Microelectromechanical systems (MEMS) microphone components

Abstract

In at least one embodiment, a microphone assembly is provided, comprising a housing, a first printed circuit board (PCB), and a microphone subassembly. The microphone subassembly comprises a sub-housing, a microelectromechanical system (MEMS) transducer, and a second PCB. The MEMS transducer is positioned in the sub-housing, and the second PCB supports the MEMS transducer. The first PCB defines a first acoustic path positioned below the second PCB and the MEMS transducer. The second PCB defines a first audio port positioned directly below the MEMS transducer. The housing defines a first acoustic opening, the first acoustic opening being positioned directly below the first acoustic path so that an audio input signal can pass through the first audio port and reach the underside of the MEMS transducer. The housing defines a second acoustic opening, the second acoustic opening being positioned at a distance between 3 and 30 mm from the first acoustic opening.

Description

Technical Field

[0001] Various aspects as disclosed herein generally relate to microphones, such as microelectromechanical systems (MEMS) microphones of microphone assemblies that can be adapted to form microphones with different directivity patterns (e.g., unidirectional versus omnidirectional) and / or frequency response shapes. The disclosed MEMS microphone assemblies can be used in any number of applications, including, but not limited to, active noise cancellation (ANC) technology and voice pickup in hands-free phone applications. These and other aspects are discussed in greater detail herein. Background Art

[0002] U.S. Patent No. 10,154,330 to Baumhauer et al. provides a microelectromechanical system (MEMS) microphone assembly. The assembly includes a housing, a MEMS transducer, and a plurality of substrate layers. A single MEMS transducer is positioned within the housing. The plurality of substrate layers support the single MEMS transducer. The plurality of substrate layers define: a first transmission mechanism to enable a first side of the single MEMS transducer to receive an audio input signal; and a second transmission mechanism to enable a second side of the single MEMS transducer to receive the audio input signal.

[0003] U.S. Patent No. 9,955,246 to Reese et al. provides a microelectromechanical system (MEMS) microphone assembly. The assembly includes a housing, a single microelectromechanical system (MEMS) transducer, a substrate layer, and an application housing. The single MEMS transducer is positioned within the housing. The substrate layer supports the single MEMS transducer. The application housing supports the substrate layer and defines: at least a portion of a first transmission mechanism to enable a first side of the single MEMS transducer to receive an audio input signal; and at least a portion of a second transmission mechanism to enable a second side of the single MEMS transducer to receive the audio input signal. Summary of the Invention

[0004] In at least one embodiment, a microphone assembly is provided, comprising a housing, a first printed circuit board (PCB), and a microphone subassembly. The microphone subassembly comprises a sub-casing, a microelectromechanical system (MEMS) transducer, and a second PCB. The MEMS transducer is positioned in the sub-casing, and the second PCB supports the MEMS transducer. The first PCB defines a first acoustic path positioned below the second PCB and the MEMS transducer. The second PCB defines a first audio port positioned directly below the MEMS transducer. The housing defines a first acoustic opening, the first acoustic opening being positioned directly below the first acoustic path so that an audio input signal can pass through the first audio port and reach the underside of the MEMS transducer. The housing defines a second acoustic opening, the second acoustic opening being positioned at a distance between 3 and 30 mm from the first acoustic opening.

[0005] In at least another embodiment, a microphone assembly is provided that includes a housing, a first printed circuit board (PCB), a post, and a microphone subassembly. The microphone subassembly includes a subshell, a microelectromechanical system (MEMS) transducer, and at least one port aperture. The microelectromechanical system (MEMS) transducer is positioned in the subshell to receive an audio input signal. The at least one port is positioned on the top side of the subshell. The post is positioned above the at least one port aperture to seal the subshell.

