EP4710559A1

EP4710559A1 - Improved vent assembly

Info

Publication number: EP4710559A1
Application number: EP24729654.4A
Authority: EP
Inventors: Scott ZERO
Original assignee: WL Gore and Associates Inc
Current assignee: WL Gore and Associates Inc
Priority date: 2023-05-09
Filing date: 2024-05-08
Publication date: 2026-03-18
Also published as: WO2024233586A1; KR20260005310A; WO2024233586A8; CN121079988A

Abstract

There is provided a vent assembly unit for use in an electronic housing, the vent assembly unit comprising an enclosing element and a vent assembly, the vent assembly comprising a first permeable layer, a substantially impermeable acoustic membrane, a second permeable layer, and an acoustic transducer; the first permeable layer positioned on a first side of the substantially impermeable acoustic membrane and the second permeable layer positioned on a second side of the substantially impermeable acoustic membrane; an acoustic volume is defined between the substantially impermeable acoustic membrane, the second permeable layer and the acoustic transducer; wherein the vent assembly unit is configured to be installed over an aperture in an enclosed container such that the enclosing element isolates the vent assembly from the internal volume of the enclosed container and a contained volume is defined between the vent assembly and the enclosing element, the vent assembly being configured during use such that an air pathway is provided from external of the enclosed container to the acoustic volume through the first permeable layer, through the contained volume and through the second permeable layer to the acoustic volume.

Description

Improved Vent Assembly

Field

The present disclosure relates to improved vent assemblies, improved vent assembly units comprising a vent assembly and electronic housings comprising the same.

Background

Vent assemblies used in electronic devices typically include acoustic vents. The acoustic vents are typically used to protect one or more acoustic transducers of an electronic device, such as microphones or speakers, for example, from liquids or particulates, whilst allowing the pressure within an acoustic volume defined between the acoustic transducer and the acoustic vent to be equalised with the atmospheric pressure external of the electronic device within which the acoustic transducer is installed. Accordingly, it is necessary for the acoustic vent to be permeable to air to allow the pressure equalisation and to prevent the ingress of particulates and liquids such as water.

In addition to the above required properties, it is also desirable for the acoustic vent to minimally impact the acoustics of the electronic device such that the performance of the acoustic transducer is maximised whilst protected by the acoustic vent.

Typical acoustic vents used in the art therefore use a small selection of materials that provide the required combination of features, thereby significantly limiting the possible design options of an acoustic vent. For example, materials used in existing acoustic vents and vent assemblies that are effective for use in acoustic vents include porous membranes such as those made from expanded polytetrafluoroethylene (ePTFE), for example.

However, there remains a need for alternative ways to construct acoustic vents and vent assemblies that would allow more choice in the materials that can be effectively used that both provide good acoustic performance and good protection and ventilation performance to allow device manufacturers to more closely tailor the specific performance of a vent assembly or acoustic vent for specific applications. Summary

According to a first aspect there is provided a vent assembly unit for use in an electronic housing, the vent assembly unit comprising an enclosing element and a vent assembly, the vent assembly comprising a first permeable layer, a substantially impermeable acoustic membrane, a second permeable layer, and an acoustic transducer; the first permeable layer positioned on a first side of the substantially impermeable acoustic membrane and the second permeable layer positioned on a second side of the substantially impermeable acoustic membrane; an acoustic volume is defined between the substantially impermeable acoustic membrane, the second permeable layer and the acoustic transducer; wherein the vent assembly unit is configured to be installed over an aperture in an enclosed container such that the enclosing element isolates the vent assembly from the internal volume of the enclosed container, the vent assembly being configured during use such that an air pathway is provided from external of the enclosed container to the acoustic volume through the first permeable layer through the second permeable layer to the acoustic volume.

The enclosing element may surround the vent assembly. The enclosing element may be spaced apart from at least one side of the vent assembly. A contained volume may be defined between the vent assembly and the enclosing element. The contained volume may be defined between the enclosing element and the first permeable layer and second permeable layer when the vent assembly unit is installed into an electronic housing such that the air pathway extends from the first permeable layer into the contained volume and from the contained volume into the second permeable layer.

A contained volume may be defined between the enclosing element and the at least one side of the vent assembly. The air pathway may extend through the first permeable layer into the contained volume and from the contained volume through the second permeable layer to the acoustic volume. The air pathway may extend around the substantially impermeable acoustic membrane. The air pathway may not extend through the substantially impermeable acoustic membrane.

The enclosing element may extend around the vent assembly. The enclosing element may extend around the sides of the vent assembly. The enclosing element may extend across the bottom of the vent assembly. The enclosing element may extend around the sides and the bottom of the vent assembly. The vent assembly unit may have one open side and the enclosing element may be configured to abut against the housing wall of an electronic housing of an electronic device such that the one open side is substantially closed by the housing wall. It has been found that a first permeable layer and a second permeable layer provided on either side of an acoustic membrane allows the acoustic volume between the acoustic membrane and the acoustic transducer to be ventilated around the acoustic membrane through the first permeable layer and the second permeable layer. In other words, the acoustic volume may be ventilated around the acoustic membrane rather than through the acoustic membrane.

Accordingly, the acoustic membrane is no longer required to be able to ventilate the acoustic volume directly and so the material used to form the acoustic membrane can be selected for properties that minimise the impact of the acoustic membrane on the acoustic performance of the acoustic transducer and to protect that acoustic transducer from particulates and liquids. Therefore, a substantially impermeable acoustic membrane is provided in the vent assembly unit.

The vent assembly unit may be configured to be installed such that it is positioned in fluid communication with the aperture of a housing of an electronic device.

In some embodiments the first permeable layer may be fixed to the acoustic membrane directly. The first permeable layer may be welded to the acoustic membrane. The first permeable layer may be heat welded or ultrasonically welded to the acoustic membrane.

The first permeable layer may be adhered to the acoustic membrane. A first adhesive layer may be provided between the first permeable layer and the acoustic membrane. The first adhesive layer may be substantially impermeable. The first adhesive layer may comprise a polymeric adhesive. The polymeric adhesive may be waterproof. The polymeric adhesive may be nonporous. The polymeric adhesive may comprise a polyurethane, an acrylic resin, a silicone-based polymer, or a heat-activated film, for example.

In some embodiments the second permeable layer may be fixed to the acoustic membrane directly. The second permeable layer may be welded to the acoustic membrane. The second permeable layer may be heat welded or ultrasonically welded to the acoustic membrane.

