Patent Description:
The sensitivity behavior over frequency as well as the noise behavior within an audio or ultrasonic bandwidth of a MEMS-based microphone gains more and more importance in the implementation of appropriate and very sensitive MEMS sensor devices, such as MEMS microphones, within mobile devices. MEMS microphones have specific frequency response characteristics defined by their physical properties like MEMS attributes, such as for example their sound port and ventilation hole dimensions, back volume etc. In certain applications, there is a tradeoff between physical and acoustic properties. For example, a small sound port in relation to the given package dimension could result in a low system resonance frequency, which can affect the sensitivity behavior over frequency as well as the noise within a desired audio bandwidth. Further, the system resonance can cause unwanted distortion and intermodulation effects even if it is in the ultrasonic frequency range. To shape or dampen such resonances, electrical (analog or digital) filter circuits can be implemented within the Mems device, the ASIC or somewhere externally. However, implementing electrical filter circuits can have different tradeoffs, having an influence on complexity, area, power, etc., and sometimes just touches the effect and not the root cause.

<CIT> relates to a sensor comprising two parallel acoustical filter elements, an assembly comprising a sensor and the filter, a hearable and a method.

<CIT> relates to a packaging concept to improve performance of a micro-electro-mechanical (MEMS) microphone.

<CIT> relates to systems and methods for reducing noise in microphones.

<CIT> relates to a microphone which includes a housing and a circuit board cooperatively forming an accommodation space to accommodate a MEMS chip.

<CIT> relates to an acoustic electricity conversion technology, in particular to a directional MEMS microphone.

<CIT> relates to an apparatus and method for monitoring a microphone, i.e. for monitoring for blockage of an acoustic port of a microphone device.

In addition, latest MEMS technology tends to have system resonances with very large Q factors that can be even critical in the higher ultrasonic range.

Therefore, there is a need in the field of MEMS devices, e.g., of MEMS microphones, to implement a MEMS device having improved operational characteristics, e.g., an improved frequency response and/or an improved adaptability of the frequency response for achieving an improved sensitivity behavior over frequency as well as of the noise behavior within an audio or ultrasonic bandwidth of the MEMS-based microphone.

Such a need can be solved by the MEMS device according to independent claims <NUM> and <NUM>. Further, specific implementations of the MEMS device are defined in the dependent claims.

According to an embodiment, a MEMS device comprises a package for providing an inner volume, a MEMS microphone arranged in the inner volume, a sound port through the package to the inner volume, and a passive acoustic attenuation filter acoustically coupled to the sound port.

The passive acoustic attenuation filter comprises a tube element or an extension cavity, which branches off from the sound port. The tube element or extension cavity may have a tube length to provide an attenuation center frequency of the passive acoustic attenuation filter which corresponds to a frequency or frequency range of an acoustic resonance, e.g. of a Helmholtz resonance (peak) or a back-cavity resonance etc., in the inner volume of the MEMS device.

The passive acoustic attenuation filter may be formed as a passive acoustic notch filter acoustically coupled to the sound port, and wherein the tube element has a tube length to provide a notch center frequency of the passive acoustic notch filter which corresponds to a frequency or frequency range of a Helmholtz resonance (peak) or a back-cavity resonance in the inner volume of the MEMS device.

The tube element or extension cavity may comprise a bypass tube or bypass cavity having a bypass inlet and a bypass outlet, which are acoustically coupled to the sound port, wherein the bypass inlet is arranged in the sound port acoustically upstream to the bypass outlet (= upstream with respect to sound traveling direction into the package to the MEMS device).

According to the present concept of a MEMS device, an undesired MEMS resonance behavior can be reduced by implementing the passive acoustic attenuation filter, which is coupled to the sound port of the MEMS device. Such a package level acoustic filter can shape the frequency response of the sound signal entering the microphone package. This passive acoustic attenuation filter can be understood as an additional degree of freedom in the system design of a MEMS device, e.g., a MEMS microphone. Thus, the resonance of the MEMS device can be influenced or set with the passive acoustic attenuation filter that attenuates a resonance (peak) of the MEMS device.

In the following, embodiments of the present disclosure are described in more detail with reference to the figures, in which:.

In the following description, embodiments are discussed in further detail using the figures, wherein in the figures and specification identical elements and elements having the same functionality and/or the same technical or physical effect are provided with the same reference numbers or are identified with the same name. thus, the description of these elements and of the functionality thereof as illustrated in the different embodiments are mutually exchangeable or may be applied to one another in the different embodiments.

In the following description, embodiments are discussed in detail, however, it should be appreciated that the embodiments provide many applicable concepts that can be embodied in a wide variety of semiconductor devices. The specific embodiments discussed are merely illustrative as specific ways to make and use the present concept, and do not limit the scope of the embodiments. In the following description of embodiments, the same or similar elements having the same function have associated therewith the same reference signs or the same name, and a description of such elements will not be necessarily repeated for every embodiment. Moreover, features of the different embodiments described hereinafter may be combined with each other unless specifically noted otherwise.

It is understood that when an element is referred to as being "connected" or "coupled" to another element, it may be directly connected or coupled to the other element, or intermediate elements may be present. Conversely, when an element is referred to as being "directly" connected to another element, "connected" or "coupled", there are no intermediate elements. Other terms used to describe the relationship between elements should be construed in a similar fashion (e.g., "between" versus "directly between", "adjacent" versus "directly adjacent" and "on" versus "directly on", etc.).

For facilitating the description of the different embodiments, some of the figures comprise a Cartesian coordinate system x, y, z, wherein the x-y-plane corresponds, i.e. is parallel, to a first main surface region of a substrate (= a reference plane = x-y-plane), wherein the direction vertically up with respect to the reference plane (x-y-plane) corresponds to the "+z" direction, and wherein the direction vertically down with respect to the reference plane (x-y-plane) corresponds to the "-z" direction. In the following description, the term "lateral" means a direction parallel to the x- and/or y-direction, i.e. parallel to the x-y-plane, wherein the term "vertical" means a direction parallel to the z-direction.

<FIG> shows an exemplary and general illustration of a MEMS device <NUM> with a passive acoustic attenuation filter <NUM> as a cross-sectional view (parallel to the x-z-axis), wherein the passive acoustic attenuation filter <NUM> comprises a tube extension <NUM>-<NUM>, e.g. a tube element or an extension cavity <NUM>-<NUM>, according to an embodiment.

According to an embodiment, the MEMS device <NUM> comprises a package <NUM> for providing an inner volume <NUM>, a MEMS microphone (or generally a MEMS sound transducer) <NUM> arranged in the inner volume <NUM>, a sound port <NUM> through the package <NUM> to the inner volume <NUM>, and a passive acoustic attenuation filter <NUM> acoustically coupled to the sound port <NUM>.

