CN114531632B

CN114531632B - Electronic device and electroacoustic device

Info

Publication number: CN114531632B
Application number: CN202210190520.8A
Authority: CN
Inventors: P·C·赫鲁迪; J·D·克罗斯比; G·哈提波格鲁
Original assignee: Apple Inc
Current assignee: Apple Inc
Priority date: 2019-05-28
Filing date: 2020-05-27
Publication date: 2023-12-08
Anticipated expiration: 2040-05-27
Also published as: DE102020113974A1; CN114531632A; CN112019982B; CN112019982A

Abstract

The present disclosure provides a vented acoustic transducer and related methods and systems. An electronic device has an acoustic transducer with an acoustic diaphragm. The diaphragm has opposed first and second major surfaces. The front cavity is disposed adjacent to the first major surface. The rear cavity is disposed adjacent to the second major surface. The elongate channel defines a pneumatic vent and extends from a first end fluidly coupled to the front cavity to a second end fluidly coupled to the rear cavity, thereby fluidly coupling the front cavity to the rear cavity. The elongate channel may have a high aspect ratio (L/D) to provide a significant air mass for the vent. The elongate channel may be segmented to define higher order filters. For example, the segmented channels may have cascading repeating acoustic mass units and acoustic compliance units, providing additional degrees of freedom for the pneumatic vent for tuning.

Description

Electronic device and electroacoustic device

The application is a divisional application of patent application with the application number of 202010458416.3, the priority date of 2019, 5, 28, 2020, 5, 27 and the application named as 'ventilation sound transducer and related method and system'.

Cross Reference to Related Applications

The present disclosure claims priority and benefit from U.S. patent application 62/853,626 filed on day 28 of 5 in 2019, U.S. patent application 16/880,812 filed on day 21 of 5 in 2020, and U.S. patent application 16/880,825 filed on day 21 of 5 in 2020, the contents of which are incorporated herein in their entirety for all purposes.

Technical Field

The present patent application and the subject matter disclosed herein (collectively, "disclosure") relate generally to vented acoustic transducers and related methods and systems. More particularly, but not exclusively, vent arrangements configured to exhibit complex acoustic impedances are described with respect to various electroacoustic transducers and electronic devices incorporating such transducers. Examples of electroacoustic transducers include speaker transducers and microphone transducers, including by way of example MEMS microphone transducers.

Background

Generally, sound (sometimes also referred to as acoustic signals) constitutes vibrations that propagate through a carrier medium such as, for example, a gas, a liquid, or a solid. In turn, electroacoustic transducers are devices configured to convert incoming sound into electrical signals or vice versa.

During its lifetime, an electroacoustic transducer may be exposed to various environmental pressures, such as air pressure. For example, electronic devices with electroacoustic transducers may be operated by users at different altitudes (e.g., from near sea level to high mountain environments) or even under water (e.g., when participating in water sports, such as swimming, surfing, drifting, fancy-skating, etc.). Such changes in ambient pressure may cause movement of the transducer diaphragm, thereby affecting the output of the transducer. Also, above a given threshold or rate of change, such movement may even damage the transducer.

More specifically, a large pressure gradient applied across a conventional acoustic diaphragm may bias the diaphragm to an outermost (or innermost) position of displacement. When biased by an external load, the operation of the acoustic transducer (whether configured as a speaker or microphone) may be negatively affected, or the transducer may become completely inoperable. Examples of negative effects include sound distortion or lower than normal amplitude (e.g., emitted or detected loudness).

Disclosure of Invention

The disclosed acoustic transducer includes a diaphragm and a vent for equalizing pressure across the diaphragm. More specifically, but not exclusively, certain disclosed venting arrangements allow for equalizing the air pressure (e.g., low frequency change or slow rate of change of pressure) across the diaphragm while inhibiting pressure equalization at higher frequency changes of pressure (e.g., in audible bandwidth).

The vent holes disclosed in the present disclosure define a passageway having a complex acoustic impedance. Some of the passages having complex acoustic impedances have high aspect ratios (e.g., a ratio of length to effective diameter of between about 1,000 and about 32,000, or about 1 x 10) ⁸ And about 2X 10 ⁹ The ratio of length to cross-sectional area) to provide a large acoustic mass to the passageway and to allow the vent to function as an acoustic sensor. Other ones of the passages with complex acoustic impedances, described in detail below, are segmented to define a plurality of acoustic mass elements juxtaposed with a corresponding plurality of acoustic compliance elements. As described more fully below, the acoustic mass unit may be arranged as a relatively narrow conduit, and the acoustic compliance unit may be arranged as a relatively large conduit Or a chamber.

The vent holes disclosed in the present disclosure may significantly reduce so-called "leakage noise" or "leakage noise". In general, leakage noise may be generated when the diaphragm is excited by a flow of air (or other acoustic medium) through the vent, particularly when the flow excites the diaphragm within a desired bandwidth (e.g., human audible frequency band). Such leakage noise may occur, for example, when the vent hole mainly functions as an acoustic resistor. The vent described herein may inhibit flow through the vent when exposed to pressure changes (or sounds) in a desired frequency band (e.g., between about 20Hz and about 20 kHz) as compared to a resistive vent, and may also allow flow at low frequencies or slow changes in pressure (e.g., as with changing air pressure).

Thus, the venting arrangements disclosed in the present disclosure may reduce leakage noise (which is a significant contributor to in-band noise power) while still providing a channel to equalize pressure across the diaphragm. Thus, transducers incorporating the ventilation arrangements disclosed in the present disclosure may provide improved signal-to-noise ratio signals compared to transducers incorporating primarily resistive ventilation arrangements.

Further, by equalizing the pressure across the diaphragm, the disclosed venting arrangement may reduce or eliminate external biasing forces applied to the diaphragm due to ambient pressure changes. Further, the reduced biasing force may allow the transducer to provide lower acoustic distortion and may allow the diaphragm to move through full stroke excursions over a wide range of ambient pressures. Thus, acoustic transducers incorporating the ventilation arrangements disclosed in the present disclosure may provide improved emitted or detected loudness over a wide range of ambient pressures.

According to one aspect, an electronic device has an acoustic transducer element having an acoustic diaphragm. The diaphragm has opposed first and second major surfaces. The front cavity is disposed adjacent to the first major surface of the diaphragm and the rear cavity is disposed adjacent to the second major surface of the diaphragm. The "elongate channel" defines a pneumatic vent fluidly coupling the front cavity with the rear cavity. An elongate channel extends from a first end fluidly coupled to the front cavity to a second end fluidly coupled to the rear cavity. According to one aspect, the elongate channel may be a "segmented channel" segmented into a plurality of acoustic mass units juxtaposed with a corresponding plurality of acoustic compliance units. In another aspect, the elongate channel extends circuitously from the first end to the second end.

The air pressure vent may be configured to equalize pressure between the front and rear chambers. Some disclosed electroacoustic devices also include a substrate coupled to the acoustic transducer element. The substrate may define an acoustic port that is open to the front cavity. In one aspect, the substrate further defines a pneumatic vent.

In some aspects, the substrate is a first substrate, and the electroacoustic device may include a second substrate. For example, a first substrate may be mounted to a second substrate. The electroacoustic device may further comprise an integrated circuit device mounted to the second substrate. The integrated circuit device and the acoustic transducer element may be electrically coupled to each other. The second substrate may include electrical output connections coupled with the integrated circuit device. The electroacoustic device may also have a recessed cover overlying the acoustic transducer element, the first substrate, and the integrated circuit device.

The air vent may be open to the acoustic port, the front cavity, or both.

The substrate disclosed in the present disclosure may include a plurality of juxtaposed layers. The holes may extend through multiple layers to define acoustic ports. At least one of the layers may define a corresponding section of the serpentine path. The serpentine passage may fluidly couple the anterior chamber with the posterior chamber, thereby defining an elongate channel. The serpentine path may include at least one convolution.

The first layer of the substrate disclosed in the present disclosure may define a corresponding first section of the serpentine path and the second layer may define a corresponding second section of the serpentine path. The substrate may further include an intermediate material layer separating the first and second layers from each other. The intermediate layer may define an aperture that fluidly couples a first section of the serpentine passageway with a second section of the serpentine passageway, thereby defining a convolution in the serpentine passageway.

As described above, the substrate disclosed in the present disclosure may have a first layer and a second layer. The second layer may be disposed between the first layer and the acoustic diaphragm. The second layer may include a sacrificial insulator susceptible to etching. The second layer may also include an etch stop defining a boundary of a recess extending through the sacrificial insulator. The recess may define a corresponding portion of the elongate channel.

In one aspect, the elongate channel may extend from a location adjacent the acoustic port, the front cavity, or both to a location adjacent the rear cavity.

The substrate may define a tortuous section of the pneumatic vent. The tortuous section may be open to the anterior chamber. The acoustic transducer element may be mountably coupled with the substrate and may define an aperture aligned with the tortuous section of the pneumatic vent. The aperture may be open to the rear cavity, fluidly coupling the air pressure vent (and thus the front cavity) with the rear cavity through the acoustic transducer element.

The acoustic transducer elements disclosed in the present disclosure may include a backplate and an insulator disposed between the diaphragm and the backplate.

The acoustic transducer elements disclosed in the present disclosure may include a first backplate and a corresponding first insulator disposed between the first backplate and the diaphragm. The acoustic transducer element may further comprise a second back plate and a corresponding second insulator arranged between the second back plate and the diaphragm. The diaphragm may be disposed between the first back plate and the second back plate.

The acoustic transducer elements disclosed in the present disclosure may include a first diaphragm and a second diaphragm. The acoustic transducer element may further include a back plate, a first insulator disposed between the back plate and the first diaphragm, and a second insulator disposed between the second diaphragm and the back plate. For example, the back plate may be disposed between the first diaphragm and the second diaphragm.

The diaphragms disclosed in the present disclosure may include piezoelectric actuators. The acoustic transducer element may include a first substrate defining a corresponding open port. The piezoelectric actuator may be mounted to the first substrate and extend over an open port of the first substrate. The acoustic transducer element is mountable to a second substrate defining a corresponding acoustic port, wherein the open port is aligned with the acoustic port, and the piezoelectric actuator extends across the aligned open port and acoustic port, thereby defining a boundary therebetween.

According to another aspect, an electronic device includes an acoustic transducer element having a movable diaphragm. The diaphragm has opposed first and second major surfaces, and the acoustic transducer element defines an aperture disposed adjacent the movable diaphragm. The substrate is coupled with the acoustic transducer element. The substrate defines an acoustic port that is open to the acoustic transducer element. An elongate passageway extends from a first end fluidly coupled to the acoustic port to a second end fluidly coupled to the aperture, thereby defining a pneumatic vent that couples the acoustic port to the aperture.