The second permeable layer may be adhered to the acoustic membrane. A second adhesive layer may be provided between the second permeable layer and the acoustic membrane. The second adhesive layer may be substantially impermeable. The second adhesive layer may comprise a polymeric adhesive. The polymeric adhesive may be waterproof. The polymeric adhesive may be nonporous. The polymeric adhesive may comprise a polyurethane, an acrylic resin, a silicone-based polymer, or a heat-activated film, for example. As used herein, the term “permeable layer¹’ refers to a layer that allows gas to pass through it. A permeable layer may have an airflow of at least 10 mL/min, for example. In at least some embodiments a permeable layer may have an airflow that is not so high as to significantly impact the acoustic performance of the vent assembly. For example, a permeable layer may have an airflow that is no greater than 500 mL/min and may change the insertion loss of the vent assembly by less than 3dB.

As used herein, the term “substantially impermeable acoustic membrane" refers to an acoustic membrane that substantially does not allow gas or liquid to pass through it. A substantially impermeable layer may have an airflow that is below detectable levels when measured using the ATEQ® airflow test method described herein.

The acoustic transducer may be a microphone. The acoustic transducer may be a speaker. The vent assembly may comprise a plurality of acoustic transducers. For example, the vent assembly may comprise a microphone and a speaker. Alternatively, the vent assembly may comprise a plurality of microphones or a plurality of speakers or combination thereof.

The or each acoustic transducer may be mounted onto a substrate. The or each acoustic transducer may be mounted onto a common substrate. The substrate may extend to the enclosing element and may define the enclosed volume with the enclosing element and the vent assembly.

The enclosing element may extend below the substrate. The enclosed volume may extend below the substrate.

The second permeable layer may be adhered to the substrate. A third adhesive layer may be provided between the second permeable layer and the substrate. The third adhesive layer may be substantially impermeable. The third adhesive layer may comprise a polymeric adhesive. The polymeric adhesive may be waterproof. The polymeric adhesive may be nonporous. The polymeric adhesive may comprise a polyurethane, an acrylic resin, a silicone- based polymer, or a heat-activated film, for example.

A fourth adhesive layer may be provided on the first permeable layer on the side opposed to the side adjacent to the substantially impermeable acoustic membrane. The fourth adhesive layer may be substantially impermeable. The fourth adhesive layer may comprise a polymeric adhesive. The polymeric adhesive may be waterproof. The polymeric adhesive may be nonporous. The polymeric adhesive may comprise a polyurethane, an acrylic resin, a silicone- based polymer, or a heat-activated film, for example. The fourth adhesive layer may be configured to adhere the vent assembly unit to a wall of an enclosed container, such as an electronic housing, for example.

For the avoidance of doubt, the use of terms such as “first adhesive layer”, “second adhesive layer”, “third adhesive layer”, and “fourth adhesive layer” is to differentiate between the various adhesive layers clearly and is not to be construed as implying the requirement of any of the preceding numbered adhesive layers. Each numbered adhesive layer may be provided alone or in any combination with any of the other numbered adhesive layers.

The substantially impermeable acoustic membrane may have an airflow of less than 1 mL/min. The substantially impermeable acoustic membrane may have an airflow of less than 0.5 mL/min. The substantially impermeable acoustic membrane may have an airflow of less than 0.25 mL/min. The substantially impermeable acoustic membrane may have an airflow of less than 0.1 mL/min. The substantially impermeable acoustic membrane may have an airflow of less than 0.05 mL/min. The substantially impermeable acoustic membrane may have an airflow of less than 0.01 mL/min. The substantially impermeable acoustic membrane may have an airflow of less than 0.005 mL/min. The substantially impermeable acoustic membrane may have an airflow of less than 0.001 mL/min. The substantially impermeable acoustic membrane may have an airflow that is below detectable levels using the methods described herein.

The substantially impermeable acoustic membrane may comprise silicone, polyurethane, polyethylene, polypropylene, Parylene C, Parylene N, polytetrafluoroethylene, polyether ether ketone (PEEK), polyimide, polyamide or combinations thereof.

The substantially impermeable acoustic membrane may comprise a coating. The substantially impermeable acoustic membrane may comprise a sealing coating. The sealing coating may reduce the air flow through the substantially impermeable acoustic membrane. The sealing coating may seal any pores or holes in the material of the substantially impermeable acoustic membrane. The substantially impermeable acoustic membrane may comprise a protective coating. The protective coating may protect the impermeable acoustic membrane from particulates or liquids.

The substantially impermeable acoustic membrane may have a thickness of less than 100 pm. The substantially impermeable acoustic membrane may have a thickness of less than 80 pm. The substantially impermeable acoustic membrane may have a thickness of less than 60 pm. The substantially impermeable acoustic membrane may have a thickness of less than 50 pm. The substantially impermeable acoustic membrane may have a thickness of less than 40 pm. The substantially impermeable acoustic membrane may have a thickness of less than 30 pm. The substantially impermeable acoustic membrane may have a thickness of less than 20 pm. The substantially impermeable acoustic membrane may have a thickness of less than 10 pm. The substantially impermeable acoustic membrane may have a thickness of from 0.25 pm to 100 pm. The substantially impermeable acoustic membrane may have a thickness of from 0.25 pm to 80 pm. The substantially impermeable acoustic membrane may have a thickness of from 0.25 pm to 60 pm. The substantially impermeable acoustic membrane may have a thickness of from 0.25 pm to 50 pm. The substantially impermeable acoustic membrane may have a thickness of from 0.25 pm to 40 pm. The substantially impermeable acoustic membrane may have a thickness of from 0.25 pm to 30 pm. The substantially impermeable acoustic membrane may have a thickness of from 0.25 pm to 20 pm. The substantially impermeable acoustic membrane may have a thickness of from 0.25 pm to 10 pm.

The substantially impermeable acoustic membrane may have an insertion loss at 3 kHz of less than about 30 dB. The substantially impermeable acoustic membrane may have an insertion loss at 3 kHz of less than about 20 dB. The substantially impermeable acoustic membrane may have an insertion loss at 3 kHz of less than about 10 dB. The substantially impermeable acoustic membrane may have an insertion loss at 3 kHz of less than about 5 dB. The substantially impermeable acoustic membrane may have an insertion loss at 3 kHz of less than about 1 dB. The substantially impermeable acoustic membrane may have an insertion loss at 3 kHz of from about 0.01 dB to about 30 dB. The substantially impermeable acoustic membrane may have an insertion loss at 3 kHz of from about 0.01 dB to about 20 dB. The substantially impermeable acoustic membrane may have an insertion loss at 3 kHz of from about 0.01 dB to about 10 dB. The substantially impermeable acoustic membrane may have an insertion loss at 3 kHz of from about 0.01 dB to about 5 dB. The substantially impermeable acoustic membrane may have an insertion loss at 3 kHz of from about 0.01 dB to about 1 dB.

The first permeable layer may comprise a first aperture. The second permeable layer may comprise a second aperture. The first permeable layer may comprise a first aperture and the second permeable layer may comprise a second aperture and the first aperture and the second aperture may be substantially co-axial. The first aperture and the second aperture may form a channel. The channel may extend to the acoustic transducer. The substantially impermeable acoustic membrane may span the channel.