[0006] In at least another embodiment, a microphone assembly is provided that includes a housing, a first printed circuit board (PCB), and a microphone subassembly. The microphone subassembly includes a subshell, a microelectromechanical system (MEMS) transducer, at least one port aperture, and a cover. The microelectromechanical system (MEMS) transducer is positioned in the subshell to receive an audio input signal. The at least one port is positioned on a top side of the subshell. A cover is positioned above the at least one port aperture and is movable about the first port aperture to provide multiple frequency responses based on a position of the cover relative to the first port aperture. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The embodiments of the present disclosure are particularly pointed out in the appended claims. However, other features of the various embodiments will become more apparent and will be best understood by referring to the following detailed description taken in conjunction with the accompanying drawings, in which:

[0008] Figure 1 An example of an amplitude response curve for a microphone is shown;

[0009] Figure 2 Examples of different cutoff frequencies in various car audio applications are shown;

[0010] Figure 3 An example of a MEMS microphone for achieving a single cutoff frequency is shown;

[0011] Figure 4 An example of a microphone assembly is shown;

[0012] Figure 5 shows a microphone assembly according to one embodiment;

[0013] Figure 6 shows a detailed implementation of a microphone subassembly according to one embodiment;

[0014] Figure 7 shows an example of a frequency response curve according to one embodiment;

[0015] Figure 8 shows an example of various frequency responses according to one embodiment;

[0016] Figure 9 An example of various directivities according to one embodiment is shown;

[0017] Figure 10 shows another detailed implementation of a microphone assembly according to one embodiment; and

[0018] Figures 11A to 11B 1 and 2 show top views of sub-housings of a microphone sub-assembly according to one embodiment. DETAILED DESCRIPTION

[0019] As required, detailed embodiments of the present invention are disclosed herein; however, it should be understood that the disclosed embodiments are merely exemplary of the invention that can be embodied in various alternative forms. The drawings are not necessarily drawn to scale; some features may be exaggerated or minimized to illustrate details of particular components. Therefore, the specific structural and functional details disclosed herein should not be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.

[0020] It should be understood that directional terms (e.g., "upper," "lower," "inner," "outer," "top," "bottom," etc.) that may be mentioned herein refer only to the orientation of the various components of the transducer assembly relative to the microphone assembly as shown in the accompanying drawings. These terms are provided for context and understanding of the embodiments disclosed herein.

[0021] A microphone assembly may include, but is not limited to, a microphone subassembly comprising a microelectromechanical system (MEMS)-based microphone element (e.g., transducer) or an electret condenser microphone (ECM), a printed circuit board (PCB) assembly on which the microphone element is mounted, and a housing (or shell) enclosing the aforementioned features. Therefore, it should be understood that the size of the microphone assembly is larger than that of a MEMS microphone element package (or ECM).

[0022] Customer applications may require microphone elements to provide different frequency response shapes and / or directivities. This means that different microphone element models may be required in the overall microphone assembly for various specific applications. The various embodiments described herein attempt to extend the acoustic design parameters from the microphone element level (e.g., MEMS microphone package design) (or subassembly level) to the component level. That is, by modifying the structural and geometric parameters of the component housing / shell, a single common microphone element package can be used for multiple microphone assembly designs. For example, the microphone assembly design in a vehicle may currently require different dedicated MEMS microphone elements to meet hands-free communication or active noise cancellation (ANC) applications. The various embodiments described herein can provide a single common MEMS microphone element model that can be used for both applications, where only some design features at the module housing level need to be modified.

[0023] For automotive applications, the complete microphone assembly can include a protective housing and be mounted within the vehicle body. For other applications, the microphone element and PCB can be mounted directly to the housing of a product (e.g., a cell phone). In this case, the final product housing (e.g., a cell phone) can enclose (or store) the microphone assembly within the protective housing.

[0024] Figure 1 An example of a microphone's amplitude response curve as a function of frequency is shown. Starting from the lowest frequency defined on the graph, the curve generally exhibits a rising response shape characterized by a cutoff frequency. A microphone's cutoff frequency can generally be defined as the frequency point at which the sensitivity is 3 dB (or other suitable value) lower than its normal sensitivity measured at 1 kHz. Figure 2 An example of cutoff frequencies for various applications is shown (e.g., microphones used in conjunction with ANC or microphones used in conjunction with hands-free communication implementations). These microphone-based applications may be suitable for use in vehicles. As shown, the cutoff frequency of the microphone used for ANC is less than 20 Hz, while the cutoff frequency of the microphone used for hands-free applications is greater than 200 Hz.

