EP4247006A2 - Micromechanical acoustic transducer - Google Patents

Abstract

According to a first aspect, a micromechanical sound transducer comprises a first bending transducer with a free end and a second bending transducer with a free end, which are arranged in a common plane, the free end of the first bending transducer being separated from the free end of the second bending transducer by a gap is. The second bending transducer is excited in phase with the vertical oscillation of the first bending transducer. According to a second aspect, a micromechanical sound transducer comprises a first bending transducer which is vertically excited to vibrate and a diaphragm element which extends vertically to the first bending transducer and is separated from a free end of the first bending transducer by a gap.

Description

Embodiments of the present invention relate to a micromechanical sound transducer with at least one bending actuator (generally bending transducer) and miniaturized gap as well as to a miniaturized sound transducer with a cascaded bending transducer. Additional exemplary embodiments relate to corresponding manufacturing processes.

While MEMS has found its way into almost all areas, miniaturized sound transducers are still manufactured using precision engineering. These so-called “microspeakers” are based on the electrodynamic drive system, in which a membrane is deflected using a moving coil moving in a permanent magnetic field. A major disadvantage of these conventional electrodynamic sound transducers is their low efficiency and the resulting high power consumption, often in excess of one watt. In addition, such sound transducers do not have any position sensors, so that the movement of the membrane is unregulated and high distortions occur at higher sound pressure levels. Further disadvantages include high series variations and relatively large overall heights, usually over 3 mm.

Due to high-precision manufacturing processes and energy-efficient drive principles, MEMS have the potential to overcome these disadvantages and enable a new generation of sound transducers. However, a fundamental problem to date has been the low sound pressure levels of MEMS sound transducers. The primary reason for this is the difficulty of generating sufficiently high lifting movements with the smallest possible dimensions. To make matters worse, a membrane is required to prevent an acoustic short circuit, which has a negative effect on the overall deflection due to its additional spring stiffness. The latter can be minimized by using very soft and three-dimensionally shaped membranes (e.g. with a torus), which cannot currently be manufactured using MEMS technology and are correspondingly complex and expensive to integrate in a hybrid manner.

MEMS sound transducers of various designs are discussed in publications and patents, which have not yet resulted in market-ready products due to, among other things, the problems mentioned above. These concepts are based on closed membranes, which are set into vibration and generate sound. In [Hou13, US2013/156253A1 ] is e.g. B. describes an electrodynamic MEMS sound transducer that requires the hybrid integration of a polymembrane and a permanent magnet ring. The concept of piezoelectric MEMS acoustic transducers was introduced in [Yi09, Dej12, US7003125 , US8280079 , US2013/0294636A1 ] shown. Here, piezoelectric materials such as PZT, AIN or ZnO were applied directly to silicon-based sound transducer membranes, which, however, do not allow sufficiently large deflections due to their low elasticity. Another piezoelectric MEMS sound transducer with a plate-shaped body that is deflected out of the plane in a piston shape via a membrane or several actuators is shown in [ US 20110051985A1 ] shown. Digital MEMS sound transducers based on arrays with electrostatically driven membranes, which, however, can only generate sufficiently high sound pressures at high frequencies, are described in [Gla13, US7089069 , US20100316242A1 ] described. Therefore, there is a need for a better approach.

The object of the present invention is to create a micromechanical sound transducer that represents an improved compromise between sound pressure, frequency response and manufacturing effort.

The task is solved by the independent patent claims.

Embodiments of the present invention provide a micromechanical sound transducer (eg constructed in a substrate) with a first bending transducer or bending actuator and a second bending transducer or bending actuator. The first bending actuator has a free end and, for example, at least one or two free sides and is designed to be stimulated to vertical vibration, for example by an audio signal, and to emit (or record) sound. The second bending actuator also has a free end and is arranged relative to the first bending actuator in such a way that the first and second bending actuators lie or are suspended in a common plane. Furthermore, the arrangement is designed such that a gap (e.g. in the micrometer range) is formed between the first and second bending actuators, which separates the two bending actuators from one another. The second bending actuator is always excited to oscillate in phase with the first bending actuator, which has the consequence that the gap remains essentially constant over the entire deflection of the bending actuators.

Embodiments for this aspect of the invention are based on the knowledge that by using several mutually separated bending transducers or actuators, which are separated from each other with a minimal (separation) gap, it is achieved with identical deflection of the two transducers or actuators out of the plane can be ensured that the gap between the two actuators remains almost constantly small (in the micrometer range), so that there are always high viscosity losses in the gap, which as a result prevent an acoustic short circuit between the rear volume and the front volume (of the bending actuator). Compared to previous MEMS systems, which are mostly based on closed membranes, the present concept enables a significant increase in performance. The primary reason is that, as a result of the actuator decoupling, no energy has to be used to deform additional mechanical membrane elements, which means significantly higher deflections and forces are possible. In addition, nonlinearities only occur with significantly larger movement amplitudes. While conventional systems sometimes require complex-shaped membranes or magnets that cannot yet be implemented in MEMS technology but can only be integrated hybrid with great effort, the present concept can be implemented using common silicon technology processes. This offers significant manufacturing and cost advantages. Due to the low oscillating mass due to the concept and material, systems with an extraordinarily wide frequency range and at the same time high movement amplitudes can be implemented.

According to a further aspect, a micromechanical sound transducer with a first bending transducer or bending actuator (designed to be excitable to vertical vibration) and a diaphragm element extending vertically (i.e. from the plane of the substrate and thus also from the plane of extension of the bending transducer) to the first bending transducer or bending actuator created. The diaphragm element is separated from the free end of the first bending actuator by a gap.

The insight of this aspect is that the diaphragm element can ensure that the distance between the diaphragm element and the free end of the actuator remains approximately constant over the entire range of movement of the transducer or actuator (as a result of the vibration). This achieves the same effect as above, namely that an acoustic short circuit can be prevented due to the high viscous losses at the free end (and possibly also the free sides) or in the gap. As a result, this means that the same advantages in particular with regard to the efficiency of the sound transducer, the broadband capability and the manufacturing costs.

One exemplary embodiment relates to a manufacturing method of such an actuator with a diaphragm element. This method includes the steps of: structuring a layer to form the first bending actuator and producing or depositing the vertical shutter element so that it protrudes beyond the layer of the first bending actuator. Vertical is to be understood, for example, as perpendicular (perpendicular to the plane of the substrate) or generally angled relative to the substrate (angle range 75°-105°).

Regarding the variant with the at least two bending actuators, it should be noted that, according to the exemplary embodiment, the first and second bending actuators are similar bending actuators. These can be, for example, flat, rectangular, trapezoidal or generally polygonal bending actuators. According to a further exemplary embodiment, these bending actuators can each have a triangular shape or a circular segment shape. The triangular or circular segment shape is often used in micromechanical sound transducers that include more than two bending actuators. In this respect, according to a further exemplary embodiment, the micromechanical sound transducer includes one or more further bending actuators, such as. B. three or four bending actuators.

As already explained above, either the simultaneous or in-phase control of the two bending actuators or the provision of the diaphragm element makes it possible, starting from a gap, which (in the idle state) is less than 10% or even less than 5%; 2.5%, 1%, 0.1% or 0.01% of the area of the first bending actuator, the gap remains small over the entire range of movement, that is, even with deflection it is a maximum of 15% or even only 10% (or 1 % or 0.1% or 0.01%) of the area of the first bending actuator. With regard to the variant with the diaphragm element, it should be noted that the height of the diaphragm element is dimensioned such that it is at least 30% or 50% or preferably 90% or even 100% or more of the maximum deflection of the first bending actuator in linear operation (ie linear mechanical elastic range) or the maximum elastic deflection of the first bending transducer (generally 5-100%). Alternatively, the height can be set depending on the gap width (at least 0.5 times, 1 time, 3 times or 5 times the gap width) or depending on the thickness of the bending transducer (at least 0.1 times, 0.5 times times, 1 time, 3 times or 5 times thickness). These dimensioning regulations for the two variants enable the The entire deflection range and thus also over the entire sound level range has the functionality/prevention of acoustic short circuits explained above.

According to a further exemplary embodiment, not only can a diaphragm element be arranged opposite the free end, but also, for example, on the non-clamped sides around the bending actuator. This is particularly useful if the bending actuator is a bending actuator clamped on one side.

According to one exemplary embodiment, the diaphragm element can have a varying geometry in its cross section (e.g. a geometry curved/inclined towards the actuator), so that the slot has a largely constant cross section along the actuator movement. According to exemplary embodiments, the panel can form a mechanical stop in order to prevent mechanical overload.

According to a further exemplary embodiment, a micromechanical sound transducer is created which includes a control which controls the second bending actuator so that it is excited to oscillate in phase with the first bending actuator. In addition, according to a further exemplary embodiment, it can be advantageous if a sensor system is provided which detects the vibration and/or the position of the first and/or the second bending actuator in order to enable the controller to control the two bending actuators in phase. In contrast to previous systems, which usually have no sensors or only record the deflection of the drive (not just the membrane), with this principle the actual position of the sound-generating element can be determined using the easily integrated sensors. This is a great advantage and enables significantly more precise and reliable detection. This forms the basis for controlled excitation (closed loop), with which external influences, aging effects and non-linearities can be electronically compensated.

