Shielded Acoustic Transducer

Abstract

Provided herein is an acoustic device including an acoustic transducer, an acoustic channel proximate to the acoustic transducer, and a membrane cover spanning the acoustic channel, where installation of the membrane cover reduces the signal-to-noise ratio (SNR) of the acoustic transducer by less than 1.5 dB, and after the membrane cover comes into contact with water, the SNR of the acoustic device reduces by less than 1.0 dB, as measured using a method described herein.

Description

[Technical field]

[0001] Field The present disclosure relates to an acoustic device that includes a protected acoustic transducer covered with an acoustic vent. [Background technology]

[0002] background Acoustic devices, including microphones and speakers, typically include acoustic transducers that receive or transmit sound, respectively, at frequencies audible to the human ear, typically in the range of about 16 Hz to 20 kHz. In at least some applications, it is necessary to encase the acoustic transducer of an acoustic device with a protective cover to protect the acoustic transducer from water and particulates.

[0003] When an acoustic transducer is covered with a protective cover that can prevent the ingress of particulates or liquids into the acoustic device, the acoustic performance of the device is often compromised because the acoustic impedance of the protective cover reduces the effective signal-to-noise ratio of the acoustic transducer.

[0004] Protective covers used to protect acoustic transducers often sacrifice acoustic performance in order to ensure that the acoustic transducer is adequately protected from particulates, particularly water. Thus, there is a need for an improved protective cover that provides adequate protection from water and particulates while minimizing the acoustic performance of the acoustic transducer.

[0005] Alternatively, a protective cover with improved acoustic performance is provided that has a significantly reduced ability to protect the acoustic transducer from particulates, particularly water. This type of protective cover may be sufficient for applications where protection from water is less important.

[0006] Still further, it is desirable for protective covers to maintain acoustic performance, for example, even after contact with water. Protective covers that maintain acoustic performance after contact with water or immersion in water often have relatively poor initial acoustic performance, while protective covers with good initial acoustic performance often experience a significant decrease in acoustic performance after contact with water or immersion in water.

[0007] Thus, there remains a need for an improved acoustic device that includes an improved protective cover. Summary of the Invention

[0008] overview According to a first aspect, there is provided an acoustic device including an acoustic transducer, an acoustic channel proximate to the acoustic transducer, and a membrane cover spanning the acoustic channel; when the membrane cover is attached, the signal-to-noise ratio (SNR) of the acoustic transducer is reduced by less than 1.5 dB, as measured using the methods described herein; The SNR of the acoustic device degrades by less than 2.0 dB after the acoustic device is immersed in water at a depth of at least 0.5 m for at least 10 minutes.

[0009] Typically, attaching a membrane cover over an acoustic transducer typically significantly impacts the performance of the acoustic transducer by at least reducing the signal-to-noise ratio (SNR) of the acoustic transducer. In other words, the SNR of the acoustic device before attaching the membrane cover is typically significantly better than after attaching the membrane cover.

[0010] An acoustic channel can be a passageway that extends from an acoustic transducer to the exterior of the acoustic device. Thus, sound can travel from the exterior of the acoustic device to the acoustic transducer through the acoustic channel. In at least some embodiments, the acoustic channel can be an acoustic cavity.

[0011] Membrane covers for acoustic applications are typically either resistive or reactive. Primarily resistive membrane covers are typically sufficiently rigid and / or have sufficiently high airflow so that they do not bend, flex, or vibrate in response to acoustic energy passing therethrough. Primarily reactive membrane covers are typically sufficiently flexible so that they bend, flex, or vibrate in response to acoustic energy passing therethrough.

[0012] Primarily resistive membrane covers significantly degrade acoustic performance by reducing the SNR of the acoustic device due to an increase in the noise floor at high frequencies.

[0013] A primarily reactive membrane cover has minimal impact on the noise floor at high frequencies compared to a primarily resistive membrane cover, but suffers from greater loss of sensitivity at low frequencies resulting in a higher noise floor, lowering the SNR and therefore compromising acoustic performance.

[0014] Furthermore, when the acoustic device comes into contact with water, the acoustic performance of the acoustic device may further degrade. This degradation of SNR may be due to physical changes in the membrane cover caused by contact with water. For example, after a significant water load is applied to the acoustic device, such as immersing the acoustic device in water, the membrane cover may deform due to the additional pressure of water on the membrane cover. This deformation may not recover or may not recover completely after the water load is applied (i.e., after the device is removed from the water and dried). The deformation of the membrane cover often reduces the acoustic performance of the membrane cover, and therefore the acoustic performance of the acoustic device may often be significantly reduced after the water load is applied. This degradation in performance is typically more significant for a primarily reactive membrane cover than for a primarily resistive membrane cover.

[0015] How to measure the SNR of an acoustic transducer or device and how to measure changes or degradation in SNR is described in the detailed description below.

[0016] The "signal-to-noise ratio (SNR)" in dB referred to herein is defined as 10 times the logarithm of the ratio of the standard signal output of a microphone to the noise output produced by its self-noise, as defined by the following formula (Kinsler et al., 1999: International Organization for Standardization, 2019):

[0017]

number

[0018] The standard signal is typically generated by a sound calibrator or calibrated sound source with a 94 dB sound pressure level (SPL) tone at a sound frequency of 1 kHz. The sum of the powers, both signal power and noise power, was calculated over the measurement frequency range 100 Hz to 10 kHz, applying an A-weighting filter to the spectrum. While SNR is a relative measure and is only valid for a given signal level, the self-noise is an absolute measure of the quality of the microphone. However, the SNR at the calibrated SPL provides a measure of the self-noise, since it is obtained by subtracting the self-noise from the level of the standard signal.

