Improved vent

Abstract

There is provided a vent comprising a membrane and a first layer provided on a first side of the membrane, the first layer defining an aperture such that the membrane is exposed through the aperture, the aperture having a major dimension and a minor dimension, wherein the membrane has a machine direction and a transverse direction and the major dimension of the aperture of the first layer is oriented at an angle to the machine direction of the membrane of less than 90 degrees.

Description

[0001] Improved Vent

[0002] Field

[0003] The present disclosure relates to the field of acoustic vents, more specifically to improved acoustic vents and electronic devices comprising the same.

[0004] Background

[0005] Electronic devices that comprise acoustic transducers such as speakers and microphones often comprise vents or vent assemblies that protect such acoustic transducers from the contact with contaminants such as particulates or liquids. Such vents or vent assemblies typically occlude an aperture in the housing of the electronic device through which sound travels from or to the speaker or microphone respectively.

[0006] The materials used to make up the vents or vent assemblies are required to be resistant to the passage of particulates and liquids, especially liquid water, whilst also maximising the transmission of sound through them.

[0007] However, typical materials that meet these stringent requirements have been found to sometimes be prone to wrinkling of the membrane, either during manufacture or the assembly process. Such wrinkling can impact the acoustic performance of the membrane and can also impact the visual appearance of the vent and so any device within which they are installed.

[0008] Accordingly, there remains a need for improved vents and vent assemblies that have improved acoustic performance and improved visual appearance.

[0009] The present disclosure is intended at least in part to address at least one of these issues.

[0010] Summary

[0011] According to a first aspect there is provided a vent comprising a membrane and a first layer provided on a first side of the membrane, the first layer defining an aperture such that the membrane is exposed through the aperture, the aperture having a major dimension and a minor dimension, wherein the membrane has a machine direction and a transverse direction and the major dimension of the aperture of the first layer is oriented less than 90 degrees to the machine direction of the membrane.

[0012] As used herein, the term “machine direction” refers to the dominant dimension along which the membrane was processed during manufacture of the vent. For example, the machine direction may be the direction at which the membrane is taken from a roll of membrane and passed through rollers during manufacture of the vent. The term “transverse direction” as used herein refers to the direction or dimension that is 90 degrees to the machine direction.

[0013] Typically, the machine direction corresponds to the dimension of the membrane with the highest stiffness as measured using methods described herein. Accordingly, the machine direction of the membrane may run along a stiff dimension of the membrane.

[0014] The membrane may be an expanded membrane.

[0015] The membrane may comprise a fibrillated material. Accordingly, the membrane may comprise a material that includes a microstructure of fibrils. The fibrils may be interconnected at nodes and therefore, the microstructure may be a node and fibril structure.

[0016] The membrane may comprise a material selected from the group: polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), polyvinylidene fluoride (PVDF), polyethylene (PE), polyetherketoneketone (PEKK), polyether ether ketone (PEEK), poly(tetramethyl-p- silphenylenesiloxane) (PTMPS), polydimethylsiloxane (PDMS), polyparaxylylene (PPX), polyamide 6, polyurethane, thermoplastic polyurethane, polypropylene, polyimide (PI), or polyacrylonitrile (PAN) or combinations thereof.

[0017] In some embodiments the membrane may comprise a material selected from the group: PTFE, PE, PI or PEKK.

[0018] In embodiments where the membrane comprises an expanded material, the expanded material may be selected from the group: expanded PTFE (ePTFE), expanded FEP (eFEP), expanded PVDF (ePVDF), expanded polyethylene (ePE), expanded PEKK (ePEKK), expanded PEEK (ePEEK), expanded PTMPS (ePTMPS), expanded polydimethylsiloxane (ePDMS), expanded PPX (ePPX), expanded polyamide 6, expanded polyurethane, expanded thermoplastic polyurethane, expanded polypropylene, expanded polyimide, or expanded polyacrylonitrile (PAN) or combinations thereof.

[0019] The membrane may comprise an expanded material selected from the group: ePTFE, ePE, or ePEKK.

[0020] Typically, the aperture has an elongated shape that is larger in a first dimension than in an orthogonal second dimension. The major dimension of the aperture may be the first dimension and the minor dimension may be the second dimension. Therefore, the aperture may have an aspect ratio of the major dimension to minor dimension (“AR”) of greater than 1 .

[0021] The aperture may have a regular shape. The aperture may have at least one plane of symmetry. The aperture may have a major axis that extends along an at least one plane of symmetry. The major dimension may extend along the major axis. The aperture may have a second plane of symmetry. The aperture may have a minor axis that extends along the second plane of symmetry. The minor dimension may extend along the minor axis. The aperture may have a shape selected from ellipse, stadium, trapezium or rectangle. A stadium shape may also be referred to as a lozenge shape. The aperture may have a shape with two orthogonal symmetry planes. For example, the aperture may have a shape selected from an elongated hexagon, or an elongated octagon.

[0022] The aperture may have an irregular shape. For example, the aperture may have a generally elliptical, stadial, trapezoidal or rectangular shape with jagged or irregularly shaped edge.

[0023] In some embodiments the major dimension of the aperture may be oriented at an angle to the machine direction of the membrane of less than 45 degrees. The major dimension of the aperture may be oriented at an angle to the machine direction of the membrane of less than 25 degrees. The major dimension of the aperture may be oriented at an angle to the machine direction of the membrane of less than 10 degrees.

[0024] The major dimension of the aperture may be oriented at an angle to the machine direction of the membrane of from 0 degrees to 89 degrees. The major dimension of the aperture may be oriented at an angle to the machine direction of the membrane of from 0 degrees to 45 degrees. The major dimension of the aperture may be oriented at an angle to the machine direction of the membrane of from 0 degrees to 30 degrees. The major dimension of the aperture may be oriented at an angle to the machine direction of the membrane of from 0 degrees to 20 degrees. The major dimension of the aperture may be oriented at an angle to the machine direction of the membrane of from 0 degrees to 10 degrees. The major dimension of the aperture may be oriented at an angle to the machine direction of the membrane of from 0 degrees to 5 degrees.

[0025] For the avoidance of doubt, the ranges provided above are intended to include the end points of the ranges. The major dimension of the aperture may be oriented such that it is substantially parallel to the machine direction of the membrane. That is, the major dimension of the aperture may be oriented at an angle to the machine direction of the membrane of 0 degrees or from 0 degrees to 2 degrees.

[0026] In some embodiments, the aperture may have an aspect ratio of the major dimension to the minor dimension (AR) greater than 1. The aperture may have an AR greater than 1.1. the aperture may have an AR greater than 1 .2. the aperture may have an AR greater than 1 .4.

[0027] The aperture may have an AR from 1.1 to 3.0. The aperture may have an AR of from 1.2 to 1 .9. The aperture may have an AR of from 1 .2 to 1 .7.

[0028] For the avoidance of doubt, an aperture having an AR of 1 has a “major” dimension that is equal to a “minor” dimension. In other words, the dimensions of an aperture having an AR of 1 are equal. For example, an aperture having an AR of 1 may be a circle or square. The terms “major” and “minor” are used for terms of comparison and are given their standard meaning for apertures having an AR that is greater than 1.

