in a perspective view the embodiment from Fig. 3 with substrate levels;

Fig. 5

shows a cross-sectional view of the ear canal, eardrum and auricle of a human ear;

Fig. 6a

shows in a perspective view elements of a bending transducer according to an embodiment of the present invention in an excitation state;

Fig. 6b

shows in a perspective view elements of the bending transducer from Fig. 6a according to an embodiment of the present invention in a further excitation state;

Fig. 7

shows a cross-sectional view of the bending transducer according to the embodiment of Fig. 6a along the cutting plane A;

Fig. 8

shows a perspective view of a bending transducer system according to a further advantageous embodiment of the present invention;

Fig. 9

shows a cross-sectional view of a bending transducer according to a further advantageous embodiment of the present invention.

Detailed description of the embodiments according to the figures

Before embodiments of the present invention are explained in more detail below with reference to the drawings, it is pointed out that identical, functionally identical or equivalent elements, objects and/or structures in the different figures are provided with the same or similar reference numerals, so that the description of these elements shown in different embodiments is interchangeable or can be applied to one another.

Fig. 1 shows a perspective view of a bending transducer system according to an embodiment of the present invention in the form of a layered component 100, which comprises a first bending transducer system 1 and a second bending transducer system 2, which are stacked on top of one another. The component 100 can comprise further bending transducer systems which are arranged in layers on the bending transducer system 1 and/or on the bending transducer system 2, for example. A bending transducer system 1 or a bending transducer system 2 comprises a plurality of bending transducers 3, 4 which have the same or different predefined lengths. An arrangement of the bending transducers 3, 4 of different lengths is shown as an example on the surface of the bending transducer system 1. The bending transducer 3 - indicated by a continuous line - is longer than the bending transducer 4 - which is indicated by a short dashed line. In the present exemplary embodiment, both the bending transducer system 1 and the bending transducer system 2 are L-shaped, so that the two bending transducer systems 1 and/or 2 stacked on top of one another stack to form an L-shaped component 100. The individual legs of the L-shaped component 100 are of different lengths. In an area of a shorter leg of the L-shaped component 100, further bending transducers 4 and bending transducers 5 - indicated by a dot-dash line - are arranged, which have a third length. The lengths of the individual bending transducers 3, 4 and 5 are, for example: bending transducer 3 from 1000 µm to 4000 µm; bending transducer 4 from 500 µm to 2000 µm; bending transducer 5 from 100 µm to 1000 µm.

According to a preferred embodiment, the individual length ratios can be selected, for example: bending transducer 3 to bending transducer 4 between 1:1.5 to 1:3; bending transducer 3 to bending transducer 5 between 1:1.5 to 1:3; or the length ratio of the bending transducer 4 to the bending transducer 5 between 1:1.5 to 1:3.

In the present embodiment, the individual bending transducer systems 1 or 2 are composed of bending transducers 3, 4 and 5, which are arranged parallel to one another in a plane of the bending transducer system 1 or the bending transducer system 2, with the individual bending transducers 3, 4 and 5 being aligned along the longer leg of the L-shaped component 100. Openings 13 are provided on the star side in the longitudinal direction of the component 100, which enable the cavities contained in the bending transducer system 1 or bending transducer system 2 - not shown here - to be connected to the environment. Due to the L-shape of the component 100, the individual bending transducers 3, 4 and 5 are arranged in such a way that short bending transducers 4, 5 are arranged in the shorter leg of the L-shaped component 100, with the longer bending transducers 3 being arranged in the longer leg of the L-shaped component.

In this embodiment, the bending transducers 3, 4 and 5 are aligned along the longest side of the component. However, embodiments can also deviate from this and include a bending transducer alignment along the shortest side of the bending transducer system 1 and/or 2 or component 100. The openings 13 are then not arranged in the area 13, but always in the area of the clamps of the bending transducers 3, 4 clamped on both sides or in the area of the clamp 14 and the freely movable end of a bending transducer 5 clamped on one side.