The first permeable layer may have an airflow rate of at least 10 mL/min as measured using the method described herein. The first permeable layer may have an airflow rate of at least 15 mL/min. The first permeable layer may have an airflow rate of at least 20 mL/min. The first permeable layer may have an airflow rate of at least 25 mL/min. The first permeable layer may have an airflow rate of at least 30 mL/min. The first permeable layer may have an airflow rate of from 10 mL/min to 500 mL/min. The first permeable layer may have an airflow rate of from 15 mL/min to 500 mL/min. The first permeable layer may have an airflow rate of from 20 mL/min to 500 mL/min. The first permeable layer may have an airflow rate of from 25 mL/min to 500 mL/min. The first permeable layer may have an airflow rate of from 30 mL/min to 500 mL/min.

In at least some embodiments the first permeable layer may be configured to maximise airflow through the first permeable layer, to minimise the ingress of fluid into and through the first permeable layer and to minimise the impact of the first permeable layer on the acoustic performance of the vent assembly.

The first permeable layer may comprise a material selected from a polymer, a composite, a textile, a metal, or a ceramic material.

The first permeable layer may comprise a polymer selected from polyethylene (PE), polypropylene (PP), Parylene C, Parylene N, polyphenylene sulfide (PPS) or polyethylene napthalate (PEN), polyamide, polyester, or a fluoropolymer such as polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene- (perfluoroalkyl) vinyl ether copolymer (PFA), polytetrafluoroethylene (PTFE) and copolymers of the same.

The first permeable layer may comprise a polymer selected from polyethylene (PE), polypropylene (PP), Parylene C, Parylene N, polyphenylene sulfide (PPS) or polyethylene napthalate (PEN) or copolymers of the same.

The first permeable layer may comprise a fibrous polymer. The first permeable layer may comprise a textile. The textile may comprise a woven, nonwoven or knitted material. The textile may comprise a polymeric material. The textile may comprise a natural material.

The first permeable layer may comprise a metal such as a stainless steel, titanium, aluminum, copper, or alloy thereof.

The first permeable layer may comprise a coating. The coating may be hydrophobic. Accordingly, the coating may prevent or reduce the ingress of water into or through the first permeable layer. The coating may prevent or reduce the ingress of oils into or through the first permeable layer.

The first permeable layer may comprise a polymer foam.

The first permeable layer may have a thickness of less than 1 mm. The first permeable layer may have a thickness of less than 0.8 mm. The first permeable layer may have a thickness of less than 0.6 mm. The first permeable layer may have a thickness of less than 0.5 mm. The first permeable layer may have a thickness of less than 0.4 mm. The first permeable layer may have a thickness of less than 0.3 mm. The first permeable layer may have a thickness of less than 0.2 mm. The first permeable layer may have a thickness of less than 0.1 mm. The first permeable layer may have a thickness of less than 0.05 mm. The first permeable layer may have a thickness of less than 0.03 mm. The first permeable layer may have a thickness of less than 0.02 mm. The first permeable layer may have a thickness of less than 0.01 mm.

The first permeable layer may have a thickness of from 1 mm to 0.005 mm. The first permeable layer may have a thickness of from 1 mm to 0.01 mm. The first permeable layer may have a thickness of from 1 mm to 0.02 mm. The first permeable layer may have a thickness of from 1 mm to 0.03 mm. The first permeable layer may have a thickness of from 1 mm to 0.05 mm. The first permeable layer may have a thickness of from 1 mm to 0.1 mm. The first permeable layer may have a thickness of from 0.8 mm to 0.005 mm. The first permeable layer may have a thickness of from 0.6 mm to 0.005 mm. The first permeable layer may have a thickness of from 0.5 mm to 0.005 mm. The first permeable layer may have a thickness of from 0.4 mm to 0.005 mm. The first permeable layer may have a thickness of from 0.3 mm to 0.005 mm. The first permeable layer may have a thickness of from 0.2 mm to 0.005 mm. The first permeable layer may have a thickness of from 0.1 mm to 0.005 mm. The second permeable layer may have an airflow rate of at least 10 mL/min as measured using the method described herein. The second permeable layer may have an airflow rate of at least 15 mL/min. The second permeable layer may have an airflow rate of at least 20 mL/min. The second permeable layer may have an airflow rate of at least 25 mL/min. The second permeable layer may have an airflow rate of at least 30 mL/min. The second permeable layer may have an airflow rate of from 10 mL/min to 500 mL/min. The second permeable layer may have an airflow rate of from 15 mL/min to 500 mL/min. The second permeable layer may have an airflow rate of from 20 mL/min to 500 mL/min. The second permeable layer may have an airflow rate of from 25 mL/min to 500 mL/min. The second permeable layer may have an airflow rate of from 30 mL/min to 500 mL/min.

In at least some embodiments the second permeable layer may be configured to maximise airflow through the second permeable layer, to minimise the ingress of fluid into and through the second permeable layer and to minimise the impact of the second permeable layer on the acoustic performance of the vent assembly.

The second permeable layer may comprise a material selected from a polymer, a composite, a textile, a metal, or a ceramic material.

The second permeable layer may comprise a polymer selected from polyethylene (PE), polypropylene (PP), Parylene C, Parylene N, polyphenylene sulfide (PPS) or polyethylene napthalate (PEN), polyamide, polyester, or a fluoropolymer such as polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene- (perfluoroalkyl) vinyl ether copolymer (PFA), polytetrafluoroethylene (PTFE) and copolymers of the same.

The second permeable layer may comprise a polymer selected from polyethylene (PE), polypropylene (PP), Parylene C, Parylene N, polyphenylene sulfide (PPS) or polyethylene napthalate (PEN) or copolymers of the same.

The second permeable layer may comprise a fibrous polymer.

The second permeable layer may comprise a textile. The textile may comprise a woven, nonwoven or knitted material. The textile may comprise a polymeric material. The textile may comprise a natural material. The second permeable layer may comprise a metal such as a stainless steel, titanium, aluminum, copper, or alloy thereof.

The second permeable layer may comprise a polymer foam.

The second permeable layer may comprise a coating. The coating may be hydrophobic. Accordingly, the coating may prevent or reduce the ingress of water into or through the second permeable layer. The coating may prevent or reduce the ingress of oils into or through the second permeable layer.