[0029] The first layer may comprise an adhesive material. The first layer may comprise a pressure sensitive adhesive. The first layer may comprise an acrylic adhesive. The first layer may comprise a heat activated film adhesive. The first layer may comprise a polymeric material, for example, rubber. The first layer may comprise a rubber gasket. The first layer may comprise a layer configured to restrain the membrane to the first layer, for example at the boundary of the aperture. In this context, restrain may be taken to encompass at least the following; clamping, pinning, bonding. The first layer may comprise an adhesive supported on a film support. The film support may comprise polyester.

[0030] In some embodiments the vent may comprise a second layer provided on a second side of the membrane. The second side of the membrane may be on the opposed side of the membrane to the first side of the membrane. The second layer may define an aperture such that the membrane is exposed through the aperture. The aperture may have a major dimension and a minor dimension. The major dimension of the aperture of the second layer may be substantially aligned with the major dimension of the aperture of the first layer. The aperture defined by the second layer may have the same shape as the aperture defined by the first layer. The aperture defined by the second layer may have the same dimensions as the aperture defined by the first layer. The second layer may comprise an adhesive material. The second layer may comprise a cured adhesive material. The second layer may comprise a pressure sensitive adhesive. The second layer may comprise an acrylic adhesive. The second layer may comprise an adhesive supported on a film support. The second layer may comprise polyester film.

[0031] The vent of the present aspect may be less prone to wrinkling of the membrane of the vent. The vent of the present aspect may be substantially resistant to wrinkling of the membrane of the vent. The membrane may be substantially resistant to wrinkling during the manufacturing process. The membrane may be substantially resistant to wrinkling during use. For example, the membrane may be substantially resistant to wrinkling during use when the vent is installed within the housing of an electronic device.

[0032] The term “wrinkling” as used herein refers to deformation of the membrane that comprises an undulation of the membrane within the aperture defined by the first aperture, and within the aperture defined by the second aperture where present. Accordingly, a “wrinkled” membrane comprises a series of peaks and troughs (or “waves”) and the extent of wrinkling of the membrane or “waviness” can be characterised by measuring the average peak height (Wc) of the undulations of the membrane and the root mean square height (Wq) of those undulations. A large value of Wc or Wq corresponds to a membrane with more wrinkling / greater waviness than a membrane with a low value of Wc or Wq.

[0033] The membrane may have an at least reduced average peak height (Wc) compared to membranes of vents having a major dimension oriented at 90 degrees to the machine direction of the membrane using the method described herein.

[0034] The membrane may have a Wc that is less than the Wc of a membrane of a vent with an aperture that has an aspect ratio of 1. The membrane may have a Wc that is less than the Wc of a membrane of a vent with an aperture of the same cross-sectional area that has an aspect ratio of 1.

[0035] The membrane may have a Wc of less than 1.5 pm. The membrane may have a Wc of less than 1.2 pm. The membrane may have a Wc of less than 1 pm.

[0036] The membrane may have an at least reduced root mean square height (Wq) compared to membranes of vents having a major dimension oriented at 90 degrees to the machine direction of the membrane using the method described herein. The membrane may have a Wq that is less than the Wq of a membrane of a vent with an aperture that has an aspect ratio of 1 . The membrane may have a Wq that is less than the Wq of a membrane of a vent with an aperture of the same cross-sectional area that has an aspect ratio of 1 .

[0037] The membrane may have an improved Sound Pressure Level (SPL, dB) as measured using the method described herein. The membrane may have a SPL that is greater than that of a membrane of a vent with an aperture of the same cross-sectional area that has an aspect ratio of 1 as measured using the method described herein. The membrane may have a SPL that is greater than that of a membrane of a vent with an aperture of the same cross-sectional area that has an aspect ratio of 1 as measured using the method described herein at a frequency of from 100 Hz to, and including, 20kHz. The membrane may have a SPL that is greater than that of a membrane of a vent with an aperture of the same cross-sectional area that has an aspect ratio of 1 as measured using the method described herein at a frequency of 1 kHz. The membrane may have a SPL that is greater than that of a membrane of a vent with an aperture of the same cross-sectional area that has an aspect ratio of 1 as measured using the method described herein at a frequency of from 100 Hz to 2.5 kHz. The membrane may have a SPL that is greater than that of a membrane of a vent with an aperture of the same cross- sectional area that has an aspect ratio of 1 as measured using the method described herein at a frequency of from 100 Hz to 2 kHz. The membrane may have a SPL that is greater than that of a membrane of a vent with an aperture of the same cross-sectional area that has an aspect ratio of 1 as measured using the method described herein at a frequency of from 100 Hz to 10 kHz. The membrane may have a SPL that is greater than that of a membrane of a vent with an aperture of the same cross-sectional area that has an aspect ratio of 1 as measured using the method described herein at a frequency of from 100 Hz to 5kHz. The membrane may have a SPL that is greater than that of a membrane of a vent with an aperture of the same cross-sectional area that has an aspect ratio of 1 as measured using the method described herein at a frequency of from 100 Hz to 1kHz. The membrane may have a SPL that is greater than that of a membrane of a vent with an aperture of the same cross-sectional area that has an aspect ratio of 1 as measured using the method described herein at a frequency of from 500 Hz to 10 kHz. The membrane may have a SPL that is greater than that of a membrane of a vent with an aperture of the same cross-sectional area that has an aspect ratio of 1 as measured using the method described herein at a frequency of from 100 Hz to 2 kHz. The membrane may have a SPL that is greater than that of a membrane of a vent with an aperture of the same cross-sectional area that has an aspect ratio of 1 as measured using the method described herein at a frequency of from 100 Hz to 1.5 kHz. The membrane may have a SPL that is greater than that of a membrane of a vent with an aperture of the same cross- sectional area that has an aspect ratio of 1 as measured using the method described herein at a frequency of from 500 Hz to 1 kHz.

[0038] The membrane may have a greater SPL compared to a membrane having a machine direction oriented at 90 degrees to the major dimension in an aperture having the same aspect ratio. The difference in SPL may be calculated as SPL (0 degrees) minus SPL (90 degrees). The membrane may have a SPL that is at least 0.25 dB greater than a membrane having a machine direction oriented at 90 degrees to the major dimension in an aperture having the same aspect ratio. The membrane may have a SPL that is at least 0.5 dB greater than a membrane having a machine direction oriented at 90 degrees to the major dimension in an aperture having the same aspect ratio.

[0039] The membrane may have a SPL that is at least 0.25 dB greater than a membrane having a machine direction oriented at 90 degrees to the major dimension in an aperture having the same aspect ratio as measured at 1 kHz. The membrane may have a SPL that is at least 0.5 dB greater than a membrane having a machine direction oriented at 90 degrees to the major dimension in an aperture having the same aspect ratio as measured at 1 kHz.

[0040] The membrane may have a SPL that is at least 0.25 dB greater than a membrane having a machine direction oriented at 90 degrees to the major dimension in an aperture having the same aspect ratio as measured from 100 Hz to 10 kHz. The membrane may have a SPL that is at least 0.5 dB greater than a membrane having a machine direction oriented at 90 degrees to the major dimension in an aperture having the same aspect ratio as measured from 100 Hz to 10 kHz.