The bending transducers 3, 4 and 5 are arranged in such a way that short bending transducers 5 are arranged near the openings 13. On the one hand, this has the advantage that a higher packing density can be achieved within the bending transducer system 1 and/or 2, resulting in higher sound pressures. On the other hand, resonances can be avoided, which has a positive effect on the sound quality.

In the present embodiment, a control unit 21 is arranged adjacent to the layered component 100 in such a way that it complements the L-shape of the component 100 and forms the component 100 into a rectangular structure. This makes practical use of the existing installation space available between the legs of the L-shaped component 100, resulting in a particularly compact structure.

Embodiments are not limited to the L-shaped design of the external dimensions of the component. Further embodiments are not limited to the illustrated arrangement of the bending transducers 3, 4 and 5, rather the arrangement can differ for each bending transducer system 1 or 2 (cf. Fig. 9 ).

Fig. 2 shows in a perspective view the embodiment from Fig. 1 . In addition, a substrate plane 9 of a substrate layer is shown, which runs parallel to the substrate layer. It is also shown that a common movement plane 10 is formed from the movement directions 6, 7 and 8 of the respective bending transducers, wherein the deformable elements of the bending transducers 3, 4 and 5 oscillate coplanarly in a common flat substrate layer or movement plane 10. The movement plane 10 and the substrate plane 9 are arranged parallel to one another.

Fig. 3 shows in a perspective view an embodiment of a component 100 with two stacked bending transducer systems 1 and 2, which have an oval outer shape. The openings 13 are preferably arranged in the area of the clamps 14 of the bending transducers 3, 4 clamped on both sides or in the area of the clamp 14 and the freely movable end of a bending transducer 5 clamped on one side. An oval outer geometry or shape of the component 100 has the advantage that it can be arranged tilted in a cylindrical or almost cylindrical housing of an ultra-mobile terminal device.

This embodiment shows an arrangement of the bending transducers 3, 4 and 5 along the longest orientation of the oval component geometry. However, embodiments can equally contain different orientations of the bending transducers 3, 4 and 5. In addition, embodiments can contain different orientations of the bending transducers 3, 4 and 5 for each layered bending transducer system 1 or 2, 2+n.

Further preferred embodiments are not limited to this oval shape and are adapted or adaptable to the available space and acoustic conditions in order to achieve maximum sound pressure.

Fig. 4 shows in a perspective view the embodiment from Figure 3 . In addition, a substrate plane 9 is shown, which runs parallel to the substrate layer, wherein the deformable elements of the bending transducers 3, 4 and 5 oscillate coplanarly in a common planar substrate layer or movement plane 10. It is also shown that a movement plane 10 is formed from the movement directions 6, 7 and 8 of the respective bending transducers. The movement plane 10 and the common planar substrate layer or substrate plane 9 are arranged parallel to one another.

The Fig. 5 shows a sectional view of the auditory canal 31, the eardrum 32 and the auricle 30. It can be seen that the auditory canal has a cylindrical geometry or shape. 101 represents the external dimensions of an ultra-mobile terminal device, for example the outer shell of its housing, which are adapted to the auditory canal 31 and essentially seal it off from the environment. Such housings 101 can be adapted to the respective user, but must be manufactured individually in complex, usually additive and slow processes. However, they enable an ultra-mobile terminal device to fit optimally in the auditory canal 31. Embodiments can also use a geometry adapted to the individual have different, simplified geometries that are manufactured using cost-effective processes, such as injection molding. These geometries do not provide an optimal fit of the ultra-mobile terminal or its housing 101 in the ear canal, which is why high sound pressures with high sound quality are required to compensate for these inaccuracies. The tilted arrangement of the component 100 or the bending transducer system 1 or 2 with respect to the longitudinal axis 11 of the housing 101 makes it possible to enlarge the acoustically active surface of the component 100 or the bending transducer system 1 or 2 in order to, on the one hand, arrange a higher number of bending transducers 3, 4 and 5 in the bending transducer system 1 or 2 and/or, on the other hand, to integrate longer bending transducers 3, 4 and 5 in the bending transducer system 1 or 2. The component 100 or the bending transducer system 1 or 2 is tilted about a transverse axis 105 of the ultra-mobile terminal in relation to the longitudinal axis 106, wherein the angle of inclination α between the movement plane 10 and the longitudinal axis 106 is in a range between 90° and 180°, preferably 150° and 170°, particularly preferably 160°.