According to one exemplary embodiment, the bending actuators can also have a so-called “cascading”. This therefore means that the first and/or the second bending actuator each comprise at least a first and a second bending element. These elements are connected in series. According to exemplary embodiments, “connected in series” means that the first and second bending elements have a clamped end and a free end and the second bending element has its clamped end attacks the free end of the first bending actuator and forms the free end of the entire bending actuator with its free end. The connection between the two bending elements can be formed, for example, by a flexible element. Optionally, the micromechanical sound transducer can have an additional frame, which is provided, for example, in the area of the transition between the first and the second bending element. This serves for stiffening and mode decoupling. With regard to the two bending elements, it should be noted that, according to a preferred exemplary embodiment, these are controlled with different control signals, so that, for example, the inner bending element or the inner bending elements are used for higher frequencies, while the further outer bending elements are controlled to oscillate in a lower frequency range .

According to a further aspect, a micromechanical sound transducer is created with at least one, preferably two bending actuators, each bending actuator comprising a first and a second bending element which are connected in series. According to a further exemplary embodiment, such bending actuators can also have a flexible connection instead of a separation gap.

Embodiments of this aspect of the invention are based on the knowledge that by connecting several bending elements of a bending actuator in series, it can be achieved that different bending actuators are responsible for different frequency ranges. For example, the internal bending actuator can be designed for a high frequency range, while the frequency range further out is operated for the low frequency range. In contrast to usual membrane approaches, the concept described enables cascading with several individually controllable actuator stages. In addition, the frequency-separated control in combination with the piezoelectric drives can achieve significant increases in energy efficiency. The good mode decoupling also offers advantages in terms of playback quality. Other advantages include: B. the realization of particularly space-saving multi-way sound transducers.

In this exemplary embodiment of the bending actuator with cascading, the developments as explained above can also be used in accordance with additional exemplary embodiments. In particular, the features relating to the exact design of the cascading, e.g. B. the connecting element or the frame. Furthermore, the sub-aspects relate to the flat, rectangular, trapezoidal or triangular (generally polygonal) bending actuator geometry relevant for cascaded transducer configurations.

Another exemplary embodiment relates to a method for producing a micromechanical sound transducer with cascaded bending actuators. The method includes the steps of: providing a first layer that forms the first (and the second) bending actuator with the (respectively) first and second bending elements and connecting the (respectively) first and second bending elements.

According to one exemplary embodiment, it would be conceivable to nest actuators one inside the other and/or to design them of different sizes, for example in order to cover different frequency ranges.

Fig. 1a

eine schematische Darstellung eines mikromechanischen Schallwandlers mit zwei Biegeaktuatoren gemäß einem Basisausführungsbeispiel;

Fig. 1b

eine schematische Darstellung eines mikromechanischen Schallwandlers mit einem Biegeaktuator sowie einem vertikalen Blendenelement gemäß einem weiteren Basisausführungsbeispiel;

Fig. 1c

eine schematische Darstellung eines Biegeaktuators mit einer beliebig angrenzenden Struktur zur Illustration der Verbesserung der Konzepte aus den Fig. 1a und 1b gegenüber dem Stand der Technik;

Fig. 2a-c

schematische Querschnitte möglicher Aktuatorelemente gemäß Ausführungsbeispiel;

Fig. 3a-d

schematische Draufsichten von Biegeaktuatorkonfigurationen gemäß Ausführungsbeispielen;

Fig. 4

ein schematisches Diagramm zur Illustration eines simulierten Schalldruckpegels für unterschiedliche Ausführungsbeispiele;

Fig. 5

eine schematische Darstellung eines mikromechanischen Schallwandlers mit zwei Biegeaktuatoren, die jeweils eine Kaskadierung umfassen, gemäß Ausführungsbeispielen;

Fig. 6a-c

schematische Draufsichten auf Biegeaktuatorkonfigurationen mit Kaskadierung gemäß Ausführungsbeispielen;

Fig. 7

ein schematisches Diagramm zur Illustration eines simulierten Schalldruckpegels mit einer Biegeaktuatorkonfiguration mit Kaskadierung;

Fig. 8a,b

schematische Ansichten oder Teilansichten einer Draufsicht auf eine Biegeaktuatorkonfiguration mit Kaskadierung gemäß einem weiteren Ausführungsbeispiel;

Fig. 9

ein schematisches Diagramm zur Illustration einer mittels FEM-simulierten Auslenkung eines mikromechanischen Schallwandlers mit Kaskadierungen gemäß einem Ausführungsbeispiel;

Fig. 10a-c

schematische Draufsichten auf Biegeaktuatoren mit seitlich angeordneten Blendenelementen gemäß Ausführungsbeispielen;

Fig. 11a-d

schematische Darstellungen zur Illustration eines Prozessablaufs bei der Herstellung eines mikromechanischen Schallwandlers gemäß Ausführungsbeispielen;

Fig. 12

eine schematische Darstellung eines Arrays mit einer Vielzahl an mikromechanischen Schallwandlern gemäß einem Ausführungsbeispiel;

Fig. 13a-i

zeigt schematische Darstellungen von unterschiedlichen Implementierungen der in Fig. 1b erläuterten Blendenstrukturen gemäß Ausführungsbeispielen;

Fig. 14a-c

schematische Darstellungen von mikromechanischen Schallwandlern mit einem Deckel gemäß zusätzlichen Ausführungsbeispielen;

Fig. 15a-h

schematische Darstellungen von Draufsichten auf mikromechanische Schallwandler gemäß Ausführungsbeispielen; und

Fig. 16

eine schematische Darstellung eines zweiseitig eingespannten mikromechanischen Schallwandler gemäß Ausführungsbeispielen.

Further training is defined in the subclaims. Embodiments of the present invention have been explained below using the figures. Show it:

Fig. 1a

a schematic representation of a micromechanical sound transducer with two bending actuators according to a basic embodiment;

Fig. 1b

a schematic representation of a micromechanical sound transducer with a bending actuator and a vertical diaphragm element according to a further basic embodiment;

Fig. 1c

a schematic representation of a bending actuator with an arbitrarily adjacent structure to illustrate the improvement of the concepts from the Fig. 1a and 1b compared to the state of the art;

Fig. 2a-c

schematic cross sections of possible actuator elements according to the exemplary embodiment;

Fig. 3a-d

schematic top views of bending actuator configurations according to exemplary embodiments;

Fig. 4

a schematic diagram illustrating a simulated sound pressure level for different embodiments;

Fig. 5

a schematic representation of a micromechanical sound transducer with two bending actuators, each comprising a cascade, according to exemplary embodiments;

Fig. 6a-c

schematic top views of bending actuator configurations with cascading according to exemplary embodiments;

Fig. 7

a schematic diagram illustrating a simulated sound pressure level with a cascading bending actuator configuration;

Fig. 8a,b

schematic views or partial views of a top view of a bending actuator configuration with cascading according to a further exemplary embodiment;

Fig. 9

a schematic diagram to illustrate an FEM-simulated deflection of a micromechanical sound transducer with cascades according to an exemplary embodiment;

Fig. 10a-c

schematic top views of bending actuators with laterally arranged diaphragm elements according to exemplary embodiments;

Fig. 11a-d

schematic representations to illustrate a process flow in the production of a micromechanical sound transducer according to exemplary embodiments;

Fig. 12

a schematic representation of an array with a plurality of micromechanical sound transducers according to an exemplary embodiment;

Fig. 13a-i

shows schematic representations of different implementations of the in Fig. 1b explained aperture structures according to exemplary embodiments;

Fig. 14a-c

schematic representations of micromechanical sound transducers with a cover according to additional exemplary embodiments;

Fig. 15a-h

schematic representations of top views of micromechanical sound transducers according to exemplary embodiments; and

Fig. 16

a schematic representation of a double-sided clamped micromechanical sound transducer according to exemplary embodiments.

Before exemplary embodiments of the present invention are explained in detail below with reference to the accompanying drawings, it should be noted that elements and structures with the same effect are provided with the same reference numerals so that the description of them can be applied to one another or interchangeable.

Fig. 1a shows a sound transducer 1 with a first bending actuator 10 and a second bending actuator 12. Both are arranged or clamped in a plane E1, as can be seen from the clamping 10e and 12e. The clamping can be realized in that the bending actuators 10 and 12 are etched out of a common substrate (not shown), so that the bending actuators 10 and 12 are connected to the substrate on one side and there is a (common) cavity (not shown) under the actuators 10 and 12 shown) is formed. At this point it should be noted that the bending actuators 10 and 12 shown here can, for example, be prestressed, so that the illustration either shows a rest state or also shows a deflected snapshot (in this case, the rest state is shown by the dashed line). As can be seen, the two actuators 10 and 12 are arranged horizontally next to one another, so that the actuators 10 and 12 or at least the clamps 10e and 12e lie in a common plane E1. This statement preferably refers to the rest state, whereby in the prestressed case the level E1 refers primarily to the common clamping areas 10e and 12e.

The two actuators 10 and 12 are arranged opposite each other, so that between them there is a gap 14 of, for example, 5 µm, 25 µm or 50 µm (generally in the range between 1 µm and 90 µm, preferably less than 50 µm or less than 20 µm). This gap 14, which separates the two cantilevered bending actuators 12 and 14, can be referred to as a decoupling gap. The decoupling gap 14 varies only minimally over the entire deflection range of the actuators 10 and 12, for example by a factor of 1, 1.5 or 4 (generally in the range 0.5-5), i.e. H. Variation of less than +500%, +300%, +100% or +75% or less than +50% of the gap width (at rest) in order to be able to dispense with additional sealing, as will be explained below.