[0041] The membrane may have a percentage change in SPL (% 5SPL) of at least 0.1 % relative to a comparative vent that has an aperture defined in a first layer that has an aspect ratio of major dimension to minor dimension of 1 as measured using the methods described herein. The membrane may have a % 5SPL of at least 0.2% relative to a comparative vent that has an aperture defined in a first layer that has an aspect ratio of major dimension to minor dimension of 1 as measured using the methods described herein. The membrane may have a % 5SPL of at least 0.3% relative to a comparative vent that has an aperture defined in a first layer that has an aspect ratio of major dimension to minor dimension of 1 as measured using the methods described herein. The membrane may have a % 5SPL of at least 0.4% relative to a comparative vent that has an aperture defined in a first layer that has an aspect ratio of major dimension to minor dimension of 1 as measured using the methods described herein. The membrane may have a % 5SPL of at least 0.5% relative to a comparative vent that has an aperture defined in a first layer that has an aspect ratio of major dimension to minor dimension of 1 as measured using the methods described herein.

[0042] The percentage change in SPL (% 6SPL) may be calculated as:

[0043] % SSPLAR = ((SPLX-SPLARI) / SPLARI) X 100, (1) where SPLARI is the measured SPL for a membrane in a vent having an aperture with an aspect ratio of 1 , and SPLx is the measured SPL for the membrane in question as measured at the same frequency and same angle with an AR>1. Accordingly, a positive % SSPLAR corresponds to improved performance (i.e. a higher SPL for the article in question compared to a vent having an aperture with an aspect ratio of 1 (AR1)) and a negative % SSPLAR corresponds to reduced performance.

[0044] The membrane may have an improved % SSPLAR at a frequency of 100 Hz. The membrane may have an improved % SSPLAR at a frequency of 500 Hz. The membrane may have an improved % 5SPL at a frequency of 1 kHz. The membrane may have an improved % SSPLAR at a frequency of 2 kHz. The membrane may have an improved % SSPLAR at a frequency of from 100 Hz to 2.5 kHz. The membrane may have an improved % SSPLAR at a frequency of from 500 Hz to 2.5 kHz. The membrane may have an improved % SSPLAR at a frequency of from 1 kHz to 2.5 kHz.

[0045] In a second aspect there is provided a vent comprising a membrane and a first layer provided on a first side of the membrane, the first layer defining an aperture such that the membrane is exposed through the aperture, the aperture having a major dimension and a minor dimension, wherein the membrane has a first dimension and a second dimension, the first dimension being orthogonal to the second dimension and the membrane having a greater stiffness in the first dimension than in the second dimension, wherein the major dimension of the aperture of the first layer is oriented at an angle to the first dimension of the membrane of less than 90 degrees.

[0046] The first dimension typically corresponds to the machine direction as defined above for the first aspect.

[0047] For the avoidance of doubt, optional features of the vent of the first aspect are optional features of the second aspect, and features of the first aspect corresponding to the machine direction of the membrane apply to the first dimension of the membrane in the second aspect. In a third aspect there is provided an electronic device comprising a housing, a vent of the first aspect and an acoustic transducer, the housing defining an aperture and the vent spanning the aperture such that the vent is positioned between the exterior of the housing and the acoustic transducer.

[0048] The acoustic transducer may be a microphone or a speaker.

[0049] The electronic device may be personal communication device.

[0050] According to a fourth aspect there is provided a method of making a vent according to the first aspect or the second aspect, the method comprising the steps: providing a roll of membrane; providing a first sheet of adhesive defining a plurality of apertures; unrolling a length of membrane from the roll of membrane in a machine direction; applying the first sheet of adhesive to the membrane such that the plurality of apertures are oriented at an angle of less than 90 degrees to the machine direction to form a laminate sheet; and cutting the laminate sheet to form the vent of the first aspect or the second aspect.

[0051] Typically, the apertures of the plurality of apertures are elongate and have a major dimension and a minor dimension.

[0052] As the membrane is unrolled, the membrane may be stretched in the machine direction. The membrane and first sheet of adhesive may be contacted and fed between a pair of rollers to form the laminate sheet. Pressure may be applied to the membrane and first sheet of adhesive to form the laminate sheet. The membrane of the vent formed by the method may have a strong direction that corresponds to the machine direction. The strong direction may have a higher strength than in the transverse direction that is at right angles or perpendicular to the machine direction or strong direction.

[0053] The machine direction of the membrane of the vent formed by the method of the present aspect may have a higher Young’s modulus than in the transverse direction. The machine direction of the membrane of the vent formed by the method of the present aspect may have a higher tension than in the transverse direction. One aperture of the adhesive sheet corresponds to the aperture of the vent of the first aspect. For the avoidance of doubt, features of the aperture of the first aspect are features of the aperture of the adhesive sheet of the method of the present aspect.

[0054] The membrane used in the present aspect corresponds to the membrane of the vent of the first aspect. For the avoidance of doubt, features of the membrane of the first aspect are features of the membrane of the method of the present aspect.

[0055] The method may comprise a step of providing a second sheet of adhesive defining a plurality of apertures. The method may comprise a step of applying the second sheet of adhesive to the membrane such that the plurality of apertures are oriented at an angle of less than 90 degrees to the machine direction to form a laminate sheet. The step of applying the second sheet of adhesive to the membrane may be carried out after the step of applying the first sheet of adhesive to the membrane. The step of applying the second sheet of adhesive to the membrane may be carried out at the same time as the step of applying the first sheet of adhesive to the membrane. The apertures of the plurality of apertures of the first sheet of adhesive and the apertures of the plurality of apertures of the second sheet of adhesive may be oriented at the same or substantially the same angle to the machine direction of the membrane.

[0056] Accordingly, the laminate sheet comprising a first sheet of adhesive and a second sheet of adhesive may be a sandwich laminate with the membrane provided between the first sheet of adhesive and the second sheet of adhesive.

[0057] Brief Description of the Figures

[0058] Embodiments of the present invention will now be described, by way of non-limiting example, with reference to the accompanying drawings.

[0059] Figure 1 : A top down view of a vent according to an embodiment where the machine direction (MD) of the membrane of the vent is aligned with the major dimension of the aperture;

[0060] Figure 2: A top down view of a vent according to an embodiment where the machine direction (MD) of the membrane of the vent is perpendicular to the major dimension of the aperture;

[0061] Figure 3: A top down view of a vent according to the art;

[0062] Figure 4: A side cross-sectional view of a vent according to an embodiment;

[0063] Figure 5: A side cross-sectional view of a vent according to an embodiment;

[0064] Figure 6: A top down view of a vent according to an embodiment where the machine direction (MD) of the membrane of the vent is aligned with the major dimension of the aperture; Figure 7: A top down view of a vent according to an embodiment where the machine direction (MD) of the membrane of the vent is perpendicular to the major dimension of the aperture;

[0065] Figure 8: A plot of % SSPLAR from 100 to 10000 Hz for vents having an expanded polyethylene membrane and a stadium aperture with an aspect ratio of from 1.2 to 2.1 with the major dimension of the aperture at 90 degrees to the machine direction or at 0 degrees to the machine direction;