The substrate may include a plurality of juxtaposed layers, and the opening may extend through the plurality of layers to define the acoustic port. At least one of the layers may define a corresponding channel defining a section of the passageway. The passageway may comprise a tortuous passageway having at least one convolution.

At least one of the layers may include a first layer and a second layer. The first layer may define a corresponding first channel and the second layer may define a corresponding second channel. The first channel and the second channel may be fluidly coupled to each other, thereby defining a convolution in the elongate channel.

The plurality of juxtaposed layers may include a first layer and a second layer. The second layer may be disposed between the first layer and the acoustic transducer element. The second layer may include a sacrificial insulator susceptible to etching and an etch stop defining a boundary of a channel extending through the sacrificial insulator. The channels may define corresponding portions of the elongate passage.

The acoustic transducer element may include a backplate and an insulator disposed between the diaphragm and the backplate.

The acoustic transducer element may include a first backplate and a corresponding first insulator disposed between the first backplate and the diaphragm. The acoustic transducer element may include a second backplate and a corresponding second insulator disposed between the second backplate and the diaphragm. The diaphragm may be disposed between the first back plate and the second back plate.

The diaphragm of the acoustic transducer element may be a first diaphragm. The acoustic transducer element may further include a back plate and a first insulator disposed between the back plate and the first diaphragm. The acoustic transducer element may further include a second diaphragm and a second insulator disposed between the second diaphragm and the back plate. The back plate may be disposed between the first diaphragm and the second diaphragm.

The diaphragm of the acoustic transducer element may comprise a piezoelectric actuator. The diaphragm may be mounted to the substrate and the piezoelectric actuator may extend over the acoustic port.

The disclosure also discloses an associated computing environment that may incorporate the techniques.

The foregoing and other features and advantages will become more apparent from the following detailed description, which proceeds with reference to the accompanying drawings.

Drawings

Referring to the drawings wherein like numerals indicate like parts throughout the several views and the present specification, aspects of the principles disclosed herein are described by way of example, and not by way of limitation.

Fig. 1 shows a cross-sectional view taken through a package for an acoustic transducer (e.g., a MEMS microphone transducer).

Fig. 2 schematically shows a cross-sectional view taken through a package for an acoustic transducer having an acoustically resistive air pressure vent. Fig. 2 is annotated with an electrical simulation of an acoustic path through the package.

Fig. 3 shows a graph comparing contributions of several noise sources to the total acoustic noise for a packaged transducer as in fig. 2.

Fig. 4 schematically shows a cross-sectional view taken through a package for an acoustic transducer, the package having an air pressure vent exhibiting a complex acoustic impedance. Fig. 4 is annotated with an electrical simulation of an acoustic path through the package.

Fig. 5 shows a graph comparing contributions of several noise sources to the total acoustic noise for a packaged transducer as in fig. 4.

Figure 6 shows an isometric view of a substrate defining a high aspect ratio pneumatic vent taken along line A-A in figure 7.

Fig. 7 shows a plan view of the substrate shown in fig. 6 from above.

Fig. 8 shows a plan view of an acoustic transducer with acoustic transducer elements mounted to a substrate from above as in fig. 6 and 7.

Fig. 9 shows an exploded cross-sectional view of the acoustic transducer shown in fig. 8, taken along line A-A in fig. 7.

Fig. 10 shows an exploded cross-sectional view of another acoustic transducer taken along line A-A in fig. 7.

Fig. 11 shows an exploded cross-sectional view of yet another acoustic transducer taken along line A-A in fig. 7.

Fig. 12 shows an exploded cross-sectional view of yet another acoustic transducer taken along line A-A in fig. 7.

Figure 13 shows an exploded cross-sectional view of a packaged microphone transducer having a package substrate incorporating a high aspect ratio air vent, taken along line A-A in figure 7.

Figure 14 shows an exploded cross-sectional view of a packaged microphone transducer having a package substrate incorporating a high aspect ratio air vent structured therein, taken along line A-A in figure 7.

Fig. 15 shows a graph of filter response of a number of high aspect ratio (second order) pneumatic vents defined by a substrate for an acoustic transducer (e.g., fig. 6-12).

Fig. 16 shows a graph of filter response of a number of high aspect ratio air vent holes defined by a substrate for an acoustic transducer package (e.g., fig. 13 and 14).

Fig. 17A and 17B show perspective views of a portion of a segmented channel defining pneumatic vents.

Fig. 17C shows a two-dimensional projection of the segmented channels shown in fig. 17A and 17B onto a plane.

Fig. 18 shows a circuit simulation of an acoustic filter defined by a segmented channel defining pneumatic vents.

Fig. 19 shows a perspective view of a segmented channel defined by cascading six repeating duct and chamber units.

Fig. 20 shows a two-dimensional projection of the segmented channel shown in fig. 19.

Fig. 21A shows a graph demonstrating the low frequency roll-off of several different order acoustic filters, each defined by a respective segmented channel with a corresponding cascade of repeating duct and chamber units. Fig. 21B shows a variation of the low frequency roll-off of several segmented channels with repeating tubing and chamber units like a cascade, although each cascade has different dimensions.

Fig. 22A and 22B show respective graphs of frequency and phase responses of microphones ventilated with different segmented channels.

Fig. 23 shows a perspective view of a segmented channel with cascading duplicate piping and chamber units.

Fig. 24 shows a two-dimensional projection of the segmented channel shown in fig. 23.

Fig. 25 shows a perspective view of another segmented channel with cascading duplicate piping and chamber units.

Fig. 26 shows a two-dimensional projection of the segmented channels shown in fig. 25.

FIG. 27 illustrates a block diagram of a computing environment suitable for implementing the disclosed technology.

Detailed Description

Various principles relating to vented acoustic transducers and transducer packages, and related methods and systems, are described below with reference to specific features. For example, some principles relate to pneumatic vents for transducer elements, and other principles relate to pneumatic vents for transducer packages. More particularly, but not exclusively, certain aspects relate to vents having complex acoustic impedances to equalize the air pressure across an acoustic diaphragm. The vents described in the context of a particular configuration are merely specific examples of contemplated vent arrangements selected as convenient illustrative examples of the disclosed principles. Nonetheless, one or more of the principles disclosed may be incorporated in various other arrangements of acoustic transducers, modules, and systems to achieve any of a variety of corresponding system characteristics.

Thus, vented acoustic transducers, modules, and systems (and associated techniques) having properties different from those specifically illustrated herein may embody one or more of the principles of the present disclosure and may be used in applications not described in detail herein. Accordingly, such alternative embodiments may also fall within the scope of the present disclosure.

I. Summary of the invention

The speaker may emit an acoustic signal in the carrier medium by vibrating or moving an acoustic diaphragm to cause or otherwise induce a pressure change or other vibration in the carrier medium. For example, an electromagnetic speaker arranged as a direct radiator may induce a time-varying magnetic flux in a coil (e.g., wire wound around a bobbin) attached to a diaphragm. The coil may be exposed to a magnetic field (e.g., of a permanent magnet), and a resultant force between the magnetic flux emanating from the coil and the one or more magnetic fields may cause the coil, and thus the diaphragm, to move.

Instead, the microphone transducer may be configured to convert an incoming acoustic signal into, for example, an electrical signal. The acoustic diaphragm of a microphone transducer (e.g., a MEMS microphone transducer) may vibrate, move, or otherwise respond to pressure changes received through the surrounding or adjacent carrier medium. Movement of the diaphragm may cause a corresponding response in the electronic component. For example, movement of the diaphragm in a capacitive MEMs microphone can change the capacitance of the device, thereby causing an observable time-varying voltage signal in the circuit. As another example, movement of the piezoelectric diaphragm may generate a time-varying electrical signal by means of a piezoelectric response to movement. The time-varying electrical response generated with either type of microphone transducer may be converted into a machine-readable form (e.g., digitized) for subsequent processing.

Thus, electroacoustic transducers in the form of speakers (sometimes referred to simply as "acoustic transducers") may convert incoming signals (e.g., electrical signals) to sound, while acoustic transducers in the form of microphones may convert incoming sound to electrical (or other) signals. As used herein, the term "audio signal" may refer to an electrical response (e.g., analog or digital signal) carrying audio information or data that may be converted to or from sound.

The acoustic transducer may be mounted to a substrate (or base) and covered or enclosed by a housing (or cover) to define an enclosed acoustic chamber partially bounded by a diaphragm. With such an arrangement, the diaphragm may cause an acoustic response in the chamber when the diaphragm transmits or receives acoustic energy.

Reference is now made to fig. 1, 2 and 4, which illustrate and briefly describe a component package, for example for a microphone transducer. In fig. 1, a component package 100 has a substrate 102 defining a first major surface 104 and an opposing second major surface 106. The substrate 102 also defines at least one aperture 101a, the aperture 101a extending through the substrate from the first major surface 104 to the second major surface 106, thereby defining a sound entry opening 101 (sometimes referred to as an acoustic port) through the substrate 102. The microphone transducer 103 is mountably coupled to the substrate 102 on the first major surface 104 and has a sound responsive diaphragm (e.g., as in fig. 2 and 4) acoustically coupled to a sound inlet opening 101 defined by the substrate, allowing sound to enter a front cavity defined in part by the microphone transducer. A cover 109 mounted to the substrate 102 covers the microphone transducer 103 and defines a rear cavity 112.

The pressure gradient between the front and rear chambers 110, 112 may apply a biasing force to the diaphragm. Some of the disclosed electroacoustic devices 103 and transducer elements 107 are pneumatically ventilated, for example, to equalize the air pressure on opposite sides of the diaphragm. Alternatively, some transducer packages 100 are pneumatically vented, for example, to equalize the air pressure on opposite sides of the diaphragm.

Such a vent transducer and package may mitigate or eliminate movement of the diaphragm caused by changes in ambient pressure, and thus may mitigate or eliminate the effect of changes in ambient pressure on the transducer output. Further, the vent transducer and package may mitigate or eliminate the possibility of damaging the transducer due to changes in ambient pressure.

In some aspects, the concepts disclosed herein relate generally to vented acoustic transducers and related methods and systems. Some of the disclosed concepts relate to components configured to equalize static or low frequency pressure differentials across an acoustic diaphragm. For example, some disclosed transducers and packages have vent arrangements configured to exhibit complex acoustic impedances. Some vents incorporate an elongated tortuous path that fluidly couples the front cavity of the transducer with the back cavity of the transducer, providing a compact arrangement for the vent with complex acoustic impedance that may be quite long compared to the cross-section of the vent, even the overall size of the transducer or the overall size of the package. Other vents incorporate a segmented passageway having multiple acoustic mass elements juxtaposed with corresponding multiple acoustic compliance elements, thereby providing a higher order filter.