The actuators 10 and 12 are preferably driven piezoelectrically. Each of these actuators 10 and 12 can, for example, have a layer structure and in addition to the piezoelectric active layers have one or more passive functional layers. Alternatively, electrostatic, thermal or magnetic drive principles are also possible. If a voltage is applied to the actuators 12, this or, in the piezoelectric case, the piezoelectric material of the actuators 10 and 12 is deformed and causes the actuators 10 and 12 to bend out of the plane. This bending results in the displacement of air. With a cyclic control signal, the respective actuator 10 and 12 is then excited to oscillate in order to emit (or in the case of a microphone, record) a sound signal. The actuators 10 and 12 or the corresponding control signal are designed so that adjacent actuator edges or the free end of the actuators 10 and 12 experience an almost identical deflection from the plane E1. The free ends are marked with the reference numbers 10f and 12f. Since the actuators 10 and 12 or the free ends 10f and 12f move parallel to one another, they are in phase. In this respect, the deflection of the actuators 10 and 12 is referred to as being in phase.

As a result, a constant deflection profile is formed in the overall structure of all actuators 10 and 12 in the driven state, which is only interrupted by the narrow decoupling slots 14. Since the gap width of the decoupling slots is in the micrometer range, high viscous losses are achieved on the gap side walls 10w and 12w, so that the air flow passing through here is significantly throttled. This means that the dynamic pressure equalization between the front and back of the actuators 10 and 12 cannot take place quickly enough, so that an acoustic short circuit is reduced regardless of the actuator frequency. This means that a narrowly slotted actuator structure behaves fluidly like a closed membrane in the acoustic frequency range under consideration.

Fig. 1b shows another variant of how an actuator of a micromechanical sound transducer can achieve good sound pressure behavior without a seal. The exemplary embodiment Fig. 1b shows the sound transducer 1' comprising the actuator 10, which is firmly clamped at the point 10e. The bending actuator 10 may be etched from a substrate (not shown) to form a cavity (not shown) beneath it. The free end 10f can be excited to oscillate over an area B. A vertically arranged aperture element 22 is provided opposite the free end 10f. This diaphragm element is preferably at least as large or larger than the movement range B of the free end 10f. The diaphragm elements 22 preferably extend on the front and/or back of the actuator, that is to say from the plane E1 (substrate plane). viewed from a lower level and a higher level (e.g. perpendicular to the substrate). Between the diaphragm element 22 and the free end 10f there is a gap 14 'comparable to the gap 14 Fig. 1a intended.

The diaphragm element 22 makes it possible to keep the width of the provided decoupling gap 14 'approximately the same even in the deflected state (see B). Thus, in this configuration with the adjacent edges, no significant openings arise as a result of the deflection, such as in Fig. 1c shown.

Fig. 1c shows an actuator 10, which is also clamped at point 10e. Opposite, an arbitrarily adjacent structure 23 is provided without vertical extension and without movement. As a result of a deflection of the actuator 10, an opening occurs in the area of the free end 10f of the actuator. This opening is provided with the reference symbol "o". Depending on the deflection, these opening cross sections 14o can be significantly larger than the decoupling slots (cf. Fig. 1a and 1b ) or generally a coupling slot in the idle state. The opening can allow air to flow between the front and back, resulting in an acoustic short circuit.

According to exemplary embodiments, the side surface of the aperture element 22 or the aperture element 22 can be adapted to the movement of the actuator 10 in the deflection region B. Specifically, a concave shape would be conceivable.

Both structure 1 Fig. 1a as well as the structure 1' Fig. 1b makes it possible to prevent the acoustic short circuit by providing means which keep the decoupling gap 14 or 14 'approximately constant over the entire range of movement.

As explained above, according to one embodiment, a piezoelectric material may be used. Fig. 2 shows three different cross sections of possible actuator elements in the representations ac. In Fig. 2a a unimorphic structure is shown. A passive layer 10p, 12p, a piezoelectric layer 10pe or 12pe is also applied here.

Fig. 2b shows a bimorph structure. Here, two piezoelectric layers 10pe_1 or 12pe_1 and 10pe_2 or 12pe_2 as well as a passive intermediate layer 10p or 12p are provided.

In Fig. 2c A piezoelectric layer stack is shown, each with two piezoelectric layers 10pe_1 or 12pe_1 and 10pe_2 and 12pe_2.

All piezo actuators shown from the Fig. 2a to 2c So they have in common that they consist of at least two layers, namely a piezoelectric layer 10pe or 12pe and another layer, such as. B. a passive layer 10p, 12p or a further piezoelectric layer 10pe_2, 12pe_2 is formed. The piezoelectric layers 10pe, 12pe, 10pe_1, 12pe_1, 10pe_2, 12 pe_2 can be designed as multilayer systems with additional separating layers (see layers 10p, 12p) and/or can themselves be formed from any number of sublayers (see dashed lines). The contact is made, for example, by flat or interdigital electrodes.

According to an alternative exemplary embodiment, a thermal drive can also be used, which can have a multi-layer structure analogous to the piezoelectric actuators. Basically, the structure of a thermal drive corresponds to the structure as it relates to Fig. 2a-c is explained for piezoelectric layers, whereby thermally active layers are used instead of piezoelectric layers.

Referring to Fig. 3a-c are different actuator arrangements, comprising at least two opposite actuators (cf. Fig. 3b ) explained.

Fig. 3a shows an actuator arrangement with four actuators 10', 11', 12' and 13'. Each of these actuators 10' to 13' is triangular and clamped on one side along the hypotenuse. According to one exemplary embodiment, the triangles are right-angled triangles, so that the right-angled tips of the actuators 10' to 13' all meet at one point. As a result, the feedback gaps 14 extend between the catheters.

According to exemplary embodiments, the individual actuators 10' to 13' can also be further subdivided, as indicated by the dashed lines. When subdivided, of course, the clamping is no longer along the hypotenuse, but along one of the legs, while the decoupling gaps then extend along the hypotenuse and along the other leg.

Regardless of whether there are four or eight actuators, the triangular design enables the adjacent free ends (separated by the respective column 14) to experience the same deflection as possible.

Fig. 3b basically shows the top view of the exemplary embodiment Fig. 1a , whereby it is just indicated here that both the actuator 10 and the actuator 12, e.g. B. can be subdivided along the axes of symmetry (see dashed line).

Fig. 3c shows a further embodiment in which the entire sound transducer is arranged in the shape of a circular segment and has a total of four 90 ° segments as actuators 10 "to 13", which in turn are separated from each other by the separation gap 14. In this circular sound transducer, the individual actuators 10" to 13" can be further subdivided, as indicated by the dashed lines.

All exemplary embodiments from the Figures 3a to 3c have in common that they are clamped at the edge, as indicated by the respective area 10e' to 13e' or 10e and 12e or 10e" to 13e".

Furthermore, it should be noted at this point that, as shown in the exemplary embodiments Figs. 3a-3c is shown, the separation columns 14 preferably extend along the lines of symmetry. In the exemplary embodiments with more than two actuators, this means that the separation gaps meet in the center of gravity of the total area of the sound transducer according to a preferred exemplary embodiment.

Fig. 3d shows (in plan view) another version of a micromechanical sound transducer with four (here rectangular or square) actuators 10", 11", 12" and 13", which are in the form of four quadrants of a rectangle or squares are arranged. The four actuators 10''' to 13''' are separated from each other by two intersecting separation gaps 14. Each of the actuators 10''' to 13''' is clamped at a corner, ie on both sides, on the outer edge.

Referring to Fig. 4 shows the influence of the gap width. Fig. 4 shows the resulting sound pressure level SPL over a frequency range from 500 Hz to 20 kHz for four different gap widths (5 µm, 10 µm, 25 µm and 50 µm). In the frequency range shown, the reduction in the sound pressure level SPL (acoustic short circuit) is negligible for gap widths of less than 10 µm and the structure behaves acoustically like a closed membrane. As can be seen further, in the higher frequency range (e.g. above 6000 Hz) the influence of the gap width decreases significantly. Compared to systems with closed membranes, the present systems are characterized by significantly higher efficiency due to the decoupling of the individual actuators. The latter manifests itself in very high deflections and sound pressure levels. There are also further advantages in terms of linearity.

Referring to Fig. 5 An exemplary embodiment will now be explained using a corresponding further aspect. Fig. 5 shows a structure of a micromechanical sound transducer 1" with two actuators 10* and 12*. The two actuators 10* and 12* each include an inner stage and an outer stage. This means that the actuator 10* has a first actuator element 10a* (outer stage) and a second actuator element 10i* (inner stage). Analogously to this, the actuator 12* comprises the actuator element 12a* and the actuator element 12i*.

As shown here, the outer steps 10a* and 12a* are always clamped, namely over the areas 10e* and 12e*. The opposite end of the actuators 10a* and 12a* is referred to as the free end. The inner steps 10i* and 12i* are coupled to this free end by means of optional connecting elements 17. The coupling is carried out in such a way that the coupling is carried out, for example, via one end of the inner actuator elements 10i* or 12i*, namely in such a way that the opposite ends of the inner actuators 10i* or 12i* serve as free ends. In other words, this means that the actuator 10* or 12* is constructed in such a way that the inner stage 10i* (or 12i*) is connected in series with the outer stage 10a* (12a*).

As shown here, a decoupling gap 14* is formed between the free ends of the elements 10i* and 12i*. This is not necessarily designed for all exemplary embodiments in the same way as the decoupling gap, which is used in connection with the above exemplary embodiments (cf. Fig. 1a ) was explained. This means that, analogous to the above exemplary embodiments, the actuators 10* and 12* are separated from one another only by a decoupling gap 14 that is a few micrometers wide and are preferably designed in such a way that adjacent structural edges (free edges of the inner elements 10e* and 12e*) During operation, the same deflection (synchronous or in-phase) as possible from the plane E1 (in which the actuators 10* and 12* or the clamping areas 10e* and 12e* are arranged) is experienced. An alternative would be to connect the internal ones Elements 10i* and 12i* in the area of the gap shown, for example possible using a flexible material.