[0019] When the acoustic transducer of the acoustic device is covered with a membrane cover, it can be considered a protected acoustic transducer.

[0020] In some embodiments, the membrane cover can include a membrane. The membrane can be made of a polymer.

[0021] The polymer may be selected from the group consisting of polytetrafluoroethylene (PTFE), polyethylene (PE), poly(ethylene-co-tetrafluoroethylene) (ETFE), ultra-high molecular weight polyethylene (UHMWPE), polyparaxylylene (PPX), polylactic acid (PLLA), and any combination or blend thereof.

[0022] The polymer may be selected from the group consisting of polytetrafluoroethylene (PTFE), poly(ethylene-co-tetrafluoroethylene) (ETFE) or polyparaxylylene (PPX) and any combination or blend thereof.

[0023] In some embodiments, the polymer can be PTFE. The polymer can be PE.

[0024] The polymer is an expanded (expanded, expanded, stretched or foamed) polymer. The polymer can be selected from expanded PTFE (ePTFE) and expanded polyethylene (ePE), and combinations and blends thereof. For example, the polymer can be ePTFE. The polymer can be ePE.

[0025] The membrane cover can include a coating. The coating can be disposed on the membrane. The coating can provide the membrane cover with improved performance. For example, the coating can increase the water resistance of the membrane cover.

[0026] The membrane covering can have a water entry pressure (WEP) of at least 15 kPa. The membrane covering can have a WEP of at least 20 kPa. The membrane covering can have a WEP of at least 25 kPa. The membrane covering can have a WEP of at least 30 kPa. The membrane covering can have a WEP of at least 35 kPa. The membrane covering can have a WEP of at least 40 kPa. The membrane covering can have a WEP of at least 45 kPa. The membrane covering can have a WEP of at least 50 kPa.

[0027] The membrane cover can have a water entry pressure (WEP) of about 15 kPa to about 200 kPa. The membrane cover can have a WEP of about 20 kPa to about 200 kPa. The membrane cover can have a WEP of about 25 kPa to about 200 kPa. The membrane cover can have a WEP of about 30 kPa to about 200 kPa. The membrane cover can have a WEP of about 35 kPa to about 200 kPa. The membrane cover can have a WEP of about 40 kPa to about 200 kPa. The membrane cover can have a WEP of about 45 kPa to about 200 kPa. The membrane cover can have a WEP of about 50 kPa to about 200 kPa.

[0028] In some embodiments, the acoustic device can include a housing, which can include an acoustic channel, which can extend from the acoustic transducer to an exterior of the acoustic device, and a membrane cover can span and occlude the acoustic channel.

[0029] The membrane cover can be porous. The membrane cover can have a maximum pore size of about 1 to about 20 μm. The membrane cover can have a maximum pore size of about 1 to about 15 μm. The membrane cover can have a maximum pore size of about 3 to about 10 μm. The membrane cover can have a maximum pore size of about 4 to about 10 μm. The membrane cover can have a maximum pore size of about 5 to about 10 μm.

[0030] The membrane can be porous. The membrane can have a maximum pore size of about 1 to about 20 μm. The membrane can have a maximum pore size of about 1 to about 15 μm. The membrane can have a maximum pore size of about 3 to about 10 μm. The membrane cover can have a maximum pore size of about 4 to about 10 μm. The membrane cover can have a maximum pore size of about 5 to about 10 μm.

[0031] The membrane cover must be designed to ensure that the airflow across the membrane cover is at least 3 cm. 3 / cm 2 The membrane cover is designed to ensure that the airflow across the membrane cover is at least 5 cm 3 / cm2 The membrane cover is designed to ensure that the airflow across the membrane cover is at least 7 cm 3 / cm 2 The membrane cover is designed to ensure that the airflow across the membrane cover is at least 10 cm 3 / cm 2 The membrane is designed to have an air flow across it of at least 3 cm. 3 / cm 2 The membrane is designed to have an air flow across it of at least 5 cm. 3 / cm 2 The membrane can be configured to have an air flow across the membrane of at least 7 cm. 3 / cm 2 The membrane can be configured to have an air flow across it of at least 10 cm. 3 / cm 2 It can be seconds.

[0032] The membrane cover is designed to ensure that the airflow across the membrane cover is 3 cm. 3 / cm 2 seconds~30cm 3 / cm 2 The membrane cover can be designed to have an airflow across the membrane cover of 5 cm 3 / cm 2 seconds~30cm 3 / cm 2 The membrane cover can be designed to have an airflow of 7 cm across the membrane cover. 3 / cm 2 seconds~30cm 3 / cm 2 The membrane cover can be designed to have an air flow across the membrane cover of 10 cm 3 / cm 2 seconds~30cm 3 / cm 2 The membrane can be designed to have an air flow across it of 3 cm. 3 / cm 2 seconds~30cm 3 / cm 2 The membrane can be designed to have an air flow across it of 5 cm 3 / cm 2 seconds~30cm 3 / cm 2The membrane can be designed to have an air flow across it of 7 cm 3 / cm 2 seconds~30cm 3 / cm 2 The membrane can be designed to have an air flow across it of 10 cm 3 / cm 2 seconds~30cm 3 / cm 2 It can be seconds.