Referring again to fig. 1, the microphone transducer 103 may have a sound responsive element 107, sometimes referred to as an "acoustic transducer element". The transducer 105 shown also includes a substrate 105 supporting the acoustic transducer elements, for example, on which the acoustic transducer elements are formed during manufacture. The substrate 105 defines a sound entry opening 105a that allows sound waves to enter the sound transducer element, for example, from the sound entry opening 101 of the package substrate 102.

Many configurations of the acoustic transducer elements are possible, several of which are described below by way of example. For example, the microphone transducer 103 may comprise, for example, a microelectromechanical system (MEMS) microphone. A flexible diaphragm spaced apart from the capacitive back plate provides one arrangement of acoustic transducer elements for a MEMS microphone, as described more fully below. However, it is contemplated that the microphone transducer may be any type of electroacoustic transducer operable to convert sound into an electrical output signal, such as, for example, a piezoelectric microphone, a dynamic microphone, or an electret microphone.

In the schematic diagrams of the MEMS microphones in fig. 2 and 4, each sound responsive element 207, 307 includes a corresponding diaphragm 220, 320 and backplate 222, 322, the backplate 222, 322 being mountably coupled with the substrate 205, 305. Each diaphragm is spaced apart from the corresponding backplate by a spacer, thereby defining a respective gap disposed between the diaphragm and backplate. In fig. 2 and 4, each respective acoustic diaphragm 220, 320 may define a boundary between the front cavity 210, 310 and the rear cavity 212, 312. As sound enters the front chamber, a corresponding pressure gradient is formed between the front and rear chambers 210, 310, 212, 312, thereby perturbing the respective diaphragms 220, 320. When the diaphragm moves with respect to the corresponding back plate due to sound, the capacitance of the acoustic transducer element changes corresponding to the sound pressure level. The change in capacitance may be observed to produce an electrical signal corresponding to the change in sound pressure level. The electrical signal or electrical signal derived therefrom (e.g., after processing to digitize or remove noise or echo) is sometimes referred to in the art as an audio signal.

As described above, the front chambers 210, 310 and the corresponding rear chambers 212, 312 may be fluidly coupled to each other, for example, to equalize pressure between the rear and front chambers. For example, the diaphragm 220 may be perforated, as schematically shown in fig. 2. Such perforations may define an acoustically resistive vent that fluidly couples the front cavity with the rear cavity. Nonetheless, an acoustically resistive vent can produce a significant level of so-called "leakage noise," as when the diaphragm is excited by an air flow through the vent that is driven by pressure changes having frequencies within a desired frequency band (e.g., a human audible frequency band).

Alternatively, as schematically shown in fig. 4, for example, a vent with complex acoustic impedance may significantly reduce leakage noise (fig. 5). A vent having a complex acoustic impedance may inhibit flow through the vent when exposed to pressure changes (or sounds) in a desired frequency band, as compared to a resistive vent, and may also allow flow at low frequency changes in pressure (e.g., as in changing air pressure). Although fig. 4 schematically illustrates a vent hole having a complex acoustic impedance throughout the diaphragm 320, fig. 4 should not necessarily be construed as requiring the vent hole to extend through the diaphragm, although this may be an option in some arrangements.

In other arrangements, a vent having a complex acoustic impedance may extend through the structure adjacent the diaphragm rather than the diaphragm itself, thereby fluidly coupling the front 310 and rear 312 chambers. For example, an elongated channel may extend from the front cavity 310 to the back cavity 312, fluidly coupling them together and defining a vent hole having a complex acoustic impedance. The elongate channel as disclosed herein may provide sufficient air mass to prevent airflow through the vent when exposed to pressure changes above a threshold frequency. In some aspects, the elongate channel may be defined by a high aspect ratio channel, and in other aspects, the elongate channel may be segmented to provide higher order filters.

Nevertheless, providing high aspect ratio vents in a defined volume (e.g., in an electroacoustic transducer or other electronic device) presents certain difficulties and is not straightforward. For example, the length of such vent holes may be several orders of magnitude greater than the nominal size of the acoustic transducer device, or several orders of magnitude greater than the nominal size of the acoustic transducer package.

However, as shown in fig. 6, the tortuous channel 610 may define a high aspect ratio air vent suitable for incorporation into the transducer component 103 (e.g., within the substrate 105) or the transducer package 100 (e.g., within the substrate 102). Alternatively, multiple mass and compliance units as shown in fig. 17A-17C may be assembled together to define a segmented channel that provides a higher order roll-off than the tortuous channel 610. With the disclosed vent having a complex acoustic impedance, low frequency pressure changes (such as, for example, due to weather changes, changes in the altitude of the user, or pressurization of the passenger cabin on the aircraft) may be equalized between the front and rear chambers 110, 112. Such vents may significantly reduce noise in the audible frequency band due to leakage through the pneumatic vent.

Further details of the disclosed principles are described below. Section II describes the principles typically associated with microphone packages. Section III describes principles relating to a substrate defining a tortuous path adapted to provide a pneumatic vent having a complex acoustic impedance. Section IV describes principles related to a vented microphone transducer and a vented package for the microphone transducer. Section V describes several attributes of improved performance that may be obtained by incorporating the disclosed ventilation arrangement. And section VI describes principles relating to a general purpose computing environment in which the disclosed technology may be implemented.

As used herein, the terms "serpentine," "meandering," "circuitous," and "serpentine" are used synonymously and are intended to imply structures that may, but are not necessarily, curved, straight, ordered, disordered, spiral, or interleaved or wound with, within, or through other structures.

II microphone package

Referring again to fig. 1, the microphone transducer 103 may be mounted on or otherwise operatively coupled with another substrate 102, such as a package-level substrate and/or an interconnect substrate. The microphone package 100 may also include a cover 109 overlying the acoustic transducer 103. The cover 109 may be recessed to define a cavity or back volume 112 for the transducer 103.

In fig. 1, the package substrate 102 defines a sound entry region 101 that is acoustically coupled to a sound entry opening 105a defined by the substrate 105 of the microphone package 103. The sound entry region 101 may be a single hole or may be defined by a plurality of holes 101a defining a perforated region of the substrate 102. In either arrangement, the sound entry region 101 is acoustically coupled and in many cases fluidly coupled with the sensitive region of the sound responsive element 107 of the microphone transducer 103. The unoccupied open chamber defined by the substrate 102, substrate 105, and the sensitive area of the microphone transducer 103 is sometimes referred to in the art as the "front cavity".

The acoustic port 105a through the microphone substrate 105 may be the same size and shape as the sound entry region 101 of the microphone package 100, or the acoustic port 105a 150 may be larger or smaller than the sound entry region 101, or otherwise have a different shape.

A typical package-level substrate 102 may have a thickness measured between about 0.250mm and about 0.65mm (e.g., between about 0.300mm and about 0.600mm, or between about 0.400mm and about 0.500 mm). The exemplary substrate 102 may have coordinate dimensions measured as about 4.000mm by about 3.500mm when viewed from above (e.g., in a plane orthogonal to the direction of "thickness") as in fig. 7. For example, in selected aspects, each in-plane coordinate dimension may be measured as between about 2.500mm and about 6.000mm, such as, for example, between about 3.000mm and about 5.000mm, or between about 3.300mm and about 4.100 mm.

Each aperture 101a defining the acoustic entry region 101 through the substrate 102 may be an unplated through-hole having a diameter of between about 50 μm and about 200 μm, such as, for example, between 75 μm and about 150 μm, for example, between about 90 μm and about 110 μm. The sound entry region 101 may have a characteristic dimension, such as a hydraulic diameter in selected aspects, of between about 1.000mm and about 3.000mm, such as, for example, between about 1.200mm and about 2.400mm, such as, for example, between about 1.4mm and about 2.2 mm. Of course, other configurations and dimensions of the sound entry region 101 are possible. The dimensions listed above have been selected to represent one particular configuration of the many configurations contemplated by the present disclosure.

The sound entry region 101 and each respective aperture 101a have corresponding characteristic dimensions. The flow or acoustic properties of the holes may vary with the selected reference size of the holes. In some cases, the reference dimensions of a given structure may be defined in a manner that enables, for example, acoustic or flow comparisons of structures having different shapes. For example, the reference dimension of the circle may be the diameter of the circle. On the other hand, the reference size of the square may be the side length of the square, or the ratio of the area of the square to the perimeter of the square. Such ratios are sometimes referred to in the art as hydraulic diameters. For a circle, the ratio decreases to the diameter of the circle.

Still referring to fig. 1, the microphone package has an integrated circuit device 115 (e.g., an application specific integrated circuit or ASIC) mounted to the package substrate 102. Bond wires 113 electrically couple the integrated circuit device with the acoustic transducer element 107. For capacitive MEMS microphones, the ASIC 115 may include circuitry for applying a charge on the acoustic transducer element 107, and when the diaphragm (not shown in fig. 1) deforms, the ASIC may observe a voltage change (e.g., a capacitance change) caused by the diaphragm deformation. The voltage change may correspond to an acoustic wave that causes the diaphragm to flex.

The package substrate 102 may have electrical output connections (not shown) coupled to the integrated circuit device 115. In addition, the package substrate 102 may have electrical traces or other electrical couplers that extend from the contacts to another area defined by the substrate (e.g., a second external electrical contact). Thus, the package substrate 102 may electrically couple external portions of the circuit with the ASIC 115.

The package 100 may be mounted to and electrically coupled with an interconnect substrate (not shown). In general, an interconnect substrate may include a plurality of electrical conductors configured to transmit electrical signals or power or ground signals from one interconnect location (e.g., a pad) to another interconnect location (e.g., another pad). For example, the packaged components (e.g., the packaged microphone transducer 100) may be soldered or otherwise electrically coupled with one or more interconnect locations defined by the interconnect substrate.

The interconnect substrate may electrically couple the packaged component 100 with one or more other components (e.g., memory device, processing unit, power supply) that are physically separate from the packaged component. In addition to the microphone transducer, one or more other components may be electrically coupled with electrical conductors in the interconnect substrate, thereby electrically coupling the microphone package with such other components. Examples of other components may include a processing unit, various types of sensors, and/or other functions and/or computing units of a computing environment or other electronic device.