According to optional exemplary embodiments, the individual cascaded steps can rest on a frame 19. In this exemplary embodiment, the frame 19 is arranged such that the clamped ends of the inner steps 10i* and 12i* rest on the same frame 19. In general, however, it is said that the frame 19 is preferably arranged so that it lies in the area of the connection points (cf. connection elements 17). The frame makes it possible to suppress parasitic vibration modes and unwanted mechanical deformations.

Even if it was assumed in the above exemplary embodiments that two actuators 10* and 12*, each with an inner and outer actuator stage with the actuator elements 10a*, 10i*, 12a*, 12i*, should be noted at this point that according to further exemplary embodiments a micromechanical sound transducer with only one actuator (e.g. the actuator 10*) is created, which has the first stage 10a* and the second stage 10i* in a corresponding series arrangement. This actuator can, for example, swing freely relative to a fixed end, so that a gap is formed between them, or can also be flexibly connected to a fixed end. According to a further exemplary embodiment, there would also be a diaphragm, such as that in Fig. 1b is explained, conceivable.

Referring to Fig. 6a to 6c Three acoustic transducers according to the embodiment are explained in a schematic top view, in which the configurations are made from Fig. 3a to 3c is expanded to include cascading (two-stage cascading configurations).

Fig. 6a shows a micromechanical sound transducer with four actuators 10*' to 13*', each of the actuators 10*' to 13*' having two actuator elements 10a*' or 10i*' to 13i*' or 13a*'. The inner elements 10i*' to 13i*' each have a triangular shape (with respect to the area), while the outer elements 10a*' to 13a*' have a trapezoidal shape (with respect to the area). The smaller leg of the trapezoidal actuator 10a*' to 13a*' is connected to the hypotenuse leg of the triangular actuator 10i*' to 13i*' via connecting elements 17. In this exemplary embodiment, the optional connecting elements are preferably arranged at the corners of the trapezoid or triangle.

Fig. 6b essentially shows the electromechanical sound transducer in a top view Fig. 5 with the inner actuators 10i* and 12i* and the outer actuators 10a* and 12a*. Here too, connecting elements 17 are provided at the corners of the rectangular inner and outer elements 10i*, 10a*, 12i* and 12a*.

Fig. 6c shows the cascaded actuators 10*" to 13*", starting from the circular segment-shaped micromechanical sound transducer, each actuator having an inner actuator element and an outer actuator element. The inner actuator elements 10i*" to 13i*" are designed as circular segment-shaped elements, while the outer elements 10a*" to 13a*" are designed as circular disk segments. The connection is again made via connecting elements 17.

All exemplary embodiments from the Fig. 6a to 6c have in common that, according to preferred exemplary embodiments, the actuators 10*' to 13*' or 10* to 12* or 10*" to 13*" are separated from one another by separation gaps 14. Additional separation gaps 15 can also be provided between the inner actuators (for example 10i*' and 10a*'), which are only bridged by the connecting elements 17. In other words, this means that the outer steps (for example 10a* and 12a* in Fig. 6b ) are connected to the second inner stages 10i* and 12i* via at least one connecting element, but preferably via two or more spaced-apart connecting elements 17. The connecting elements can be designed as mechanical spring elements or joints.

As in connection with Fig. 3a-c explained, the actuators can also be further subdivided, so that any number of actuators are created per actuator element 10* or 12* (see dashed line).

Now that the structure of the sound transducers has been explained, their function will be discussed below: In the driven state, the actuators of the outer stage deflect the inner stage out of the plane, with the actuators of the inner stage exerting a further deflection. The result is a deflected structure that behaves acoustically like a closed membrane due to the high viscous losses in the decoupling slots.

Alternatively, the cascaded overall structure can also have three or more stages. The different stages can either have identical or different drive signals be controlled. In the case of different drive signals, the stages can be operated in different frequency ranges and e.g. B. form a multi-way sound transducer with a particularly small space requirement.

At this point it should be noted that this is in relation to Fig. 1b The principle of flow diaphragms explained can also be extended to multi-piece cascaded systems, e.g. B. to minimize acoustic losses between connecting elements and actuators or intermediate stages.

With reference to the above exemplary embodiments, it should be noted that the ones in the Fig. 6a to 6c Explained variants can be combined in any way according to additional exemplary embodiments. For example, it is possible that instead of the four inner actuator elements 10a*' to 13a*' Fig. 6a only two inner actuator elements 10i* and 12i*, as shown in Fig. 6b are shown. Furthermore, it is also conceivable that only one inner actuator element, e.g. B. also in combination with a cover (see exemplary embodiment Fig. 1b ) is provided.

Fig. 7 shows a graph of simulated sound pressure over the frequency range, broken down into inner and outer stages. As can be seen, the outer stage serves the low frequency range (maximum sound pressure at around 1500 Hz) while the inner stage serves the higher frequency range (maximum sound pressure at around 10000 Hz). In the present case, a MEMS sound transducer with a chip size of 1x1 cm was assumed and measured at a distance of 10 cm.

Fig. 8 illustrates the concept of cascading using the example of a concrete two-stage design. In Fig. 8a the top view is shown, where in Fig. 8b an enlarged detail of the connection area is shown.

As per the Fig. 8a As can be seen, the two-piece design has external actuators 10a*' and internal actuators 10i*'. In terms of configuration, this is in Fig. 8a The design shown differs from the design Fig. 8a comparable. In the exemplary embodiment shown here, the decoupling slots 14 are identified by solid lines. As shown in particular in the magnification Fig. 8b can be seen, respective decoupling slots 14 are also provided between the individual stages.

As opposed to Fig. 6a is here in the design Fig. 8a also additionally illustrates the frame structure 19*', whose lateral dimensions are smaller than the lateral dimensions of all internal steps 10e*'.

Like based on Fig. 8b As can be seen, folded springs serve as connecting elements 17*', the spaces between which have decoupled filling structures 17f*', e.g. B. are made of a material of spring or actuator. Analogously, the spaces 14 between the actuators of both stages also have such filling structures 17f*'.

In Fig. 9 is a deflection profile of the example design obtained using FEM simulation Fig. 8a and b shown in three-dimensional cross section. As illustrated by the deflection values illustrated by hatching, an almost constant deflection profile is formed despite the decoupling slots, which is only interrupted by the narrow decoupling slots 14.

Referring to Fig. 10 will be an extension of the design Fig. 1a as well as the design Fig. 1b explained. The configuration Fig. 10a is comparable to the configuration Fig. 1b , whereby the diaphragm element 22 provided opposite the actuator 10 clamped on one side (cf. clamping 10e) is not only provided in the area of the free end 10f, but also extends along the sides of the actuator, i.e. along the entire decoupling slot 14 '. The laterally arranged panel elements are marked with the reference numerals 22s.

Fig. 10b is based on a sound transducer configuration with two opposite actuators 10 and 12, as z. Am Fig. 3b is shown. These are again actuators clamped on one side (cf. clamping 10e or 12e). In this exemplary embodiment, a vertically arranged diaphragm element 22s extends along the lateral decoupling slots 14.

Both the exemplary embodiment Fig. 10a as well as the exemplary embodiment Fig. 10b Through the use of the laterally arranged aperture elements 22s in the structures shown here with discontinuous deflection profiles, a good fluidic separation of the front and back is possible.

Fig. 10c shows a further variant in which four actuators 10", 11", 12" and 13" extend from a central surface 16. The four actuators 10"" to 13"" are each trapezoidal and are clamped on one side relative to the surface 16 over their short side. The four actuators 10"" to 13"" are separated from each other via four diagonally arranged separation gaps 14 (which extend as an extension of the diagonal of the surface 16), so that the long side of the actuators 10"" to 13"" can swing freely. In order to enable a "sealing" against the edge areas, a (circumferential) vertically formed aperture element 22s is provided along the long side of the trapezoidal actuators 10"" to 13"".

Fig. 12 shows a micromechanical sound transducer in array form. The micromechanical sound transducer shown here has eight sound transducers 1, for example in relation to Fig. 1a were explained. These eight sound transducers 1 are arranged in two rows and four columns. This means that a large area and thus a high sound pressure can be achieved. If one assumes that each actuator of the sound transducer 1 and a base area of 5 x 5 mm, this creates a “membrane area” of 200 mm ² , so to speak. In general, the sound transducer shown in this way can be scaled as desired, so that sound transducer sizes of, for example, 1 cm in length or more (generally in the range from 1 mm to 50 cm) can be achieved.

Even if in the exemplary embodiment shown here Fig. 12 The micromechanical sound transducer 1 is an example Fig. 1a was explained, it should be noted at this point that any other sound transducers as explained above, such as. B. the sound transducer 1 ' Fig. 1b or the cascaded sound transducers Fig. 5 can be used. Other shapes and arrangements are also conceivable.

According to further exemplary embodiments, the individual actuators explained above can be provided with sensors. The sensors make it possible to determine the actual deflection of the actuators. These sensors are typically connected to the control of the actuators, so that the control signal for the individual actuators is readjusted around a feedback loop in such a way that the individual actuators oscillate in phase. The sensor system can also have the purpose of detecting non-linearities and distorting the signal during control in such a way that non-linearities can be compensated for or reduced.