The second permeable layer may have a thickness of less than 1 mm. The second permeable layer may have a thickness of less than 0.8 mm. The second permeable layer may have a thickness of less than 0.6 mm. The second permeable layer may have a thickness of less than 0.5 mm. The second permeable layer may have a thickness of less than 0.4 mm. The second permeable layer may have a thickness of less than 0.3 mm. The second permeable layer may have a thickness of less than 0.2 mm. The second permeable layer may have a thickness of less than 0.1 mm. The second permeable layer may have a thickness of less than 0.05 mm. The second permeable layer may have a thickness of less than 0.03 mm. The second permeable layer may have a thickness of less than 0.02 mm. The second permeable layer may have a thickness of less than 0.01 mm.

The second permeable layer may have a thickness of from 1 mm to 0.005 mm. The second permeable layer may have a thickness of from 1 mm to 0.01 mm. The second permeable layer may have a thickness of from 1 mm to 0.02 mm. The second permeable layer may have a thickness of from 1 mm to 0.03 mm. The second permeable layer may have a thickness of from 1 mm to 0.05 mm. The second permeable layer may have a thickness of from 1 mm to 0.1 mm. The second permeable layer may have a thickness of from 0.8 mm to 0.005 mm. The second permeable layer may have a thickness of from 0.6 mm to 0.005 mm. The second permeable layer may have a thickness of from 0.5 mm to 0.005 mm. The second permeable layer may have a thickness of from 0.4 mm to 0.005 mm. The second permeable layer may have a thickness of from 0.3 mm to 0.005 mm. The second permeable layer may have a thickness of from 0.2 mm to 0.005 mm. The second permeable layer may have a thickness of from 0.1 mm to 0.005 mm.

The vent assembly may comprise a support that is configured to support the substantially impermeable acoustic membrane. The support may increase the physical resistance of the substantially impermeable acoustic membrane. The support may increase the burst pressure of the substantially impermeable acoustic membrane.

The support may comprise a mesh. The support may comprise a lattice. The support may comprise a material that is substantially rigid. The support may be planar and the support may be resistive to deformation out of the plane of the support.

The support may be spaced apart from the substantially impermeable acoustic membrane. The support may be spaced apart from the substantially impermeable acoustic membrane by an adhesive layer. The support may be spaced apart from the substantially impermeable acoustic membrane such that the substantially impermeable acoustic membrane is unimpeded to allow vibration for transmission of acoustic energy.

The support may have a minimal impact on the acoustic performance of the substantially impermeable acoustic membrane. The support may have an insertion loss that is lower than the insertion loss of the substantially impermeable acoustic membrane. The support may have an insertion loss of less than about 5 dB. The support may have an insertion loss of less than about 1 dB. The support may have an insertion loss of less than about 0.5 dB. The support may have an insertion loss of less than about 0.1 dB. The support may have an insertion loss of from about 0.001 dB to about 5 dB. The support may have an insertion loss of from about 0.001 dB to about 1 dB. The support may have an insertion loss of from about 0.001 dB to about 0.5 dB.

The support may be the first permeable layer. The support may be the second permeable layer.

In a second aspect there is provided an electronic device comprising a housing, the housing comprising a wall comprising a wall aperture and defining an internal volume, and a vent assembly unit provided occluding the aperture, the vent assembly unit comprising an enclosing element and a vent assembly, the vent assembly comprising a first permeable layer, a substantially impermeable acoustic membrane, a second permeable layer, and an acoustic transducer, the first permeable layer positioned on a first side of the substantially impermeable acoustic membrane and the second permeable layer positioned on a second side of the substantially impermeable acoustic membrane; wherein an acoustic volume is defined between the substantially impermeable acoustic membrane, the second permeable layer and the acoustic transducer, wherein a channel is formed from the aperture to the acoustic transducer through the first permeable layer and the second permeable layer and the substantially impermeable acoustic membrane spans the channel, wherein an air pathway is provided from external of the electronic housing to the acoustic volume through the aperture, the first permeable layer and the second permeable layer, wherein the vent assembly is separated from the internal volume by the enclosing element such that the vent assembly is isolated from the internal volume by the enclosing element.

The vent assembly unit may be the vent assembly unit according to the first aspect.

The enclosing element may surround the vent assembly. The enclosing element may be spaced apart from at least one side of the vent assembly. The enclosing element may define an enclosed volume between the enclosing element and the first permeable layer and second permeable layer such that the air pathway extends from the first permeable layer into the enclosed volume and from the enclosed volume into the second permeable layer.

An enclosed volume may be defined between the enclosing element and the at least one side of the vent assembly. The air pathway may extend through the first permeable layer into the enclosed volume and from the enclosed volume through the second permeable layer to the acoustic volume. The enclosing element may extend around the vent assembly. The enclosing element may extend around the sides of the vent assembly. The enclosing element may extend across the bottom of the vent assembly. The enclosing element may extend around the sides and the bottom of the vent assembly. The vent assembly unit may have one open side and the enclosing element may abut against the housing wall of the housing of the electronic device such that the one open side is substantially closed by the housing wall.

The acoustic transducer may be mounted onto a substrate.

The internal volume may comprise electronic components of the electronic device. The electronic components of the electronic device may be protected from moisture that may pass through the first permeable layer by the enclosing element.

The first permeable layer may comprise a first aperture.

The substantially impermeable acoustic membrane may have a thickness of from 0.25 to 50 pm.

The vent assembly may comprise a support configured to support the substantially impermeable acoustic membrane.

The second permeable layer may comprise a second aperture.

For the avoidance of doubt, features of the vent assembly unit and the vent assembly of the first aspect may be features of the vent assembly and the vent assembly of the second aspect.

According to a third aspect, there is provided a vent assembly unit for use in an electronic housing, the vent assembly unit comprising an enclosing element and a vent assembly, the vent assembly comprising a first permeable layer, a substantially impermeable acoustic membrane, a second permeable layer and a substrate; the first permeable layer positioned on a first side of the substantially impermeable acoustic membrane and the second permeable layer positioned on a second side of the substantially impermeable acoustic membrane; an acoustic volume is defined between the substantially impermeable acoustic membrane, the second permeable layer and the substrate; wherein the vent assembly unit is configured to be installed over an aperture in an enclosed container such that the enclosing element isolates the vent assembly from the internal volume of the enclosed container, the vent assembly being configured during use such that an air pathway is provided from external of the enclosed container to the acoustic volume through the first permeable layer through the second permeable layer to the acoustic volume.

The substrate may be configured to receive one or more acoustic transducers. The vent assembly unit comprising one or more acoustic transducers may be a vent assembly according to the first aspect.

Features of the vent assembly unit of the first aspect may be features of the third aspect excluding features of the acoustic transducer.

Brief Description of the Figures

Embodiments of the present invention will now be described, by way of non-limiting example, with reference to the accompanying drawings.

Figure 1 : A cross-sectional side view of a vent assembly unit according to an embodiment;

Figure 2: A cross-sectional side view of a vent assembly unit installed within an electronic device housing;

Figure 3: A cross-sectional side view of a vent assembly unit according to an embodiment;

Figure 4: A cross-sectional side view of a vent assembly unit installed within an electronic device housing;

Figure 5: A cross-sectional side view of a vent assembly unit according to an embodiment; and

Figure 6: A cross-sectional side view of a vent assembly unit according to an embodiment in a test configuration.