In one aspect, the interconnect substrate (not shown) may be a laminate substrate having one or more layers of electrical conductors juxtaposed with alternating layers of dielectric or electrically insulating material (e.g., FR4 or polyimide substrates). Some interconnect substrates are flexible, such as being flexible or bendable to some extent, without damaging the electrical conductors or delamination of juxtaposed layers. The electrical conductors of the flexible circuit board may be formed of copper alloy and the intermediate layer separating the conductive layers may be formed of polyimide or other suitable material, for example. Such flexible circuit boards are sometimes referred to in the art as "flex circuits" or "flex elements. Likewise, the pliable component may be perforated or otherwise define one or more through holes.

Although not shown, the microphone package 100 may define a plurality of exposed electrical contacts configured to be soldered or otherwise electrically connected with corresponding interconnect locations defined by the interconnect substrate. In one aspect, the electrical contacts are exposed on the same side (e.g., bottom side 106) of the transducer package 100 as the sound entry region 101. The interconnect substrate may define apertures or other venting areas (not shown) configured to allow acoustic signals to pass therethrough in an acoustically transparent manner or with selected damping measurements, with the ambient environment being acoustically coupled to the sensitive areas of the microphone transducer 103 by the interconnect substrate. In an alternative arrangement, the electrical contacts are exposed on the top side 104 of the substrate 102.

III. substrate with meandering, serpentine or serpentine channel

Fig. 6 schematically illustrates a high aspect ratio channel 610 defined by a substrate 600. The substrate 600 in fig. 6 may represent any of the substrates shown in fig. 1, such as the transducer substrate 105 or the package-level substrate 102.

Still referring to fig. 6, the substrate 600 may define an inlet 612 to the tortuous path 610. Whether the vent is incorporated at the component level or the package level, the inlet 612 may be fluidly coupled to the front cavity 110. For example, when the vent 610 is incorporated in the transducer substrate 105, the inlet 612 of the vent 610 may be fluidly coupled with the acoustic port 105a at a location adjacent to the acoustic transducer element 107. Alternatively, when the vent 610 is incorporated in the package substrate 102, the vent may be fluidly coupled with the front cavity 110 at a location adjacent to the sound entry region 101.

In either configuration, the channel 610 may extend through the substrate 600 primarily circumferentially around the opening 614. For example, the channel 610 may steadily spiral around the opening 614 and extend radially outward. Alternatively, as shown in fig. 6, the channels 610 may extend circumferentially around the substrate aperture 614 from the inlet 612 at a substantially constant radial position and step or otherwise extend outwardly in a primarily radial direction at a position 613 near the inlet 612. The circuitous channel 610 may continue around the aperture 614 at each successive radial position until the channel 610 has a desired path length from the inlet 612. The terminal portion 616 of the channel 610 may define an outlet region from the channel at a location laterally or radially outward of the aperture 614 defined by the substrate 600. In fig. 6, the terminal portion 616 of the channel defines a substantially circular outlet fluidly coupled to the channel. Although not shown in fig. 6, the terminal portion 616 of the channel 610 may extend to and open from the outer perimeter 618 of the substrate 600, thereby directly coupling the channel with the rear cavity of the transducer (e.g., the rear cavity 112 in fig. 1).

Fig. 6 schematically illustrates the cavity 620 occupied by the apparatus supported by the substrate 600 or mounted to the substrate 600. In fig. 6, the cavity 620 may represent an acoustic transducer element of an acoustic transducer (e.g., acoustic transducer element 107 in fig. 1), or the cavity 620 may represent an acoustic transducer (e.g., MEMS microphone 103 in fig. 1) mounted to a package substrate (e.g., substrate 102 in fig. 1). In either case, the device represented by cavity 620 may define an aperture 622 extending from the terminal portion 616 of the channel 610 to the rear cavity and through the device represented by the cavity.

In yet another arrangement, when the overall size of the substrate 600 exceeds the overall size of the device represented by the cavity 620, the terminal portion 616 of the channel may extend to an area of the substrate (not shown) disposed laterally outward of the cavity 620. Such channels may directly couple the front cavity with the rear cavity of the transducer without requiring a vent hole to extend through the transducer or other structure.

Still referring to fig. 6, the substrate 600 may have a base layer 602 formed of silicon (Si) or another suitable substrate material. The insulator layer 604 may cover the base layer and may be made of silicon dioxide (SiO ₂ ) Or polyimide or another suitable insulator. The holes 614 may extend through multiple layers of the substrate. The insulator layer 604 may define a section of the tortuous path 610. For example, insulator layer 604 may be a sacrificial layer that has been selectively etched to define channels 610 between walls 611 of the remaining insulator. In one arrangement, the channel may be defined by a lateral etch stop material, such as, for example, silicon nitride (SiN). The etch stop 615 (fig. 9) may define channel walls 611a, 611b (fig. 6 and 9) because the sacrificial material may be selectively etched to remove material between juxtaposed walls 615 of the etch stop, thereby defining a recess and forming a corresponding portion of the tortuous channel 610 extending around the aperture 614.

The high aspect ratio pneumatic vent may have a ratio of characteristic length to characteristic diameter ("L/D ratio") of between about 1,000 and about 32,000, such as, for example, between about 2,000 and about 16,000, or, for example, between about 4,000 and about 8,000. For example, a vent measurement length having a hydraulic diameter of 25 μm and an L/D ratio of 32,000 is about 800mm, while a vent measurement length having the same cross section and an L/D ratio of 8,000 is about 200mm. The length of both vent examples is several orders of magnitude larger than the coordinate size of the package for the microphone transducer.

As another example, the substrate 105 (fig. 1) for the microphone transducer 103 may define a vent having a hydraulic diameter of about 5 μm and a channel length of about 80mm, providing an L/D ratio of 16,000. As another example, a vent having a hydraulic diameter of 5 μm and a channel length of about 5mm measured has an L/D ratio of 1,000.

Generally, the channel length of the vent may be measured longitudinally along a centerline through the vent from the vent inlet to the vent outlet. The centerline of the vent having a cross-sectional shape that varies with longitudinal position may be defined by a curve passing through the centroid of each cross-section defined by the vent from the inlet to the outlet. An example of a characteristic diameter of the vent may be the hydraulic diameter of the vent (e.g., the area of the cross section divided by the wetted perimeter of the cross section).

Venting microphone transducer and package

Referring now to fig. 7, 8 and 9, a vented microphone transducer will be described using a high aspect ratio vent as an illustrative example of a vent having a complex acoustic impedance, but a segmented vent or other higher order vent may be substituted for the high aspect ratio vent. The substrate 600 shown in fig. 7 defines a high aspect ratio air pressure vent 610 extending circuitously outward from an acoustic port 614, generally as described above in connection with fig. 6. As shown in fig. 6 and 7, the elongate pneumatic vent 610 may extend circuitously from a first end 612 fluidly coupled with the front cavity 614 to a second end 616 fluidly coupled with the rear cavity of the transducer (e.g., through an aperture 622 in fig. 6). In fig. 8, an acoustic transducer element 800 is shown in top plan view, the acoustic transducer element 800 being mounted to a substrate 600 in covering relation to a channel 610. The exploded view in fig. 9 shows a side elevation view of the substrate 600 and the acoustic transducer element 800 in cross section taken along line A-A in fig. 7.

As shown in fig. 9, the acoustic transducer element 800 has a single backplate 810 separated from the acoustic diaphragm 802 by an insulator layer 804. The backplate 810 has a plurality of layers including a conductive layer (e.g., polysilicon) and an insulator layer (e.g., siN). The diaphragm may be formed of silicon (Si), polysilicon, silicon nitride (SiN), or another material suitable for forming a deflectable diaphragm for use in a capacitive microphone transducer.

As shown in fig. 8 and 9, the backplate 810 defines a plurality of holes 812 that fluidly couple the back face 803 of the diaphragm 802 and the rear cavity (e.g., the rear cavity 112 of fig. 1) and acoustically couple. The insulator layer 804 defines a hole 805 having an outer perimeter (e.g., circumference) disposed outside of the open area of the backplate 810. The holes 805 defined by the insulator may be larger, smaller, or the same size as the acoustic ports 614 defined by the substrate. The outer peripheral region 806 of the diaphragm may be attached or bonded to the insulator layer 804 and may cover and contact the wall 611 defining the tortuous path 610, thereby closing the distal edge of the path 610 (relative to the layer 602). The closed distal edge of the channel, in combination with the walls defined by the sacrificial layer 604 and the floor defined by the layer 602, may define a closed circuitous path extending from the inlet 612 to the outlet 616 (fig. 7).

Fig. 10 shows an alternative configuration of an acoustic transducer. In fig. 10, the substrate is constructed similar to the substrate 600 described in connection with fig. 7, 8 and 9. Also, the acoustic transducer element 1000 may be in contact with the substrate 600, attached or mounted to the substrate 600 to encapsulate the channel 610 defined by the substrate 600 in a manner similar to that described in connection with fig. 7, 8 and 9.

However, unlike the acoustic transducer element 800 in fig. 9, the acoustic transducer element 1000 in fig. 10 has a diaphragm 1002 disposed between opposing first and second backplate 1008, 1010. An insulator 10007, 1009 separates the diaphragm 1002 from each respective backplate 1008, 1010. Each backplate 1008, 1010 may be formed in a similar manner as the backplate 810 in fig. 9. Similarly, diaphragm 1002 may be formed from a material similar to diaphragm 802 in fig. 9. Likewise, each backplate 1008, 1010 may define a corresponding plurality of apertures to fluidly and acoustically couple the diaphragm with front and rear cavities (e.g., front and rear cavities 110, 112 in fig. 1), respectively, of the diaphragm.

Fig. 11 shows yet another alternative configuration of an acoustic transducer. In fig. 11, a substrate 600 is constructed similar to the substrate described in connection with fig. 7-10. Also, the acoustic transducer element 1100 may be in contact with the substrate 600, attached or mounted to the substrate 600 to encapsulate the channel 610 defined by the substrate 600 in a manner similar to that described in connection with fig. 7-10.

However, unlike the acoustic transducer elements 800 and 1000 in fig. 9 and 10, the acoustic transducer element 1100 in fig. 11 has a back plate 1100 disposed between opposing first and second diaphragms 1101 and 1102. An insulator 1107, 1109 separates each respective diaphragm 1101, 1102 from the backplate 1110. The backplate 1110 may be formed in a similar manner as the backplate described above in connection with fig. 9 and 10. Similarly, each diaphragm 1101, 1102 may be formed of similar materials as diaphragms 802, 1002 described above in connection with fig. 9 and 10.