[0066] Figure 9: A plot of % SSPLAR from 100 to 10000 Hz for a vents having an expanded polyethylene membrane and a rectangular aperture with an aspect ratio of from 1.2 to 2.1 with the major dimension of the aperture at 90 degrees to the machine direction or at 0 degrees to the machine direction;

[0067] Figure 10: A plot of root mean square height (Wq) for vents having an expanded polyethylene membrane and a stadium aperture with an aspect ratio of from 1.2 to 2.1 with the major dimension of the aperture at 90 degrees to the machine direction (filled circles) or at 0 degrees to the machine direction (open circles) and for vents having an expanded polyethylene membrane and a rectangular aperture with an aspect ratio of from 1.2 to 2.1 with the major dimension of the aperture at 90 degrees to the machine direction or at 0 degrees to the machine direction;

[0068] Figure 11 : A plot of average peak height (Wc) for vents having an expanded polyethylene membrane and a stadium aperture with an aspect ratio of from 1.2 to 2.1 with the major dimension of the aperture at 90 degrees to the machine direction (filled circles) or at 0 degrees to the machine direction (open circles) and for vents having an expanded polyethylene membrane and a rectangular aperture with an aspect ratio of from 1.2 to 2.1 with the major dimension of the aperture at 90 degrees to the machine direction or at 0 degrees to the machine direction;

[0069] Figure 12: A plot of delta SPL (0 degree minus 90 degrees) for vents having an expanded polyethylene membrane and a rectangular aperture with an aspect ratio of from 1.2 to 2.1 ;

[0070] Figure 13: A plot of delta SPL (0 degree minus 90 degrees) for vents having an expanded polyethylene membrane and a stadium shaped aperture with an aspect ratio of from 1 .2 to 2.1 ;

[0071] Figure 14: A plot of average peak height (Wc) for vents having an expanded polyethylene membrane and a rectangular aperture with an aspect ratio of from 1.2 to 2.1 with the major dimension of the aperture at 90 degrees to the machine direction or at 0 degrees to the machine direction and for vents having an expanded polyethylene membrane and a rectangular aperture with an aspect ratio of from 1.2 to 2.1 with the major dimension of the aperture at 90 degrees to the machine direction or at 0 degrees to the machine direction;

[0072] Figure 15: A plot of root mean square height (Wq) for vents having an expanded polyethylene membrane and a rectangular aperture with an aspect ratio of from 1.2 to 2.1 with the major dimension of the aperture at 90 degrees to the machine direction or at 0 degrees to the machine direction and for vents having an expanded polyethylene membrane and a rectangular aperture with an aspect ratio of from 1.2 to 2.1 with the major dimension of the aperture at 90 degrees to the machine direction or at 0 degrees to the machine direction;

[0073] Figure 16: A plot of % SSPLAR from 100 to 10000 Hz for vents having an expanded dense polyethylene membrane and a rectangular aperture with an aspect ratio of 1.7 and 2.1 with the major dimension of the aperture at 0 degrees to the machine direction;

[0074] Figure 17: A plot of % SSPLAR from 100 to 10000 Hz for vents having an expanded polytetrafluoroethylene (ePTFE) membrane and a rectangular aperture with an aspect ratio of from 1.2 to 2.1 with the major dimension of the aperture at 90 degrees to the machine direction or at 0 degrees to the machine direction;

[0075] Figure 18: A plot of Wq for vents having an ePTFE membrane and a rectangular aperture with an aspect ratio of from 1.2 to 2.1 with the major dimension of the aperture at 90 degrees to the machine direction or at 0 degrees to the machine direction;

[0076] Figure 19: A plot of Wc for vents having an ePTFE membrane and a rectangular aperture with an aspect ratio of from 1.2 to 2.1 with the major dimension of the aperture at 90 degrees to the machine direction or at 0 degrees to the machine direction;

[0077] Figure 20: A plot of delta SPL (0 degree minus 90 degrees) for vents having an expanded polytetrafluoroethylene membrane and a rectangular aperture with an aspect ratio of from 1.2 to 2.1 ;

[0078] Figure 21 : A plot of % SSPLAR from 100 to 10000 Hz for vents having an expanded polytetrafluoroethylene (ePTFE) membrane and a rectangular aperture with an aspect ratio of from 1.2 to 2.1 with the major dimension of the aperture at 90 degrees to the machine direction or at 0 degrees to the machine direction;

[0079] Figure 22: A plot of delta SPL (0 degree minus 90 degrees) for vents having an expanded polytetrafluoroethylene membrane and a rectangular aperture with an aspect ratio of from 1.2 to 2.1 ;

[0080] Figure 23: A plot of Wc for vents having an ePTFE membrane and a rectangular aperture with an aspect ratio from 1 .2 to 2.1 with the major dimension of the aperture at 90 degrees to the machine direction or at 0 degrees to the machine direction;

[0081] Figure 24: A plot of Wq for vents having an ePTFE membrane and a rectangular aperture with an aspect ratio from 1 .2 to 2.1 with the major dimension of the aperture at 90 degrees to the machine direction or at 0 degrees to the machine direction;

[0082] Figure 25: A plot of % SSPLAR from 100 to 10000 Hz for vents having an PEKK membrane and a rectangular aperture with an aspect ratio of from 1 .2 to 2.1 with the major dimension of the aperture at 90 degrees to the machine direction or at 0 degrees to the machine direction; Figure 26: A plot of delta SPL (0 degree minus 90 degrees) for vents having an PEKK membrane and a rectangular aperture with an aspect ratio of from 1 .2 to 2.1 ;

[0083] Figure 27: A schematic side view of a nip roller machine that is used to laminate an adhesive layer comprising a plurality of apertures to a membrane;

[0084] Figure 28: An image of a vibrometry scan showing operational deflection shape of high frequency mode vibrations of the (3,1) split mode pair for rectangular shaped apertures having a machine direction perpendicular to the major dimension of the aperture;

[0085] Figure 29: An image of a vibrometry scan showing operational deflection shape of high frequency mode vibrations of the (3,1) split mode pair for rectangular shaped apertures having a machine direction parallel (at 0 degrees) to the major dimension of the aperture;

[0086] Figure 30: An image of a vibrometry scan showing operational deflection shape of high frequency mode of the (1 ,1) split mode pair for a circular aperture; and

[0087] Figure 31 : A schematic of an exemplary stadium shaped vent with the dimensions denoted;

[0088] Figure 32: A schematic of an exemplary rectangular shaped vent with the dimensions denoted;

[0089] Figure 33: Plots of delta SPL for vents having an expanded polyethylene membrane and a rectangular aperture with an aspect ratio of from 1.2 to 2.1 for a range of angles of the major dimension of the vent aperture to the machine direction of the membrane; and

[0090] Figure 34: Plots of delta SPL for vents having an electrospun polyimide membrane and a rectangular aperture with an aspect ratio of from 1.2 to 2.1 for a range of angles of the major dimension of the vent aperture to the machine direction / stiff dimension of the membrane.

[0091] Detailed Description

[0092] 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.