[0025] Figure 3An example of a MEMS microphone transducer 100 for achieving a single cutoff frequency is shown. The transducer 100 includes a diaphragm 102, a backplate 104, and a baffle 106. The diaphragm 102 typically moves under acoustic pressure excitation. The backplate 104 is provided with a plurality of holes to allow sound waves to pass therethrough, which is considered to be acoustically transparent. The diaphragm 102 and the backplate 104 form a capacitor that converts the mechanical movement of the diaphragm 102 into an electrical (e.g., voltage) output of the transducer 100. The diaphragm 102 defines a path 108 that produces a cutoff frequency for the audio output signal. When assembled in a MEMS microphone package (or microphone assembly), the baffle 106 and the package shell ( Figure 3 Path 108 is a path (not shown) that ensures that external sound waves can only pass from one side of the diaphragm 102 to the other side via path 108. Low-frequency sound waves with longer wavelengths can more easily pass through path 108 to reach both sides of the diaphragm 102. This can result in a smaller or no net pressure difference (e.g., no net motion) between the two sides of the diaphragm 102 at low frequencies than at high frequencies. This effectively forms a first-order low-pass filter with a cutoff frequency that is proportional to the size of path 108. Therefore, in order to change the cutoff frequency of the MEMS microphone transducer 100, the size of path 108 needs to be adjusted. Therefore, existing embodiments may require the use of different MEMS elements for each individual application with a specific cutoff frequency target or a specific frequency response.

[0026] Figure 4 An example of a microphone assembly 200 (or assembly 200) is shown. The microphone assembly 200 includes a protective housing or shell 202, a microphone subassembly 204, electronic circuitry 206, and a printed circuit board (PCB) 208. The electronic circuitry 206 can be mounted on the PCB 208 along with the microphone subassembly 204 and perform any number of audio processing applications, such as, but not limited to, ANC, hands-free operation, etc. The electronic circuitry 206 can interface with the microphone subassembly 204 to perform operations related to the aforementioned audio applications.

[0027] Microphone subassembly 204 includes a subhousing 220, a MEMS transducer (or microphone) 222, an application-specific integrated circuit (ASIC) 224, and a PCB base 226. MEMS transducer 222 and ASIC 224 are positioned on PCB base 226. Subhousing 220 encapsulates MEMS transducer 222 and ASIC 224 and is sealed (typically by welding) along its perimeter to PCB base 226. It should be appreciated that MEMS transducer 222 may also be implemented as an ECM. PCB base 226 defines a first audio port 228. PCB 208 defines a first acoustic path 230, and a base portion of housing 202 defines a first acoustic opening 237. First acoustic path 230 and first acoustic opening 237 are vertically axially aligned with first audio port 228. Although not shown, MEMS transducer 222 includes a diaphragm that oscillates or is excited in response to audio pressure impinging on the diaphragm. The underside of the diaphragm is exposed to the environment to enable audio signals to enter the first audio port 228 provided by the PCB base 226, the first acoustic path 230 provided by the PCB 208, and the first acoustic opening 237 provided by the housing 202. The ASIC 224 provides an electrical output indicative of the sound captured by the MEMS transducer 222.

[0028] Figure 5 2 shows a microphone assembly 300 according to one embodiment. The assembly 300 includes a protective housing 202, a microphone subassembly 204, an electronic circuit 206, and a PCB 208. Similarly, as described above in conjunction with Figure 4 As described, the electronic circuit 206 can be mounted on the PCB 208 along with the microphone subassembly 204 and perform any number of audio processing applications, such as, but not limited to, ANC, hands-free operation, etc. The electronic circuit 206 can interface with the microphone subassembly 204 to perform operations related to the aforementioned audio applications.