Fig. 12 shows yet another alternative configuration of an acoustic transducer. In fig. 12, a substrate 600 is constructed similar to the substrate described in connection with fig. 7-11. Also, the acoustic transducer element 1200 may be in contact with the substrate 600, attached or mounted to the substrate 600 to encapsulate the channel 610 defined by the substrate in a manner similar to that described in connection with fig. 7-11. Although fig. 9, 10, 11, and 12 illustrate exploded views thereof, it should be understood and appreciated that each respective acoustic transducer element 800, 1000, 1100, and 1200 is in contact with or otherwise physically coupled to or supported by the substrate 600 illustrated in these figures.

However, unlike the acoustic transducer elements described above in connection with fig. 9-11, the diaphragm 1202 in fig. 12 is a piezoelectric actuator that overlies and extends across an acoustic port 614 defined by the substrate 600. In fig. 12, the acoustic transducer element comprises a first substrate 1201 defining a corresponding open port 1203. The piezoelectric actuator 1202 is mounted to the first substrate and extends across an open port 1203 of the first substrate. The acoustic transducer element 1202 is mounted to a second substrate 600 defining an acoustic port 614. When the acoustic transducer element 1200 and the second substrate 600 are assembled together, the open port of the acoustic transducer element is aligned with the acoustic port 614 and the piezoelectric actuator 1202 extends across the aligned open port and acoustic port, thereby defining a boundary therebetween.

The diaphragm 1202 may include a thin film piezoelectric material such as, for example, aluminum nitride (AlN) and scandium aluminum nitride (AlScN). Other suitable materials for forming piezoelectric diaphragm 1202 may include, for example, pb (Zr, ti) O ₃ And other piezoelectric materials now known or developed in the future.

The peripheral region of each acoustic transducer element described above in connection with fig. 9-12 may define a through hole 822 aligned with the outlet 616 of the tortuous vent and overlying the outlet 616. The aperture 822 may fluidly couple the vent outlet 616 with the rear cavity of the transducer, thereby coupling a front cavity (e.g., the front cavity 110 in fig. 1) with a rear cavity (e.g., the rear cavity 112 in fig. 1) through the tortuous passageway 616 and the aperture 822.

The tortuous channels described above in connection with fig. 9-12 represent a high aspect ratio arrangement of vent holes having complex acoustic impedances. The vent is formed in or by a substrate of the microphone transducer (e.g., substrate 105 in fig. 1). However, as described above in connection with FIG. 6, vents having higher order complex acoustic impedances may be formed in or by the transducer substrate. Also, the package-level substrate (e.g., substrate 102 in fig. 1) may also define high aspect ratio vents having complex acoustic impedances, as well as higher order vents of the type described more fully below. Fig. 13 and 14 depict two package-level substrates defining vents with complex acoustic impedances suitable for use in a package of an acoustic transducer. While fig. 13 and 14 show their exploded views, it is to be understood and appreciated that each respective acoustic transducer 1302, 1402 is in contact with or otherwise physically coupled to the corresponding substrate 1301, 1401 shown in these figures or supported by the corresponding substrate 1301, 1401 shown in these figures.

Fig. 13 depicts an exploded view of a MEMS microphone transducer mounted to a package-level substrate defining a vent with complex acoustic impedance implemented as a tortuous path, similar to the arrangement shown in fig. 6. The MEMS microphone transducer 1302 shown in fig. 13 may incorporate acoustic transducer elements according to any of the arrangements described above in connection with fig. 9-12. As shown in fig. 6, the substrate 1301 has an upper layer 1304 and a lower layer 1303. The upper layer 1304 of the multilayer substrate 1301 shown in fig. 13 has been selectively etched (or otherwise processed) to define high aspect ratio acoustic pathways 1307. The microphone transducer 1302 may define an aperture 1310, which aperture 1310 fluidly couples an outlet 1309 of a passageway 1307 to a back chamber 1330 of the microphone. And, a passageway 1307 extends from the inlet 1306 to the outlet 1309, fluidly coupling the acoustic port 1305 or other region of the front cavity 1320 with the back cavity 1330 of the microphone transducer 1302 through the passageway 1307 and the aperture 1310. More specifically, the passageway 1307 may extend along an outwardly expanding spiral, for example, the radius of curvature of the passageway may continuously increase as one moves from an inlet 1306 to a longitudinal position of the outlet 1309 along the passageway. Alternatively, the passages may extend circumferentially around the acoustic port 1305 at a substantially constant radius, and in selected areas of the substrate, the passages may extend in a primarily radial direction from one ring to an adjacently disposed ring of successively larger radius. A channel 1307 may be defined between the juxtaposed walls 1308. Fig. 6 and 7 depict a high aspect ratio vent 610 having a sequence of successively larger radius rings joined together by relatively short radially extending sections 613. As with the channel 610 in fig. 6, the channel 1307 may extend to the outer perimeter of the substrate or laterally outward from the MEMS component 1302, directly coupling the front cavity 1320 with the rear cavity 1330.

Fig. 14 depicts an exploded view of a MEMS microphone transducer 1402 mounted to an alternative arrangement of package-level substrate 1401 defining high aspect ratio vent 1410. In fig. 14, the substrate 1401 has four layers (although more or fewer layers are possible), with alternating insulating layers 1404, 1406 being substantially continuous and alternating sacrificial layers 1403, 1405 having been selectively etched (or otherwise processed) to define corresponding sections 1410, 1412 of the high aspect ratio acoustic path. As with the package-level substrate described above, the substrate 1401 in fig. 14 defines a sound entrance region (or acoustic port) 1407. The inlet 1411 of the vent is fluidly coupled with the acoustic port 1407, thereby providing a direct fluid coupling of the first serpentine section 1410 of the vent with the front cavity 1420. Similar to the vent described above in connection with fig. 13, the first serpentine segment 1410 extends through successively larger radius passages until it merges with the first outlet region 1414.

Fig. 14 shows a substantially continuous layer 1406 overlying a first serpentine section 1410. Layer 1406 defines an aperture 1416 or open through-hole aligned with a first outlet region 1414 of first serpentine segment 1410. The upper layer 1405 of the substrate 1401 defines a second serpentine segment 1412 of the pneumatic vent and the aperture 1416 fluidly couples the first serpentine segment 1410 with the second serpentine segment 1412. The second serpentine segment 1412 extends circumferentially around the acoustic port 1407 through successively smaller radius passages until the second serpentine segment 1412 merges with the second outlet region 1418. The successively smaller radius passages may be defined by a continuously decreasing radius spiral or may have sections of substantially constant radius with adjacent sections joined together with a predominantly radially extending section, as in the ring shown in fig. 6. In some arrangements, layer 1406 may be omitted, providing a direct coupling between first serpentine segment 1410 and second serpentine segment 1412. As with the acoustic transducer 1302 shown in fig. 13, the acoustic transducer 1402 shown in fig. 14 may define a through-hole 1419 that fluidly couples the second outlet region 1418 with the rear cavity 1430. The overall bulk density of the high aspect ratio vent may be further increased by including one or more convolutions (or other changes in channel direction) as just described (e.g., a combination of an outwardly expanding section 1410 and an inwardly contracting section 1412).

V. performance examples

An acoustic vent having an L/D ratio between about 1,000 and about 32,000 has a large acoustic mass, as does the high aspect ratio vent described above. Thus, such vents, when excited by pressure changes having a frequency above a threshold frequency, may inhibit flow through the vent, thereby reducing leakage noise as compared to leakage noise generated by primarily resistive acoustic vents. For example, vents described herein having complex acoustic impedances may significantly reduce leakage noise at frequencies above a threshold between about 30Hz and about 150Hz (such as above a threshold frequency between about 40Hz and about 100Hz, e.g., above a threshold frequency between about 50Hz and about 80 Hz). In other words, such vents may act as, for example, low pass filters to the airflow having a cutoff frequency between about 30Hz and about 150 Hz.

The graph in fig. 15 shows a representative acoustic response to a component level vent. The graph in fig. 16 shows a representative acoustic response to a package-level vent. Both graphs generally depict a similar trend, for example, as the aspect ratio of the high aspect ratio vent increases, the resonant frequency of the air pressure vent decreases, as does the magnitude of the resonance.

In a general sense it is preferable to reduce the resonance peak as much as possible, but this may drive the aspect ratio towards even higher than 32,000. Thus, cavities that may be used to deploy high aspect ratio pneumatic vents may impose an upper threshold on the feasible length of the vent. Nevertheless, compensation using a Digital Signal Processor (DSP) is possible when manufacturing tolerances can be controlled sufficiently such that the resonant frequency is substantially the same between devices. Such a DSP may be implemented in software, firmware, or hardware (e.g., ASIC). The DSP processor may be a special-purpose processor such as an Application Specific Integrated Circuit (ASIC), a general-purpose microprocessor, a Field Programmable Gate Array (FPGA), a digital signal controller, or a set of hardware logic structures (e.g., filters, arithmetic logic units, and special-purpose state machines), and may be implemented in a general-purpose computing environment as described herein.

That is, if a given ventilation arrangement exhibits a significant resonance peak (e.g., as in the response shown in fig. 15 and 16 at low aspect ratios), the structure may be physically better responsive to infrasound inputs or inputs at or near the acoustic edge. Thus, a low frequency input such as a footstep does not have many perceptible "sounds" associated with it, and if it overlaps with a resonance peak in the vent response, it can theoretically produce a significant level of low frequency noise, which in turn can significantly increase the high output level of the transducer. Thus, the user may hear the increased noise level without actually knowing the corresponding physical stimulus driving the noise. Alternatively, the compensation (e.g., by the DSP) may remove some or all of the resonance generated by the excitation at or below the acoustic edge.

Further, such enhanced sensitivity at or below the acoustic edge may be utilized to detect events, for example, infrasound events such as footsteps. By way of example, resonance generated by an external source may be detected by a microphone transducer or circuitry that receives audio signals from the transducer. In addition, the source or class of infrasound activity selected may have unique spectral characteristics. Thus, in some cases, a microphone or system may be able to detect the presence of an infrasound event and classify the event, for example, individually corresponding to the level of resonance, or with respect to energy content in other frequency bands.