According to an embodiment, the sound port <NUM> (or the volume of the sound port <NUM>) and the tube extension <NUM>-<NUM> of the passive acoustic attenuation filter <NUM> cooperate and/or interact for providing the acoustic filtering and/or attenuation effect, i.e. the passive acoustic attenuation filter functionality of the resulting passive acoustic attenuation filter <NUM>. As discussed in detail below, the dimensions of the sound port <NUM> and of the tube extension <NUM>-<NUM> of the passive acoustic attenuation filter <NUM> may be adapted to each other for providing the acoustic filtering and/or attenuation effect, i.e. the passive acoustic attenuation filter functionality of the resulting filter arrangement <NUM>.

As shown in <FIG>, the MEMS device <NUM> may be arranged in the housing <NUM> having an interior volume <NUM>, wherein the housing <NUM> has the access opening or sound port <NUM> to the interior volume <NUM> of the MEMS device <NUM> and the passive acoustic attenuation filter <NUM>. The MEMS sound transducer <NUM> is arranged in the housing <NUM>, for example, adjacent to the sound opening <NUM>. The housing <NUM> may then comprise, for example, a substrate <NUM> and a cap element <NUM>, which may be at least partially electrically conductive. In an exemplary arrangement, the MEMS sound transducer <NUM> (MEMS microphone) can subdivide the interior volume <NUM> into a front volume <NUM>-<NUM> and a back volume <NUM>-<NUM>, wherein the front volume <NUM>-<NUM> is situated in the region between the sound port <NUM> and the MEMS microphone <NUM>, and wherein the back volume <NUM>-<NUM> is situated on the opposite side of the MEMS sound transducer <NUM> with respect thereto in the interior volume <NUM> of the housing <NUM>. The MEMS sound transducer <NUM> may comprise different configurations, such as a single membrane and single backplate (= counter-electrode) configuration, a (e.g. sealed) dual membrane configuration or a dual-backplate configuration, for example.

In the following, a number of different implementations and realizations of the passive acoustic attenuation filter <NUM> having a tube extension <NUM>-<NUM>, e.g. in form of a tube element or an extension cavity <NUM>-<NUM>, are generally described together with the technical effects thereof.

Thus, the passive acoustic attenuation filter <NUM> may comprise a tube element or an extension cavity <NUM>-<NUM> which branches off from the sound port <NUM>. The tube element or extension cavity <NUM>-<NUM> may have a tube length "I" to provide an attenuation center frequency of the passive acoustic attenuation filter <NUM>. Thus, the tube length "I" of the tube element or extension cavity <NUM>-<NUM> may be set to correspond or match to a frequency or frequency range of an acoustic resonance, e.g. of a Helmholtz resonance (peak) or a back-cavity resonance etc., in the inner volume <NUM> of the MEMS device <NUM>.

According to an embodiment, the passive acoustic attenuation filter <NUM> may be formed as a passive acoustic "notch" filter acoustically coupled to the sound port <NUM>, wherein the tube element <NUM>-<NUM> has a tube length I to provide a notch center frequency of the passive acoustic notch filter <NUM>. The notch center frequency of the passive acoustic notch filter <NUM> may be set to correspond or match to a frequency or frequency range of an acoustic resonance, e.g. a Helmholtz resonance (peak) or a back-cavity resonance, in the inner volume <NUM> of the MEMS device <NUM>.

Thus, the tube element <NUM>-<NUM> may comprises a length "I" which corresponds to quarter of the wavelength (= λ/<NUM>) of the wavelength or of the center wavelength of a wavelength range of the sound traveling through the sound port <NUM> into the package <NUM> to the MEMS device <NUM> and of the (corresponding) wavelength or wavelength range of an acoustic resonance, e.g. of a Helmholtz resonance (peak) or a back-cavity resonance etc., to be acoustically attenuated in the inner volume <NUM> of the MEMS device <NUM>. The tube element (tube extension or extension cavity) <NUM>-<NUM> has a tube inlet 16a, which is acoustically coupled or connected to the sound port <NUM>.

Each tube element <NUM>-<NUM> of the plurality of tube elements <NUM>-<NUM> has a tube inlet 16a, which is acoustically coupled or connected to the sound port <NUM>.

According to an embodiment, the package <NUM> comprises the substrate structure <NUM> and the lid structure <NUM>, wherein the sound port <NUM> extends through the substrate structure <NUM>, and wherein the passive acoustic attenuation filter <NUM> is part of the substrate structure <NUM>.

Thus, the tube element <NUM>-<NUM> may be integrated in the substrate structure <NUM>, may be integrated in different layers (or planes) of the substrate structure <NUM> or may be attached (e.g. as an assembly part or component) to the substrate structure <NUM>.

In the following, some further implantations and design options for the tube element or extension cavity <NUM>-<NUM> of the passive acoustic attenuation filter <NUM> are generally described.

According to a further embodiment, the passive acoustic attenuation filter <NUM> may comprise a plurality of tube elements <NUM>-<NUM> which branch off from the sound port <NUM>. See also <FIG> and the associated description.

The plurality of parallel tube elements <NUM>-<NUM> may have the same dimensions for providing the same attenuation center frequency. Thus, each of the tube elements <NUM>-<NUM> may comprises a length "I" which corresponds to quarter of the wavelength (= λ/<NUM>) of the wavelength or of the center wavelength of a wavelength range of the sound traveling through the sound port <NUM> into the package <NUM> to the MEMS device <NUM> and of the (corresponding) wavelength or wavelength range of an acoustic resonance, e.g. of a Helmholtz resonance (peak) or a back-cavity resonance etc., to be acoustically attenuated in the inner volume <NUM> of the MEMS device <NUM>.

According to a further embodiment, a subset of the plurality of parallel tube elements <NUM>-<NUM> may have a different dimension "l1" with respect to the remaining tube elements <NUM>-<NUM> for providing a different attenuation center frequency with respect to the attenuation center frequency of the remaining tube elements <NUM>-<NUM>. Thus, a subset of the tube elements <NUM>-<NUM> may comprises a length "I" which corresponds to a quarter of the wavelength (= λ/<NUM>) of the wavelength or of the center wavelength of a wavelength range of the sound traveling through the sound port <NUM> into the package <NUM> to the MEMS device <NUM> and of the (corresponding) wavelength or wavelength range of an acoustic resonance, e.g. of a Helmholtz resonance (peak) or a back-cavity resonance etc., to be acoustically attenuated in the inner volume <NUM> of the MEMS device <NUM>. A further subset of the tube elements <NUM>-<NUM> may comprises a length "l1" which corresponds to a quarter of the wavelength (= λ/<NUM>) of a further wavelength or of a further center wavelength of a wavelength range of the sound traveling through the sound port <NUM> into the package <NUM> to the MEMS device <NUM> and of the (corresponding) further wavelength or wavelength range of an acoustic resonance, e.g. of a Helmholtz resonance (peak) or a back-cavity resonance etc., to be further acoustically attenuated in the inner volume <NUM> of the MEMS device <NUM>.