Background: Since the actuators also form the sound-generating element, aging effects and non-linearities can be measured directly during operation and, if necessary, compensated electronically. This represents a major advantage over usual membrane-based ones Systems in which either no sensors are present or only the behavior of the drives can be detected, but not of the sound-generating membrane element.

The position detection is preferably carried out via the piezoelectric effect. For this purpose, one or more areas of the piezoelectric layer on the actuators can be provided with separate sensor electrodes, via which a voltage or charge signal that is approximately proportional to the deflection can be picked up. In addition, several piezoelectric layers can also be realized, with at least one layer being partially used for position detection. A combination of different piezoelectric materials is also possible, arranged either one above the other or next to one another (e.g. PZT for actuators, AIN for sensors).

As an alternative to piezoelectric sensor elements, it is also possible to integrate thin-film strain gauges or additional electrodes for capacitive position detection. If the actuator structures are made of silicon, piezoresistive silicon resistors can also be integrated directly.

All of the above-mentioned aspects have in common that a membrane-free concept for generating high sound pressures that is completely compatible with MEMS manufacturing processes is created. All exemplary embodiments enable a particularly small size. The optional cascading enables the realization of integrated multi-way sound transducers. According to further developments, the control can be designed using integrated position sensors in such a way that the emitted sound has minimized distortion.

The following table lists possible materials for the individual functional elements. function materials Piezoelectric layer PZT, PNZT, AlN, AlScN, ZnO, BCZT, KNN Passive layer Si, poly-Si, SiN, SiNO, SiOz, AlN, metals Frame Si, metals, glass, [piezoelectric layer], [passive layer] Dazzle Si, metals, glass, polymers, [piezoelectric layer], [passive layer] Fasteners [passive layer], [piezoelectric layer]

Possible dimensions are as follows: - Actuator surface 50× ^50µm2 - 5× ^5cm2 - Decoupling slot 0.1µm - 40µm - Deflection amplitude 0.01µm - 3mm

Such converters can be operated, for example, with a first eigenmode of 10 Hz to 300 kHz. The excitation frequency is selected, for example, statically up to 300 kHz.

The actuator structures described are suitable for areas of application in which sound is to be generated in a frequency range between 10 Hz and 300 kHz with the smallest possible component volumes (<10 cm ³ ). This primarily applies to miniaturized sound transducers for wearables, smartphones, tablets, laptops, headphones, hearing aids but also ultrasound transducers. Overall, other applications in which fluids are displaced can also be considered (e.g. fluid mechanical and aerodynamic drive and guide structures, inkjets).

Embodiments create a miniaturized device for displacing gases and liquids with at least one bending actuator that can be deflected out of the plane, characterized in that the device contains narrow opening slots with such a high flow resistance that the device is in the acoustic and ultrasonic frequency range (20 Hz to 300 kHz) behaves fluidly almost like a closed membrane.

According to further exemplary embodiments, the device can include the following features: decoupling slots in the actuator materials, the total length of which accounts for a maximum of 5% of the total actuator area and has an average length-to-width ratio of over 10. In addition, according to exemplary embodiments, the device can be designed in such a way that openings created in the deflected state make up less than 10% of the total actuator area, so that a high fluidic separation between the front and back is achieved even without a closed membrane.

According to a further exemplary embodiment, the device can have two or more opposite, separate actuators.

According to a further exemplary embodiment, the actuators can be driven piezoelectrically, electrostatically, thermally, electromagnetically or by means of a combination of several principles. According to an additional embodiment it would also be It is conceivable that the device is designed with two or more actuator stages coupled via connecting elements.

According to a further exemplary embodiment, it would also be conceivable for the device to have two or more actuator stages that are controlled with separate signals and thus form a two-way or multi-way sound transducer.

Referring to the exemplary embodiment Fig. 5 or 6a to c It should be noted that each actuator element 10a*, 12a*, 10i* and 12i* is an active, individually controllable element. This can be actuated, for example, piezoelectrically or with another principle explained here.

According to a further exemplary embodiment, the device has a frame structure for stiffening and mode decoupling.

In the above exemplary embodiments, the actuators were explained in particular as actuators clamped on one side. At this point it should be noted that two-sided clamping (cf. Fig. 3d ) or general multi-sided clamping would be conceivable.

Further exemplary embodiments create a device with flow diaphragms to reduce the opening cross sections between the front and back in the deflected state. According to a further exemplary embodiment, the device can have sensor elements for position detection and control.

According to additional exemplary embodiments, the device can be designed for generating sound or ultrasound in air (gaseous medium), i.e. in the range from 20 Hz to 300 kHz. Further areas of application include the generation and control of air flow, e.g. B. for cooling.

Reference is made below to: Fig. 11 a possible manufacturing process for the above sound transducers is explained. The exemplary embodiment shown here from the Fig. 11a-d enables the production of the exemplary embodiment as shown, for example, in Fig. 1b is shown. However, through a slight modification, the exemplary embodiments from the other figures, in particular, are also used with the method shown here Fig. 1a detectable.

In the first in Fig. 11a In the step shown, a passive layer 50p is applied to a substrate 48 before a piezoelectric layer 50pe with two electrodes 50e is provided.

The substrate 48 may be an SOI (Silicon on Insulator) wafer that includes an SI substrate. SiO2 layers 50p are then placed on this with the in Fig. 1b marked insulators 50pi and Si insulation layers, such as. B. piezoelectric functional layers (PZT) 50pe deposited. The corresponding metal electrodes (Pt, Au, Mo, ....) 50e can then be deposited.

In a next step, which in Fig. 11b is shown, the electrodes 50e, the PZT 50pe and the insulation layer 50p are then structured. This creates, for example, the trenches 50g in the piezoelectric layer 50pe. Structuring can be done by wet or dry etching. Depending on the desired product design, either the step of structuring or introducing the trench 50g is carried out in such a way that it only has minimal dimensions in order to produce the product Fig. 1a to produce or have larger dimensions, so that the intermediate product shown here is then developed in the direction of the product from 1b.

To get the product out Fig. 1a To produce, a small trench of 50g is applied and then the in Fig. 11c step shown is skipped, then as in Fig. 11d shown to open the back using a single or multi-stage etching process and to expose the movable structures. In this step, the substrate below the passivation layer 50p is removed, particularly in the area aligned with the structuring piezoelectric actuators 50pe. This creates cavity 48c.

To a product as it relates to Fig. 1b is explained, the optional step described in Fig. 11c is shown, carried out. Fig. 11c illustrates the application of the vertically extending diaphragm elements 57. These are introduced here into the trenches 50g of the piezoelectric layer 50pe. Optionally, the lateral position of the trenches 57 can be selected so that they are aligned with areas of the structured passivation layer 50p, so that, for example, the vertical diaphragm element 75 extends the wall of a trench in the passive layer 50p. The diaphragm elements 57 can be applied, for example, by galvanic deposition and preferably in such a way that the diaphragm elements 57 protrude from the layer of piezoelectric elements 50p.

After the aperture elements 57 have been applied, the same applies as above with regard to the exemplary embodiment Fig. 1a explains the single or multi-stage etching of the back of the substrate 48 to produce the cavity 48c. As illustrated here, individual areas of the substrate 48 can remain standing so that the frame 48f is formed within the cavity 48c. This framework corresponds to, for example, in Fig. 5 explained framework 19.

MEMS technologies can be adopted in the manufacturing steps explained, so that the product explained above can be manufactured using conventional manufacturing processes.

Although some aspects have been described in connection with a device, it is understood that these aspects also represent a description of the corresponding method, so that a block or a component of a device is also to be understood as a corresponding method step or as a feature of a method step. Analogously, aspects that have been described in connection with or as a method step also represent a description of a corresponding block or detail or feature of a corresponding device.

The following is based on the basic exemplary embodiment Fig. 1b different implementations of the aperture 22 explained. In all exemplary embodiments discussed below, it is assumed that the panel 22*, 22 ^etc. is separated from the bending actuator 10 (firmly clamped at the reference point 10e) with a gap 14', so that the free end 10f of the bending actuator 10 is along the vertical extent of the panel element 22* or 22 ^etc. can move. It should be noted that aspects of the exemplary embodiments discussed below or of the exemplary embodiments for the panel already discussed can be combined with one another as desired (e.g. lid with rounded/slanted sides (panels)) or asymmetrical panel with lid and stop... ).

Fig. 13a shows a schematic cross section of a panel structure. This shows that the aperture structure 22* consists of several segments 22a*, 22b* and 22c*. The segment 22a* extends from the substrate plane (plane of the reference point 10e), in which the bending actuator 10 lies, for example in the rest position, out of the substrate, while the segment 22b* lies in this plane of the reference point 10e. The segment 22c* lies in the substrate or extends from the substrate surface into the substrate. All segments 22a*, 22b*, 22c* shown can have different geometries, ie longitudinal and transverse dimensions as well as variable cross sections, according to exemplary embodiments. Furthermore, according to further exemplary embodiments, it would be conceivable for the individual segments 22a*, 22b* and 22c* to also have different materials or material characteristics. For example, the segment 22c* and 22b* may be formed by the substrate itself while the segment 22a* is grown.

According to further exemplary embodiments, it would of course also be conceivable that more than the three segments 22a*, 22b* and 22c* shown are provided.

It should be noted that the middle position in the above and following exemplary embodiments does not necessarily have to correspond to the rest position, but can also be shifted upwards or downwards as desired (electrically or mechanically preloaded).