By arranging the actuators relative to the housing axis, the deformable elements are positioned in an anti-parallel manner with respect to the orientation of the eardrum. This minimizes resonances in the ear canal.

Embodiments are not limited to the illustrated tilting about the transverse axis of the housing 101. It is of course also possible to tilt the component 100 about the longitudinal and vertical axes 106 and 107 of the housing 101.

Fig. 6a shows in a perspective view elements of a component 100' according to an embodiment of the present invention in an excitation state.

In particular, the Figure 6a in a perspective and highly simplified representation of a section of a component 100' from a substrate, without showing a cover wafer 18 and handling wafer 19.

The acoustic device can advantageously be constructed monolithically from several layers, or from substrates of different materials that are connected or bonded to one another via a common layer. This can be done, for example, in the form of an arrangement of a cover wafer 18 above or a handling wafer 19 below a common device wafer 20.

A cavity 11 is formed from a device wafer 20 by partially removing the material, which cavity is defined by a border 17 and the respective movable elements or electrodes of the bending transducers 3 ₂ , 3 ₄ and 4 ₂ , as well as by the substrate in the region of the clamping 14. Embodiments include alternative borders 17 of the cavity 11. On the one hand, the border 17 can be firmly connected to the substrate, on the other hand, the border 17 can consist of adjacent electrodes of a further bending transducer system 100', formed from further bending transducers 3, 4 and 5. The bending transducers 3 ₂ , 3 ₄ , 4 ₂ , and 3 ₁ , 3 ₂ , 4 ₁ shown are clamped on both sides in this embodiment and connected to the substrate via the respective clamping 14. Embodiments also include one-sided clamping, which has the advantage of a large deflection of the freely movable end compared to two-sided clamping.

The bending transducers 3, 4 and 5 can be clamped on one side or both sides in a bending transducer system 1 and/or 2. It is sensible to clamp the shorter bending transducers 4, 5, which are arranged in the area of the openings 13, on one side and to clamp the longer bending transducers 3, which are arranged towards the center of the component, on both sides. This advantageously results in a larger vibration amplitude at higher frequencies of the shorter, one-sidedly clamped bending transducers 5, since these are characterized by an advantageous ratio of mass to bending transducer length.

Furthermore, the basic functional principle for interaction with a volume flow, for example for generating sound or pumping a fluid, is shown in such a bending transducer system 1 and/or 2. In a first time interval, the bending transducers _{3 1 ,} 3 ₂ , 4 ₁ as well as 3 ₂ , 3 ₄ and 4 ₂ move in the direction of the opposite edge 17 of the cavity 11 and thus reduce the volume within this cavity 11. A volume flow 16 resulting from this volume reduction transports the fluid contained in the cavity 11 out of the cavity 11 through the openings 13.

The Figure 6b further shows the basic functional principle for interacting with a volume flow, for example for generating sound or for pumping a fluid in such a bending transducer system 1 and/or 2. In a second time interval, the bending transducers 3 ₁ , 3 ₂ , 4 ₁ as well as 3 ₂ , 3 ₄ and 4 ₂ move away from the opposite edge 17 of the cavity 11 and thus increase the volume of the cavity 11. The volume flow 16 resulting from this volume increase transports the fluid through the openings 13 into the cavity 11.

Alternative embodiments do not contain a border 17 firmly connected to the substrate, but rather additional bending transducers, not shown here, which can be clamped on one and/or both sides. In this case, in the first time interval, the adjacent bending transducer systems 1 and 2 would move away from one another in order to increase the volume of the cavity 11 and move towards one another in order to reduce the volume of the cavity. Further embodiments can comprise a combination of borders 17 firmly connected to the substrate and/or no borders 17 firmly connected to the substrate.