[0093] 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

[0094] Method of measuring Wc and Wg

[0095] Optical micrographs were collected using a Keyence VR-3000 One-shot 3D Measurement Microscope at a magnification of 80x. Image files were post processed in the VR-3000 Series Analyzer Software and levelled (correct for any tilt of sample relative to sample stage) prior to evaluating waviness. To evaluate waviness the [Line R] function button was selected from the functions toolbar and the measurement type was set to waviness. A 2 point profile line was drawn vertically that spanned the entire length of the membrane. Cutoff filter values were set to default (none) and the evaluation length of the 2 point vertical profile line was automatically set by the Keyence post processing software. The software then automatically calculates the Waviness parameters of interest, which are the mean waviness height, Wc, and the root mean square waviness height, Wq. The Keyence Analyzer Software calculates roughness and waviness parameters in compliance with ISO4287:1997 Surface roughness- Definitions.

[0096] Method of measuring orientation of major dimension of aperture re machine direction of membrane

[0097] The angle between the machine direction of the membrane and the major dimension of an aperture was controlled using pre-made adhesive templates in AutoCAD that are laser cut with pre-defined aperture sizes, orientation angles and aspect ratios. The membrane is then placed onto a pay-off roller on a mini-laminator (schematically shown in Figure 27) and fed through two nip rollers. An adhesive template with pre-cut ID shapes is inserted into the nip roller parallel with the membrane and the two are laminated together. An identical pre-cut template is placed over the membrane laminated onto the bottom template to make captive parts such that the membrane is sandwiched between two layers of pressure sensitive adhesive. A feed tray is used prior to the nip rollers to maintain alignment between the major axis of the apertures in the template and the unspooling direction of the membrane as the two are fed through the nip rollers and laminated together. The orientation angle between the machine direction of the polymer and the major dimension of the aperture in the finished parts is confirmed / measured using scanning laser doppler Vibrometry.

[0098] Vibrometry was used to visualize the vibrational mode shapes of the membrane within a vent which can then be used to identify the orientation of the dimension of highest stiffness (typically the machine direction) of the polymer. For example, the machine direction of the polymer with a rectangular aperture is always oriented orthogonal to the nodal lines of a high frequency split mode pair like the (3,1) mode, for example, and example images are shown in Figures 28 and 29. For circle and lozenge / stadium shaped apertures the nodal lines of the high frequency (1 ,1) vibrational mode can be used as shown in Figure 30, for example.

[0099] For the examples shown in Figures 28 and 29 both have the major dimension of the aperture oriented horizontally. However, the nodal lines of the mode run horizontally for Figure 28 and vertically for Figure 29. Accordingly, the angle between the major dimension of the aperture and the machine direction is 90 degrees. The angle between the major dimension of the aperture and the machine direction for the example of Figure 29 is 0 degrees. In other words, the machine direction of the membrane and the major dimension of the aperture are aligned.

[0100] Method of measuring sound pressure level

[0101] The Sound Pressure Level (SPL) of example vents was made by detecting an acoustic test signal after it passes through the vent.

[0102] The acoustic response of the samples, measured in units of dB, was measured using a MEMS microphone fixture placed inside a Bruel & Kjaer 4232 anechoic box at a distance of 6.5 cm from an internal speaker. SoundCheck 5.0 software and AmpConnect hardware (both acquired commercially from Listen Inc) were used to record the output response curve. An SCM-3 reference microphone (Listen Inc.) and calibrator (Bruel & Kjaer) were used to generate a calibration sequence prior to measuring the sample. A sample fixture was designed to accept the sample coupon which holds the sample to be tested. The speaker performs a frequency sweep at 94 dB sound pressure level over a frequency range from 100 Hz to 10 kHz. The measurement microphones measure the acoustic response as a sound pressure level in dB over the frequency range. In general, the dB SPL value can be compared against a predetermined baseline signal measured at the same 94 dB reference level without a sample being present or to another sample that was prepared at a different angle or aspect ratio. A larger dB SPL value at a given frequency corresponds to better acoustic performance.

[0103] General

[0104] With reference to Figures 1 and 4, a vent 1 comprises a membrane 2 and a first adhesive layer 4 (acting as a first layer), the first adhesive layer 4 defining an aperture 6 having a stadium shape. The aperture 6 has a major dimension 8 and a minor dimension 10. The membrane 2 comprises expanded polyethylene and the machine direction (MD) of the membrane 2 is oriented to be parallel to the major dimension 8 of the aperture 6. The first adhesive layer 4 comprises a pressure sensitive acrylic adhesive. Referring to Figure 2, a comparative vent 20 comprises a membrane 22 and a first adhesive layer 24, the first adhesive layer 24 defining an aperture 26 having a stadium shape. The aperture 26 has a major dimension 28 and a minor dimension 30. The membrane 22 comprises expanded polyethylene and the machine direction (MD) of the membrane 22 is oriented to be perpendicular to the major dimension 28 of the aperture 26. The first adhesive layer 24 comprises a pressure sensitive acrylic adhesive. In addition, with reference to Figure 3, a standard vent 40 comprises a membrane 42 and a first adhesive layer 44 (acting as a first layer), the first adhesive layer 44 defining an aperture 46 having a circular cross-sectional shape. Accordingly, the aperture 46 has a diameter 48 and an aspect ratio of 1 (i.e. the width dimension equals the length dimension). The membrane 42 comprises expanded polyethylene. The first adhesive layer 44 comprises a pressure sensitive acrylic adhesive.

[0105] Figure 5 shows an alternative vent 50 in cross-section that corresponds to the features of the example of Figure 1 with a second adhesive layer 52 (acting as a second layer) provided on a second side of the membrane 2 that defines an aperture 54 that has the same shape and dimensions as the aperture 6 defined in the first adhesive layer 4.

[0106] With reference to Figure 6 a vent 60 comprises a membrane 62 and a first adhesive layer 64 (acting as a first layer), the first adhesive layer 64 defining an aperture 66 having a rectangular shape. The aperture 66 has a major dimension 68 and a minor dimension 70. The membrane 62 comprises ePTFE and the machine direction (MD) of the membrane 62 is oriented to be parallel to the major dimension 68 of the aperture 66. The first adhesive layer 64 comprises a pressure sensitive acrylic adhesive.

[0107] Referring to Figure 7 a comparative vent 80 comprises a membrane 82 and a first adhesive layer 84 (acting as a first layer), the first adhesive layer 84 defining an aperture 86 having a rectangular shape. The aperture 86 has a major dimension 88 and a minor dimension 90. The membrane 82 comprises ePTFE and the machine direction (MD) of the membrane 82 is oriented to be perpendicular to the major dimension 88 of the aperture 86. The first adhesive layer 84 comprises a pressure sensitive acrylic adhesive.

[0108] An exemplary method (100) of making a vent according to the present disclosure is shown by the schematic of Figure 27. A first sheet of adhesive 110 is provided as a template having apertures 112 defined therein. The first sheet of adhesive 110 is formed from a double sided pressure sensitive adhesive sheet. In this example, the first sheet of adhesive is 2 ft long by 4 in wide. The specific adhesives used for each example are detailed below. One side of the adhesive liner was removed and adhered to a comparably sized 165-pm-thick piece of low- tac PET release liner. A drawing was created in AutoCAD that specified the size, shape and orientation angle of an array of acoustic vents to be cut. The AutoCAD drawing was then loaded into the laser control software and the adhesive sheets placed inside the laser bay for cutting. This first round of cutting cuts out the active area or inside of the parts.