Fig. 13b shows another form of the aperture structure, here the aperture structure 22**. The aperture structure 22** or in particular the segment that extends out of the substrate plane has a beveled cross section that extends towards the actuator 10. This ensures that the gap 14 'has a relatively constant width regardless of the position of the actuator 10. The background to this is that the side of the aperture structure 22** that is directly opposite the actuator 10 extends approximately along the movement path (circular path around the fixed point 10e). Like here in Fig. 13b shown, the aperture 22** can be beveled either only upwards and/or downwards. The asymmetrical structure shown here is only an example, so that of course the lower segment of the aperture structure 22** can also be beveled in an analogous manner in order to achieve a symmetrical structure.

This exemplary embodiment of the diaphragm structure 22** with the slanted inside has the advantage that gap expansion can be reduced or compensated for at larger amplitudes. From a manufacturing perspective, a bevel can e.g. B. can be realized by adapting the paint profile or the etching process.

Fig. 13c shows a further development of the aperture structure 22** Fig. 13b , namely the aperture structure 22***. The panel structure 22*** has a curved/rounded inside on. This rounding extends along the circular arc-shaped movement path of the actuator 10 or the free end 10f of the actuator 10. Even if the rounded inside is only shown here on the side that extends out of the substrate, this rounded inside can of course also be on the aperture structure side in the Substrate level present. Analogous to the exemplary embodiment Fig. 13b The gap expansion at large amplitudes is reduced or compensated for by the aperture structure 22*** with the rounded inside. From a manufacturing perspective, rounding can e.g. B. be realized by adjusting the paint profile or the etching profile.

Fig. 13d shows another aperture structure, namely the aperture structure 22****. Here, the cross section at the end of the aperture structure 22**** has a widening or an overhang, which serves as a mechanical stop for the actuator 10 or the free end 10f of the actuator. This stop advantageously enables mechanical overload protection.

Fig. 13e shows another aperture structure 22*****, in which the aperture structure 22***** is constructed asymmetrically. The background to this is that there are actuators 10 that are primarily deflected on one side, so that a vertical expansion of the aperture 22***** is sufficient in one direction, here in the direction out of the substrate plane. Even if the deflection of the actuator 10 or the expansion of the diaphragm structure 22***** is shown here upwards (out of the substrate plane), this can of course also be the other way around according to exemplary embodiments, that is to say that both elements are in the Extend substrate in. It should be noted here that the shift in the rest position of the actuator can be realized by an electrical offset in the control signal or a mechanical projection (e.g. layer stress in the actuator layers).

Fig. 13f shows an example of a panel structure 22****** with a small expansion. The aperture structure 22****** can then be realized as flat if the deflection of the actuator (10) is small. For example, the height of the aperture 22****** is in the range of the actuator thickness. This variant has advantages in terms of production, as additionally applied aperture structure areas can be dispensed with.

Fig. 13g shows an example of an aperture structure 22*******, which consists of a substrate area 23s and the actual aperture element 22*******. The upper panel structure 22******* can z. B. as a galvanically constructed metal or as a polymer (SU8, BCB, ....) or made of glass or silicon. The lower aperture structure 23s consists primarily of the substrate (e.g. silicon or glass) itself and can be provided with additional layers according to further exemplary embodiments.

Fig. 13h shows another aperture structure without an additional element applied. It is assumed here that the bending actuator 10 oscillates in particular into the substrate plane, so that a diaphragm element that protrudes from the substrate plane can be dispensed with. Here the aperture element consists of the substrate element 23s, which forms the lower aperture structure. It should be noted at this point that, as already explained above, the rest position of the actuator 10 can be shifted downwards via mechanical pretension or an electrical offset, so that the diaphragm element 23s formed here is sufficient. During operation, the actuator can only be deflected downwards, so that no upward aperture is required and the manufacturing effort is then reduced.

Fig. 13i shows another aperture structure 22********, which essentially consists of a thin layer applied to the substrate element 23s. Depending on the desired actuator deflection, the layer thickness of the diaphragm element 22******** can be in the range of the actuator thickness. The substrate 23s can (but does not have to) also act as a panel structure and is flush with the panel structure 22******** or can also have an offset.

Referring to Fig. 14a to 14c Further exemplary embodiments are explained in which the micromechanical sound transducer is expanded to include a further substrate 220a, 220b and 220c (lid). According to exemplary embodiments, the further substrate 220a, 220b, 220c forms the aperture structure.

Fig. 14a shows a substrate 220a designed as a lid, which is placed on a substrate 23s above a cavity 23k of the bending actuator 10, so that the bending actuator 10 can swing within the lid 220a or within the space defined by the lid interior 220a and the cavity 23. The lid 220a is arranged on the side opposite to the free end such that the inner side wall of the lid 220a is separated from the end 10e by the gap 140. Since in this exemplary embodiment the cover 220a is completely closed, the bending actuator 10, for example, emits the sound through the cavity 23k.

In this exemplary embodiment, it should be noted that in all of the above exemplary embodiments or in the explanation thereof, it is essentially assumed that the sound is emitted from the substrate. Of course, according to exemplary embodiments, it is also conceivable that the sound is led out through the substrate or through a cavity of the substrate.

At this point it should be noted that Fig. 14a represents a cross section through the substrate 220a, with the further substrate extending, for example, in a circular or angular manner around the bending actuator 10 in order to create a (back) volume or generally a cover for it. From a manufacturing perspective, it should be noted that the cover 220a can be produced, for example, by a second structured substrate (i.e. a substrate with a cavity) (cf. reference numeral 221k). This second substrate is then applied to the substrate with the bending actuator 10, so that the cavity 221k is aligned with the cavity 23 at least in some areas (in the area of the gap 140).

Fig. 14b shows a further exemplary embodiment with a modified cover 220b, with the remaining structure assuming the same actuator 10 and the substrate 23s. The lid 220b differs from the lid 220a in that it has optional sound openings 222o and 222s. The sound opening 222o or the plurality of sound openings 222o are applied to the main surface of the lid 220b, while the opening 222s is provided laterally. It should be noted at this point that, according to exemplary embodiments, it is also sufficient that an opening, either the opening 222o or the opening 222s, is provided. The enclosed air volume in the cavity 221k can be ventilated through these openings 222o and 222s. The openings can be used for sound to escape or to enable pressure equalization. Several openings can together form one or more lattice structures that protect the actuator from mechanical influences and dust.

Fig. 14c shows another sound transducer with a cover 220c which has an opening 222o. The bending actuator is provided on another substrate 230s which has a side opening 232s. The substrate 230s is applied to a further substrate 233s or a cover 233s, so that the cavity 230k is closed. This further substrate 233s can also have optional sound openings 233o. This creates a volume that is closed or ventilated via at least one of the optional openings 232s, 233o, 222o. The volume is essentially formed by the cavities 221k and 230k and at least one or more openings open. The openings can be used for sound to escape or allow for pressure equalization. Multiple openings may cooperate to form one or more grid structures that protect the actuator 10 from mechanical impact and dust.

Below are references to the Figures 15a to 15h Different actuator geometries explain the opposite geometries Fig. 10 are expanded. In illustrations, the actuator is provided with the reference number 100 or 100_1 to 100_4, while the aperture is provided with the reference number 225. A coupling slot, which is provided with the reference number 140, always extends between the actuator and the diaphragm.

It should be mentioned that in exemplary embodiments the actuator geometry can be combined with one another in any way (e.g. Fig 15f with rounded or triangular actuators).

Fig. 15a shows a top view of a rounded actuator 100, while Fig. 15b a top view of a triangular actuator 100 shows. The same or different actuators 100 can be combined with one another in any way, for example using Fig. 15c, 15d and 15e is shown.

Fig. 15c shows here triangular-shaped actuators 100_1 to 100_4, which in total describe a square surface, the four actuators 100_1 to 100_4 being separated from one another by a cross-shaped aperture structure 225. The slot 145 is again provided between the actuators 100_1 to 100_4 and the aperture structure 225. Alternatively, arrangements with 3, 5, 6... actuators would also be conceivable. It should also be noted that the total area does not necessarily have to be square, but can also be polygonal.

Fig. 15d shows two opposing square actuators 100_5 and 100_6, which describe a square. The square actuators 100_5 and 100_6 each form three free corners, which are limited by the H-shaped panel 225 with the associated slot 140.

Fig. 15e shows four circular segment-shaped actuators 100_7 to 100_10, which are similar to Fig. 15c are separated from each other by a cross-shaped panel 225 with a slot 140.

In the variant of Fig. 15c the hypotenuse of each triangular actuator 100_1 to 100_4 is clamped, while in the exemplary embodiment Fig. 15e The circular segment arcs 100_7 to 100_10 are firmly clamped. Alternatively, arrangements with 3, 5, 6... actuators would also be conceivable. It should also be noted that the total area does not necessarily have to be square, but can also be polygonal.

By combining different actuators, e.g. B. Realize reusable systems, as shown in the Fig. 15f, Fig. 15g and Fig. 15h is shown.

Fig. 15f combines, for example, three differently shaped but each square actuators 100_11 to 100_13, each of which is clamped on one of the four sides, with three of the four sides forming free ends. A labyrinth-shaped panel 225 is provided between the free ends, which separates the actuators 100_11 to 100_13 using the slots 140. All actuators 100_11 to 100_13, for example, have different sizes (areas) and can therefore be designed for different frequency ranges.

