EP4258683A1 - Geschützter schallwandler - Google Patents

Geschützter schallwandler Download PDF

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Publication number
EP4258683A1
EP4258683A1 EP22181676.2A EP22181676A EP4258683A1 EP 4258683 A1 EP4258683 A1 EP 4258683A1 EP 22181676 A EP22181676 A EP 22181676A EP 4258683 A1 EP4258683 A1 EP 4258683A1
Authority
EP
European Patent Office
Prior art keywords
acoustic
membrane
cover
snr
acoustic device
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP22181676.2A
Other languages
English (en)
French (fr)
Inventor
Ramamoorthy VENKATTARAMAN
Jonathan STASTKA
Chad Banter
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
WL Gore and Associates GK
WL Gore and Associates Inc
Original Assignee
WL Gore and Associates GK
WL Gore and Associates Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by WL Gore and Associates GK, WL Gore and Associates Inc filed Critical WL Gore and Associates GK
Priority to PCT/US2023/065182 priority Critical patent/WO2023196756A1/en
Publication of EP4258683A1 publication Critical patent/EP4258683A1/de
Pending legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/08—Mouthpieces; Microphones; Attachments therefor
    • H04R1/083—Special constructions of mouthpieces
    • H04R1/086—Protective screens, e.g. all weather or wind screens
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/02—Casings; Cabinets ; Supports therefor; Mountings therein
    • H04R1/023—Screens for loudspeakers