[0033] The membrane cover is designed to ensure that the airflow across the membrane cover is 3 cm. 3 / cm 2 seconds~20cm 3 / cm 2 The membrane cover can be designed to have an airflow across the membrane cover of 5 cm 3 / cm 2 seconds~20cm 3 / cm 2 The membrane cover can be designed to have an airflow of 7 cm across the membrane cover. 3 / cm 2 seconds~20cm 3 / cm 2 The membrane cover can be designed to have an air flow across the membrane cover of 10 cm 3 / cm 2 seconds~20cm 3 / cm 2 The membrane can be designed to have an air flow across it of 3 cm. 3 / cm 2 seconds~20cm 3 / cm 2 The membrane can be designed to have an air flow across it of 5 cm 3 / cm 2 seconds~20cm 3 / cm 2 The membrane can be designed to have an air flow across it of 7 cm 3 / cm 2 seconds~20cm 3 / cm 2 The membrane can be designed to have an air flow across it of 10 cm 3 / cm 2 seconds~20cm 3 / cm 2 It can be seconds.

[0034] The membrane can have an MPA of less than about 3.0 g / m2. The membrane can have an MPA of less than about 2.5 g / m2. 2 The membrane may have an MPA of about 2.0 g / m 2 The membrane has an MPA of about 1.7 g / m 2 The membrane may have an MPA of about 1.5 g / m 2 It can be less than.

[0035] The membrane has an MPA of approximately 1.1 g / m 2 ~About 3.0g / m 2 The membrane can have an MPA of about 1.1 g / m 2 ~about 2.5g / m 2 The membrane can have an MPA of about 1.1 g / m 2 ~about 2.0g / m 2 The membrane can have an MPA of about 1.1 g / m 2 ~Approx. 1.7g / m 2 The membrane can have an MPA of about 1.1 g / m 2 ~Approx. 1.5g / m 2 It can be.

[0036] The membrane has an MPA of approximately 1.3 g / m 2 ~About 3.0g / m 2 The membrane can have an MPA of about 1.3 g / m 2 ~about 2.5g / m 2 The membrane can have an MPA of about 1.3 g / m 2 ~about 2.0g / m 2 The membrane can have an MPA of about 1.3 g / m 2 ~Approx. 1.7g / m 2 The membrane can have an MPA of about 1.3 g / m 2 ~Approx. 1.5g / m 2 It can be.

[0037] The membrane has an MPA of approximately 1.3 g / m 2 ~About 3.0g / m 2 The membrane can have an MPA of about 1.5 g / m 2 ~About 3.0g / m 2 The membrane can have an MPA of about 1.7 g / m2 ~About 3.0g / m 2 The membrane has an MPA of about 2.0 g / m 2 ~About 3.0g / m 2 It can be.

[0038] The membrane may include an open or substantially open microstructure. The microstructure may include voids such that at least 30% of the membrane's microstructure is void. The microstructure may include voids such that at least 50% of the membrane's microstructure is void. The microstructure may include voids such that at least 70% of the membrane's microstructure is void. Typically, the voids in the microstructure allow air to pass through the membrane. Thus, at least a majority of the voids in the microstructure are free of obstructions or other materials that would impede the passage or flow of air through the membrane. The membrane cover may be free of elastomers. The membrane may be free of elastomers.

[0039] The SNR of the acoustic transducer may be degraded by less than about 1.5 dB compared to the SNR of the acoustic transducer without the membrane cover. The SNR of the acoustic transducer may be degraded by less than about 1.3 dB compared to the SNR of the acoustic transducer without the membrane cover. The SNR of the acoustic transducer may be degraded by less than about 1.0 dB compared to the SNR of the acoustic transducer without the membrane cover. The SNR of the acoustic transducer may be degraded by less than about 0.7 dB compared to the SNR of the acoustic transducer without the membrane cover. The SNR of the acoustic transducer may be degraded by less than about 0.5 dB compared to the SNR of the acoustic transducer without the membrane cover.

[0040] The SNR of the acoustic transducer may be reduced by about 0.1 dB to about 1.5 dB compared to the SNR of the acoustic transducer without the membrane cover. The SNR of the acoustic transducer may be reduced by about 0.1 dB to about 1.3 dB compared to the SNR of the acoustic transducer without the membrane cover. The SNR of the acoustic transducer may be reduced by about 0.1 dB to about 1.0 dB compared to the SNR of the acoustic transducer without the membrane cover. The SNR of the acoustic transducer may be reduced by about 0.1 dB to about 0.7 dB compared to the SNR of the acoustic transducer without the membrane cover. The SNR of the acoustic transducer may be reduced by about 0.1 dB to about 0.5 dB compared to the SNR of the acoustic transducer without the membrane cover.

[0041] The SNR of the acoustic device, as measured using the methods described herein, may decrease by less than about 1 dB after immersing the acoustic device in water. The SNR of the acoustic device, as measured using the methods described herein, may decrease by less than about 0.75 dB after immersing the acoustic device in water. The SNR of the acoustic device, as measured using the methods described herein, may decrease by less than about 0.5 dB after immersing the acoustic device in water. The SNR of the acoustic device, as measured using the methods described herein, may decrease by less than about 0.25 dB after immersing the acoustic device in water. The SNR of the acoustic device, as measured using the methods described herein, may decrease by less than about 0.1 dB after immersing the acoustic device in water.