Fig. 7 shows a cross-sectional view of a section of a component 100' along the cutting plane A of the Figure 6a . Shown are the handling wafer 19 and cover wafer 18, which form the vertical boundary of the cavity 11, which is limited by the bending transducers 3 ₁ and 3 ₂ and the edge 17 in the area of the device wafer 20. The structure is a layer stack, with the individual layers being mechanically firmly connected to one another, in particular by a material bond. These layers are not shown in the figure. The layer-by-layer arrangement of electrically conductive layers enables a simple design, since the cavity 11 can be retained by selectively removing it from the layer 20 and bending transducer structures can remain by suitably adjusting the manufacturing processes. Alternatively, it is also possible to arrange the bending transducer structures in whole or in part in the cavity 11 by other measures or processes, for example by creating and/or positioning them in the cavity 11. In this case, the bending transducer structures can be formed differently from the parts of the layer 20 remaining in the substrate, ie can have different materials.

The Figure 8 shows in a perspective view an alternative embodiment of a layered component 100 with an upper bending transducer system 1, which has vertically arranged openings 13 ₁ in a cover wafer 18 ₁ for connecting the cavities 11 with the environment. A second bending transducer system 2 is arranged below the upper, first bending transducer system 1 and has laterally arranged openings 13 in a device wafer 20. Embodiments are not limited to the system shown comprising two bending transducer systems 1 and 2, rather, only one bending transducer system 1 or 2 or a plurality of bending transducer systems 1, 2, ..., n can be arranged. A control unit 21 is arranged in the immediate vicinity, which has a Part of the component 100 and which leads to a restriction of the available installation space of the bending transducer system 1 and which is connected to the bending transducer systems (not shown). Further openings in the handling wafer 19 of the upper bending transducer system 1 can be arranged such that they are connected to openings in the cover wafer 18 of the second bending transducer system 2. Embodiments include that a handling wafer 19 of the first bending transducer system 1 can be dispensed with if - in anticipation of Fig. 9 - the device wafer 20' of the second bending transducer system 2 can take over this function.

The Figure 9 shows in a cross-sectional view an embodiment of an alternative component 100" with an upper bending transducer system 1 that has vertically arranged openings 131 in the cover wafer 18. In this embodiment, the device wafers 20 and 20' are mechanically connected to one another, in particular by means of a material bond, via a common substrate layer 22, which represents both a cover wafer and a handling wafer. This embodiment shows by way of example how openings 13 ₁ , 13' ₁ , 13" ₁ can be arranged in the cover, handling or device wafer in order to be optimally arranged with respect to the direction of sound. The direction of sound can therefore be determined via the volume flow interacting with the environment, which is determined by the movement of the deformable elements or the bending transducer 3 ₁ , 3 ₂ , 3' ₁ and 3' ₂ of the component 100".

Furthermore, the arrangement of the bending transducer system as a sound transducer system is left to the expert. The technical teaching taken up here reveals to the expert features of how a large number of bending transducers must be arranged in order to achieve high acoustic quality with a broad frequency range in a limited, predefined installation space.

In addition, the person skilled in the art can derive technical teachings as to how a plane of movement which is formed by a plurality of directions of movement and can be inclined relative to a longitudinal axis and/or transverse axis and/or vertical axis of the space surrounding the sound transducer system.

• zur fluiddynamischen Dämpfung
• zur Signalverarbeitung
• zur Drahtlosen Kommunikation
• zur Spannungstransformation
• zur Speicherung von Daten
• zur Versorgung mit Energie

Predefined spaces are, for example, the geometric dimensions, determined by the ear canal, additional sensors or system technology:

• for fluid dynamic damping
• for signal processing
• for wireless communication
• for voltage transformation
• for storing data
• for the supply of energy

It is advantageous for short bending transducers in a bending transducer system to be arranged where there is little space available and/or in the area of the openings that connect the cavities with the environment. These openings are located in the area of the outer limits of the bending transducer system. In contrast, long bending transducers are mainly arranged centrally in the bending transducer system. This has the advantage of making optimal use of the available space in order to achieve a high packing density of the individual bending transducers and thereby increase the sound pressure level. In addition, longer bending transducers enable lower resonance frequencies due to their lower rigidity. Short bending transducers are characterized by a comparatively high rigidity, which enables high resonance frequencies. If these bending transducers are arranged in the area of the openings that connect the cavities with the environment, resonances can be avoided and the sound quality can thus be improved.