VI vent with higher order complex acoustic impedance

Referring now to fig. 17A, 17B and 17C, another example of a vent having a complex acoustic impedance with a second order roll-off is shown and described. The segmented elongate channel 1700, as shown in fig. 17A, 17B and 17C, may define a pneumatic vent between the front and rear cavities of the MEMS microphone. In fig. 17A, the substrate walls defining the segmented channels 1700 are omitted to reveal the open interior cavities of the segmented channels. In other words, the shaded area of the segmented channel in fig. 17A depicts the open cavity within the channel 1700 occupied by acoustic media (e.g., air). The segmented channel 1700 has chamber portions 1701a, 1701b and conduit portions 1703a, 1703b juxtaposed to the chamber portions. The cross-sectional area of each conduit portion is substantially smaller than the corresponding cross-sectional area of the adjacent chamber portion. For example, in FIG. 17a, the cross-sectional area of tunnel portions 1703a, 1703b in the y-z plane is significantly smaller than the cross-sectional area of chamber portions 1701a, 1701b in the y-z plane.

The tunnel portion 1703b extends from one of the chamber portions 1701a to an adjacent chamber portion 1701b, providing a cross-sectional area contraction from the chamber portion 1701a to the tunnel portion 1703b and a cross-sectional area expansion from the tunnel portion to the adjacent chamber portion 1701 b. Thus, the chamber portion of the segmented channel 1700 provides acoustic compliance to the segmented channel and the conduit portion of the segmented channel provides acoustic mass to the segmented channel. In the following discussion, the conduit portion of the segmented channels is commonly referred to as a mass unit, and the chamber portion of the segmented channels is commonly referred to as a compliance unit.

In fig. 17B, the segmented channels 1700 are shown with shading removed to reveal internal fluid connections between the compliance cells 1701a, 1701B and the mass cells 1703a, 1703B, while still showing edges and corners of each cell. FIG. 17C shows a two-dimensional projection of the passageway defined by segmented channel 1700 onto the x-y plane. The mass 1703a extends from an open proximal end 1702 to an open distal end 1704. The open proximal end 1702 of the mass unit 1703a may be fluidly coupled with a front cavity (not shown) or other acoustic chamber of a microphone transducer. The open distal end 1704 of the mass unit 1703a can be fluidly coupled to the compliance unit 1701a through a selected face of the compliance unit (e.g., a proximal face 1705a (fig. 17A) along the x-axis).

Similarly, mass 1703b extends from an open proximal end to an open distal end. The open proximal end of the mass unit 1703b may be fluidly coupled to the compliance unit 1701a by a selected face (e.g., a face disposed distally of the proximal face 1705a along the x-axis). The open distal end of the mass unit 1703b can be fluidly coupled to the compliance unit 1701b by a selected face of the compliance unit (e.g., proximal face 1705b (fig. 17A)). A selected face of the second compliance unit 1701b (e.g., a face disposed distally of the proximal face 1705b along the x-axis) may define an opening 1706. The opening 1706 may be directly or indirectly fluidly coupled with the back cavity or other acoustic chamber of the microphone transducer.

Each compliance unit 1701a, 1701b has a relatively larger open interior cavity (e.g., cross-sectional area and length) than the open interior cavity (e.g., cross-sectional area and length) of each respective mass unit 1703a, 1703 b. Although the dimensions of the compliance units 1701a, 1701b are shown as being identical in fig. 17A, the dimensions of each compliance unit 1701a, 1701b may be selected differently from each other to provide a desired overall tuning of the segmented channel 1700. Similarly, the dimensions of the mass units 1703a, 1703b may be the same or different from each other.

Thus, the segmented channel may provide relatively more degrees of freedom than the meandering high aspect ratio channel, and thus relatively more flexibility in tuning. For example, the length (e.g., along the x-axis in fig. 17A, 17B, and 17C) and cross-sectional area (e.g., in the y-z plane) of each mass unit 1703a, 1703B may be selected to achieve a desired acoustic mass within each section. Furthermore, viscous losses associated with each mass unit 1703a, 1703b may be adjusted by adjusting the relative position in the y-z plane. Also, while only a single mass element 1703a, 1703b is shown for each section of the channel 1700, more than one mass element may extend between adjacent compliance elements (e.g., elements 1701a, 1701 b) to reduce the acoustic mass of a given section, thereby providing additional options to adjust the response of the segmented channel 1700. One or more additional segments (each having a corresponding mass unit and a corresponding compliance unit) may be added to the segmented channel 1700 shown in fig. 17A, 17B, and 17C.

Fig. 18 shows an analog circuit 1800 representing a segmented channel with four cascaded mass cells and a compliance cell. In circuit 1800, resistive element R ₁ Inductance element L ₁ And a capacitance element C ₁ Similar to the acoustic conductance, acoustic compliance and acoustic mass of the first sections (1701 a,1703 a) of the channel 1700, respectively. Similarly, a resistance element R ₂ Inductance element L ₂ And a capacitance element C ₂ The acoustic conductance, acoustic compliance and acoustic mass are respectively similar to those of the second sections (1701 b,1703 b) of the channel 1700.

Still referring to FIG. 18, element R ₃ 、L ₃ C ₃ And R is ₄ 、L ₄ C ₄ A third segment (e.g., cells 1901c, 1903c in fig. 19) and a fourth segment (e.g., cells 1901d, 1903d in fig. 19) corresponding to the mass cell and compliance cell, respectively. As shown in fig. 18 and 19, the cascading mass and compliance structure may achieve higher order roll-off than, for example, a two-segment channel 1700. The roll off order increases corresponding to an increase in the number of repeating mass/compliance units.

For example, the segmented channel 1900 as shown in fig. 19 and 20 includes a fifth cascade of mass cells and compliance cells (e.g., cells 1901e, 1903 e) and a sixth cascade (e.g., cells 1901f, 1903 f). As shown in fig. 21A, the segments of the cascade mass unit and compliant unit may reduce the cutoff frequency of the segmented pneumatic vent 1900, e.g., as compared to the segmented channel 1700. By achieving a steeper roll-off, higher order vents may be used to filter out vent noise at higher frequencies over the noise spectrum than is achieved with high aspect ratio vents. Thus, higher order vents may be used to improve the signal-to-noise ratio of the microphone.

The size of each mass and compliance unit may be tuned to achieve a desired roll-off for a given microphone back cavity and a selected number of cascaded sections of mass and compliance units. For example, viscous losses through the high mass unit can be tuned to adjust damping. More generally, each of the cascade segments may be tuned to have a selected combination of acoustic mass and acoustic compliance (e.g., high/high, high/low, low/high, respectively) to achieve a desired cut-off frequency and corresponding microphone frequency response. Fig. 21B shows an example of roll-off variation for different tuning of a given cascade of mass and compliance cells.

In one illustrative example, when used for a volume of 2.5mm ³ The size of the segmented channel 1900 (having 6 segments) can be selectively tuned to provide a selected roll-off frequency when the back chamber is pneumatically vented. For example, the x, y, and z dimensions of each compliance cell 1901n may be selected to be 400 μm, 500 μm, and 400 μm, respectively, and the x and y dimensions of each mass cell 1903n may be selected to be 60 μm and 10 μm, respectively. The z-axis dimension t of each mass unit may be varied and the corresponding roll-off frequency determined. In this example, the z-axis dimension t varies from 20 μm to 50 μm in 5 μm increments, and the resulting low frequency roll-off occurs at 8Hz, 12Hz, 16Hz, 23.5Hz, and 32.5Hz, respectively.

Reference is now made to fig. 22A and 22B, which show the frequency response and the phase response, respectively, of a microphone back whose back cavity is air pressure vented using different second order underdamped vents. Notably, when the low frequency roll-off falls below a lower threshold frequency (e.g., 20 Hz), the frequency response 2201 and the phase response 2202 flatten out over an audible bandwidth. Furthermore, the higher order vent holes described herein may be used to reduce or minimize phase mismatch common in conventional designs. Although the response shown in fig. 22A and 22B is generated by a second order filter, the response will also be flattened with a higher order filter as shown, for example, in fig. 19.

Also, in some aspects, the elongate segmented channels may be easier to manufacture, package, and reliably tune than the high aspect ratio vent holes described above. For example, the segmented channels as described above may have a total volume of about one tenth of the total volume required for a high aspect ratio vent as described above in connection with, for example, fig. 6. In addition, segmented channels may provide more degrees of freedom for tuning the filtering provided by the channels.

Furthermore, as with the vent 1900 shown in fig. 19, there is no need to combine cascade sections of higher order segmented vents in a single coordinate direction. Rather, each successive section of the mass unit and compliance unit may be added to the previous section in any orientation according to any physical constraints imposed by a given microphone or package. Also, the number of cascade segments (e.g., vent orders) may be selected according to each desired application.

For example, in fig. 23 and 24, a segmented vent 2300 is shown having six segments arranged in a U-shape parallel to the x-y plane. More specifically, the first section has a compliance unit 2301a and a mass unit 2303a. The mass unit 2303a has a main longitudinal axis extending in the y-axis direction from a proximal end (e.g., coupled with the anterior chamber, not shown) to a distal end that is open to the x-z plane of the compliance unit 2301 a.

The second section is oriented in a different direction, rotated 90 degrees about the z-axis. For example, the proximal end of the mass element 2303b of the second section is coupled with the y-z plane of the compliance element 2301a, and the mass element 2303b extends in the x-axis direction to couple with the y-z plane of the compliance element 2301 b. The third section (cells 2303c and 2301 c) is oriented substantially as the second section. However, the fourth section (mass 2303d and compliance 2301 d) is rotated 90 degrees in the opposite direction to the rotation of the second section, providing the fourth section with an orientation similar to the orientation of the first section (mass 2303a and compliance 2301 a). And, the fifth section (mass 2303e and compliance 2301 e) is again rotated another 90 degrees about the z-axis relative to the fourth section, thereby orienting the fifth section 180 degrees relative to the second section. The sixth section (mass 2303f and compliance unit 2301 f) is oriented the same as the fifth section, with channels 2306 provided to couple compliance unit 2301f with a rear cavity (not shown).

Fig. 25 and 26 show yet another alternative arrangement of segmented vents. In fig. 25 and 26, these sections are arranged to provide the vent 2500 with an L-shape parallel to the x-z plane. Other arrangements are also possible. For example, the sixth sections 2501f, 2503f shown in fig. 25 as extending from the previous section in the z-axis direction may alternatively extend from the previous section in the y-axis direction.

Generally, such segmented vents can be made compact in one or more coordinate directions by adding successive segments in different orientations than previous segments. For example, as shown in fig. 23, the vent defined by the segmented channels may loop back on itself, providing a desired number of segments (e.g., to achieve a desired higher order filter) while not extending in a single coordinate direction. By including one or more convolutions (or other changes in channel direction or orientation), the overall packing density of the segmented channel vent can be further increased.