Detailed Description

While the making and using of various embodiments of the present invention are discussed in detail below, it should be appreciated that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed herein are merely illustrative of specific ways to make and use the invention and do not delimit the scope of the invention.

To facilitate the understanding of this invention, a number of terms are defined below. Terms defined herein have meanings as commonly understood by a person of ordinary skill in the areas relevant to the present invention. Terms such as “a”, “an” and “the” are not intended to refer to only a singular entity, but include the general class of which a specific example may be used for illustration. The terminology herein is used to describe specific embodiments of the invention, but their usage does not delimit the invention, except as outlined in the claims.

Test Methods

Thickness measurement

Substrate thickness of permeable layers and membranes are measured using a Mitutoyo Litematic VL50S thickness gauge. In cases where either are provided from a manufacturer, the thickness reported by the manufacturer may be used.

Insertion loss measurement

A venting assembly is constructed between a steel plate and a cap both having 1.5 mm diameter circular apertures, such that the apertures in the steel plate and cap are aligned and a substantially impermeable acoustic membrane is suspended between the two apertures in the steel plate and the cap; permeable layers having apertures larger than the apertures in the steel plates are adhered with adhesive between each face of the acoustic membrane and each steel plate, aligning the apertures of the steel plates and permeable layers. An impermeable ring of PET is adhered with adhesive on both of its faces to each of the steel plates, around the permeable layers and the substantially impermeable membrane such that a contained volume is created between the first permeable layer, the PET ring, and the second permeable layer. Inside a 4232 anechoic test box obtained from Bruel & Kjaer, a face plate is located at a distance of about 6.5 cm from an internal driver or speaker, said face plate having a central aperture in communication with an InvenSense INMP510 MEMS measurement microphone. The speaker is excited to produce an external stimulus at 1 Pa of sound pressure (94 dB SPL) over the frequency range from 100 Hz to 20 kHz. The acoustic response is measured under the following conditions: (a) with the aperture uncovered (b) with the aperture covered with the venting assembly sample, the transducer of the measurement microphone in fluid communication with the circular aperture of the steel plate of the venting assembly, and the attachment between that steel plate and the cap in solid contact. The difference in the response between (a) and (b) is reported in dB (at a specified frequency) as the acoustic loss due to the venting assembly. In comparative tests, the permeable layers in the above construction may be replaced with impermeable layers, and/or the PET ring may be omitted, and/or openings in the PET ring may be introduced, and/or a permeable acoustic membrane may be substituted for the substantially impermeable acoustic membrane, and/or a support plate may be included.

Airflow Measurement

ATEQ® airflow test is a method for measuring laminar volumetric flow rates of air through venting assemblies. Venting assemblies are clamped between a steel plate and a cap such that a flow pathway is created through the aperture in the steel plate, into the aperture in the first permeable layer, through the first permeable layer, into the contained volume (created between the PET ring and the first and second permeable layers), through the second permeable layer, and through the aperture in the cap. Since the acoustic membrane is substantially impermeable, no airflow will travel through the acoustic membrane. An ATEQ® 570/D520 Premier D Compact Flow Tester is used to measure airflow rate (mL/min) through the venting assembly by challenging it with 1.2 kPa of air pressure through the aperture in the steel plate.

Pressure Equilibration Test

A pressure equilibration test is a test method for measuring the time it takes to equilibrate a pressure difference built up between a simulated acoustic cavity and the environment through a sample (either a vent assembly or permeable layer). A pressure vessel is pressurized through a pressure inlet and contains two Freescale Semiconductor MPX4250A pressure transducers. The simulated acoustic cavity (microphone cavity) is created at the interface of the sample and a pressure transducer, the sample either a vent assembly or permeable layer constructed as described in the airflow measurement test. The sample is attached to the pressure transducer at ambient pressure before being put in the pressure vessel. The pressure transducer with the attached sample measures the pressure in the simulated microphone cavity while the other pressure transducer measures the pressure of the environment in the pressure vessel. The pressure vessel is pressurized to 27.6 kPa (4 psi) using compressed air and a regulator. The pressures measured by the pressure transducers are recorded until the pressures are equal or until a pre-defined amount of time has passed. The data for pressure differential over time between the two transducers can then be described by parameters such as the exponential decay time constant, T, which can be used as a measure of material performance. 3T corresponds to time for 95% of initial pressure to be equilibrated. A higher T corresponds to slower equilibration and lower breathability. Water entry pressure (WEP) test

The water entry pressure test can be applied to venting assemblies like those described in the acoustic insertion loss test method above. Such a venting assembly is clamped and sealed in a sample holder, and water pressure is applied to one side. The sample is pressurized with water at a specified pressure and held for a specified duration. If water does not intrude through the aperture in the steel plate, through the first permeable layer, into the contained volume, and through the second permeable layer to be visible on the opposite side during the specified duration, the sample is deemed to have passed the WEP test. After the test duration, the sample can be disassembled and it can be determined whether water has passed through the first permeable layer, or into the enclosed volume, or both, or none of the above. This WEP test can also be completed on a venting assembly constructed using a second steel plate that does not have an aperture. Such a construction would mimic water pressurization into a sealed volume.

The following examples are illustrative of the principles and concepts of the disclosure and are not to be construed as limiting to the scope of the disclosure. It will be appreciated that features of each example can be combined with the features of the other examples as appropriate.

Example 1

With reference to Figure 1 , a vent assembly unit 1 comprises vent assembly 2 and an enclosing element 4. The vent assembly 2 comprises a first breathable layer 6 (acting as a first permeable layer) comprising porous polyethylene (PE), an impermeable membrane 8 (acting as a substantially impermeable acoustic membrane) comprising polyethylene (PE), a second breathable layer 10 (acting as a second permeable layer) comprising porous PE, and a microphone 12 (acting as an acoustic transducer) mounted on a substrate 14. The first breathable layer 6 forms a ring with a central aperture having a diameter of 1.6 mm. The second breathable layer 10 forms a ring with a central aperture having a diameter of 1.6 mm. An acoustic pathway is formed through the aperture of the first breathable layer 6, the impermeable membrane 8 and the aperture of the second breathable layer 10. An adhesive layer 16 comprising an acrylic adhesive is provided between the first breathable layer 6 and the impermeable membrane 8, between the impermeable membrane 8 and the second breathable layer 10 and between the second breathable layer 10 and the substrate 14. A further adhesive layer 18 comprising acrylic adhesive is provided on the first breathable layer 6. An acoustic volume 20 is defined between the impermeable membrane 8, the microphone 12 and the second breathable layer 10.