According to a further embodiment, the tube element or extension cavity <NUM>-<NUM> may alternatively comprise a bypass tube or bypass cavity having a bypass inlet and a bypass outlet, which are acoustically coupled to the sound port <NUM>, wherein the bypass inlet is arranged in the sound port acoustically upstream to the bypass outlet (= upstream with respect to the sound traveling direction in to the package to the MEMS device). See also <FIG> and the associated description.

According to a further embodiment (as described in detail below), the sound port <NUM> may (alternatively) extend through the lid structure <NUM>, wherein the passive acoustic attenuation filter <NUM> may be part of the lid structure <NUM>. Thus, the tube element <NUM>-<NUM> may be integrated in the lid structure <NUM>, may be integrated in different layers of the lid structure <NUM> or may be attached (e.g. as an assembly part or component) to the lid structure <NUM>.

According to a further embodiment (as described in detail below), the passive acoustic attenuation filter <NUM> may be part of a filter device (e.g. an assembly part or component) attached to the package <NUM> at the sound port <NUM>, wherein the filter device <NUM> comprises the sound port <NUM> and the tube element <NUM>-<NUM>.

According to a further embodiment (as described in detail below), the tube element <NUM>-<NUM> of the passive acoustic attenuation filter <NUM> may comprise a spiral tube <NUM>-<NUM> extending around the sound port <NUM>. The spiral tube <NUM>-<NUM> may comprise a varying or changing cross-section.

According to a further embodiment (as described in detail below), the tube element of the passive acoustic attenuation filter <NUM> may be filled with a medium or fluid <NUM> (e.g. a liquid, gas or gel) having a different speed of sound than the medium of the environmental atmosphere.

In the following, some technical effects of the above-described MEMS device <NUM> with passive acoustic attenuation filter <NUM> are summarized, wherein the passive acoustic attenuation filter <NUM> is acoustically coupled to the sound port <NUM>.

The described concept of the passive acoustic attenuation filter <NUM> implements a package level acoustic filter into the microphones acoustic inlet (sound port <NUM>) design, wherein the passive acoustic attenuation filter <NUM> can shape the frequency response of the sound signal entering the package <NUM> of the MEMS device <NUM>.

The passive, acoustic filter element <NUM> can be understood as an additional degree of freedom in the system design of a MEMS microphone. The passive acoustic attenuation filter <NUM> can attenuate the MEMS device's, e.g. MEMS microphone's, resonance peak without adding noise in the band of interest.

The MEMS device <NUM> with the passive acoustic attenuation filter <NUM> can be implemented in or on the laminate (substrate structure) <NUM> or the lid (lid structure) <NUM> of the MEMS device <NUM> as extended variant of the standard acoustic inlet (sound port) <NUM>. The passive acoustic attenuation filter <NUM> may be implemented directly with PCB manufacturing processes or by embedding/implementing dedicated acoustic filter elements <NUM> (filter assembly parts). These filter elements <NUM> may be manufactured with 3D printing, silicon-wafer, PCB, or other technologies.

Considering a conventional bottom port microphone, the passive acoustic attenuation filter <NUM> of the present disclosure can be implemented as a branch of the main acoustic inlet (sound port) <NUM> in the microphone laminate (substrate structure) <NUM>.

Passive acoustic attenuation filters can beneficially influence system Helmholtz resonance behavior without additional power consumption of the MEMS device of otherwise necessary electronic filter circuits. Additionally or alternatively, the passive acoustic attenuation filter can, for example, attenuate standing-wave resonances in the back-cavity of the MEMS device or the eigen-resonances (= natural resonances) of the membrane (the frequency at which a system tends to oscillate in the absence of any driving or damping force).

A passive acoustic attenuation filter can be implemented as a passive acoustic notch filter.

Passive acoustic attenuation filters in a parallel configuration can target different frequencies, such as e.g. back-cavity standing waves resonances at frequencies in the ultrasound band that are independent from the end application of the MEMS device, in order to optimize the overall frequency response of the system.

Passive acoustic attenuation filter <NUM> does not introduce non-linear behavior or clipping and does not introduce additional noise, such as broadband noise, in the audio band.

<FIG> shows an exemplarily illustration of a MEMS device <NUM> with a passive acoustic attenuation filter <NUM> having a plurality of parallel tube extensions <NUM>-<NUM> according to a further embodiment. <FIG> shows a bottom port configuration, wherein the sound port <NUM> extends through the substrate structure <NUM>.

According to the further embodiment, the passive acoustic attenuation filter <NUM> may comprises a plurality of tube elements <NUM>-<NUM> which branch off from the sound port <NUM>.

According to a further embodiment, a subset of the plurality of parallel tube elements <NUM>-<NUM> may have a different dimension "l1" with respect to the remaining tube elements <NUM>-<NUM> for providing a different attenuation center frequency with respect to the attenuation center frequency of the remaining tube elements <NUM>-<NUM>.

Thus, a subset of the tube elements <NUM>-<NUM> may comprise a length "I" which corresponds to a quarter of the wavelength (= λ/<NUM>) of the wavelength or of the center wavelength of a wavelength range of the sound traveling through the sound port <NUM> into the package <NUM> to the MEMS device <NUM> and of the (corresponding) wavelength or wavelength range of an acoustic resonance, e.g. of a Helmholtz resonance (peak) or a back-cavity resonance etc., to be acoustically attenuated in the inner volume <NUM> of the MEMS device <NUM>. A further subset of the tube elements <NUM>-<NUM> may comprises a length "l1" which corresponds to a quarter of the wavelength (= λ/<NUM>) of a further wavelength or of a further center wavelength of a wavelength range of the sound traveling through the sound port <NUM> into the package <NUM> to the MEMS device <NUM> and of the (corresponding) further wavelength or wavelength range of an acoustic resonance, e.g. of a Helmholtz resonance (peak) or a back-cavity resonance etc., to be further acoustically attenuated in the inner volume <NUM> of the MEMS device <NUM>.

All the parallel configurations with the plurality of tube elements or tube extensions <NUM>-<NUM> can eventually be extended to arrays of acoustic filters <NUM> and can target one single frequency (to be attenuated), or also subsets of the branches <NUM>-<NUM> or each single branch can be targeting a different frequency (to be attenuated) in order to optimize the overall frequency response of the system <NUM>. That applies for example to back-cavity standing waves resonances in the inner volume <NUM> that usually happen at a well-defined frequency in the ultrasound band and that is pretty much independent from the end-application of the MEMS microphone <NUM>.