[0042] The SNR of the acoustic device, as measured using the methods described herein, may decrease by about 0.0 to about 1.0 dB after immersion of the acoustic device in water. The SNR of the acoustic device, as measured using the methods described herein, may decrease by about 0.0 to about 0.75 dB after immersion of the acoustic device in water. The SNR of the acoustic device, as measured using the methods described herein, may decrease by about 0.0 to about 0.5 dB after immersion of the acoustic device in water. The SNR of the acoustic device, as measured using the methods described herein, may decrease by about 0.0 to about 0.25 dB after immersion of the acoustic device in water. The SNR of the acoustic device, as measured using the methods described herein, may decrease by about 0.0 to about 0.1 dB after immersion of the acoustic device in water.

[0043] The SNR of the acoustic device, as measured using the methods described herein, may decrease by about 0.1 to about 1.0 dB after immersion of the acoustic device in water. The SNR of the acoustic device, as measured using the methods described herein, may decrease by about 0.1 to about 0.75 dB after immersion of the acoustic device in water. The SNR of the acoustic device, as measured using the methods described herein, may decrease by about 0.1 to about 0.5 dB after immersion of the acoustic device in water. The SNR of the acoustic device, as measured using the methods described herein, may decrease by about 0.1 to about 0.25 dB after immersion of the acoustic device in water. The SNR of the acoustic device, as measured using the methods described herein, may decrease by about 0.1 to about 0.1 dB after immersion of the acoustic device in water.

[0044] When determining the degradation in SNR of the acoustic device after immersion in water, the acoustic device may be immersed in water to a particular depth. The acoustic device may be immersed in water to a depth of at least 0.1 meters. The acoustic device may be immersed in water to a depth of at least 0.5 meters. The acoustic device may be immersed in water to a depth of at least 1 meter. The acoustic device may be immersed in water to a depth of at least 1.5 meters. The acoustic device may be immersed in water to a depth of at least 2 meters. The acoustic device may be immersed in water to a depth of at least 2.5 meters. For example, the acoustic device may be immersed in water to a depth of 0.5 meters. The acoustic device may be immersed in water to a depth of 1 meter. The acoustic device may be immersed in water to a depth of 1.5 meters. The acoustic device may be immersed in water to a depth of 2 meters. The acoustic device may be immersed in water to a depth of 2.5 meters.

[0045] When determining the degradation of the SNR of the acoustic device after immersion in water, the acoustic device can be immersed in water for a particular period of time. The acoustic device can be immersed in water for 10 minutes. The acoustic device can be immersed in water for 20 minutes. The acoustic device can be immersed in water for 30 minutes. The acoustic device can be immersed in water for at least 10 minutes. The acoustic device can be immersed in water for 20 minutes. The acoustic device can be immersed in water for at least 30 minutes.

[0046] For example, in some embodiments, the SNR of an acoustic device may degrade by less than 1.0 dB after the acoustic device is submerged in water 2 meters deep for 30 minutes. In some embodiments, the SNR of an acoustic device may degrade by less than 1.0 dB after the acoustic device is submerged in water 1.5 meters deep for 30 minutes. In some embodiments, the SNR of an acoustic device may degrade by less than 1.0 dB after the acoustic device is submerged in water 1 meter deep for 30 minutes. In some embodiments, the SNR of an acoustic device may degrade by less than 1.0 dB after the acoustic device is submerged in water 0.5 meters deep for 30 minutes.

[0047] Those skilled in the art will readily appreciate that the above method for water immersion ("water loading") of an acoustic device is applicable to any of the SNR requirements described herein, and not just the exemplary reduction in SNR provided in the paragraph above.

[0048] In some embodiments, an acoustic device includes an acoustic transducer, an acoustic channel proximate to the acoustic transducer, and a membrane cover spanning the acoustic channel; The membrane cover has a mass per area (MPA) of 3.0 g / m 2 a membrane made of polytetrafluoroethylene (PTFE) of less than the signal-to-noise ratio (SNR) of the acoustic transducer is reduced by less than 1.5 dB compared to the SNR of an acoustic transducer without a membrane cover, as measured using the methods described herein; The SNR of the acoustic device, measured using the methods described herein, decreases by less than 1.0 dB after immersing the acoustic device in water.

[0049] In a second aspect, an acoustic cover is provided, the acoustic cover including a membrane, the acoustic cover configured to cover an acoustic transducer, thereby protecting the acoustic transducer, and to reduce a signal-to-noise ratio (SNR) of the acoustic transducer by less than 1.5 dB compared to the signal-to-noise ratio (SNR) of the acoustic transducer without the acoustic cover, as measured using a method described herein.

[0050] The membrane can include a polymer. The polymer can be selected from the group consisting of polytetrafluoroethylene (PTFE), polyethylene (PE), poly(ethylene-co-tetrafluoroethylene) (ETFE), ultra-high molecular weight polyethylene (UHMWPE), polyparaxylylene (PPX), polylactic acid (PLLA), and any combination or blend thereof. For example, the polymer is PTFE.

[0051] The polymer can be selected from the group consisting of polytetrafluoroethylene (PTFE), poly(ethylene-co-tetrafluoroethylene) (ETFE) or polyparaxylylene (PPX) and any combination or blend thereof. For example, the polymer is PTFE.

[0052] The polymer can be PTFE or PE.

[0053] The polymer can be an expanded polymer. The polymer can be selected from expanded PTFE (ePTFE) and expanded polyethylene (ePE), and combinations and blends thereof. For example, the polymer can be ePTFE. The polymer can be ePE.