Advantages of a tilted arrangement in a tube-like space, such as an ear canal.

The ear canal is approximately a cylinder with the dimensions L X D = 25 mm X 0.7 mm (Wiki).

The transverse acoustic resonance of the closed ear canal (λ/2) is therefore at U _T ≈ 235 kHz, the corresponding longitudinal resonance at U _L = 6.6 kHz. A headphone membrane in "normal, ie radial" orientation is excited by the longitudinal mode at U _L = 6.6 kHz and thus generates an undesirable, audible additional resonance.

A headphone diaphragm in an "axial" position is, as a first approximation, only excited by the transverse mode at U _T ≈ 235 kHz. This is much better because it is acoustically completely irrelevant!

Of course, the size of the bending transducer system (analogous to the membrane) should be chosen so that the low natural frequencies of the membrane do not cause interference. It should therefore not be too large. At a 60° inclination, the first natural frequency of an ideal membrane is around 2 x 6.6 kHz = 13.2 kHz. Based on everything we know about "real headphones", this is OK.

Due to the tilted arrangement of the bending transducer system, a larger base area of the bending transducer system can be arranged in the available space, on which in turn longer or more bending transducers can be arranged. By using a larger number of bending transducers, higher sound pressures can be achieved.

Another advantage is that openings can be optimally arranged in the direction of the sound given by the external dimensions. For example, Figure 8 vertically arranged openings, which are then arranged almost in the direction of sound when the component is tilted in the ear canal.

The application thus describes a further development with regard to the optimization of the sound quantity (sound pressure level) and sound quality that can be provided by the component in a specific environment.

High integration requirements relate to adaptation to the available installation space in general as well as to the system design from several components. For example, in ultra-mobile devices (e.g. hearables smartwatches), the energy storage devices in particular as well as any other HMI components (tactile surfaces, displays) are subject to strict limits of the installation space design (cylindrical/cuboid-shaped or flat/plate-shaped). In order to achieve a minimization of the installation space, it is necessary to adapt the sound transducer to the remaining installation space and thus enable a high sound quantity.

In addition, aspects of sound quality cannot be neglected when designing systems (ultra-mobile, such as hearables or wearables in general). Specifically, a specific design of the transducer groups can achieve sound generation that is adapted to the geometric conditions in terms of sound radiation. The main drivers are frequency-dependent effects, whereby disturbing resonances can occur, particularly at high frequencies.

With the present invention, both the sound quality and sound quality can be significantly improved.

The principle of the bending transducer according to the invention is based on the NED (Nanoscopic Electrostatic Drive) and is in WO 2012/095185 A1 described. NED is a novel MEMS (micro electromechanical system) actuator principle. The basic principle is that a silicon beam moves laterally in a plane, the substrate plane, which is defined by a silicon disk or wafer. The silicon beam, which is connected to the substrate in a cavity, interacts with a volume flow. Furthermore, the component comprises an electronic circuit arranged in a layer of the layer stack, wherein the electronic circuit is connected to the electromechanical bending transducer and which is designed to deflect the bending transducer based on an electrical signal.