<FIG> shows an exemplarily MEMS device <NUM> with a passive acoustic attenuation filter <NUM> where the tube element <NUM>-<NUM> is exemplarily implemented as a Herschel-Quincke tube. <FIG> shows a bottom port configuration, where the sound port <NUM> extends through the substrate structure <NUM>.

According to the embodiment of <FIG>, the tube element or extension cavity <NUM>-<NUM> of the passive acoustic attenuation filter <NUM> may implemented as a bypass tube or bypass cavity having a bypass inlet <NUM>-a and a bypass outlet <NUM>-b, which are acoustically coupled to the sound port <NUM>. A shown in <FIG>, the bypass inlet 16a is arranged in the sound port <NUM> acoustically upstream to the bypass outlet 16b. The term "upstream" in the sound port <NUM> relates to the sound traveling direction into the package <NUM> to the MEMS device <NUM>.

According to a further embodiment, the tube element <NUM>-<NUM> of the passive acoustic attenuation filter <NUM> may be filled with a medium or fluid <NUM> (e.g. a liquid, gas or gel) having a different speed of sound than the medium of the environmental atmosphere.

The tube element or extension cavity <NUM>-<NUM> of the passive acoustic attenuation filter <NUM> may be implemented as a Herschel-Quincke tube, which comprises a parallel branch <NUM>-<NUM> to a main acoustic path <NUM>. Its purpose is to create an acoustic attenuation filter, e.g. an acoustic notch filter, in order to acoustically attenuate defined frequency components of an acoustic signal traveling through the acoustic system, i.e. through the sound port <NUM> and into the package <NUM>. In an implementation (e.g. an ideal case), the radiuses of the parallel branch <NUM>-<NUM> and the main acoustic path (sound port) <NUM> are equal, wherein (only) plain waves are assumed to be propagating in the filter system <NUM> (with smooth interfaces). The parallel branch (= tube element) <NUM>-<NUM> comprises the length "I", wherein the (vertical) distance between the center of the bypass inlet <NUM>-a and the center of bypass outlet <NUM>-b comprises the length "lSP".

From the relation <MAT> the minimum length of the parallel branch for the cancellation (attenuation) of the component with λ wavelength can be deducted as <MAT> wherein "lsp" is the length of the main acoustic path, "l" is the length of the parallel branch and "m" is an integer (with the assumption m = <NUM>). As an example for wavelength λ in the range of <NUM> to <NUM>, the length I of the parallel branch <NUM>-<NUM> may have dimensions in the range of <NUM> to <NUM>. A sound port <NUM> may, for example, have a radius r of <NUM> and a length lSP of <NUM> with an HQ-tube <NUM>-<NUM> of equal cross section as the main inlet <NUM>. For example, an attenuation of the resonance peak may be in the range of <NUM> dB, depending on the specific dimensions of the sound port <NUM> and the tube element <NUM>-<NUM>.

<FIG> shows an example of Helmholtz resonance attenuation of a typical microphone inlet (<NUM> radius <NUM> length) with an Herschel-Quincke tube <NUM>-<NUM> of equal cross section as the main inlet <NUM> according to an embodiment. In this case, the optimization brings to a Herschel-Quincke tube of <NUM> (~<NUM> resonance) and an attenuation of the resonance peak of 8dB. <FIG> takes into account a possible (simple and inexpensive) way of producing the cavities/tubes <NUM>-<NUM>. For example, a first PCB (= printed circuit board) is milled to form the desired cavities <NUM>-<NUM>. Afterwards the stacking of an additional PCB finalizes the final substrate <NUM> in for of a PCB stack (see also <FIG>). This way avoids the need to etch or modify middle layers (e.g. dielectric layers) of a PCB which is complex (and expensive) and sometimes not even possible.

The geometric constraints (length "I" and cross-sectional area) for the HQ tube element <NUM>-<NUM> can be relaxed, for example, allowing the radius of the HQ tube element <NUM>-<NUM> to be different than the one of the main inlet (sound port) <NUM>.

<FIG> exemplarily shows the attenuation in a MEMS device <NUM> with the passive acoustic attenuation filter <NUM> having the tube element <NUM>-<NUM> in form of a Herschel-Quincke tube. As is evident form the depiction in <FIG>, the tube element <NUM>-<NUM> may be tuned to attenuate the desired frequency or frequency range, comparable to a notch filter, but implemented as a passive element. The passive acoustic attenuation filter <NUM> may be, when implemented as a Herschel-Quincke tube <NUM>-<NUM>, adapted to attenuate a specific frequency or a frequency band by changing the length of the parallel branch <NUM>-<NUM>. Additionally or alternatively, the Herschel-Quincke tube may be adapted by changing the portion of the main acoustic path that is shunted by the parallel branch. The longer the shunted portion of the main acoustic path, the better is the attenuation. For the exemplary results depicted in <FIG>, the Herschel-Quincke tube has a radius that is less than half the radius of the sound port, here <NUM> and <NUM>, respectively. The attenuation notch becomes wider in bandwidth. An attenuation may be more effective and flat.

Embodiments of the present concept for providing the MEMS device <NUM> with the passive acoustic attenuation filter <NUM> allows to realize an attenuation of the requested frequency, frequencies or frequency ranges without an noise impact in the audio band. Considering the PSD (PSD = power spectrum density) of MEMS device <NUM> with the passive acoustic attenuation filter <NUM> having the tube element <NUM>-<NUM> in form of a Herschel-Quincke tube, it can be seen how there is a broadening of the resonance peak with no effect in the audio band. This (critical) feature cannot be achieved with traditional techniques which reduce the Q factor of the resonance and show a significant impact on the noise at all frequencies.

An additional optimization parameter is the portion (length lSP) of the main inlet <NUM> that is shunted by the HQ-tube element <NUM>-<NUM>. An optimization can show that the longer the shunted part lSP the better, but already the equipartitioned case (<NUM>/<NUM> of the full inlet <NUM>) shows good results.

<FIG> exemplarily shows the attenuation in a MEMS device <NUM> with the passive acoustic attenuation filter <NUM> having the tube element <NUM>-<NUM> in form of a Herschel-Quincke tube <NUM>-<NUM> in the equipartitioned case (<NUM>/<NUM> of the full inlet <NUM>).

Considering the phase delay of the wave in the added branch <NUM>-<NUM> and considering the basic equation for the ideal case <MAT> with "f" is fixed to the frequency to be canceled and with "v" is the speed of sound of the medium. Considering the basic equation, it can be derived that reducing "v" (= low "v") can reduce the needed length "I" for a destructive interference.