[0029] Similarly, if combined Figure 4As described, microphone assembly 204 includes a sub-housing 220, a microphone transducer 222 (MEMS or ECM), an ASIC 224, and a PCB base 226. The MEMS transducer 222 and the ASIC 224 are positioned on the PCB base 226. The PCB base 226 defines a first audio port 228a, which is positioned directly below the microphone transducer 222. A first acoustic path 230 is defined by the PCB 208. The base 227 of the housing 202 defines a first acoustic opening 237a and a second acoustic opening 237b. When assembled, the first audio port 228a provided by the PCB base 226, the first acoustic path 230 provided by the PCB 208, and the first acoustic opening 237a provided by the housing 202 are axially aligned in a vertical direction. The second acoustic opening 237b directly opens into the cavity or volume 302 defined by the housing 202. The first acoustic opening 237a and the second acoustic opening 237b can be positioned on the same surface of the housing 202 (e.g., the base 227) and separated by a distance d. Distance d is preferably within a range of 3 to 30 mm. When the microphone assembly 300 is configured as a unidirectional microphone, the microphone output sensitivity is proportional to the value of d. If d is too small, this may result in very low microphone sensitivity, which may not be optimal. When the microphone assembly 300 is configured as an omnidirectional microphone with various cutoff frequencies, the assembly 300 relies on the sound pressure amplitudes presented at the first acoustic opening 237a and the second acoustic opening 237b to be similar to each other. If d is too large, this may result in a difference in the sound pressure amplitudes presented at the first acoustic opening 237a and the second acoustic opening 237b. It should be appreciated that the second acoustic opening 237b can also be positioned along any of the vertically extending sidewalls of the housing 202 while maintaining the cumulative distance d within the preferred range.

[0030] The first acoustic opening 237a, the first acoustic path 230, and the first audio port 228a enable the underside of the microphone transducer 222 to communicate with the sound field outside the assembly 300. The sub-shell 220 defines at least one second audio port 228b (hereinafter referred to as the port hole 228b) positioned on its top side. Similarly, the second acoustic opening 237b allows the sound field outside the assembly 300 to enter the cavity or volume 302 defined by the housing 202. This can then enable the top side of the microphone transducer 222 to communicate with the external sound field through the port hole 228b. When the microphone assembly 300 is configured as an omnidirectional microphone with various cutoff frequencies, the size of the opening area of ​​the port hole 228b determines the cutoff frequency. If the port hole 228b is circular, the preferred diameter range is between 0.01 mm and 1 mm. This results in a cutoff frequency that may be suitable for hands-free microphone applications. If the port holes 228b are of other geometries and / or take on various forms, the effective total open area is preferably within a range equivalent to the area provided by a circular port hole having a diameter of 0.01 mm to 1 mm.

[0031] The post 304 can be positioned on the top side of the sub-housing 220 and mounted directly on the top of the port hole 228b. The post 304 can be integrated with the housing 202. The post 304 extends from the top side of the sub-housing 220 to the underside of the top portion 309 of the housing 202. When provided, the post 304 can serve as a sealing mechanism and seal the port hole 228b. The first acoustic resistance element 310a (e.g., cloth, sintered material, foam, micro-machined or laser-drilled array, etc.) can be positioned below the base 227 of the housing 202. The first acoustic resistance element 310a can be placed directly below or above the first acoustic opening 237a. The second acoustic resistance element 310b (e.g., cloth, sintered material, foam, micro-machined or laser-drilled array, etc.) can also be positioned below the base 227 of the housing 202. The second acoustic resistance element 310b can be placed directly below or above the second acoustic opening 237b. The addition of the first acoustic resistance element 310 a and the second acoustic resistance element 310 b also serves as an ingress protection mechanism that prevents foreign particles and moisture from the external environment from entering the interior of the microphone assembly 300 .