[0054] In some embodiments where the membrane is a PTFE membrane, the PTFE membrane has a mass per area (MPA) of 3.5 g / m 2 The PTFE membrane can have an MPA of less than 3.0 g / m 2 The PTFE membrane can have an MPA of less than 2.5 g / m 2 The PTFE membrane can have an MPA of less than 2.0 g / m 2 The PTFE membrane can have an MPA of less than 1.7 g / m 2 The PTFE membrane can have an MPA of less than 1.5 g / m 2 It can be less than.

[0055] The PTFE membrane has an MPA of 1.1 g / m 2 ~3.0g / m 2 The PTFE membrane can have an MPA of 1.1 g / m 2 ~2.5g / m 2 The PTFE membrane can have an MPA of 1.1 g / m 2 ~2.0g / m 2 The PTFE membrane can have an MPA of 1.1 g / m 2 ~1.7g / m 2 The PTFE membrane can have an MPA of 1.1 g / m 2 ~1.5g / m2 It can be.

[0056] PTFE membrane has an MPA of 1.3 g / m 2 ~3.0g / m 2 The PTFE membrane can have an MPA of 1.3 g / m 2 ~2.5g / m 2 The PTFE membrane can have an MPA of 1.3 g / m 2 ~2.0g / m 2 The PTFE membrane can have an MPA of 1.3 g / m 2 ~1.7g / m 2 The PTFE membrane can have an MPA of 1.3 g / m 2 ~1.5g / m 2 It can be.

[0057] PTFE membrane has an MPA of 1.3 g / m 2 ~3.0g / m 2 The PTFE membrane can have an MPA of 1.5 g / m 2 ~3.0g / m 2 The PTFE membrane can have an MPA of 1.7 g / m 2 ~3.0g / m 2 The PTFE membrane can have an MPA of 2.0 g / m 2 ~3.0g / m 2 It can be.

[0058] In some embodiments where the membrane is a PE membrane, the PE membrane has a mass per area (MPA) of 3.5 g / m 2 The PE film can have an MPA of less than 3.0 g / m 2 The PE film has an MPA of 2.5 g / m 2 The PE film can have an MPA of less than 2.0 g / m 2 The PE film can have an MPA of 1.7 g / m 2 The PE film can have an MPA of less than 1.5 g / m 2 It can be less than.

[0059] The PE membrane has an MPA of 1.1 g / m 2~3.0g / m 2 The PE membrane can have an MPA of 1.1 g / m 2 ~2.5g / m 2 The PE membrane can have an MPA of 1.1 g / m 2 ~2.0g / m 2 The PE membrane can have an MPA of 1.1 g / m 2 ~1.7g / m 2 The PE membrane can have an MPA of 1.1 g / m 2 ~1.5g / m 2 It can be.

[0060] PE membrane has an MPA of 1.3g / m 2 ~3.0g / m 2 The PE film can have an MPA of 1.3 g / m 2 ~2.5g / m 2 The PE film can have an MPA of 1.3 g / m 2 ~2.0g / m 2 The PE film can have an MPA of 1.3 g / m 2 ~1.7g / m 2 The PE film can have an MPA of 1.3 g / m 2 ~1.5g / m 2 It can be.

[0061] PE membrane has an MPA of 1.3g / m 2 ~3.0g / m 2 The PE membrane can have an MPA of 1.5 g / m 2 ~3.0g / m 2 The PE film can have an MPA of 1.7 g / m 2 ~3.0g / m 2 The PE membrane can have an MPA of 2.0 g / m 2 ~3.0g / m 2 It can be.

[0062] The acoustic covering can have a water entry pressure (WEP) of at least 15 kPa. The acoustic covering can have a WEP of at least 20 kPa. The acoustic covering can have a WEP of at least 25 kPa. The acoustic covering can have a WEP of at least 30 kPa. The acoustic covering can have a WEP of at least 35 kPa. The acoustic covering can have a WEP of at least 40 kPa. The acoustic covering can have a WEP of at least 45 kPa. The acoustic covering can have a WEP of at least 50 kPa.

[0063] In some embodiments, the acoustic cover may be configured, when attached to the acoustic device, to reduce the SNR of an acoustic transducer of the acoustic device by less than 1.0 dB after the acoustic cover comes into contact with water, compared to the SNR of the acoustic transducer without the acoustic cover.

[0064] Thus, the acoustic cover may be the membrane cover in the acoustic device of the first aspect.

[0065] In some embodiments, the acoustic cover has an airflow across the membrane cover of at least 5 cm 3 / cm 2 The membrane cover may be provided with an airflow of at least 7 cm across the membrane cover. 3 / cm 2 The membrane cover may be configured to provide an airflow across the membrane cover of at least 10 cm. 3 / cm 2 It can be seconds (F).