Also, as described herein, vents with complex acoustic impedances may be disposed in any selected compact orientation between the back and front cavities, over the MEMS device, or anywhere within the package, substrate, or cover. For example, the segmented channels described with respect to any of fig. 17A-26 may replace the high aspect ratio vent described above in connection with any of fig. 1-16. Similarly, the segmented channels may be fabricated using the techniques described above in connection with the high aspect ratio vent described above with respect to fig. 1-16. In the foregoing discussion, the conduit portion and the chamber portion of the segmented channels are generally described as rectangular prismatic structures in a Cartesian coordinate system. However, the pipe portion and the chamber portion are not limited thereto; they may have other regular or irregular three-dimensional shapes. Furthermore, those regular or irregular three-dimensional shaped wetted surfaces may have smooth or rough contours, e.g., the surfaces may be flat, curved or undulating (e.g., smooth or have discontinuous slopes), which may result from a given manufacturing process. Nevertheless, the nominal size of each segment may be selected in the manner described above to achieve the desired overall tuning of the segmented channels.

Computing environment

FIG. 27 illustrates a generalized example of a suitable computing environment 2700 in which the techniques can be implemented. The computing environment 2700 is not intended to suggest any limitation as to the scope of use or functionality of the technology disclosed herein, as each technology may be implemented in different general-purpose or special-purpose computing environments. For example, each of the disclosed techniques may be implemented with other computer system configurations, including wearable devices and/or handheld devices (e.g., mobile communication devices, and more particularly, but not exclusively, commercially available from Apple inc. (Cupertino, ca.)/HomePod ^TM /Devices), multiprocessor systems, microprocessor-based or programmable consumer electronics, embedded platforms, network computers, minicomputers, mainframe computers, smart phones, tablets, data centers, audio appliances, and the like. Each of the disclosed techniques may also be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a communications connection or network. In a distributed computing environment, program modules may be located in both local and remote memory storage devices.

The computing environment 2700 includes a memory 2720 and at least one central processing unit 2710. In fig. 27, this most basic configuration 2730 is included within the dashed line. The central processing unit 2710 executes computer executable instructions and may be a real or virtual processor. In a multi-processing system or in a multi-core central processing unit, multiple processing units execute computer-executable instructions (e.g., threads) to increase processing speed, and thus, multiple processors may be concurrently running, although processing unit 2710 is represented by a single functional block. The processing unit may comprise an Application Specific Integrated Circuit (ASIC), a general purpose microprocessor, a Field Programmable Gate Array (FPGA), a digital signal controller, or a set of hardware logic structures arranged to process instructions.

Memory 2720 may be volatile memory (e.g., registers, cache, RAM), non-volatile memory (e.g., ROM, EEPROM, flash memory, etc.), or some combination of the two. Memory 2720 stores software 2780a, which when executed by a processor, may, for example, implement one or more of the techniques described herein.

The computing environment may have additional features. For example, the computing environment 2700 includes storage 2740, one or more input devices 2750, one or more output devices 2760, and one or more communication connections 2770. An interconnection mechanism (not shown) such as a bus, controller, or network interconnects the components of the computing environment 2700. Typically, operating system software (not shown) provides an operating environment for other software executing in the computing environment 2700, and coordinates activities of the components of the computing environment 2700.

Storage 2740 may be removable or non-removable and may include alternative forms of machine-readable media. Generally, machine-readable media include magnetic disks, magnetic tapes or cassettes, non-volatile solid state memories, CD-ROMs, CD-RWs, DVDs, magnetic tapes, optical data storage devices, and carrier waves, or any other machine-readable medium which can be used to store information and which can be accessed within the computing environment 2700. Storage 2740 may store instructions for software 2780b, which may implement the techniques described herein.

Storage 2740 may also be distributed over a network such that software instructions are stored and executed in a distributed fashion. In other aspects, some of these operations may be performed by specific hardware components that contain hardwired logic. Alternatively, those operations may be performed by any combination of programmed data processing components and fixed hardwired circuitry components.

The one or more input devices 2750 may be any one or more of the following: a touch input device such as a keyboard, keypad, mouse, pen, touch screen, touch pad, or trackball; a voice input device such as a microphone transducer, voice recognition software, and a processor; a scanning device; or another device that provides input to the computing environment 2700. For audio, the input device 2750 may include a microphone or other transducer (e.g., a sound card or similar device that accepts audio input in analog or digital form), or a computer-readable medium reader that provides audio samples to the computing environment 2700.

The output device 2760 may be any one or more of a display, a printer, a speaker transducer, a DVD writer, or another device that provides output from the computing environment 2700.

Communication connection 2770 enables communication with another computing entity over a communication medium (e.g., a connection network). The communication connection may include a transmitter and a receiver adapted to communicate over a Local Area Network (LAN), a Wide Area Network (WAN) connection, or both. LAN and WAN connections may be facilitated by a wired or wireless connection. If the LAN or WAN connection is wireless, the communication connection may include one or more antennas or antenna arrays. The communication medium conveys information such as computer-executable instructions, compressed graphics information, processed signal information (including processed audio signals), or other data in a modulated data signal. Examples of communication media for so-called wired connections include fiber optic cables and copper wire. A communication medium for wireless communication may include electromagnetic radiation within one or more selected frequency bands.

A machine-readable medium is any available medium that can be accessed within computing environment 2700. By way of example, and not limitation, within the computing environment 2700, machine-readable media include memory 2720, storage 2740, communication media (not shown), and any combination of the preceding. The tangible machine-readable (or computer-readable) medium does not include a transitory signal.

As described above, some of the disclosed principles may be embodied in a tangible, non-transitory machine-readable medium (such as a microelectronic memory) having instructions stored thereon. The instructions may program one or more data processing components (collectively referred to herein as "processors") to perform the processing operations described above, including estimation (such as by control unit 52), calculation(s), measurement, adjustment, sensing, measurement, filtering, addition, subtraction, inversion, comparison, and decision making. In other aspects, some of these operations (of the machine process) may be performed by specific electronic hardware components that contain hardwired logic components (e.g., dedicated digital filter blocks). Alternatively, those operations may be performed by any combination of programmed data processing components and fixed hardwired circuitry components.

VIII, other embodiments and examples

The previous description is provided to enable any person skilled in the art to make or use the disclosed principles. Arrangements other than those specifically described above are contemplated based on the principles disclosed herein and any accompanying changes in the configuration of the corresponding apparatus or changes in the order of method acts described herein without departing from the spirit or scope of the disclosure. Various modifications to the examples described herein will be readily apparent to those skilled in the art.

For example, an electronic device may have an acoustic transducer element with an acoustic diaphragm. The diaphragm may have opposed first and second major surfaces. The front cavity may be disposed adjacent to the first major surface of the diaphragm. The rear cavity may be disposed adjacent the second major surface of the diaphragm. The substrate may be coupled with the acoustic transducer element and the segmented channel may define a pneumatic vent fluidly coupling the front cavity with the rear cavity. The segmented channel may extend from a first end fluidly coupled to the front cavity to a second end fluidly coupled to the rear cavity, and a portion of the segmented channel may extend through the substrate.

In one embodiment, the pneumatic vent may be configured to equalize pressure between the front and rear chambers.

The segmented channel may have, for example, a plurality of conduit portions and a plurality of chamber portions. Each conduit portion may extend from one of the chamber portions to an adjacent chamber portion, providing a cross-sectional area constriction from each respective chamber portion into the corresponding conduit portion and a cross-sectional area expansion from the respective conduit portion into the corresponding adjacent chamber portion.

The substrate may define an acoustic port that is open to the front cavity. In one embodiment, the substrate is a first substrate, and the electroacoustic device may have a second substrate. The first substrate may be mounted to the second substrate. The electroacoustic device may also have an integrated circuit device mounted to the second substrate. The integrated circuit device and the acoustic transducer element may be electrically coupled to each other. The second substrate may have electrical output connections coupled with the integrated circuit device. The electroacoustic device may further comprise a recessed cover overlying the acoustic transducer element, the first substrate and the integrated circuit device.

In another embodiment, the substrate further defines a segmented channel. In addition, the segmented channel may have a plurality of conduit portions and a plurality of chamber portions. Each conduit portion may extend from one of the chamber portions to an adjacent chamber portion, providing a cross-sectional area constriction from each respective chamber portion into the corresponding conduit portion and a cross-sectional area expansion from the respective conduit portion into the corresponding adjacent chamber portion.

In one embodiment, the area of the segmented channel may be open to the acoustic port. The substrate may have a plurality of juxtaposed layers, and the aperture may extend through the plurality of layers to define the acoustic port. In another embodiment, the area of the segmented channel is open to the anterior chamber.

At least one of the layers may define a corresponding portion of a segmented channel having a conduit portion and a corresponding chamber portion. The conduit portion may have a cross-sectional area that is substantially smaller than a corresponding cross-sectional area of the chamber portion.

The segmented channels may have a plurality of relatively narrow conduit portions juxtaposed with a corresponding plurality of relatively wide chamber portions. The segmented channel may define at least one convolution between the conduit portion and the chamber portion.

The at least one layer may include a first layer and a second layer. Each respective portion of the segmented channels defined by the first layer and each respective portion of the segmented channels defined by the second layer may be fluidly coupled together to define convolutions in the segmented channels. In another embodiment, such a substrate may include an intermediate layer of material separating the first and second layers from each other. The intermediate layer may define an aperture that fluidly couples a segment of the segmented channel defined by the first layer with a segment of the segmented channel defined by the second layer.

In another embodiment, a substrate has a first layer and a second layer. The second layer may be disposed between the first layer and the acoustic diaphragm. The second layer may have a sacrificial insulator susceptible to etching and an etch stop defining a boundary of a recess extending through the sacrificial insulator. The recess may define a corresponding portion of the segmented channel.

According to one embodiment, a first end of the segmented channel may be disposed adjacent to the acoustic port, the front cavity, or both, and a second end of the segmented channel may be disposed adjacent to the rear cavity.

The portion of the segmented channel extending through the substrate may have a conduit portion and a corresponding chamber portion. The conduit portion may have a first end that opens to the forward cavity and a second end that opens to the corresponding chamber portion.

The acoustic transducer element may be mountably coupled with the substrate and may define an aperture aligned with the segmented channel. For example, the aperture may be open to the rear cavity, thereby fluidly coupling the front cavity with the rear cavity.

In one embodiment, the acoustic transducer element has a back plate and an insulator. An insulator may be disposed between the diaphragm and the backplate.

In another embodiment, the acoustic transducer element has a first back plate and a corresponding first insulator disposed between the first back plate and the diaphragm. The acoustic transducer element may also have a second back plate and a corresponding second insulator disposed between the second back plate and the diaphragm. The diaphragm may be disposed between the first back plate and the second back plate.