[0032] It should be appreciated that any one or more of the post 304, the first acoustic resistance element 310a, and the second acoustic resistance element 310b may or may not be used on the assembly 300. The use of the post 304, the first acoustic resistance element 310a, and the second acoustic resistance element 310b may provide the assembly 300 with a different frequency response or directivity pattern. For example, if the post 304, the first acoustic resistance element 310a, and the second acoustic resistance element 310b are not implemented on the assembly 300, the port hole 228b is not sealed and both sides of the microphone diaphragm are exposed to the external sound field. In this case, the port hole 228b effectively acts as a bonding Figure 3Path 108 of the explanation. Thus, the microphone subassembly 204 allows for an ascending frequency response with a cutoff frequency determined by the size of the opening area of ​​the port hole 228b. The microphone assembly 300 functions as an omnidirectional microphone with an ascending frequency response, such as Figure 7 The waveform 402 of the graph depicted in FIG. Waveform 402 shows a cutoff frequency above 200 Hz, which may be preferred for applications such as hands-free communication.

[0033] In the case where the post 304 is used to seal the port hole 228b in the assembly 300 and the first and second acoustic resistance elements 310a, 310b are not present, only the underside of the microphone diaphragm is exposed to the external sound field. In this case, the microphone subassembly 204 and thus the microphone assembly 300 are implemented with Figure 7 The waveform 404 of the graph depicted in FIG. 4 shows an omnidirectional microphone with a flat frequency response. The waveform 404 shows a cutoff frequency below 20 Hz, which may be preferred for applications such as ANC.

[0034] In the case where the microphone assembly 300 is arranged as an omnidirectional microphone having various cutoff frequencies by using or not using the post 304, it may not be necessary to implement the first acoustic resistance element 310a and the second acoustic resistance element 310b. However, in practice, it may be preferable to include the first acoustic resistance element 310a and the second acoustic resistance element 310b having a small resistance value to serve as an ingress protection mechanism to prevent the intrusion of foreign particles and moisture.

[0035] Without post 304 but with first and second acoustically resistive elements 310a and 310b, microphone assembly 300 can also be configured to provide a unidirectional (cardioid) response characteristic. In situations where the audio source or talker is located to the left of assembly 300, it may be desirable to direct the pickup sensitivity beam (polar pattern) to the left (θ = 0°) while discriminating against unwanted sound pickup from other directions (e.g., from the right or rear of microphone assembly 300). Without post 304, microphone assembly 300 allows external sound or audio signals to enter first acoustic opening 237a, thereby reaching the underside of transducer 222 (and therefore the diaphragm). Similarly, external sound or audio signals are transmitted through second acoustic opening 237b, thereby reaching the upper side of transducer 222 (and therefore the diaphragm). The output of microphone subassembly 204 can be a function of the subtraction, or "acoustic gradient," between the two sound pressures impinging on either side of transducer 222 (or diaphragm). Due to the different transmission paths, there is a relative phase delay corresponding to the time difference between the sound source arriving at the two sides of the transducer 222. Such a phase delay enables the microphone assembly 300 to achieve desired performance, such as a certain polar pattern.

[0036] In order to achieve the desired cardioid directivity shape, a certain acoustic resistance level R of the second acoustic resistance element 310b may be required. sb To satisfy the delay distance d and the acoustic compliance C v A specific mathematical relationship is determined. Generally speaking, R sb Should be with d / C v The quotient is proportional to C v The value of is determined by the combined air volume of the second acoustic opening 237b, the cavity 302, the port hole 228b, and the volume 231 enclosed by the sub-housing 220 of the microphone element 204. It should be noted that the first acoustic resistance element 310a may be omitted or included. The acoustic resistance value of the first acoustic resistance element 310a may be smaller than the acoustic resistance value of the second acoustic resistance element 310b and may be used to prevent the intrusion of foreign particles and moisture.

[0037] Figure 8 Depicted is a diagram according to one embodiment when configured as Figure 5 The unidirectional microphone is an example of a simulated frequency response shape of the microphone assembly 300. Specifically, Figure 8 The frequency response ratio in dB of the electrical output of the microphone assembly 300 and the acoustic input transmitted to the first acoustic opening 237a from various directions indicated by θ is plotted versus frequency.