[0066] The preferred and optional features of the membrane cover of the first aspect are the preferred and optional features of the acoustic cover of the second aspect. [Brief description of the drawings]

[0067] BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention will now be described, by way of non-limiting example, with reference to the accompanying drawings, in which:

[0068] [Figure 1] FIG. 1 is a schematic side view of an embodiment of an acoustic device. [Diagram 2] FIG. 2 is a plot of the change in SNR (delta (Δ) SNR) and the change in SNR after water loading (SNRWC) for an embodiment MPA mounted across an aperture having an inner diameter (ID) of A) 1.2 mm, and B) 1.0 mm and 1.6 mm. [Diagram 3] FIG. 3 is a comparison of acoustic impedance (Rayls) as a function of frequency for a 1.47 gsm or g / m2 film and a 4.26 gsm or g / m2 film. [Figure 4] FIG. 4 shows the typical performance of a predominantly reactive ePTFE membrane (eWEP) before and after water loading. [Diagram 5] FIG. 5 is a chart of the change in SNR after water challenge for a primarily reactive membrane and a primarily resistive membrane. [Figure 6] FIG. 6 is a plot of ΔSNR for ePE (open diamond) and ePTFE (open circle) membranes mounted across an aperture with an inner diameter (ID) of 1 mm. [Figure 7] FIG. 7 is a plot of ΔSNR (closed diamond) and SNR after water loading (SNR(Wc), open diamond) of an ePE film across an aperture with an inner diameter of 1 mm. [Figure 8] FIG. 8 is a plot of ΔSNR and SNR after water loading (SNR(Wc)) of an ePE membrane across an aperture with an inner diameter of 1.5 mm. [Figure 9] FIG. 9 is a schematic side view of an embodiment of an acoustic device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0069] Detailed Description Although the making and use of various embodiments of the invention are described in detail below, it should be understood that the invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments described herein are merely illustrative of specific ways to make and use the invention and do not limit the scope of the invention.

[0070] In order to facilitate understanding of the present invention, certain terms are defined below. Terms defined herein have meanings commonly understood by one of ordinary skill in the art relevant to the present invention. Terms such as "a," "an," and "the" do not refer to only a single entity, but include general classes of which specific examples can be used to illustrate. While the terms used herein are used to describe particular embodiments of the present invention, their use is not intended to limit the present invention, except as outlined in the claims.

[0071] Test Method Measuring SNR The following method was used to measure the SNR of an acoustic device including a microphone (corresponding to an acoustic transducer) before installation of the membrane cover, after installation of the membrane cover, and after applying a water load to the acoustic transducer as described below.

[0072] The MEMS microphone system (acoustic device) was placed inside an anechoic box and 10 cm away from the acoustic source. First, the signal level output of the MEMS microphone was obtained by driving the acoustic source with a single frequency excitation of 1 Pa at 1 kHz. The noise output of the microphone was obtained without signal excitation to capture the noise floor of the MEMS microphone. The SNR of the MEMS microphone can then be estimated using the following equation:

[0073]

number

[0074] An A-weighting filter was applied to both the signal level output and microphone noise output measurements.

[0075] The MEMS microphone used in the following examples was a Knowles commercial top port microphone-SPH1642HT5H-1, and a membrane cover was attached to the device to cover the microphone. The SNR of the microphone without the membrane cover was 65dB.

[0076] Before attaching the membrane cover of each example, the SNR of the microphone of the acoustic device was measured (SNR i ) The membrane cover was placed over the microphone and the SNR of the acoustic device was measured again (SNR f The change in SNR (ΔSNR) was determined as the SNR of the acoustic device after the membrane cover was attached minus the SNR of the acoustic device before the membrane cover was attached.

[0077] Measurement of SNR after water loading The acoustic devices with the membranes of Examples 1 and 2 and Comparative Example 1 were immersed in water to a depth of 2 m for 30 minutes. The acoustic devices were then removed, dried, and the SNR of the acoustic devices was measured again. The difference between the SNR of the device before immersion in water and the SNR of the device after immersion in water was determined (SNR WC ).

[0078] The acoustic device with the membrane of Example 3 attached was immersed in water to a depth of 0.5 m for 30 minutes. The acoustic device was then removed, dried, and the SNR of the acoustic device was measured again. The difference between the SNR of the device before immersion in water and the SNR of the device after immersion was determined (SNR WC ).

[0079] Thickness measurement The film thickness was measured using a non-contact method using an optical digital micrometer (controller LS-7600, laser LS-7010MR, target LS-7010MT, provided by Keyence (UK) Ltd, UK). The film sample was placed on a cylindrical stem with a hemispherical head. Minimal tension was applied to the film to prevent it from stretching. The cylindrical stem was placed between the laser and the target / sensor. The contact point of the laser beam height was recorded and this difference provides the film thickness.

[0080] Acoustic impedance measurement Acoustic impedance was measured using standard test methods as specified in ASTM specification ASTM 2611-17.

[0081] Water Entry Pressure (WEP) WEP is related to the intrusion of water through a material. The WEP value was determined by the following procedure: A test sample (a circular membrane sample of 1.5 mm diameter) was held in a sample holder with a clamp. The sample was then pressurized with water. The pressure at which water intrudes through the membrane was recorded as the Water Entry Pressure (WEP).

[0082] Air permeability Air permeability was measured by clamping the test sample in a 14 cm diameter circular gasketed flange fixture. The upstream side of the sample fixture was connected to a flow meter in series with a source of dry compressed air. The downstream side of the sample fixture was open to the atmosphere.

[0083] The test was performed by applying 1.3 cm of water air pressure upstream of the sample and recording the air flow rate through an in-line flow meter (a ball float rotameter).

[0084] Results are reported in Fraser Number, which has units of cubic cm / square cm / second.

[0085] Airflow Resistance Rayl is a measure of a sample's resistance to airflow. The pressure drop (ΔP) through the sample (4 cm diameter) was measured at a fixed air flow rate of 10 standard cubic feet per minute (scfh). The pressure drop was converted to Rayl units using the following formula:

[0086]

number

[0087] For acoustically resistive materials, airflow resistance is directly related to the acoustic resistivity.