On the other hand, an extremely high speed of sound "v" idea may exploit another kind of tube resonance and not destructive interference. When the added path plus the shunted portion (= length lSP) are a multiple of the wavelength "λ" (entire λ), the intuitive physical effect is that the waves travel in loop in the branch <NUM>-<NUM> and the shunted portion (length lSP) of the sound-port <NUM> and never go to the output of the sound port <NUM>. In addition, a small phase delay along the added tube element <NUM>-<NUM> may be achieved, wherein the path added by the branch <NUM>-<NUM> can be "neglected". This small phase delay approach (method) can additionally be enhanced by the resonance added by a membrane (= the first and second aperture interfaces 30a, 30b, as shown in <FIG> below, when the tube element <NUM>-<NUM> is filled with a medium), that is usually tuned to the application. Thus, the resulting effect is similar to a drum-like silencer.

<FIG> shows a schematic view comprising the passive acoustic attenuation filter <NUM> according to a further embodiment. The substrate structure <NUM> may comprise one or more layers of a laminate <NUM>-<NUM>,. , <NUM>-n, e.g. planes, such as n layers with n ≥ <NUM>, <NUM>, <NUM>, etc. The exemplarily depicted substrate structure comprises seven layers (n = <NUM>) of a laminate <NUM>. The passive acoustic attenuation filter <NUM> may be implemented in the layers <NUM>-n of the laminate <NUM>.

As exemplarily shown, the substrate structure <NUM> may comprise metallization layers M1, M2, M3, which are separated by and/or embedded in an insulation (dielectric) material of the substrate structure <NUM>.

According to an embodiment, the substrate structure <NUM> may be adapted to comprise the tube element <NUM>-<NUM> by structuring at least one (or a plurality) of the layers <NUM>-n of the laminate <NUM>. The substrate structure <NUM> may be adapted to comprise the tube extension <NUM>-<NUM>, e.g. a λ/<NUM> tube extension <NUM>-<NUM> within at least one of the layers <NUM>-n of the laminate <NUM> that forms the substrate structure <NUM>. There may be one or more tube elements <NUM>-<NUM> formed within at least a portion of a layer or layers <NUM>-n of laminate of a substrate structure <NUM>. <FIG> shows two tube elements <NUM>-<NUM>.

The passive acoustic attenuation filter <NUM> can be implemented in the laminate (substrate structure) <NUM> of the MEMS device <NUM> as extended variant of the standard acoustic inlet (sound port) <NUM>. The tube element(s) <NUM>-<NUM> of the passive acoustic attenuation filter <NUM> may be implemented directly with PCB manufacturing processes or by embedding (= implementing) dedicated acoustic filter elements <NUM>-<NUM>.

<FIG> shows a MEMS device <NUM> with a passive acoustic attenuation filter <NUM> where the tube element <NUM>-<NUM> is implemented as a Herschel-Quincke tube <NUM>-<NUM> in the layers of a laminate <NUM> configured as the substrate structure <NUM>. The laminate <NUM> may comprise one or more layers <NUM>-n.

According to an embodiment, the substrate structure <NUM> may be adapted to comprise the tube element <NUM>-<NUM> by structuring a plurality of the layers <NUM>-n of the laminate <NUM>. The substrate structure <NUM> may be adapted to comprise the tube extension <NUM>-<NUM>, e.g. a Herschel-Quincke tube <NUM>-<NUM>, within the layers <NUM>-n of the laminate <NUM> that forms the substrate structure <NUM>. There may be one or more tube elements <NUM>-<NUM> formed within at least a portion of a layer or layers <NUM>-n of laminate of a substrate structure <NUM>. <FIG> shows one tube elements <NUM>-<NUM>.

The passive acoustic attenuation filter <NUM> can be implemented in the laminate (substrate structure) <NUM> of the MEMS device <NUM> as extended variant of the standard acoustic inlet (sound port) <NUM>. The tube element(s) <NUM>-<NUM> of the passive acoustic attenuation filter <NUM> may be implemented directly with PCB manufacturing processes or by embedding (implementing) dedicated acoustic filter elements <NUM>-<NUM>.

<FIG> shows an exemplarily illustration of a MEMS device <NUM> with the passive acoustic attenuation filter <NUM> according to a further embodiment. The passive acoustic attenuation filter <NUM> is exemplarily implemented as a dedicated filter element (e.g. as an assembly part or component) <NUM> that is inserted into and fixed to a cavity or recess <NUM>-<NUM> of the laminate (= substrate) <NUM>, wherein the tube element <NUM>-<NUM> is configured as a spiral around the main inlet <NUM>. The depicted tube element <NUM>-<NUM> of the passive acoustic attenuation filter <NUM> is exemplarily implemented as a λ/<NUM> tube extension.

According to an embodiment, the dedicated element (filter device) <NUM> may comprise the sound port <NUM> or at least a portion of the sound port <NUM> and the tube element <NUM>-<NUM> of the passive acoustic attenuation filter <NUM>. The tube element <NUM>-<NUM> of the passive acoustic attenuation filter <NUM> may comprise a spiral tube <NUM>-<NUM> extending around the sound port <NUM>. The spiral tube <NUM>-<NUM> may comprise a varying or changing cross-section.

<FIG> shows a MEMS device <NUM> with the passive acoustic attenuation filter <NUM> exemplarily implemented as Herschel-Quincke tube <NUM>-<NUM>, such as a parallel branch <NUM>-<NUM>, implemented as a dedicated element <NUM> (filter device) that is implemented into a cavity <NUM>-<NUM> in the laminate <NUM>.

According to an embodiment, the passive acoustic attenuation filter <NUM> with the tube element <NUM>-<NUM> may be implemented as a dedicated filter element (filter device) <NUM> that is implemented into the <NUM>-<NUM> cavity in the laminate <NUM>. The dedicated element <NUM> may comprise the sound port <NUM> or at least a portion of the sound port <NUM> and the tube element <NUM>-<NUM> of the passive acoustic attenuation filter <NUM>. The dedicated element (filter device) <NUM> may be arranged in the cavity or recess <NUM>-<NUM> in the laminate <NUM>, such that the tube element <NUM>-<NUM> of the dedicated element (filter device) <NUM> branches off from the sound port <NUM> and is acoustically coupled to the sound port <NUM>. The parallel branch (= tube element) <NUM>-<NUM> comprises the length "I", wherein the (vertical) distance between the center of the by-pass inlet <NUM>-a and the center of bypass outlet <NUM>-b comprises the length "lSP".