[0038] Figure 9 is shown above combined Figure 5 A simulated graph illustrating one example of the cardioid polar directivity or spatial filtering attributed to microphone assembly 300 is shown.

[0039] Figure 6A detailed view of a microphone subassembly 204 according to one embodiment is shown. The transducer 222 includes a movable diaphragm 102 and a backplate 104 that is immovable but acoustically transparent due to multiple through-holes distributed therein. The transducer 222 and ASIC 224 are positioned on a PCB base 226 and enclosed within a cavity 231 formed by the sub-housing 220. As described above, the PCB base 226 defines a first audio port 228a, and the sub-housing 220 defines a port aperture 228b. External audio signals can reach the underside of the diaphragm 102 through the first audio port 228a and the cavity 231 sealed between the transducer 222 and the PCB base 226. Similarly, external audio signals can reach the top side of the diaphragm 102 through the port aperture 228b and the cavity 231 sealed between the transducer 222, the sub-housing 220, and the PCB base 226. Additionally, audio signals can pass from one side of diaphragm 102 to the other via path 108 defined by diaphragm 102. Diaphragm 102 is excited by the net applied sound pressure (i.e., the pressure difference between the two sides). As previously described, for external audio signals, both path 108 and audio port 228b act as leakage paths with cutoff frequencies based on their relative sizes. This aspect can affect the shape of the rising frequency response of microphone assembly 300. Because it is generally more difficult to change the dimensions of path 108 in addition to the overall dimensions of microphone subassembly 204, microphone assembly 300 discloses a method for adjusting the cutoff frequency of the rising frequency response by adjusting the sealed or unsealed state (i.e., the opening area) of port hole 228b. For example, if path 108 defined by transducer 222 of microphone subassembly 204 is kept small, such that the cutoff frequency of the rising frequency response of microphone subassembly 204 can be below 20 Hz when port hole 228b is sealed, this path can be omitted or ignored.

[0040] In view of the foregoing, the assembly 300 provides a variety of frequency response shapes or directivities while using a single microphone subassembly 204 in which the overall size of the path 108 defined by the diaphragm 102 is fixed. Depending on the use of the post 304, the first acoustic resistance element 310a, and the second acoustic resistance element 310b, and based on the values ​​of the first acoustic resistance element 310a and the second acoustic resistance element 310b, the microphone assembly 300 can behave as an omnidirectional microphone with a flat frequency response (i.e., having a cutoff frequency below 20 Hz), an omnidirectional microphone with a rising frequency response, or a unidirectional microphone with a cardioid polar directivity.

[0041] Figure 10 Another detailed view of the sub-housing 220 of the microphone sub-assembly 204 is shown according to one embodiment. A removable cover 400 is placed over the port hole 228b. In one example, the cover 400 may correspond to tape or other suitable material. Similar to Figure 5In addition to the function of the center column 304, the cover 400 can serve as a sealing mechanism and seal the port hole 228b. In another example, the cover 400 can slide relative to the port hole 228b. The first guide rail and the second guide rail can be axially spaced apart from each other and positioned on the top side of the sub-shell 220. The cover 400 can slide along the first guide rail and the second guide rail to provide different coverage levels of the port hole 228b ranging from 0% to 100%. When the cover 400 is removed from the port hole 228b, the port hole 228b can be fully opened. Conversely, the port hole 228b can be completely closed or covered by the cover 400. The cover 400 can also be positioned in any number of positions relative to the port hole 228b so that the port hole 228b is not covered, partially covered, or completely covered.