Fig. 15g shows two actuators 100_14 and 100_15, the first 100_14 being a square small actuator. The further, larger actuator 100_15 is also square, but has a recess 100_15a for the other actuator 100_14. The recess 100_15a is arranged so that both actuators are clamped on the same side. These actuators 100_14 and 100_15 can be decoupled in their movement by a slot 140 provided between the two actuators 100_14 and 100_15. The larger actuator 100_15 can be used for the low frequency range, for example, while the inner actuator 100_14 can be used for the high frequency range.

Fig. 15h shows a similar structure of the actuators 100_14 and 100_15, whereby in addition to the separation by means of the slot 140 of the two actuators 100_14 and 100_15, a further aperture 225 is also provided. Both exemplary embodiments ( Fig. 15g and 15h ) have in common that the panels 225 including slot 140 are arranged at least along the free ends of the large actuator 100_15 with the recess 100_15a, in which the small actuator 100_14 is arranged. Through such internal nesting or provision of larger and smaller actuators, it is generally possible to cover different frequency ranges with different actuators.

Fig. 16 shows a schematic top view of a bending actuator 10** clamped on two or more sides (see areas 10e1 and 10e2), which has at least one free side 10f** (here 2). As explained above, this free side 10f** can be acoustically separated by an opposite aperture 22** (here 2, corresponding to the variants explained) with a gap 14** in between.

In the above exemplary embodiments, it was assumed in particular that a sound transducer for emitting sound (loudspeaker) should be created, which is why a bending actuator was always mentioned. Of course, the principle is also reversible, so that a microphone is formed by the sound transducer according to an exemplary embodiment, in which the bending transducer (cf. bending actuator) is designed to be excited, for example by air, to oscillate (for example vertically) in order to produce a oscillation depending on this to emit an electrical signal (generally to detect the acoustic waves from the environment). According to a further exemplary embodiment, a component is created that includes both loudspeaker and microphone based on the concepts explained above. Here the two components can be formed on the same substrate, which is advantageous from a manufacturing perspective.

Additional embodiments and aspects of the invention are described below, which may be used alone or in combination with any of the features, functionality and details described herein.

According to a first aspect, a micromechanical sound transducer 1, 1', 1", constructed in a substrate, may have the following features: a first bending transducer 10 extending along a plane of the substrate and having a free end 10f or a free side and is designed to be excited to vibrate vertically in order to emit or receive sound; and a diaphragm element 22 extending vertically to the first bending transducer 10 and extending through a gap 14 from the free end 10f or the free side of the first bending transducer 10 is separated.

According to a second aspect with reference to the first aspect, the shutter element 22 may protrude from the plane of the substrate.

According to a third aspect with reference to the second aspect, the shutter element 22 may protrude from a stationary portion of the substrate.

According to a fourth aspect, with reference to any one of the first to third aspects, the first bending transducer 10 may be excitable to vibrate out of the plane of the substrate or may be excitable to vibrate perpendicular to the plane of the substrate.

According to a fifth aspect with reference to one of the first to fourth aspects, the height of the aperture element 22 may be at least 50% or at least 100% of the maximum deflection of the first bending transducer 10 in linear operation or the maximum elastic deflection of the first bending transducer 10 or at least 3- times a width of the gap 14 or at least 1 times a thickness of the bending transducer 10 or at least 0.1% or 1% of the length of the bending transducer 10.

According to a sixth aspect with reference to one of the first to fifth aspects, the micromechanical sound transducer 1, 1 ', 1" may include a diaphragm element 22 extending vertically to the first bending transducer 10 and separated from the movable sides of the first bending transducer 10 by a gap 14 is.

According to a seventh aspect with reference to any one of the first to sixth aspects, the shutter element 22 may have a varying geometry in its cross section.

According to an eighth aspect with reference to the seventh aspect, the geometry may vary such that a surface facing the bending transducer 10 is curved or inclined along a movement path of the free end upon vertical vibration of the bending transducer 10.

According to a ninth aspect with reference to the seventh or eighth aspect, the shutter element 22 may include a mechanical stop for the bending transducer 10.

According to a tenth aspect, referring to any one of the first to ninth aspects, the shutter element 22 may asymmetrically extend out of the plane of the substrate and into the plane of the substrate.

According to an eleventh aspect, referring to any one of the first to ninth aspects, the shutter element 22 may symmetrically extend out of the plane of the substrate and into the plane of the substrate; and/or wherein the aperture element 22 can have the same height extension out of the plane of the substrate and into the plane of the substrate, starting from the rest position of the bending transducer 10.

According to a twelfth aspect, referring to any one of the first to eleventh aspects, the substrate may form a shutter structure or a part of the shutter structure within the substrate.

According to a thirteenth aspect with reference to one of the first to twelfth aspects, the micromechanical sound transducer 1, 1 ', 1" may have a cover which is placed on the substrate in the area of the first bending transducer 10, so that at least the first bending transducer 10 as well as the Aperture element 22 is covered by the lid or the first substrate 233s.

According to a fourteenth aspect, referring to the thirteenth aspect, the lid 220a, 220b, 220c may form the shutter member 22.

According to a fifteenth aspect, with reference to the thirteenth or fourteenth aspect, the micromechanical sound transducer 1, 1', 1" in the lid may have one or more openings; and/or the micromechanical sound transducer 1, 1', 1" in the substrate may have one or have several sound openings.

According to a sixteenth aspect, with reference to any one of the first to fifteenth aspects, the micromechanical sound transducer 1, 1', 1" may include a second bending transducer 12 having a free end disposed in a common plane e1 with the first bending transducer 10, and that Aperture element 22 may be arranged between the free end of the first bending transducer 10 and the free end of the second bending transducer.

According to a seventeenth aspect, with reference to any one of the first to sixteenth aspects, the micromechanical sound transducer 1, 1', 1" may include a second bending transducer 12 having a free end 12f and arranged in a common plane e1 with the first bending transducer 10, so that the free end 10f of the first bending transducer 10 is separated from the free end 10f of the second bending transducer 12 by a gap 14, the second bending transducer 12 being excited in phase with the vertical vibration of the first bending transducer 10.

According to an eighteenth aspect with reference to the seventeenth aspect, the first and second bending transducers 10, 12 may be similar bending transducers.

According to a nineteenth aspect, with reference to any one of the first to sixteenth aspects, the first and/or second bending transducer 12 may be a flat, trapezoidal or rectangular bending transducer.

According to a twentieth aspect, with reference to any one of the first to nineteenth aspects, the first and/or second bending transducers 10, 12 may be a triangular or circular segment-shaped or rounded bending transducer.

According to a twenty-first aspect, with reference to any one of the seventeenth to nineteenth aspects, the micromechanical sound transducer 1, 1', 1" may include one or more further bending transducers arranged in the common area so that their free ends are separated from the free ends 10f, 12f of the first and/or second bending transducer 10, 12 are separated by a gap 14, wherein the at least one further bending transducer is excited to vertical vibration in phase with the vertical vibration of the first and/or second bending transducer 10, 12.

According to a twenty-second aspect with reference to one of the seventeenth to twenty-first aspects, the micromechanical sound transducer 1, 1 ', 1 "may include a controller that controls the first and second bending transducers 12 so that they are excited in phase with the vertical vibration.

According to a twenty-third aspect with reference to one of the first to twenty-second aspects, the micromechanical sound transducer 1, 1 ', 1" may comprise a sensor system which is designed to detect the vertical vibration and/or the position of the first and/or the second bending transducer 12 capture.

According to a twenty-fourth aspect, with reference to any one of the first to twenty-third aspects, the gap 14 may be less than 10% or less than 5% or less than 1% or less than 0.1% or less than 0.01% of the area of the first bending transducer 10.

According to a twenty-fifth aspect, with reference to one of the first to twenty-fourth aspects, the gap 14 may be less than 15% or less than 10%, 5%, 1%, 0.1% or 0.01% of the area of the first bending transducer 10 when deflection.

According to a twenty-sixth aspect, with reference to any one of the first to twenty-fifth aspects, the gap 14 may exist in the rest state of the first bending transducer 10.

According to a twenty-seventh aspect with reference to any one of the first to twenty-sixth aspects, the first bending transducer 10 may be clamped on one side or on multiple sides relative to the substrate and/or a base element.

According to a twenty-eighth aspect, with reference to any one of the first to twenty-seventh aspects, the first bending transducer 10 or a second bending transducer 12 may each include first and second bending elements connected in series so as to form the respective bending transducer.

According to a twenty-ninth aspect with reference to the twenty-eighth aspect, the first bending element may have a clamped end and a free end 10f and the second bending element may engage the free end 10f of the first bending element 10 with its clamped end and the free end with its free end 10f 10f, 12f of the first and/or second bending transducer 12.

According to a thirtieth aspect with reference to the twenty-eighth or twenty-ninth aspect, the first bending element may be connected to the second bending element via a flexible element.

According to a thirty-first aspect with reference to any one of the twenty-eighth to thirtieth aspects, the micromechanical sound transducer may include a frame.

According to a thirty-second aspect with reference to the thirty-first aspect, the frame may be disposed in the region of the transition between the first and second flexure elements.

According to a thirty-third aspect with reference to any one of the twenty-eighth to thirty-second aspects, the first bending element and the second bending element may be driven with different control signals.

According to a thirty-fourth aspect, a method for producing a micromechanical sound transducer constructed in a substrate, having a first bending transducer 10 extending along a plane of the substrate, and a diaphragm element 22 extending vertically to the first bending transducer 10, may comprise the following steps: patterning a layer to form the first flexure transducer 10 to have a free end 10f or side and to be excited to vibrate vertically to emit or receive sound; and realization of the vertical diaphragm element 22 so that it protrudes beyond the layer of the first bending transducer 10 and is separated from the free end 10f of the first bending transducer 10 by a gap 14.