[0109] Next, the final release liner was removed from the adhesive sheet 110 and the adhesive sheet 100 was loaded into the feed tray 120 of a mini-laminator.

[0110] The first sheet of adhesive 110 is inserted into a feed tray 120 and is fed (in the direction shown by arrow 115) to a pair of nip rollers 130. The first adhesive sheet 110 can be orientated as required to provide the required orientation of the apertures 112 for forming the vents of the present disclosure (for example, as discussed above in Figures 1 to 7).

[0111] The method 100 comprises providing a roll of membrane 150 and unrolling a length of membrane 155 from the roll of membrane 150 in a machine direction MD. The length of membrane 155 is also fed to nip rollers 130 where the membrane 155 is contacted with the first adhesive sheet 110 forming a laminate 160 at an output 140 from the nip rollers 130. The feed tray 110 aligns the first adhesive sheet with the membrane 155 which is placed on a payoff roller and fed into a nip roller 130 where the membrane 155 is laminated to the adhesive sheet 110. The resulting laminate 160 is then cut to form the vent according to the present disclosure, wherein one aperture 112 of the first adhesive sheet 110 corresponds to an aperture of the vent.

[0112] A second adhesive sheet may be provided to form a second adhesive layer 54 as shown in Figure 5. The second adhesive sheet can also be fed to the nip rollers 130 and contacted with the length of membrane 155 such that the membrane 155 is sandwiched between the first adhesive sheet 110 and the second adhesive sheet. The resulting laminate can be cut to form the vent 50 of Figure 5.

[0113] Where two layers of adhesive are provided, a second layer of adhesive (for example, a double sided adhesive sheet measuring 4inches x 24inches) is adhered to 5-pm-thick layer of PET (4inches x 24inches) and loaded into the laser bay for cutting. Once cut, this layer will be placed on top of the laminate 160 (i.e the membrane 155 which has already been laminated to the first adhesive sheet 110 with precut apertures 112) to form a captive layer. The final layered assembly of the laminate 160 and the second adhesive sheet is loaded back into the laser and the laser performs the final cuts of each individual part in the array. It is possible to use die cutting as opposed to laser cutting, and die cutting was used in example 16 below. The stack-up of all the finished parts (including the low-tac liner beneath the parts) is 165-um- thick low-tac PET release liner / double sided adhesive / membrane / double sided adhesive / 50um-thick-PET.

[0114] The individual parts were picked off the release liner and carefully adhered to a pre-cut FR4 coupon having matching active area and aspect ratio. For example, rectangular parts having AR = 1.7 were adhered to FR4 coupons that were pre-cut to have a rectangular opening in the center with a matching AR = 1.7 aspect ratio. Circular parts having AR = 1 were adhered to FR4 coupons pre-cut to have a circular opening with AR = 1. The FR4 was obtained commercially from McMaster Carr (product # 1331T37) and laser cut into coupons. The coupons are 381 urn thick and serve as a platform to mount the sample to for acoustic testing, for example.

[0115] Materials

[0116] Figures 8 to 13 show analysis of vents of examples 1 to 12 comprising an expanded polyethylene membrane. The method of making the polyethylene membrane is not particularly limited and any method known in the art may be used, as long as the membrane has the required properties. 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.

[0117] 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.

[0118] The polyethylene membrane of the present disclosure may be made by a “gel process” for producing a dense polyethylene film, which is described in numerous documents such as US 4,948,544. For example, the polyethylene membrane may be formed by dissolving a polyethylene polymer in a solvent to form a solution, shaping the solution into a tape or sheet at a temperature above the solution temperature of the polyethylene polymer, cooling the tape or sheet to a temperature below the solution temperature to achieve gelation of the tape or sheet, removing the solvent from the gelled tape or sheet and biaxially stretching the gelled tape or sheet above the melt temperature to form the dense polyethylene membrane.

[0119] A starting resin was used to make the membrane that had a molecular weight of 4,300,000 g / mol, according to the supplier. The resulting membrane in examples 1 to 12 had a mass per area of 2.63 g / m2, an airflow of 4.9 L / hr at 12 mbar and 2.99 cm2, a thickness of 9.6 pm, an ultimate tensile strength in a first direction of 76 MPa, an ultimate tensile strength in a second direction (orthogonal to the first direction) of 65 MPa. The properties are also outlined in Table I .The starting resin used to make the membrane that had a molecular weight of 4,300,000 g / mol, according to the supplier

[0120] The adhesive used for the formation of the vents analysed in Figures 8 to 13 (examples 1 to 12) was a pressure sensitive adhesive purchased from Nitto Denko with part number: Nitto Denko No. 5605R.

[0121] Figures 14 and 15 show analysis of vents of examples 14 to 19 comprising an expanded polyethylene membrane having the properties outlined in Table 1 , and manufactured according to the same methods as outlined above for examples 1 to 12. The membrane is a gel-processed ultra-high-molecular-weight polyethylene (LIHMWPE) membrane with a mass per area of 3.65 g / m2, an airflow of 4 L / hr at 12 mbar and 2.99 cm2, a thickness of 12 pm, an ultimate tensile strength in a first direction of 78.4 MPa, an ultimate tensile strength in a second direction (orthogonal to the first direction) of 63.3 MPa was used as a precursor in this example. The starting resin used to make the membrane had a molecular weight of 4,300,000 g / mol, according to the supplier. The adhesive used for the formation of the vents analysed in Figures 14 and 15 (examples 14 to 19) was a pressure sensitive adhesive purchased from Nitto Denko with part number: Nitto Denko No. 5605R.

[0122] Figure 16 shows analysis of vents comprising densified expanded polyethylene membrane which was formed according to the teachings of US4948544, which is hereby incorporated- by-reference in its entirety. The membrane has the properties as outlined in Table 1. The adhesive used for the formation of the vents analysed in Figure 16 was a pressure sensitive adhesive purchased from Nitto Denko with part number: Nitto Denko No. 5605BRN.

[0123] Figures 17 to 20 show analysis of vents of examples 20 to 25 comprising an expanded polytetrafluoroethylene (ePTFE) membrane obtained from W. L. Gore & Associates, Inc. under part number GAW344, manufactured according to the teachings of US3953566 and each of which are hereby incorporated-by-reference in their entirety. The adhesive used for the formation of the vents analysed in Figures 17 to 20 was a pressure sensitive adhesive purchased from Tesa SE with part number: Tesa 4972 The properties of the membrane are shown in Table 1.

[0124] Figures 21 to 24 show analysis of vents of examples 26 to 31 comprising an expanded polytetrafluoroethylene (ePTFE) membrane obtained from W. L. Gore & Associates, Inc. under part number GAW337, manufactured according to the teachings of US3953566, which is hereby incorporated-by-reference in its entirety. The adhesive used for the formation of the vents analysed in Figures 17 to 20 was a pressure sensitive adhesive purchased from Tesa SE with part number: Tesa 4972. The properties of the membrane are shown in Table 1.

[0125] The examples of Figures 25 and 26 included a Polyetherketoneketone (PEKK) material (NovaSpire™ PEKK AM) having mechanical properties shown in Table 1 was obtained commercially through Solvay Specialty Polymers. The adhesive used for the formation of the vents analysed in Figures 25 and 26 was a pressure sensitive adhesive purchased from Nitto Denko with part number: Nitto Denko No. 5605R.