[0088] Mass per area From a representative sample of the membrane, an area of ​​100 cm 2 Cut out five circles of 100 mm. The mass of each circle is measured on an analytical balance in grams accurate to three decimal places. The grams per 100 square centimeters are converted to grams per square meter by multiplying by 100. The mass per area values ​​are averaged and calculated as grams per square meter (g / m 2 )

[0089] Membranes used in the examples Expanded polytetrafluoroethylene (ePTFE) membranes were produced according to the teachings of U.S. Patent No. 5,814,405 to Branca et al. and U.S. Patent No. 7,306,729 to Bacino et al., which are incorporated herein by reference in their entireties. The prepared dry precursor tapes were stretched at varying stretch ratios to produce ePTFE membranes according to the following examples.

[0090] Expanded polyethylene (ePE) membranes were produced in the following manner. Ultra-high molecular weight polyethylene (UHMWPE) resin was obtained with a molecular weight of about 7.6 million g / mol. Tapes were prepared according to the method described in U.S. Pat. No. 9,926,416 to Sbriglia et al., incorporated herein by reference in its entirety, to produce tapes with a thickness of 0.14 mm. The tapes were preheated at 135° C. for 30 seconds, and then expanded in the machine direction at 150% / sec with an expansion ratio of 1.5:1 and in the transverse direction at 300% / sec with an expansion ratio of 2:1 to produce membranes. The membranes were preheated at 160° C. for 15 seconds, and then expanded in the machine direction at 0.7% / sec with an expansion ratio of 4.5:1 and in the transverse direction at 1.4% / sec with an expansion ratio of 8:1.

[0091] Example 1 1, acoustic device 1 includes a device body 2, a channel 4, an acoustic cavity 6, and a membrane cover 8. The acoustic cavity 6 extends from the device body 2 to the channel 4. A microphone 10 is provided in the channel 4, and the membrane cover 8 spans the channel 4. The channel had an inside diameter (ID) of 1.2 mm. Thus, the membrane cover 8 occludes the channel 4, ensuring that the microphone 10 is protected from foreign objects.

[0092] The membrane cover 8 comprises an ePTFE membrane made according to the method described above, expanded at a modified expansion ratio to produce a membrane having a thickness of 50.6 μm, and is adhered to the device body 2. The ePTFE membrane has a mass per area of ​​1.5 g / m 2 It was.

[0093] Before attaching the membrane cover 8, the signal-to-noise ratio (SNR) of the acoustic device 1 is measured, and the initial SNR, SNR i After the membrane cover 8 is installed, the SNR of the acoustic device is measured again to obtain the final SNR, SNR f The change in SNR of an acoustic device is given by ΔSNR = SNR f -SNR i It was decided.

[0094] Next, the acoustic device 1 was subjected to a water load by immersing the acoustic device 1 in water at a depth of 2 meters for 30 minutes. The SNR and SNRwc of the acoustic device 1 after the water load were measured and compared with ΔSNR.

[0095] Example 2 An acoustic device as described above in Example 1 was prepared and provided with a membrane cover 12.

[0096] The membrane cover 12 comprises an ePTFE membrane made according to the method described above, expanded at a modified expansion ratio to produce a membrane having a thickness of 96.3 μm, and is adhered to the device body 2. The ePTFE membrane has a mass per area of ​​2.9 g / m 2 It was.

[0097] ΔSNR was calculated as above and SNRwc was measured as above in Example 1.

[0098] Example 3 9, acoustic device 20 includes a housing 22 disposed on a substrate 24 and an aperture 26 in substrate 24. An acoustic transducer 28 and an acoustic channel 30 extending from the acoustic transducer through aperture 26 to the exterior of acoustic device 20 are provided in housing 22. Additionally, an application specific integrated circuit (ASIC) 32 is provided in housing 22 for receiving data from acoustic transducer 28. An ePE film 34, fabricated according to the method described above, occludes across aperture 26, thereby occludes across acoustic channel 30. ePE film 34 had a thickness of 12.9 μm. ePE film 34 had a mass per area of ​​0.9 g / m 2 It was.

[0099] ΔSNR was calculated as above and SNRwc was measured as described above for Example 1.

[0100] Comparative Example 1 Comparative acoustic devices include devices as described above with a membrane cover 14 attached.

[0101] The membrane cover 14 comprises an ePTFE membrane made according to the method described above and expanded at a modified expansion ratio to produce a membrane thickness of 125.8 μm, and is adhered to the device body 2. The membrane cover 14 has a mass per area of ​​4.3 g / m 2 The ePTFE membrane was included.

[0102] As mentioned above for Example 1, the SNR i , SNR f was measured, ΔSNR was calculated, and SNRwc was measured.

[0103] Comparative Example 2 The comparative acoustic device includes a device as described above with a membrane cover 16 attached.

[0104] The membrane cover 16 comprises an ePTFE membrane commercially available from WLGore & Associates, Inc. under part number PE13. A commercially available example of this product has an MPA of 5.3 g / m 2 , air permeability is 7.4cm 3 / cm 2 seconds, and the ΔSNR was found to be −4.0 dB.

[0105] As described in Example 1 above, the SNR i , SNR f was measured, ΔSNR was calculated, and SNRwc was measured.

[0106] The ΔSNR and SNRwc of the examples and comparative examples are shown in Table 1 below.