According to a thirty-fifth aspect, a micromechanical sound transducer 1, 1', 1" may include a first bending transducer 10 having a free end 10f or side and configured to be excited to vibrate vertically to emit or receive sound ; wherein the first bending transducer 10, 12 can comprise a first and a second bending element which are connected in series in order to form the first bending transducer, wherein the first bending element can each be controlled with a first control signal and the second bending element can be controlled with a second control signal .

According to a thirty-sixth aspect, referring to the thirty-fifth aspect, the first control signal may be different from the second control signal.

According to a thirty-seventh aspect, with reference to the thirty-sixth aspect, the first control signal and the second control signal may be derived from a common source signal and the first control signal may be modified from the second control signal.

According to a thirty-eighth aspect, with reference to the thirty-sixth or thirty-seventh aspect, the first control signal may have a different or partially overlapping frequency range from the second control signal, or the first control signal and the second control signal may be derived from a common source signal and the first control signal may undergo different frequency filtering have as the second control signal.

According to a thirty-ninth aspect with reference to the thirty-eighth aspect, the first control signal may have a lower frequency range than the second control signal.

According to a fortieth aspect, with reference to any one of the thirty-fifth to thirty-ninth aspects, the micromechanical sound transducer 1, 1', 1" may include a second bending transducer 12 having a free end 12f and disposed in a common plane e1 with the first bending transducer 10 , wherein the second bending transducer 10, 12 may include first and second bending elements 10, 12 connected in series so as to form the second bending transducer.

According to a forty-first aspect with reference to one of the thirty-fifth to fortieth aspects, the first bending element may have a clamped end and a free end and the second bending element may engage the free end of the first bending element 10 with its clamped end and the free end with its free end 10f, 12f of the first and/or second bending transducer 10, 12.

According to a forty-second aspect with reference to any one of the thirty-fifth to forty-first aspects, the first bending member may be connected to the second bending member via a flexible member.

According to a forty-third aspect, referring to any one of the thirty-fifth to forty-second aspects, the micromechanical sound transducer may include a frame.

According to a forty-fourth aspect with reference to the forty-third aspect, the frame may be disposed in the region of the transition between the first and second flexure elements.

According to a forty-fifth aspect with reference to any one of the thirty-fifth to forty-fourth aspects, the first bending element and the second bending element may be driven with different control signals.

According to a forty-sixth aspect with reference to any one of the thirty-fifth to forty-fifth aspects, the first and/or second bending transducers 10, 12 may be a flat, trapezoidal or rectangular bending transducer.

According to a forty-seventh aspect, with reference to any one of the thirty-fifth to forty-sixth aspects, the first and/or second bending transducers 12 may be a triangular or circular segment-shaped bending transducer.

According to a forty-eighth aspect, with reference to any one of the thirty-fifth to forty-seventh aspects, the micromechanical sound transducer 1, 1', 1" may include one or more further bending transducers disposed in the common area so that their free ends are separated from the free ends 10f, 12f of the first and/or second bending transducer 12 are separated by a gap 14, wherein the at least one further bending transducer 12 can be excited to vertical vibration in phase with the vertical vibration of the first and/or second bending transducer 10, 12.

According to a forty-ninth aspect, with reference to any one of the thirty-fifth to forty-eighth aspects, the gap 14 may be less than 10%, or less than 5%, or 1%, or 0.1%, or less than 0.01% of the area of the first bending transducer 10.

According to a fiftieth aspect with reference to one of the thirty-fifth to forty-ninth aspects, the gap 14 can be less than 15% or less than 10%, 5%, 1% or 0.1%, or less than 0.01% of the area of the first bending transducer 10 be.

According to a fifty-first aspect, a method for producing a micromechanical sound transducer according to one of the thirty-fifth to fiftieth aspects, which includes a first bending transducer 10, may comprise the following steps: providing a first layer in a common plane e1, which has at least the first bending transducer 10 each with one first and a second bending element, so that the first bending transducer 10 has a free end 10f; and connecting the respective first bending element to the second bending element of the respective first bending transducer.

According to a fifty-second aspect, with reference to any one of the first to thirty-third or thirty-fifth to forty-ninth aspects, two bending transducers 10 may be supported with their clamped end opposite a substrate 23s, the geometry of the first of the two bending transducers being enclosed by the geometry of the second of the two bending transducers 10 or enclosed.

According to a fifty-third aspect with reference to the fifty-second aspect, the second of the two bending transducers 10 may include a recess for the first of the two bending transducers 10.

According to a fifty-fourth aspect with reference to the fifty-second or fifty-third aspect, the two bending transducers may be separated by a slot or a slot with an aperture.

According to a fifty-fifth aspect with reference to the fifty-second, fifty-third or fifty-fourth aspect, the two bending transducers may be controllable with two different control signals or with two control signals for two different frequency ranges.

Sources

[Hou13] Houdouin et al., Acoustic vs electric power response of a high-performance MEMS microspeaker, IEEE SENSORS 2014 [Dej12] Dejaeger et al., Development and Characterization of a Piezoelectrically Actuated MEMS Digital Loudspeaker, Procedia Engineering 47 (2012) 184 - 187 [Gla13] Glacer et al., Reversible acoustical transducers in MEMS technology, Proc. DTIP 2013 , [Yi09] Yi et al., Performance of packaged piezoelectric microspeakers depending on the material properties, Proc. MEMS 2009, 765-768

Claims (15)

Micromechanical sound transducer (1, 1', 1") with a first bending transducer (10), which has a free end (10f) or a free side and is designed to be excited to vibrate vertically in order to emit or record a sound; wherein the first bending transducer (10, 12) comprises a first and a second bending element which are connected in series in order to form the first bending transducer, wherein the first bending element can each be controlled with a first control signal and the second bending element can be controlled with a second control signal ; wherein the first bending element has a clamped end and a free end and the second bending element engages with its clamped end on the free end of the first bending element (10) and with its free end the free end (10f, 12f) of the first bending transducer (10, 12) and wherein the first bending element is connected to the second bending element via a flexible element or a connecting element (17). Micromechanical sound transducer (1, 1', 1") according to claim 1, in which the first control signal differs from the second control signal. Micromechanical sound transducer (1, 1', 1") according to claim 2, wherein the first control signal and the second control signal are derived from a common original signal and the first control signal is modified compared to the second control signal. Micromechanical sound transducer (1, 1', 1") according to claim 1 or 3, wherein the first control signal has a frequency range that is different from or partially overlapping the second control signal, or wherein the first control signal and the second control signal are derived from a common original signal and the first Control signal has undergone a different frequency filtering than the second control signal. Micromechanical sound transducer (1, 1', 1") according to claim 4, wherein the first control signal has a lower frequency range than the second control signal. Micromechanical sound transducer (1, 1', 1") according to one of claims 1 to 5, which has a second bending transducer (12) which has a free end (12f) and with the first bending transducer (10) in a common plane (e1) is arranged, wherein the second bending transducer (10, 12) comprises first and second bending elements (10, 12) connected in series so as to form the second bending transducer. Micromechanical sound transducer (1, 1', 1") according to one of claims 1 to 6, wherein the micromechanical sound transducer has a frame; or
wherein the micromechanical sound transducer has a frame and wherein the frame is arranged in the area of the transition between the first and the second bending element. Micromechanical sound transducer (1, 1', 1") according to one of claims 1 to 7, wherein the first bending element and the second bending element are controlled with different control signals. Micromechanical sound transducer (1, 1', 1") according to one of claims 1 to 8, wherein the first bending transducer (10, 12) is a flat, trapezoidal or rectangular bending transducer; or
wherein the first bending transducer (12) is a triangular or circular segment-shaped bending transducer. Micromechanical sound transducer (1, 1', 1") according to one of claims 1 to 9, comprising one or more further bending transducers arranged in the common surface so that their free ends are separated from the free ends (10f, 12f). of the first bending transducer (12) are separated by a gap (14), the at least one further bending transducer (12) being excited to vertical vibration in phase with the vertical vibration of the first bending transducer (10, 12). Micromechanical sound transducer (1, 1', 1") according to claim 10, wherein the gap (14) is less than 10% or less than 5% or 1% or 0.1% or less than 0.01% of the area of the first bending transducer (10 ) is; and/or
wherein the gap (14) is less than 15% or less than 10%, 5%, 1% or 0.1%, or less than 0.01% of the area of the first bending transducer (10) when the deflection occurs. Method for producing a micromechanical sound transducer according to one of claims 1 to 11, which comprises a first bending transducer (10), the method comprising the following steps: Providing a first layer in a common plane (e1), which forms at least the first bending transducer (10), each with a first and a second bending element, so that the first bending transducer (10) has a free end (10f); and Connecting the respective first bending element to the second bending element of the respective first bending transducer. Micromechanical sound transducer (1, 1', 1") according to one of claims 1 to 11, wherein the first and a second bending transducer (10) are mounted with their clamped end opposite a substrate (23s), the geometry of the first bending transducer being determined by the Geometry of the second bending transducer (10) is included or enclosed. Micromechanical sound transducer (1, 1', 1") according to claim 13, wherein the second of the two bending transducers (10) has a recess for the first of the two bending transducers (10); and/or
wherein the two bending transducers are separated by a slot or a slot with a cover. Micromechanical sound transducer (1, 1', 1") according to claim 13 or 14, wherein the two bending transducers can be controlled with two different control signals or with two control signals for two different frequency ranges.

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