<FIG> shows a MEMS device <NUM> with a passive acoustic attenuation filter <NUM> with a Herschel-Quincke tube and a parallel branch <NUM>-<NUM> as the tube element <NUM>-<NUM>. The passive acoustic attenuation filter <NUM> is implemented as a dedicated element (filter device) <NUM> that is implemented into the cavity or recess <NUM>-<NUM> in a laminate <NUM>, wherein the parallel branch <NUM>-<NUM> is designed as a spiral around the main inlet (sound port) <NUM>.

According to an embodiment, a tube element <NUM>-<NUM>, such as a Herschel-Quincke tube, comprises a tube inlet <NUM>-<NUM> and a tube outlet <NUM>-<NUM>, which are acoustically coupled to the sound port <NUM> wherein the tube inlet <NUM>-a is arranged in the sound port <NUM> acoustically upstream to the tube outlet <NUM>-b. The Herschel-Quincke tube <NUM>-<NUM> may be implemented as a spiral, e.g. helical element, around the sound port <NUM> with the tube inlet 16a and the tube outlet 16b acoustically coupled to the sound port <NUM>. The parallel branch (= tube element) <NUM>-<NUM> comprises the length "I", wherein the (vertical) distance between the center of the bypass inlet <NUM>-a and the center of bypass outlet <NUM>-b comprises the length "lSP".

As shown in <FIG>, the tube element <NUM>-<NUM> may be attached as a dedicated filter device <NUM>, e.g. as a dedicated assembly part or component, to the substrate structure <NUM>, e.g. to the cavity or recess <NUM>-<NUM> of the substrate <NUM>. As shown in <FIG>, the passive acoustic attenuation filter <NUM> may be part of the dedicated filter device <NUM> mechanically fixed or attached to the package <NUM> at the sound port <NUM>, wherein the filter device <NUM> comprises (at least partially) the sound port <NUM> and the tube element <NUM>-<NUM>.

<FIG> shows a schematic view of a MEMS device <NUM> with a passive acoustic attenuation filter <NUM> having the tube element (e.g. a λ/<NUM> tube) <NUM>-<NUM>. <FIG> shows a first layer (first PCB; PCB = printed circuit board) of a substrate structure <NUM> as a substrate 20a and a second layer (second PCB) of a substrate structure <NUM> as a substrate 20b. The tube element <NUM>-<NUM> may be implemented as a λ/<NUM> tube and may be produced by milling in one or both PCBs 20a, 20b and stacking the two PCBs 20a, 20b.

Thus, the tube element <NUM>-<NUM> of the passive acoustic attenuation filter <NUM> may be integrated in the substrate structure <NUM> or may be integrated in different layers (or planes) of the substrate structure <NUM>.

According to an embodiment, the tube element <NUM>-<NUM> of the passive acoustic attenuation filter <NUM> is a part of the substrate structure <NUM>, e.g. arranged in a PCB or between two PCBs. The substrate structure <NUM> may be comprised of one or more substrates or one or more layers (PCBs) of the substrate. The tube element <NUM>-<NUM> may be integrated in the substrate structure <NUM>.

For example, a first substrate 20a that forms the first layer (first PCB) in the substrate structure <NUM> may be milled and/or structured to comprise a part of the tube element <NUM>-<NUM> in that, when the second substrate (second PCB) 20b is attached to each other, the tube element is formed with (at the surface region of) the second substrate 20b. Alternatively, parts of the tube element <NUM>-<NUM> may be divided across the two or more substrates (PCBs) that form the substrate structure <NUM>, wherein the tube element <NUM>-<NUM> is formed within the resulting substrate structure <NUM>.

<FIG> shows a schematic cross sectional view of a MEMS device <NUM> with a passive acoustic attenuation filter <NUM> having a Herschel-Quincke tube <NUM>-<NUM> as the tube element <NUM>-<NUM>. The tube element <NUM>-<NUM> may be produced by milling and stacking two PCBs 20a, 20b. <FIG> shows a first layer (first PCB) 20a of the substrate structure <NUM> as a first substrate 20a and a second layer (second PCB) 20b of the substrate structure <NUM> as a second substrate 20b.

According to an embodiment, the MEMS device <NUM> comprises the substrate structure <NUM>, wherein a sound port <NUM> extends through the substrate structure <NUM> in a bottom port configuration. The passive acoustic attenuation filter <NUM> is an integral part of the substrate structure <NUM>. The substrate structure <NUM> may be comprised of one or more substrate layers (PCBs) 20a, 20b. The first exemplarily substrate layer 20a and the second substrate layer 20b, as depicted in <FIG>, comprise at least a portion of a tube element <NUM>-<NUM>, wherein, when the first substrate 20a and the second substrate 20b are attached to each other, the tube element <NUM>-<NUM> is formed in the resulting substrate <NUM> and is acoustically coupled to the sound port <NUM>.

<FIG> shows a schematic view of a MEMS device <NUM> with the passive acoustic attenuation filter <NUM>. The MEMS device <NUM> implemented in a top port microphone configuration with a sound port <NUM> and a passive acoustic attenuation filter (e.g. filter device) <NUM>, <NUM> stacked on a lid structure <NUM>.

According to an embodiment, in a top port configuration, the sound port <NUM> may extend through the lid structure <NUM> and the passive acoustic attenuation filter <NUM> may be part of the lid structure <NUM> or fixed to the lid structure <NUM>. The passive acoustic attenuation filter <NUM> may be integrated in the lid structure <NUM>, may be integrated in different layers of the lid structure <NUM> or may be attached (e.g. as an assembly part or component) to the lid structure <NUM>. The passive acoustic attenuation filter <NUM> may be a dedicated element (filter device) <NUM> attached to the lid structure <NUM> and acoustically coupled to the sound port <NUM>. The dedicated element <NUM> may be arranged at the outside of the lid structure. Alternatively, the dedicated element <NUM> may be arranged at the inside of the lid structure <NUM>.

<FIG> shows a schematic cross-sectional view of a MEMS device <NUM> with the passive acoustic attenuation filter <NUM>. The MEMS device <NUM> is implemented as a top port microphone with a sound port <NUM> and the passive acoustic attenuation filter <NUM> (e.g. filter device <NUM>) stacked within (at the inside of) the lid structure <NUM>.

According to an embodiment, in a top port configuration, the sound port <NUM> may extend through the lid structure <NUM> and the passive acoustic attenuation filter <NUM> may be part of or may be attached to the lid structure <NUM>. The passive acoustic attenuation filter <NUM> may be integrated in the lid structure <NUM> or may be a dedicated element (filter device) <NUM> attached to the lid structure <NUM>, wherein the tube element <NUM> of the passive acoustic attenuation filter <NUM> is acoustically coupled to the sound port <NUM>. The dedicated element <NUM> may be arranged at the inside of the lid structure <NUM>. Alternatively, the dedicated element <NUM> may be arranged at the outside of the lid structure <NUM>. The passive acoustic attenuation filter <NUM> may comprise one or a plurality of the tube elements (tube extensions or cavity extensions) <NUM>-<NUM> which branch off from the sound port <NUM>.