In another embodiment, the diaphragm is a first diaphragm. The acoustic transducer element may have a back plate and a first insulator disposed between the back plate and the first diaphragm. The acoustic transducer element may also have a second diaphragm and a second insulator disposed between the second diaphragm and the back plate. The back plate may be disposed between the first diaphragm and the second diaphragm.

In yet another embodiment, the diaphragm may have a piezoelectric actuator and a substrate defining an open port. The diaphragm may be mounted to the substrate and the piezoelectric actuator may extend over the open port.

According to other embodiments, an electronic device may include an acoustic transducer element having a movable diaphragm. The diaphragm may have opposed first and second major surfaces, and the acoustic transducer element may define an aperture disposed adjacent the movable diaphragm. The substrate may be coupled with the acoustic transducer element. The substrate may define an acoustic port open to the acoustic transducer element and a segmented passageway extending from a first end fluidly coupled to the acoustic port to a second end fluidly coupled to the aperture, thereby defining a pneumatic vent coupling the acoustic port to the aperture.

For example, the substrate may have a plurality of juxtaposed layers, and the opening may extend through the plurality of layers to define the acoustic port. At least one layer may be a first layer and the substrate may have a second layer. The first layer may define a corresponding first channel and the second layer may define a corresponding second channel. The first channel and the second channel may be fluidly coupled to each other, thereby defining a convolution in the segmented passageway.

The segmented passages may have a plurality of conduit regions juxtaposed with a corresponding plurality of chamber regions. Each respective conduit region may have a cross-sectional area that is substantially smaller than a corresponding cross-sectional area of an adjacent chamber region.

Direction and other related references (e.g., upward, downward, top, bottom, left, right, rearward, forward, etc.) may be used to aid in the discussion of the figures and principles herein, and are not intended to be limiting. For example, certain terms such as "upward," "downward," "upper," "lower," "horizontal," "vertical," "left," "right," and the like may be used. These terms are used, where applicable, to provide some definite description in handling relative relationships, particularly with respect to the illustrated embodiments. However, such terms are not intended to imply absolute relationships, positions, and/or orientations. For example, with respect to an object, an "upper" surface may be changed to a "lower" surface simply by flipping the object. Nevertheless, it is the same surface and the object remains unchanged. As used herein, "and/or" means "and" or "and" or ". Furthermore, all patent and non-patent documents cited herein are hereby incorporated by reference in their entirety for all purposes.

Also, those of ordinary skill in the art will appreciate that the exemplary embodiments disclosed herein may be adapted for a variety of configurations and/or uses without departing from the principles disclosed. Applying the principles disclosed herein, various arrangements may be provided for high aspect ratio air pressure vents to reduce leakage noise. For example, the principles described above in connection with any particular example may be combined with the principles described in connection with another example described herein. Accordingly, all structural and functional equivalents to the features and method steps of the various embodiments described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are intended to be encompassed by the principles described herein and the features and acts claimed. Accordingly, neither the claims nor this detailed description should be construed in a limiting sense, and after reading this disclosure, one of ordinary skill in the art will recognize a wide variety of acoustic vents that may be designed using the various concepts described herein.

Furthermore, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. The claim features should not be construed in accordance with 35usc 112 (f) unless features are explicitly recited using the phrase "means for … …" or "steps for … …".

The appended claims are not intended to be limited to the arrangements shown herein, but rather are intended to be accorded the full scope consistent with the language of the claims, wherein reference to a feature in the singular (such as by using the articles "a" or "an") is not intended to mean "one and only one", but rather "one or more", unless specifically so stated. Furthermore, in view of the many possible embodiments to which the disclosed principles may be applied, we reserve the right to claim any and all combinations of features and techniques described herein that are understood by one of ordinary skill in the art, including all matters that come within the scope and spirit of the foregoing description to the full extent, and the literal and equivalent combinations of any claims at any time during the application for which the benefit or priority of the disclosure is set forth, more particularly, but not exclusively, in the appended claims.

Claims

1. An electronic device, comprising:

an acoustic transducer element having an acoustic diaphragm, wherein the diaphragm has opposed first and second major surfaces;

a front cavity disposed adjacent to the first major surface of the diaphragm;

A rear cavity disposed adjacent to the second major surface of the diaphragm;

a substrate coupled with the acoustic transducer element; and

a segmented channel defining a pneumatic vent fluidly coupling the front cavity with the rear cavity, wherein the segmented channel has a plurality of conduit portions and a plurality of chamber portions, wherein the segmented channel extends from a first end fluidly coupled with the front cavity to a second end fluidly coupled with the rear cavity, and wherein a portion of the segmented channel extends through the substrate.

2. The electronic device of claim 1, wherein the pneumatic vent is configured to equalize pressure between the front cavity and the rear cavity.

3. The electronic device of claim 1, wherein each conduit portion extends from one of the chamber portions to an adjacent chamber portion, thereby providing a cross-sectional area constriction from each respective chamber portion to the corresponding conduit portion and a cross-sectional area expansion from the respective conduit portion to the corresponding adjacent chamber portion.

4. The electronic device of claim 1, wherein the substrate defines an acoustic port that is open to the front cavity.

5. The electronic device of claim 4, wherein the substrate is a first substrate, and the electronic device further comprises:

a second substrate to which the first substrate is mounted;

an integrated circuit device mounted to the second substrate, the integrated circuit device and the acoustic transducer element being electrically coupled to each other, wherein the second substrate includes an electrical output connection coupled to the integrated circuit device; and

a recessed cover overlying the acoustic transducer element, the first substrate, and the integrated circuit device.

6. The electronic device of claim 4, wherein the substrate further defines the portion of the segmented channel having a plurality of conduit portions and a plurality of chamber portions, wherein each conduit portion extends from one of the chamber portions to an adjacent chamber portion, thereby providing a cross-sectional area contraction from each respective chamber portion to the corresponding conduit portion and a cross-sectional area expansion from the respective conduit portion to the corresponding adjacent chamber portion.

7. The electronic device of claim 6, wherein an area of the segmented channel is open to the acoustic port.

8. The electronic device of claim 6, wherein an area of the segmented channel is open to the front cavity.

9. The electronic device defined in claim 4 wherein the substrate comprises a plurality of juxtaposed layers and openings of the substrate extend through the plurality of layers to define the acoustic ports.

10. The electronic device of claim 9, wherein at least one of the layers defines a corresponding portion of the segmented channel having a conduit portion and a corresponding chamber portion, the conduit portion having a cross-sectional area that is less than a cross-sectional area of the corresponding chamber portion.

11. The electronic device of claim 10, wherein the segmented channel comprises a plurality of relatively narrow conduit portions juxtaposed with a corresponding plurality of relatively wide chamber portions, the segmented channel defining at least one convolution among the conduit portions and the chamber portions.

12. The electronic device of claim 10, wherein the at least one of the layers comprises a first layer and a second layer, wherein each respective portion of the segmented channel defined by the first layer and each respective portion of the segmented channel defined by the second layer are fluidly coupled together to define a respective convolution in the segmented channel.

13. The electronic device of claim 12, wherein the substrate further comprises an intermediate material layer separating the first and second layers from each other, the intermediate material layer defining an aperture fluidly coupling a section of the segmented channel defined by the first layer with a section of the segmented channel defined by the second layer.

14. The electronic device of claim 4, wherein the substrate comprises a first layer and a second layer disposed between the first layer and the acoustic diaphragm, wherein the second layer comprises an etch-susceptible sacrificial material and an etch stop defining a boundary of a recess extending through the sacrificial material, wherein the recess defines a corresponding portion of the segmented channel.

15. The electronic device of claim 4, wherein the first end of the segmented channel is disposed adjacent to the acoustic port, or adjacent to the front cavity, or adjacent to both the acoustic port and the front cavity, and the second end of the segmented channel is disposed adjacent to the rear cavity.

16. The electronic device of claim 1, wherein the portion of the segmented channel extending through the substrate has a conduit portion and a corresponding chamber portion, wherein the conduit portion has a first end that is open to the front cavity and a second end that is open to the corresponding chamber portion.

17. The electronic device of claim 16, wherein the acoustic transducer element is coupled with the substrate and defines an aperture aligned with the segmented channel, wherein the aperture is open to the rear cavity, thereby fluidly coupling the front cavity with the rear cavity.

18. The electronic device of claim 1, wherein the acoustic transducer element further comprises a backplate and an insulator, wherein the insulator is disposed between the diaphragm and the backplate.

19. An electroacoustic device comprising:

a movable diaphragm, wherein the diaphragm has opposed first and second major surfaces; and

a substrate coupled to the moveable diaphragm, wherein the substrate defines an acoustic port that is acoustically coupled to the first major surface of the diaphragm and a segmented channel that extends from a first end that is fluidly coupled to the acoustic port to a second end that is fluidly coupled to a region adjacent to the second major surface of the diaphragm, such that the segmented channel defines an air pressure vent that couples the acoustic port to the region adjacent to the second major surface of the diaphragm, wherein the segmented channel has a plurality of chamber regions and a plurality of conduit regions juxtaposed to a corresponding plurality of chamber regions.

20. The electro-acoustic device of claim 19 wherein the substrate comprises a plurality of juxtaposed layers and the opening of the substrate extends through the plurality of layers to define the acoustic port.

21. The electro-acoustic device of claim 20 wherein the at least one of the layers comprises a first layer and a second layer, the first layer defining a corresponding first channel and the second layer defining a corresponding second channel, the first and second channels being fluidly coupled to each other to define a convolution in the segmented channel.

22. The electro-acoustic device of claim 19 wherein the cross-sectional area of each respective conduit region is less than the cross-sectional area of the corresponding adjacent chamber region.

23. An electroacoustic device comprising:

a diaphragm having opposed first and second major surfaces;

a front cavity adjacent to the first major surface of the diaphragm;

a rear cavity adjacent to the second major surface of the diaphragm;

a substrate coupled with the diaphragm; and

a segmented channel in the substrate, wherein the segmented channel defines a pneumatic vent fluidly coupling the front cavity with the rear cavity, and wherein the segmented channel has a plurality of acoustic mass units and a corresponding plurality of acoustic compliance units.

24. The electro-acoustic device of claim 23 wherein the segmented channel has a plurality of segments, each segment having one or more acoustic mass units extending between each pair of adjacent acoustic compliance units.

25. The electro-acoustic device of claim 23, wherein the open interior cavity of each acoustic compliance unit is larger than the open interior cavity of an adjacent acoustic mass unit.