[0042] As described above, the external audio signal passes through the second audio port 228b to both the underside of the diaphragm 102 (e.g., via the first audio port 228a and the first acoustic path 230) and the top side of the diaphragm 102 (e.g., via the second acoustic opening 237b and the port hole 228b). Low frequency sound waves having longer wavelengths pass more easily through small openings. Therefore, depending on the size of the port hole 228b, positioning the cover 400 in different positions relative to the port hole 228b can provide omnidirectional microphones with different frequency responses without significantly changing the overall design of the microphone subassembly 204 and the microphone assembly 300. For example, where the cover 400 is not implemented or the cover 400 is positioned such that the second audio port 228b is substantially open on the assembly 300, then the assembly 300 is implemented as having a configuration such as Figure 7 4. In the case where the cover 400 completely covers the port hole 228b, the microphone assembly 300 appears to have an omnidirectional microphone with a rising frequency response as shown by the waveform 402 of the graph depicted in FIG. Figure 7 The microphone assembly 300 is an omnidirectional microphone having a flat frequency response as shown by the waveform 404 of the graph depicted in FIG. Figure 7 The cutoff frequency of the omnidirectional microphone having the rising frequency response shown by waveform 403 of the graph depicted in FIG. 4 is between waveforms 402 and 404 .

[0043] It should be appreciated that the first acoustic resistance element 310a and the second acoustic resistance element 310b can also be implemented in the microphone assembly 300 regardless of whether the cover 400 is provided. Only the first acoustic resistance element 310a and the second acoustic resistance element 310b can be provided to prevent the intrusion of foreign particles and moisture. In the case where the first acoustic resistance element 310a and the second acoustic resistance element 310b are provided without the cover 400, as long as the acoustic resistance value of the second acoustic resistance element 310b satisfies the aforementioned mathematical relationship, the microphone assembly 300 behaves as a unidirectional microphone having a cardioid directivity pattern.

[0044] Figure 11A A top view of the subhousing 220 and port aperture 228b of the microphone subassembly 204 is depicted. Figure 11B Another top view of the sub-housing 220 and port aperture 228b is depicted. In this case, the port aperture 228b can be formed as a plurality of apertures 420 in a desired pattern. One or more of the plurality of apertures 420 can be sealed (or covered) to provide a progressively adjustable cutoff frequency. For example, this aspect can enable the assembly 300 to provide omnidirectional microphones with different frequency responses without significantly changing the overall design of the microphone sub-assembly 204. It should be appreciated that the number of apertures 420 can vary based on the desired criteria of a particular implementation.

[0045] Although exemplary embodiments have been described above, it is not intended that these embodiments describe all possible forms of the present invention. Rather, the terms used in the specification are descriptive rather than restrictive, and it should be understood that various changes may be made without departing from the spirit and scope of the present invention. In addition, the features of the various implemented embodiments may be combined to form additional embodiments of the present invention.

Claims

1. A microphone assembly comprising: shell; a first printed circuit board PCB; column; and a microphone subassembly disposed within the housing, the microphone subassembly comprising: subshell; a micro-electromechanical system (MEMS) transducer positioned in the sub-housing to receive an audio input signal; and at least one port hole positioned on a top side of the subshell; wherein the housing includes the post positioned over the at least one port aperture to seal the sub-housing, and wherein the post is positioned between a top side of the sub-housing and an underside of a top side of the outer housing. 2 . The microphone assembly of claim 1 , further comprising a second PCB to support the MEMS transducer and define a first audio port.

3. The microphone assembly according to claim 2: wherein the first PCB defines a first acoustic path, the first acoustic path being positioned below the second PCB and the MEMS transducer; and The housing defines a first acoustic opening positioned directly below the first acoustic path and the first audio port to enable the audio input signal to pass through the first acoustic port and reach an underside of the MEMS transducer.

4. The microphone assembly of claim 3 , wherein the housing defines a second acoustic opening to enable the audio signal to pass to the top side of the MEMS transducer, wherein the second acoustic opening allows an acoustic field external to the microphone assembly to enter the cavity or volume defined by the housing.

5. The microphone assembly of claim 4 , wherein the second acoustic opening is positioned at a distance between 3 and 30 mm from the first acoustic opening to increase the sensitivity of the MEMS transducer and minimize the difference in sound pressure amplitude of the audio input signal at the first and second acoustic openings.

6. The microphone assembly of claim 4, wherein the first acoustic opening and the second acoustic opening are positioned on a same surface of the housing.

7. The microphone assembly of claim 4, wherein the first acoustic opening and the second acoustic opening are positioned on different surfaces of the housing.

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