<FIG> shows a schematic illustration of a MEMS device <NUM> with a passive acoustic attenuation filter <NUM> having a tube element <NUM>-<NUM> in form of a Herschel-Quincke tube element exemplarily in two corresponding schematic views. The plan view of <FIG> exemplarily depicts a length L<NUM> of the substrate <NUM>, a length L<NUM> of a filter device <NUM> comprising at least partially the sound port <NUM> with a diameter D<NUM> and the passive acoustic attenuation filter <NUM> with the tube element <NUM>-<NUM> in form of a Herschel-Quincke tube with a tube width TW. <FIG> further depicts a width B<NUM> of the substrate <NUM> and a width B<NUM> of the passive acoustic attenuation filter <NUM> or the filter device <NUM> with the passive acoustic attenuation filter <NUM>, respectively.

According to an embodiment, the filter device <NUM> with the passive acoustic attenuation filter <NUM> may be located within the substrate structure <NUM>, wherein the sound port <NUM> may be aligned with the MEMS microphone <NUM> within the MEMS device <NUM>. The height H<NUM>, as depicted in <FIG>, is the height or thickness of the substrate <NUM>, the height H<NUM> is the height or thickness of the filter device <NUM>, and the height H<NUM>-<NUM> is the height or diameter of the tube element <NUM>-<NUM> within the filter device <NUM>. The tube element <NUM>-<NUM> may have a square, rectangular, circular, ellipsoid cross-section or any other form or combination of forms. The dimension D<NUM> indicates the diameter of the sound port <NUM>.

Thus, the tube element <NUM>-<NUM> of the passive acoustic attenuation filter <NUM> may comprise a spiral tube <NUM>-<NUM> extending around the sound port <NUM>. The spiral tube <NUM>-<NUM> may comprise a varying or changing cross-section. According to the embodiment of <FIG>, the tube element or extension cavity <NUM>-<NUM> of the passive acoustic attenuation filter <NUM> may implemented as a bypass tube or bypass cavity having a bypass inlet <NUM>-a and a bypass outlet <NUM>-b, which are acoustically coupled to the sound port <NUM>.

According to the embodiment, the passive acoustic attenuation filter <NUM> may, for example, have a sound port diameter D<NUM> of <NUM>. The tube element <NUM>-<NUM> may be implemented as a Herschel-Quincke tube and may for example have a width TW of the tube of <NUM>. The tube of the Herschel-Quincke tube element <NUM>-<NUM> may have a rectangular cross-section. H<NUM> may for example be <NUM>, H<NUM> may be <NUM> and H<NUM>-<NUM> may be <NUM>. TW may for example be <NUM>. The dimensions may vary with respect to the desired wavelength to be canceled or attenuated and/or the available space within the MEMS device <NUM>. Thus, the implemented dimensions of the MEMS device can vary at least in a range of +/- <NUM> %, +/- <NUM> % or +/- <NUM> % of the indicated dimensions.

According to the embodiment, the passive acoustic attenuation filter <NUM> may be attached to the housing <NUM> or inserted into a recess <NUM>-<NUM> and may comprise at least partially the sound port <NUM> and the annular tube element <NUM>-<NUM> which is provided around the sound port <NUM> in order to form the tube element <NUM>-<NUM> of the passive acoustic attenuation filter <NUM> acoustically coupled to the sound port <NUM>. Starting from the sound port <NUM>, there is an expansion of the cross section area into the tube element <NUM>-<NUM> in order to obtain the largest possible cross section. At the end of the tube element <NUM>-<NUM> there is a reduction in cross-section area at the region of the acoustic coupling with the sound port <NUM>. The filter channel (tube element) <NUM>-<NUM> in between should be made as large as possible in order to provide a low acoustic resistance.

With a non-constant (= changing) cross-section (area) of the tube element <NUM>-<NUM> of the passive acoustic attenuation filter <NUM>, by providing a narrower cross section at the coupling (start and ending of the tube element <NUM>-<NUM>) and an expanding of the cross section of the tube element <NUM>-<NUM> as much as possible therebetween, an easier (= more effective) coupling of the tube element <NUM>-<NUM> to the sound-port <NUM> and a reduction (= minimizing) of the acoustic impedance between the sound port <NUM> to the tube element <NUM>-<NUM> may be achieved.

<FIG> shows a schematic illustration of a MEMS device <NUM> with the passive acoustic attenuation filter <NUM> having the tube element <NUM>-<NUM> in form of a Herschel-Quincke tube (a bypass branch) that may be filled with a medium or fluid <NUM>, e.g., a liquid, gas or gel, that has a different speed of sound compared to the medium of the environmental atmosphere.

As exemplarily shown in <FIG>, the passive acoustic attenuation filter <NUM> having the tube element <NUM>-<NUM> may be implemented as a dedicated filter element (e.g. as an assembly part or component) <NUM> that is implemented into a cavity or recess <NUM>-<NUM> of the laminate <NUM>.

Alternatively, the MEMS device <NUM> of <FIG> may be implemented in correspondence to the MEMS device <NUM> of <FIG> with a passive acoustic attenuation filter <NUM> having the tube element <NUM>-<NUM>.

<FIG> shows a first aperture interface 30a covering and fluidically closing the tube inlet 16a and a second aperture interface 30b covering and fluidically closing the tube outlet 16b of the tube element <NUM>. The first and second aperture interfaces 30a, 30b provide and maintain an acoustical coupling of the sound port <NUM> to the tube element <NUM>-<NUM>, which may be filled with the medium <NUM>. The acoustical coupling of the sound port <NUM> to the tube element <NUM>-<NUM> may be achieved by means of aperture interfaces 30a, 30b which seal the tube element <NUM>-<NUM> and provide an (effective) acoustic impedance coupling between the sound port <NUM> to the tube element <NUM>-<NUM>.

According to embodiments, the medium <NUM> in the tube element (filter branches) <NUM>-<NUM> may for example be Helium, Hydrogen, Perfluorobutane (PFB) or Sulfur Hexafluoride or the like. With the medium <NUM> within the tube element <NUM>-<NUM>, a size of the passive acoustic attenuation filter <NUM> may be made smaller than without the medium <NUM> within the tube element <NUM>-<NUM>. Additionally or alternatively, a filter frequency may be downshifted, for example by keeping or by changing the dimensions of the tube element <NUM>-<NUM>.