The enclosing element 4 comprises a side wall 22 that extends around and encloses the sides of the vent assembly 2 and a bottom wall 24 that extends beneath the vent assembly 2 such that a space 26 (acting as a contained volume) is provided between the side of the vent assembly 2 and the side wall 22, and between the bottom wall 24 and the substrate 14 of the vent assembly 2.

The vent assembly 2 is connected to the enclosing element 4 by connecting struts 28 such that the space 26 between the vent assembly 2 and the enclosing element 4 is maintained.

Referring to Figure 2, the vent assembly unit 1 is installed within a housing 30 of an electronic device 32. The housing 30 comprises a housing wall 34 and an aperture 36 formed within the housing wall 34. The enclosing element 4 abuts the inside of the housing wall 34 to thereby isolate the vent assembly 2 from the interior volume 38 of the housing 30. The further adhesive layer 18 fixes the vent assembly 2 to the housing wall 34 such that the impermeable membrane 8 occludes the aperture 36.

When installed, an air pathway 40 is formed from exterior of the housing 30 to the acoustic volume 20. The air pathway 40 extends through the aperture 36, the first breathable layer 6, the space 26, the second breathable layer 10 and into the acoustic volume 20. Accordingly, the acoustic volume 20 can be ventilated via the air pathway 40 without requiring the impermeable membrane 8 to allow the passage of air through it.

The isolation of the vent assembly 2 from the interior volume 38 of the electronic device 32 by the enclosing element 4 ensures that any water, for example, that passes through the first breathable layer 6 cannot contact any internal components of the electronic device 32. Furthermore, as the air pathway 40 passes through both the first breathable layer 6 and the second breathable layer 10 any intruding water is required to pass through both the first breathable layer 6 and the second breathable layer 10 before it can contact the microphone 12. Furthermore, since the enclosed volume 26 is sealed from the interior volume 38 of the housing 30, if water or another liquid is being forced through the aperture 36 such that air cannot travel from the enclosed volume 26 through the first breathable layer 6 and out the aperture 36, a hydraulic resistance to water entry through the first breathable layer 6 is created such that the pressure required to force water all the way to the acoustic volume 20 is substantially increased compared to a case where the enclosed volume 26 was not present. Example 2

With reference to Figure 3, a vent assembly unit 100 comprises vent assembly 102 and an enclosing element 104. The vent assembly 102 comprises a first breathable layer 106 (acting as a first permeable layer) comprising a polyamide non-woven material, an impermeable membrane 108 (acting as a substantially impermeable acoustic membrane) comprising silicone, a second breathable layer 110 (acting as a second permeable layer) comprising a polyamide non-woven material, a microphone 112 (acting as a first acoustic transducer) mounted on a substrate 114 and a speaker 116 (acting as a second acoustic transducer) mounted on the substrate 114. The first breathable layer 106 is heat welded to the impermeable membrane 108 to form a ring weld 118. The second breathable layer 110 is heat welded to the impermeable membrane 108 to form a ring weld 120. An adhesive layer 122 comprising acrylic adhesive is provided on the first breathable layer 106 and between the second breathable layer 110 and the substrate 114.

An acoustic volume 124 is defined between the impermeable membrane 108, the substrate 114 and the second breathable layer 110.

The enclosing element 104 comprises a side wall 126 that extends around and encloses the sides of the vent assembly 102. The substrate 114 extends to the side wall 126 of the enclosing element 104 such that a space 128 (acting as a contained volume) is provided between the side of the vent assembly 102, the side wall 126 and the substrate 114.

Referring to Figure 4, the vent assembly unit 100 is installed within a housing 130 of an electronic device 132. The housing 130 comprises a housing wall 134 and an aperture 136 formed within the housing wall 134. The enclosing element 104 abuts the inside of the housing wall 134 to thereby isolate the vent assembly 102 from the interior volume 138 of the housing 130. The adhesive layer 122 fixes the vent assembly 102 to the housing wall 134 such that the impermeable membrane 108 occludes the aperture 136.

When installed, an air pathway 140 is formed from exterior of the housing 130 to the acoustic volume 124. The air pathway 140 extends through the aperture 136, the first breathable layer 106, the space 128, the second breathable layer 110 and into the acoustic volume 124. Accordingly, the acoustic volume 124 can be ventilated via the air pathway 140 without requiring the impermeable membrane 108 to allow the passage of air through it. The isolation of the vent assembly 102 from the interior volume 138 of the electronic device 132 by the enclosing element 104 ensures that any water, for example, that passes through the first breathable layer 106 cannot contact any internal components of the electronic device 132. Furthermore, as the air pathway 140 passes through both the first breathable layer 106 and the second breathable layer 110 any intruding water is required to pass through both the first breathable layer 106 and the second breathable layer 110 before it can contact the microphone 112 or the speaker 116. Furthermore, since the enclosed volume 128 is sealed from the interior volume 138 of the housing 130, if water or another liquid is being forced through the aperture 136 such that air cannot travel from the enclosed volume 128 through the first breathable layer 106 and out the aperture 136, a hydraulic resistance to water entry through the first permeable layer 106, the contained volume 128, and the second breathable layer 110 is created such that the pressure required to force water all the way to the acoustic volume 124 is substantially increased compared to a case where the enclosed volume 128 was not present.

Example 3

In an alternative example with reference to Figure 5, a vent assembly unit 200 comprises vent assembly 202 and an enclosing element 204. The vent assembly 202 comprises a first breathable layer 206 (acting as a first permeable layer) comprising porous polyethylene (PE), an acoustic membrane 208 (acting as a substantially impermeable acoustic membrane) comprising polyurethane, a second breathable layer 210 (acting as a second permeable layer) comprising porous polyethylene, and a microphone 212 (acting as an acoustic transducer) mounted on a substrate 214. A perforated stainless steel support 216 (acting as a support layer) is provided between the acoustic membrane 208 and the second breathable layer 210. The perforated stainless steel support 216 is adhered to the acoustic membrane 208 with a layer of acrylic adhesive 217 that spaces the support 216 apart from the acoustic membrane 208 such that the support 216 is not in contact with the acoustic membrane 208. The perforated stainless steel support 216 forms an open structure and supports the acoustic membrane 208 to increase the resistance of the acoustic membrane 208 to deformation induced by exterior pressure. The second breathable layer 210 forms a ring and comprises an aperture having a diameter of 1.6 mm. An adhesive layer 218 comprising an acrylic adhesive is provided between the first breathable layer 206 and the acoustic membrane 208, between the perforated stainless steel support 216 and the second breathable layer 210 and between the second breathable layer 210 and the substrate 214. A further adhesive layer 218 comprising an acrylic adhesive is provided on the first breathable layer 206. An acoustic volume 220 is defined between the acoustic membrane 208, the microphone 212 and the second breathable layer 210.