list of reference symbols

1 First bending transducer system 2 Second bending transducer system 3 First bending transducer has first length 4 Second bending transducer has second length 5 Third bending transducer has third length 6 direction of movement of the first bending transducer 7 direction of movement of the second bending transducer 8 direction of movement of the third bending transducer 9 substrate level 10 plane of movement 11 cavity 12 angle between the plane of movement and the longitudinal axis 13 openings 14 clamping 15 edge of the cavity 16 volume flow 17 edge of the cavity 18 lid wafer 19 handling wafers 20 device wafer 21 ASIC 22 Common substrate layer 30 auricle 31 ear canal 32 eardrum 100 component 100 section of a component 101 External geometry of an ultra-mobile device, for example a housing 102 length of the component 103 width of the component 104 thickness of the component 105 A transverse axis of the ultra-mobile device 106 longitudinal axis of the ultra-mobile device 107 vertical axis of the ultra-mobile device 108 angle α

Claims (9)

1. Acoustic bending converter system (1, 2) comprising
   a plurality of bending converters (3, 4, 5) configured such that deformable elements (3₁, 3₂, 4₁; 3₂, 3₄, 4₂; 3₁, 3₂, 3'₁, 3'₂) of the bending converters (3, 4, 5) oscillate coplanarly in a common planar layer (10), characterized in that the bending converters (3, 4, 5) comprise different resonance frequencies and different expansions of the deformable elements (3₁, 3₂, 4₁; 3₂, 3₄, 4₂; 3₁, 3₂, 3'₁, 3'₂) along a common longitudinal axis that is transversal to a direction of oscillation of the deformable elements (3₁, 3₂, 4₁ ; 3₂, 3₄, 4₂; 3₁, 3₂, 3'₁, 3`₂).
2. Acoustic bending converter system (1, 2) according to claim 1, comprising:
   one or several cavities (11) where the bending converters (3, 4, 5) are arranged, and openings (13; 13₁, 13'₁, 13"₁) through which a fluidic volume flow (16) interacting with the plurality of bending converters (3, 4, 5) can pass.
3. Acoustic bending converter system (1, 2) according to claim 1 or 2, wherein the deformable element (3₁, 3₂, 4₁; 3₂, 3₄, 4₂; 3₁, 3₂, 3'₁, 3'₂) of at least one bending converter (3, 4, 5) can be electrostatically, piezoelectrically or thermomechanically deformed.
4. Acoustic bending converter system (1, 2) according to one of the preceding claims, wherein

   at least a first subset of at least one first bending converter (5) comprises at least one cantilevered deformable element, and

   at least a second subset of at least one second bending converter (3, 4) comprises one deformable element (3₁, 3₂, 4₁; 3₂, 3₄, 4₂; 3₁, 3₂, 3'₁, 3'₂) clamped on two sides each.
5. Acoustic bending converter system (1, 2) according to claim 4, wherein
   the at least first subset of at least one first bending converter (5) comprises, on average, a higher resonance frequency than the at least second subset of at least one of the second bending converters (3, 4) or vice versa.
6. Acoustic bending converter system (1, 2) according to claim 4 or 5, wherein
   the at least first subset of at least one first bending converter (5) comprises, on average, a shorter length than the at least second subset of at least one second bending converter (3, 4).
7. Acoustic bending converter system (1, 2) according to one of the preceding claims, wherein
   outer dimensions of the bending converter system (1, 2) along the common longitudinal axis are between 750 µm and 2000 µm and particularly preferred between 850 µm and 1250 µm.
8. Acoustic bending converter system (1, 2) according to one of the preceding claims, wherein
   an external surface of the bending converter system (1, 2) describes a longitudinal oval along the common longitudinal axis, a longitudinal rectangle along the common longitudinal axis or a longitudinal polygon along the common longitudinal axis, coplanar to the common planar layer.
9. Acoustic bending converter system (1, 2) according to one of the preceding claims,
   wherein

   the bending converters (3, 4, 5) are divided into groups of one or several bending converters (3, 4, 5), wherein in groups having several bending converters (3, 4, 5) the several bending converters (3, 4, 5) are arranged behind one another along the common longitudinal axis;
   and/or wherein

   in groups of several bending converters (3, 4, 5), the several bending converters (3, 4, 5) in the common planar layer (10) are arranged side by side transversal to the common longitudinal axis.

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