Thus, the result would be to either shrink the physical dimensions of the acoustic filter <NUM>, or to downshift the filter frequency by keeping the dimension of the acoustic filter <NUM>. In the case of lower speed of sound gases <NUM> (e.g. perfluorobutane PFB or Sulfur hexafluoride) the filter branch length "I" scales directly with the speed of sound, while for high speed of sound gases <NUM> (e.g. hydrogen) the additional branch <NUM>-<NUM> needs to be as short as possible (ideally same length) compared to the main branch <NUM> (= the length lSP between the center of the bypass inlet <NUM>-a and the center of bypass outlet <NUM>-b).

<FIG> shows a concept representation of one exemplary implementation option and the simulation results for the different considered cases. (see courses <NUM> to <NUM> in <FIG>).

As it can be seen, high speed of sound media <NUM> results in very compact filters <NUM> but slightly less effective, while low speed of sound media <NUM> allows the direct scaling of the branch <NUM>-<NUM> with the speed of sound ratio with respect to air (PFB speed of sound ~<NUM> times lower than air so the filters are ~<NUM> times shorter) while maintaining the excellent filtering performance.

<FIG> shows three exemplary results for a MEMS device <NUM> with the passive acoustic attenuation filter <NUM> implemented as a λ/<NUM> tube element <NUM>-<NUM>. To be more specific, <FIG> shows the effect of different tubes radii from <NUM> to <NUM> to <NUM>. <FIG> shows the basic performance for the embodiments, and especially the importance of maximizing the radius of the branch <NUM>-<NUM> so to reduce the resistance and allow for larger portion of the flow to pass through the by-pass <NUM>-<NUM>.

<FIG> shows three exemplary results for a MEMS device <NUM> with the passive acoustic attenuation filter <NUM> implemented as a λ/<NUM> tube element <NUM>-<NUM>. The results were obtained using four parallel tube elements <NUM>-<NUM> of the same length (for the specific example of <NUM>) and different tube radii for each of the resulting graphs, respectively (here, <NUM>, <NUM> and <NUM>). In comparison, it was found that λ/<NUM> tube elements <NUM>-<NUM> need approximately twice as much tubes <NUM>-<NUM> in parallel with respect to Herschel-Quincke tubes <NUM>-<NUM>. Implementing λ/<NUM> tube elements <NUM>-<NUM> may be less complex than implementing Herschel-Quincke tubes <NUM>-<NUM>.

The results of <FIG> show the noise PSD (PSD = power spectral density) of one of the cases of <FIG>. It is clearly derivable from <FIG>, that the effect of the passive acoustic attenuation filter <NUM> does not compromise the noise performance in the audio band. To be more specific, the passive acoustic attenuation filter <NUM> allows to realize an attenuation of the requested frequency, frequencies or frequency ranges without an noise impact in the audio band. Considering the PSD of the MEMS device <NUM> with the passive acoustic attenuation filter <NUM>, it can be seen how there is a broadening of the resonance peak with no effect in the audio band.

In the following, a number of technical effects of the MEMS device <NUM> with the passive acoustic attenuation filter <NUM> are summarized.

The passive acoustic attenuation filter <NUM> can beneficially influence system Helmholtz resonance behavior without additional power consumption of the MEMS device of otherwise necessary electronic filter circuits.

The system Helmholtz resonance behavior can be controlled by the passive acoustic attenuation filter <NUM>, even if there are external physical requirements for the MEMS package. In addition, attention on the detailed ultrasound behavior of the audio system may be achieved with the passive acoustic attenuation filter <NUM>. Moreover, the passive acoustic attenuation filter <NUM> may help to prevent ASIC internal nonlinear behavior/clipping of even physical nonlinear behavior/clipping of the MEMS component without additional power consumption.

The passive acoustic attenuation filter <NUM> allows to shape the frequency response behavior of the MEMS microphone very early, i.e. at the beginning of the signal processing chain of the MEMS device <NUM>.

Acoustic resonances (e.g. Helmholtz resonances) often occur in a MEMS microphone, which influence the signal behavior of the MEMS microphone. According to the present concept, the acoustic filter element <NUM> is inserted at the microphone system level in order to attenuate one or more resonance peaks (very early in the system).

The passive acoustic attenuation filter <NUM> is acoustically coupled to the sound port <NUM> of the MEMS microphone or is arranged adjacent to it and is designed as λ/<NUM> branches <NUM>-<NUM> or an HQ tube (Herschel-Quincke tube) <NUM>-<NUM>. Several acoustic filter elements <NUM>-<NUM> can also be combined, on the one hand to increase the filter efficiency for a certain resonance frequency and/or to attenuate several resonance frequencies (resonance states).

According to exemplary embodiments, the passive acoustic attenuation filter <NUM> may be inserted as an additional (independent) component in a section of the microphone package <NUM>, e.g. in a recess <NUM>-<NUM> provided for this purpose, and is glued (mechanically connected) to the package <NUM>, for example.

According to exemplary embodiments, the passive acoustic attenuation filter <NUM> allows to shape the frequency response of the microphone package <NUM>, e.g. in a frequency range from <NUM> to <NUM>, i.e., if possible, receive no resonances (standing acoustic waves) within the housing to avoid possible interference or negative influences on the MEMS component and/or the ASIC.

Although some aspects have been described as features in the context of an apparatus, it is clear that such a description may also be regarded as a description of corresponding features of a method. Although some aspects have been described as features in the context of a method, it is clear that such a description may also be regarded as a description of corresponding features concerning the functionality of an apparatus.

Depending on certain implementation requirements, embodiments of the control circuitry can be implemented in hardware or in software or at least partially in hardware or at least partially in software. Generally, embodiments of the control circuitry can be implemented as a computer program product with a program code, the program code being operative for performing one of the methods when the computer program product runs on a computer.

Claim 1:
MEMS device (<NUM>) comprising:
a package (<NUM>) for providing an inner volume (<NUM>) ,
a MEMS microphone (<NUM>) arranged in the inner volume (<NUM>),
a sound port (<NUM>) through the package (<NUM>) to the inner volume (<NUM>), and
a passive acoustic attenuation filter (<NUM>) acoustically coupled to the sound port (<NUM>),
wherein the passive acoustic attenuation filter (<NUM>) comprises a tube element (<NUM>-<NUM>), which branches off from the sound port (<NUM>), and
wherein the tube element (<NUM>-<NUM>) is implemented as a bypass tube having a tube inlet (16a) and a tube outlet (16b), which are acoustically coupled to the sound port (<NUM>) , wherein the tube inlet (16a) is arranged in the sound port (<NUM>) acoustically upstream to the tube outlet (16b), with respect to a sound traveling direction in to the package (<NUM>).