The enclosing element 204 comprises a side wall 222 that extends around and encloses the sides of the vent assembly 202 and a bottom wall 224 that extends beneath the vent assembly 202 such that a space 226 (acting as a contained volume) is provided between the side of the vent assembly 202 and the side wall 222, and between the bottom wall 224 and the substrate 214 of the vent assembly 202.

The vent assembly 202 is connected to the enclosing element 204 by connecting struts 228 between the bottom wall 224 and the substrate 214 such that the space 226 between the vent assembly 202 and the enclosing element 204 is maintained.

The vent assembly unit 200 is installed into the housing of an electronic device (not shown) as described above for example 1.

When installed, an air pathway is formed from exterior of the housing to the acoustic volume 220. The air pathway extends through the aperture of the housing upon which the vent assembly unit 200 is installed, the first breathable layer 206, the space 226, the second breathable layer 210 and into the acoustic volume 220. Accordingly, the acoustic volume 220 can be ventilated via the air pathway without requiring the acoustic membrane 208 to allow the passage of air through it. Furthermore, since the enclosed volume 226 is sealed from the interior volume of the housing, if water or another liquid is being forced through the aperture of the housing such that air cannot travel from the enclosed volume 226 through the first breathable layer 206 and out the aperture, a hydraulic resistance to water entry through the first breathable layer 206, the space 226, and the second breathable layer 210 is created such that the pressure required to force water all the way to the acoustic volume is substantially increased compared to a case where the enclosed volume 128 was not present.

Specific Examples

Example venting assemblies were made using the following method.

With reference top Figure 6 a venting assembly 250 was formed using a die cut process with a stack up from top to bottom with the following layers: a first adhesive layer 252 (Tesa 4983), a first permeable layer 254 of a lateral breathable material (LB1), a second adhesive layer 256 (Tesa 4983), a third adhesive layer 258 (Nitto 5605BRN), an acoustic membrane 260 (M), a fourth adhesive layer 262 (Nitto 5605BRN), a fifth adhesive layer 264 (Tesa 4983), a second permeable layer 266 of a lateral breathable material (LB2), and a sixth adhesive layer 268 (Tesa 4983). A circular aperture 270 is cut centrally through all materials except the acoustic membrane 260 prior to assembly. The circular aperture 270 had a diameter of 1 ,6mm and the vent assembly 250 has an outer diameter of 3.2mm diameter.

Acoustic membranes either comprised dense polyethylene comprising ultra-high molecular weight polyethylene or dense thermoplastic polyurethane.

Dense polyethylene membrane

One method known in the art to produce porous polyethylene membranes is through a wet or gel process. In this process, polyethylene is mixed with a hydrocarbon liquid and other additives. This mixture is heated over the polymer melt and extruded into a sheet. This sheet can then be orientated biaxially before and/or after the hydrocarbon liquid is extracted, producing a microporous membrane. Various process details are known, such as those disclosed in US 5,248,461 ; US 4,873,034; US 5,051 ,183; and US 6,566,012; each of which are hereby incorporated-by-reference in their entirety. Additional discussion includes Casting and stretching of filled and unfilled UHMW-polyethylene films, Ir.F.H. Assinck, Centre for polymers and composites, Eindhoven University of Technology, Nov 1995 and Porous Biaxially, drawn UHMWPE Films, H.M. Fortuin, DSM Research BV, Department of Materials Technology - Fifth Int. Conf, of Environmental Ergonomics.

A gel-processed UHMWPE membrane with a mass/area of 4.1 g/m², a bubble point of 139 psi, a thickness of 11.5 microns, a porosity of 62.0 %, a specific surface area 45.7 m²/g, a MD MTS of 228 MPa, a TD MTS of 174 MPa, a MD modulus of 442 MPa, and a TD modulus of 419 MPa made through the above referenced processes was obtained. The starting resin used to make the membrane had a molecular weight of 4,300,000 g/mol, according to the supplier.

A starting resin used to make the acoustic membrane had a molecular weight of 4,300,000 g/mol, according to the supplier. The acoustic membrane was drawn in the longitudinal/machine direction between banks of rolls at a gap distance of 36.3 cm over a heated plate set to a temperature of 128°C at a run speed of 2.13 m/min. The speed ratio between the second bank of rolls and the first bank of rolls, and hence the expansion ratio was 1.84:1.

The longitudinally drawn membrane was then drawn transversely at a temperature of approximately 145°C to a ratio of 4.94:1 at a run speed of 8 m/min at a strain rate of 4.3%/s for a residence time of 1.5 min. This was followed by a temperature treatment at 150°C for a residence time of 0.4375 min while restrained. The properties of the resultant membrane are detailed in Table 1. The resultant membrane is non-porous and has an airflow of less than 0.5 L/hr at 12 mbar and 2.99 cm². The matrix tensile strengths and mean 5-point moduli were calculated using an ASTM type D638-3 dog bone. The resulting gel-processed ultra-high- molecular-weight polyethylene (LIHMWPE) membrane with a mass per area of 4.11 g/m², a thickness of 7.4 pm, a matrix tensile strength in a first direction of (MTS MD=228 MPa), a matrix tensile strength in a second direction (orthogonal to the first direction) of (MTS TD=174 MPa).

Dense thermoplastic polyurethane

A commercially available thermoplastic non-porous polyurethane film was obtained. It was measured as having a thickness of 10 microns and a Young’s modulus of 50 MPa. For a given example vent assembly described in Table 2 below the first permeable layer and the second permeable layer comprises the same material and are provided in Table 1 below.

Table 1 : Example permeable layers used in the example vent assemblies

¹ Material airflow mean is 4559 ml/min/cm², tested by ATEQ D570 at pressure 70mbar ² Material airflow mean is 1916 ml/min/cm², tested by ATEQ D570 at pressure 70mbar

³ Material airflow mean is 613 ml/min/cm², tested by ATEQ D570 at pressure 70mbar

With reference to Figure 6, vent assemblies were assembled as described above and tested by holding the vent assembly 250 between a steel plate 272 and a cap 274. The steel plate 272 has a circular aperture 276 with a diameter of 1.5 mm. The cap 274 has a circular aperture

278 with a diameter of 1.5 mm.

Table 2: Example vent assembly units comprising membranes and lateral breathable (LB) layers and comparative examples (Examples 1 and 15).

PE = polyethylene, TPU = thermoplastic polyurethane.

1 psi = 6.9 kPa.