[0107] [Table 1]

[0108] FIG. 2A shows ΔSNR and SNRwc data for Examples 1 and 2 and Comparative Example 1, and FIG. 2B shows similar data for corresponding examples in which the inner diameters of the apertures spanned by the membrane covers are 1.0 mm and 1.6 mm.

[0109] Figure 6 shows ΔSNR data for Examples 1 to 3 and Comparative Example 1. Figures 7 and 8 show ΔSNR and SNRwc data for Example 3 mounted across apertures with inner diameters of 1 mm (Figure 7) and 1.5 mm (Figure 8).

[0110] As shown in Comparative Example 2, primarily resistive membranes have poor acoustic performance (ΔSNR of −4.0), but are typically largely unaffected by significant water loading (see FIG. 5).

[0111] A primarily reactive membrane typically has a very good SNR (see FIG. 4 "Before WEP"). However, the acoustic performance of a typical "reactive membrane" degrades significantly with water loading, whereas a primarily resistive membrane does not. This is shown in FIGS. 5 and 4 (After eWEP (1 hour)).

[0112] For example, Figure 4 shows the change in SNR of a typical reactive membrane compared to the SNR of a microphone before the membrane cover or vent was attached (ΔSNR, "before WEP"), and the change in SNR after water loading of an acoustic device including a membrane cover or vent (SNRwc, "after eWEP (1 hr)"). As can be seen, the ΔSNR of the reactive membrane is very low, but the SNRwc is very poor.

[0113] In contrast, the acoustic devices of Examples 1-3 provide good acoustic performance (ΔSNR) while also maintaining good acoustic performance (SNRwc) after water loading.

[0114] 3 shows the acoustic impedance as a function of frequency for the films of Example 1 and Comparative Example 1. As can be seen, the comparative example exhibits primarily resistive properties, while the film of Example 1 exhibits reactive and resistive properties.

[0115] While the foregoing describes approved embodiments of the invention, it will be apparent that other embodiments may be made with many different changes and modifications in shape, design, construction and arrangement of parts without departing from the invention, and it will be understood that all such changes and modifications are considered as embodiments that are part of the invention as defined in the appended claims.

Claims

1. 1. An acoustic device comprising an acoustic transducer, an acoustic channel proximate to the acoustic transducer, and a membrane cover spanning the acoustic channel, when the membrane cover is attached, the measured signal-to-noise ratio (SNR) of the acoustic transducer is reduced by less than 1.5 dB, as measured using the methods described herein; 1. An acoustic device, wherein the SNR of the acoustic device degrades by less than 2.0 dB after immersion of the acoustic device in water at a depth of at least 0.5 m for at least 10 minutes.

2. The acoustic device of claim 1 , wherein the membrane cover comprises a membrane, the membrane being made of a polymer.

3. 3. The acoustic device of claim 2, wherein the polymer is selected from the group consisting of polytetrafluoroethylene (PTFE), polyethylene (PE), poly(ethylene-co-tetrafluoroethylene) (ETFE), ultra-high molecular weight polyethylene (UHMWPE), polyparaxylylene (PPX), polylactic acid (PLLA), and any combination or blend thereof.

4. 4. The acoustic device of claim 2 or 3, wherein the polymer is an expanded polymer, the polymer being selected from expanded PTFE (ePTFE) and expanded polyethylene (ePE), and combinations and blends thereof.

5. An acoustic device according to any one of claims 1 to 4, wherein the membrane cover has a water entry pressure (WEP) of at least 15 kPa.

6. An acoustic device according to any one of claims 1 to 5, wherein the SNR of the acoustic device degrades by less than 2 dB after the acoustic device is immersed in 2 m depth of water for 30 minutes.

7. The acoustic device of any one of claims 1 to 6, wherein the acoustic device includes a housing, the housing including an acoustic channel extending from the acoustic transducer to an exterior of the acoustic device, and the membrane cover spanning the acoustic channel.

8. The membrane cover is configured to have an air flow across the membrane cover of at least 5 cm ３ / cm ２ 8. The acoustic device according to claim 1, wherein the wavelength is 100 nm to 150 nm.

9. The membrane has a mass per area (MPA) of 3 g / m ２ The acoustic device of any one of claims 1 to 8, wherein the SNR of the acoustic transducer is reduced by less than 1.5 dB compared to the SNR of the acoustic transducer without the membrane cover, as measured using the method described herein.

10. An acoustic cover comprising a PTFE membrane or a PE membrane, the acoustic cover configured to cover an acoustic transducer to protect the acoustic transducer and to reduce a signal-to-noise ratio (SNR) of the acoustic transducer by less than 1.5 dB compared to the SNR of the acoustic transducer without the acoustic cover, as measured using a method described herein.

11. The PTFE or PE membrane has a mass per area (MPA) of 3.0 g / m ２ The acoustic cover of claim 10 .

12. 12. The acoustic cover of claim 10 or 11, wherein the acoustic cover has a water entry pressure of at least 15 kPa.

13. The acoustic cover of any one of claims 10 to 12, wherein when installed on an acoustic device, the acoustic cover is configured such that after the acoustic cover comes into contact with water, the SNR of the acoustic transducer of the acoustic device is reduced by less than 2.0 dB compared to the SNR of the acoustic transducer without the acoustic cover.

14. The acoustic cover has an airflow across the membrane cover of at least 5 cm ３ / cm ２ The acoustic cover according to any one of claims 10 to 13, wherein the elastic modulus is 1 / 2.

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