[0126] Figure 34 shows delta SPL results for an electrospun polyimide membrane. The electrospun polyimide membrane was made as follows. A condensation polymerization reaction between a diamine monomer and a tetracid dianhydride was performed in a kettle with mechanical agitation in a high polar solvent. This process yielded a copolymerized polyimide acid spinning solution. The polymer solution was then spun with electrospinning equipment, in which high voltage was applied to direct the jet towards the other electrode at high speed where a collector is used to collect the fibers which are formed due to the forces on the electrospinning solution. The spun mat was heat treated to obtain an imidized copolymerized polyimide web that contains nanofibers.

[0127] The resulting polyimide nanofiber web has properties shown in Table 1 below.

[0128] T able 1 - Properties of the membranes used in the vents exemplified in the present disclosure listing: membrane material type, machine direction Young’s modulus (MD), transverse direction Young’s modules (TD), the Geometric Mean Modulus or GeoMean Modulus for short (calculated as the square root of the product of the Young’s modulus along the polymer machine direction (MD) and Young’s modulus along the polymer’s transverse direction (TD): GeoMean Modulus = Sqrt[(MD-Modulus)x(TD-Modulus)], mass per area (MPA), thickness, and porosity. Examples

[0129] Table 2 - Comparison of waviness characteristics for example vents comprising an ePE membrane with the major dimension oriented at 0 degrees or at 90 degrees to the machine direction of the membrane, having stadium shaped apertures (examples 2-6 denoted by L2 to L6 in the Figures), having rectangular shaped apertures (examples 8-12, denoted by R2 to R6 in the Figures) and comparative vents comprising an ePE membrane having a circular aperture (example 1 (comp), denoted by C1) and a square aperture (example 7 (comp) denoted by S1). The dimensions of the vent shapes according to the examples are provided in Table 6 using the same references C1 , S1 , L2 to L6, and R2 to R6.

[0130] The Wc and Wq parameters are shown in Figures 10 and 11 and corresponding SPL data for these examples is shown in Figures 8 (% SSPLAR, examples 2-6) and 9 (% SSPLAR, examples 8-12). As can be seen, the examples that have the major dimension of the aperture oriented at 0 degrees to the machine direction of the membrane (open circles) has both reduced Wc and Wq parameters indicating reduced waviness or wrinkling of the membranes and significantly improved percentage change of SPL relative to the comparative example with AR of 1 (% SSPLAR) compared to vents that have the major dimension of the aperture oriented at 90 degrees to the machine direction (filled circles) of the membrane. Delta SPL (SPLo - SPL90) is shown in Figures 12 (examples 8-12) and 13 (examples 2-6) and a clear improvement in SPL is demonstrated for all examples having the machine direction oriented at an angle of 0 degrees to the major dimension of the aperture compared to examples at 90 degrees.

[0131] Table 3 - Comparison of waviness characteristics for example vents comprising an ePE membrane with the major dimension oriented at 0 degrees or at 90 degrees to the machine direction of the membrane, having rectangular shaped apertures (examples 15-19) and a comparative vent comprising an ePE membrane having a square aperture (example 14 (comp)).

[0132] The Wc and Wq parameters are shown in Figure 14 (Wc) and Figure 15 (Wq). As can be seen, the examples that have the major dimension of the aperture oriented at 0 degrees to the machine direction of the membrane has both reduced Wc and Wq parameters indicating reduced waviness or wrinkling of the membranes compared to vents that have the major dimension of the aperture oriented at 90 degrees to the machine direction of the membrane.

[0133] The % SSPLAR for example vents comprising densified expanded polyethylene membranes and apertures that have a rectangular cross-sectional shape (denoted by R4 and R6) is shown in Figure 16. The data shows that orienting the major axis of the aperture at 0 degrees to the machine direction of the membrane improves SPL of the vent compared to vents that have an AR of 1.

[0134] Table 4 - Comparison of waviness characteristics for example vents comprising an ePTFE membrane with the major dimension oriented at 0 degrees or at 90 degrees to the machine direction of the membrane, having rectangular shaped apertures (examples 21-25, denoted by R2 to R6) and a comparative vent comprising an ePTFE membrane having a square aperture (example 20 (comp) denoted by S1).

[0135] The data of Table 4 are shown in Figures 18 and 19 and show that for example vents that have the major dimension of the aperture oriented at 0 degrees to the machine direction of the membrane has both reduced Wc and Wq parameters indicating reduced waviness or wrinkling of the membranes compared to vents that have the major dimension of the aperture oriented at 90 degrees to the machine direction of the membrane.

[0136] Further, the % SSPLAR for these examples is shown in Figure 17 and shows that for example vents that have the major dimension of the aperture oriented at 0 degrees to the machine direction of the membrane has improved % SSPLAR compared to vents that have the major dimension of the aperture oriented at 90 degrees to the machine direction of the membrane.

[0137] Delta SPL (SPLo - SPL90) is shown in Figure 20 and a clear improvement in SPL is demonstrated for all examples having the machine direction oriented at an angle of 0 degrees to the major dimension of the aperture compared to examples at 90 degrees.

[0138] Table 5 - Comparison of waviness characteristics for example vents comprising an ePTFE membrane with the major dimension oriented at 0 degrees or at 90 degrees to the machine direction of the membrane, having rectangular shaped apertures (examples 27-31 , denoted by R2 to R6) and a comparative vent comprising an ePTFE membrane having a square aperture (example 26 (comp) denoted by S1).

[0139] The data of Table 5 are shown in Figures 23 (Wc) and 24 (Wq) and show that for example vents that have the major dimension of the aperture oriented at 0 degrees to the machine direction of the membrane has both reduced Wc and Wq parameters indicating reduced waviness or wrinkling of the membranes compared to vents that have the major dimension of the aperture oriented at 90 degrees to the machine direction of the membrane.

[0140] Further, the % SSPLAR for these examples is shown in Figure 21 and shows that for example vents that have the major dimension of the aperture oriented at 0 degrees to the machine direction of the membrane has improved % SSPLAR compared to vents that have the major dimension of the aperture oriented at 90 degrees to the machine direction of the membrane.

[0141] Delta SPL (SPLo - SPL90) is shown in Figure 22 and a clear improvement in SPL is demonstrated for all examples having the machine direction oriented at an angle of 0 degrees to the major dimension of the aperture compared to examples at 90 degrees.

[0142] Further example vents comprising a PEKK membrane and an aperture having a rectangular cross-sectional shape (corresponding to R2 to R6) also demonstrate improved % SSPLAR (Figure 25) for example vents that have the major dimension of the aperture oriented at 0 degrees to the machine direction of the membrane compared to vents that have the major dimension of the aperture oriented at 90 degrees to the machine direction of the membrane. Delta SPL (SPLo - SPL90) is shown in Figure 26 and a clear improvement in SPL is demonstrated for all examples having the machine direction oriented at an angle of 0 degrees to the major dimension of the aperture compared to examples at 90 degrees.

[0143] Table 6 outlines the shapes and dimensions of the vents of the examples and Figures discussed above. Figures 31 and 32 show exemplary vent shapes with the relevant dimensions labelled.