As can be seen, comparative example 1 includes a non-permeable dense polyethylene membrane that does not include any permeable layers or lateral breathable layers and so has no airflow across it but does provide good water entry pressure (WEP) performance. In contrast the examples have lower WEP due to the provision of an alternative route for water to flow. However, the comparative examples have no way to ventilate an acoustic transducer as shown by having no airflow through it. The examples provide good ventilation with a good airflow and increased acoustic performance. Accordingly, the example vent assembly units allow the membrane to be selected purely on acoustic considerations without also requiring the membrane to provide airflow for ventilation of the acoustic transducer. The provision of an enclosing element ensures that the interior of an electronic device is protected from any water that may pass through the permeable layers during use.

While there has been hereinbefore described approved embodiments of the present invention, it will be readily apparent that many and various changes and modifications in form, design, structure and arrangement of parts may be made for other embodiments without departing from the invention and it will be understood that all such changes and modifications are contemplated as embodiments as a part of the present invention as defined in the appended claims.

Claims

1. A vent assembly unit for use in an electronic housing, the vent assembly unit comprising an enclosing element and a vent assembly, the vent assembly comprising a first permeable layer, a substantially impermeable acoustic membrane, a second permeable layer, and an acoustic transducer; the first permeable layer positioned on a first side of the substantially impermeable acoustic membrane and the second permeable layer positioned on a second side of the substantially impermeable acoustic membrane; an acoustic volume is defined between the substantially impermeable acoustic membrane, the second permeable layer and the acoustic transducer; wherein the vent assembly unit is configured to be installed over an aperture in an enclosed container such that the enclosing element isolates the vent assembly from the internal volume of the enclosed container and a contained volume is defined between the vent assembly and the enclosing element, the vent assembly being configured during use such that an air pathway is provided from external of the enclosed container to the acoustic volume through the first permeable layer, through the contained volume and through the second permeable layer to the acoustic volume.

2. The vent assembly unit of claim 1 , wherein the acoustic transducer is mounted onto a substrate.

3. The vent assembly unit of any preceding claim, wherein the substantially impermeable acoustic membrane comprises silicone, polyurethane, polyethylene, polypropylene, Parylene C, Parylene N, polytetrafluoroethylene, polyether ether ketone (PEEK), polyimide, polyamide or combinations thereof.

4. The vent assembly unit of any preceding claim, wherein the substantially impermeable acoustic membrane has a thickness of from 0.25 pm to 50 pm.

5. The vent assembly unit of any preceding claim, wherein the first permeable layer comprises a polymer selected from polyethylene (PE), polypropylene (PP), Parylene C, Parylene N, polyphenylene sulfide (PPS) or polyethylene napthalate (PEN), polyamide, polyester, or a fluoropolymer such as polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafl uoroethylene- (perfluoroalkyl) vinyl ether copolymer (PFA), polytetrafluoroethylene (PTFE) and copolymers of the same.

6. The vent assembly unit of any preceding claim, wherein the first permeable layer comprises a fibrous polymer.

7. The vent assembly unit of any preceding claim, wherein the second permeable layer comprises a polymer selected from polyethylene (PE), polypropylene (PP), Parylene C, Parylene N, polyphenylene sulfide (PPS) or polyethylene napthalate (PEN), polyamide, polyester, or a fluoropolymer such as polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene- (perfluoroalkyl) vinyl ether copolymer (PFA), polytetrafluoroethylene (PTFE) and copolymers of the same.

8. The vent assembly unit of any preceding claim, wherein the second permeable layer comprises a fibrous polymer.

9. The vent assembly unit of any preceding claim, wherein the vent assembly comprises a support that is configured to support the substantially impermeable acoustic membrane.

10. The vent assembly unit of claim 9, wherein the support comprises a mesh or lattice.

11. The vent assembly of any preceding claim, wherein an adhesive layer is provided between the first permeable layer and the substantially impermeable acoustic membrane.

12. The vent assembly of any preceding claim, wherein an adhesive layer is provided between the second permeable layer and the substantially impermeable acoustic membrane.

13. An electronic device comprising a housing, the housing comprising a wall comprising a wall aperture and defining an internal volume, and a vent assembly unit provided occluding the aperture, the vent assembly unit comprising an enclosing element and a vent assembly, the vent assembly comprising a first permeable layer, a substantially impermeable acoustic membrane, a second permeable layer, and an acoustic transducer, the first permeable layer positioned on a first side of the substantially impermeable acoustic membrane and the second permeable layer positioned on a second side of the substantially impermeable acoustic membrane; wherein an acoustic volume is defined between the substantially impermeable acoustic membrane, the second permeable layer and the acoustic transducer; a contained volume is defined between the enclosing element and the vent assembly, wherein an acoustic pathway is formed from the aperture to the acoustic transducer through the first permeable layer, the substantially impermeable acoustic membrane and the second permeable layer and the substantially impermeable acoustic membrane spans the acoustic pathway, wherein an air pathway is provided from external of the electronic housing to the acoustic volume through the aperture, the first permeable layer and the second permeable layer, wherein the vent assembly is separated from the internal volume by the enclosing element such that the vent assembly is isolated from the internal volume by the enclosing element.

14. The electronic device of claim 13, wherein the acoustic transducer is mounted onto a substrate.

15. The electronic device of any of claim 13 to claim 14, wherein the internal volume comprises electronic components of the electronic device.

16. The electronic device of any of claim 13 to claim 15, wherein the first permeable layer comprises a first aperture.

17. The electronic device of any of claim 13 to claim 16, wherein the first permeable layer comprises a polymer selected from polyethylene (PE), polypropylene (PP), Parylene C, Parylene N, polyphenylene sulfide (PPS) or polyethylene napthalate (PEN), polyamide, polyester, or a fluoropolymer such as polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene- (perfluoroalkyl) vinyl ether copolymer (PFA), polytetrafluoroethylene (PTFE) and copolymers of the same.

18. The electronic device of any of claim 13 to claim 17, wherein the substantially impermeable acoustic membrane comprises silicone, polyurethane, polyethylene, polypropylene, Parylene C, Parylene N, polytetrafluoroethylene, polyether ether ketone (PEEK), polyimide, polyamide or combinations thereof.

19. The electronic device of any of claim 13 to claim 18, wherein the substantially impermeable acoustic membrane has a thickness of from 0.25 to 50 pm.

20. The electronic device of any of claim 13 to 19, wherein the vent assembly comprises a support configured to support the substantially impermeable acoustic membrane.

21. The electronic device of any of claim 13 to claim 20, wherein the second permeable layer comprises a second aperture.

22. The electronic device of any of claim 13 to claim 21 , wherein the second permeable layer comprises a polymer selected from polyethylene (PE), polypropylene (PP), Parylene C, Parylene N, polyphenylene sulfide (PPS) or polyethylene napthalate (PEN), polyamide, polyester, or a fluoropolymer such as polyvinylidene fluoride

(PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-(perfluoroalkyl) vinyl ether copolymer (PFA), polytetrafluoroethylene (PTFE) and copolymers of the same.