[0144] Figure 31 shows a schematic of a stadium shaped vent having the dimensions h, h’, L and L’, wherein h = minor axis dimension of membrane, h’ = minor axis dimension of the vent, comprising the membrane and the adhesive boundary around the perimeter of membrane, L = major axis dimension of membrane, and L’ = major axis dimension of the vent, comprising the membrane plus the adhesive boundary around the perimeter of membrane. Additionally, a stadium (or lozenge) is a geometric shape having a rectangle with bottom and top lengths, a, and ends capped with semicircles of radius r. The active area of this shape is calculated as TTr2+ 2ra. The membrane is a circle when a= 0. The adhesive wall width corresponds to (L'-L) / 2 = (h'-h) / 2. The relevant dimensions of C1 (a circle shaped vent) and L2 to L6 (stadium shaped vents) are listed in Table 6.

[0145] Figure 32 shows an exemplary rectangular shaped vent having the dimensions A, A’, B and B’, wherein A = major axis of membrane with rectangular aperture, A’ = major axis of the vent with rectangular aperture (vent = membrane + adhesive boundary around membrane), B = minor axis of the membrane with rectangular aperture; and B’ = minor axis of the vent with rectangular aperture. The square boundary would exist when A = B. The adhesive wall width corresponds to (A’-A) / 2 = (B’-B) / 2. The active area is calculated as AB. The relevant dimensions of S1 (a square shaped vent) and R2 to R6 are shown in Table 6.

[0146]

[0147] Table 6 - Dimensions and specifications of vent shapes according to the examples of this disclosure.

[0148] Further examples using the same expanded polyethylene membrane of Examples 1-12 in a vent where the major dimension of the vent is oriented at an angle of 0, 2, 5, 10, 20, 45 and 90° to the machine direction of the membrane, having a rectangular shaped aperture.

[0149] Figure 33 shows the impact of angle of the major dimension of the vent to the machine direction of the membrane on Delta SPL for these further examples having an aspect ratio of the vent aperture of from 1.0 (i.e. a square aperture in a comparative vent) and 1.2, 1.4, 1.7, 1.9 and 2.1.

[0150] As can be seen, a significant increase in Delta SPL is shown for all angles between 0 to 45°.

[0151] Figure 34 shows the impact of angle of the major dimension of the vent to the dimension of the membrane with highest modulus on Delta SPL for electrospun polyimide membranes described in Table 1 above. As can be seen, there is minimal effect on Delta SPL for most aspect ratios of aperture, whilst a small improvement is seen for a vent aperture having an aspect ratio of 1.4. 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

Claims1. A vent comprising a membrane and a first layer provided on a first side of the membrane, the first layer defining an aperture such that the membrane is exposed through the aperture, the aperture having a major dimension and a minor dimension, wherein the membrane has a machine direction and a transverse direction and the major dimension of the aperture of the first layer is oriented at an angle to the machine direction of the membrane of less than 90 degrees.

2. The vent of claim 1 , wherein the major dimension of the aperture is oriented at an angle to the machine direction of the membrane of less than 45 degrees.

3. The vent of claim 2, wherein the major dimension of the aperture is oriented at an angle to the machine direction of the membrane of less than 25 degrees.

4. The vent of claim 3, wherein the major dimension of the aperture is oriented at an angle to the machine direction of the membrane of less than 10 degrees.

5. The vent of claim 4, wherein the major dimension of the aperture is oriented such that it is substantially parallel to the machine direction of the membrane.

6. The vent of any preceding claim, wherein the aperture has an aspect ratio of the major dimension to the minor dimension of from 1.1 to 3.0.

7. The vent of claim 6, wherein the aperture has an aspect ratio of the major dimension to the minor dimension of from 1 .2 to 1 .9.

8. The vent of claim 7, wherein the aperture has an aspect ratio of the major dimension to the minor dimension of from 1 .2 to 1 .7.

9. The vent of any preceding claim, wherein the membrane is an expanded membrane.

10. The vent of any preceding claim, wherein the membrane comprises a fibrillated material.11 . The vent of any preceding claim, wherein the membrane comprises a material selected from the group: polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP),polyvinylidene fluoride (PVDF), polyethylene (PE), polyetherketoneketone (PEKK), polyether ether ketone (PEEK), poly(tetramethyl-p-silphenylenesiloxane) (PTMPS), polydimethylsiloxane (PDMS), polyparaxylylene (PPX), polyamide 6, polyurethane, thermoplastic polyurethane, polypropylene, polyimide (PI), or polyacrylonitrile (PAN) or combinations thereof.

12. The vent of claim 11 , wherein the membrane comprise a material selected from the group: PTFE, PE, PI or PEKK.

13. The vent of any preceding claim, wherein the first layer comprises an adhesive.

14. The vent of any preceding claim further comprising a second layer provided on a second side of the membrane.

15. The vent of claim 14, wherein the second layer defines an aperture such that the membrane is exposed through the aperture.

16. The vent of claim 15, wherein the aperture has a major dimension and a minor dimension and the major dimension is aligned with the major dimension of the aperture of the first layer.

17. The vent of any preceding claim, wherein the membrane has at least reduced wrinkling as measured by the average peak height (Wc) and / or root mean square height (Wq) as measured using the methods described herein compared to membranes of vents having the major dimension of an aperture oriented at 90 degrees to the machine direction of the membrane.

18. The vent of any preceding claim, wherein the membrane has improved acoustic performance as measured by the Sound Pressure Level (SPL, dB) as measured using the method described herein.

19. The vent of claim 18, wherein the membrane has an improved SPL compared to a comparative vent that has an aperture defined in a first layer that has the same cross- sectional area and an aspect ratio of major dimension to minor dimension of 1 .

20. The vent of claim 19, wherein the membrane has a percentage change in SPL of less than -0.1 % relative to a comparative vent that has an aperture defined in a first layerthat has an aspect ratio of major dimension to minor dimension of 1 as measured using the methods described herein.

21. A vent comprising a membrane and a first layer provided on a first side of the membrane, the first layer defining an aperture such that the membrane is exposed through the aperture, the aperture having a major dimension and a minor dimension, wherein the membrane has a first dimension and a second dimension, the first dimension being orthogonal to the second dimension and the membrane having a greater stiffness in the first dimension than in the second dimension, wherein the major dimension of the aperture of the first layer is oriented at an angle to the first dimension of the membrane of less than 90 degrees.

22. An electronic device comprising a housing, a vent of any preceding claim and an acoustic transducer, the housing defining an aperture and the vent spanning the aperture such that the vent is positioned between the exterior of the housing and the acoustic transducer.

23. The electronic device of claim 22, wherein the acoustic transducer is a microphone or a speaker.

24. A method of making a vent according to any of claims 1 to 21 , the method comprising the steps: providing a roll of membrane; providing a first sheet of adhesive defining a plurality of apertures; unrolling a length of membrane from the roll of membrane in a machine direction; applying the first sheet of adhesive to the membrane such that the plurality of apertures are oriented at an angle of less than 90 degrees to the machine direction to form a laminate sheet; and cutting the laminate sheet to form the vent of any of claims 1 to 21.

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