Definitions

  • the present disclosure relates to acoustic devices that include a protected acoustic transducer covered with an acoustic vent.
  • Acoustic devices including microphones and speakers typically include an acoustic transducer that receives or transmits sound respectively. In at least some applications it is necessary to cover the acoustic transducer of the acoustic device with a protective cover to protect the acoustic transducer from water and particulates.
  • Covering the acoustic transducer with a protective cover that is able to prevent ingress of particulates or liquid into the acoustic device often impairs the acoustic performance of the device due to the acoustic impedance of the protective cover reducing the effective signal to noise ratio of the acoustic transducer.
  • Protective covers used to protect acoustic transducers often sacrifice acoustic performance to ensure that the acoustic transducer is sufficiently protected from particulates and especially from water. Accordingly, there is a need for improved protective covers that provide sufficient protection from water and particulates but impair acoustic performance of the acoustic transducer as little as possible.
  • protective covers with improved acoustic performance have been provided that have much reduced ability to protect the acoustic transducer from particulates and especially water. This type of protective cover may be sufficient for those applications where water protection is of lesser importance.
  • protective covers to retain their acoustic performance after contact with any water, for example.
  • an acoustic device comprising an acoustic transducer, an acoustic cavity proximate to the acoustic transducer and a membrane cover spanning the acoustic cavity;
  • the installation of a membrane cover over an acoustic transducer significantly impacts the performance of the acoustic transducer, typically by at least reducing the signal to noise ratio (SNR) for the acoustic transducer.
  • SNR signal to noise ratio
  • Membrane covers for acoustic applications typically are either resistive membrane covers or reactive membrane covers.
  • Predominantly resistive membrane covers are typically sufficiently stiff and/or have sufficiently high airflow such that they do not bend, flex or vibrate in response to acoustic energy passing through them.
  • Predominantly reactive membrane covers are typically sufficiently flexible such that they bend, flex or vibrate in response to acoustic energy passing through them.
  • Predominantly resistive membrane covers significantly reduce acoustic performance by reducing the SNR of the acoustic device due to an increase in the noise floor at higher frequencies.
  • Predominantly reactive membrane covers have minimum impact to the noise floor at the higher frequencies in comparison with predominantly resistive membrane covers but at lower frequencies have a higher loss in sensitivity and a higher noise floor to thereby reduce acoustic performance by reducing SNR.
  • the acoustic performance of the acoustic device may be further reduced.
  • This reduction in SNR may be due to a physical change in the membrane cover induced by the contact with water.
  • a significant water challenge such as immersion of the acoustic device in water
  • the additional pressure of the water against the membrane cover may deform the membrane cover that is not recovered or is not recovered fully after the water challenge (i.e. the device is removed from the water and dried).
  • Deformation of the membrane cover often degrades the acoustic performance of the membrane cover and therefore the acoustic performance of acoustic device is often significantly degraded after a water challenge.
  • This reduction in performance is typically more significant for predominantly reactive membrane covers than for predominantly resistive membrane covers.
  • SNR Signal-to-noise ratio
  • the standard signal is commonly generated by a sound calibrator with a 94 dB Sound Pressure Level (SPL) tone at a 1 kHz sound frequency.
  • SPL Sound Pressure Level
  • SNR is a relative measure, valid only for a given signal level, while self-noise is an absolute measure of the microphone quality.
  • SNR at a calibrated SPL will however give a measure of self-noise, because it is obtained by subtracting the self-noise from the standard signal's level.
  • the membrane cover may comprise a membrane.
  • the membrane may consist of a polymer.
  • 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.
  • PTFE polytetrafluoroethylene
  • PE polyethylene
  • ETFE poly(ethylene-co-tetrafluoroethylene)
  • UHMWPE ultra-high molecular weight polyethylene
  • PPX polyparaxylylene
  • PLA polylactic acid
  • 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.
  • PTFE polytetrafluoroethylene
  • ETFE poly(ethylene-co-tetrafluoroethylene)
  • PPX polyparaxylylene
  • the polymer may be PTFE.
  • the polymer may be an expanded polymer.
  • the polymer may be selected from expanded PTFE (ePTFE) and expanded polyethylene (ePE) and combinations and blends thereof.
  • ePTFE expanded PTFE
  • ePE expanded polyethylene
  • the polymer may be ePTFE.
  • the membrane cover may comprise a coating.
  • the coating may be provided on the membrane.
  • the coating may provide the membrane cover with improved performance.
  • the coating may increase the water resistance of the membrane cover.
  • the membrane cover may have a water entry pressure (WEP) of at least 15 kPa.
  • the membrane cover may have a WEP of at least 20 kPa.
  • the membrane cover may have a WEP of at least 25 kPa.
  • the membrane cover may have a WEP of at least 30 kPa.
  • the membrane cover may have a WEP of at least 35 kPa.
  • the membrane cover may have a WEP of at least 40 kPa.
  • the membrane cover may have a WEP of at least 45 kPa.
  • the membrane cover may have a WEP of at least 50 kPa.
  • the membrane cover may have a water entry pressure (WEP) of from about 15 kPa to about 200 kPa.
  • the membrane cover may have a WEP of from about 20 kPa to about 200 kPa.
  • the membrane cover may have a WEP of from about 25 kPa to about 200 kPa.
  • the membrane cover may have a WEP of from about 30 kPa to about 200 kPa.
  • the membrane cover may have a WEP of from about 35 kPa to about 200 kPa.
  • the membrane cover may have a WEP of from about 40 kPa to about 200 kPa.
  • the membrane cover may have a WEP of from about 45 kPa to about 200 kPa.
  • the membrane cover may have a WEP of from about 50 kPa to about 200 kPa.
  • the acoustic device may comprise a housing.
  • the housing may comprise the acoustic cavity and an acoustic channel extending from the acoustic transducer to the exterior of the acoustic device and the membrane cover may span and occlude the acoustic channel.
  • the membrane cover may be porous.
  • the membrane cover may have a maximum pore size of from about 1 to about 20 ⁇ m.
  • the membrane cover may have a maximum pore size of from about 1 to about 15 ⁇ m.
  • the membrane cover may have a maximum pore size of from about 3 to about 10 ⁇ m.
  • the membrane cover may have a maximum pore size of from about 4 to about 10 ⁇ m.
  • the membrane cover may have a maximum pore size of from about 5 to about 10 ⁇ m.
  • the membrane may be porous.
  • the membrane may have a maximum pore size of from about 1 to about 20 ⁇ m.
  • the membrane may have a maximum pore size of from about 1 to about 15 ⁇ m.
  • the membrane may have a maximum pore size of from about 3 to about 10 ⁇ m.
  • the membrane cover may have a maximum pore size of from about 4 to about 10 ⁇ m.
  • the membrane cover may have a maximum pore size of from about 5 to about 10 ⁇ m.
  • the membrane cover may have an airflow across the membrane cover of at least 5 cm 3 /cm 2 sec.
  • the membrane cover may have an airflow across the membrane cover of at least 7 cm 3 /cm 2 sec.
  • the membrane cover may have an airflow across the membrane cover of at least 10 cm 3 /cm 2 sec.
  • the membrane cover may have an airflow across the membrane cover of at least 5 cm 3 /cm 2 sec.
  • the membrane cover may have an airflow across the membrane cover of at least 7 cm 3 /cm 2 sec.
  • the membrane cover may have an airflow across the membrane cover of at least 10 cm 3 /cm 2 sec.
  • the membrane cover may have an airflow across the membrane cover of from 5 cm 3 /cm 2 sec to 30 cm 3 /cm 2 sec.
  • the membrane cover may have an airflow across the membrane cover of from 7 cm 3 /cm 2 sec to 30 cm 3 /cm 2 sec.
  • the membrane cover may have an airflow across the membrane cover of from 10 cm 3 /cm 2 sec to 30 cm 3 /cm 2 sec.
  • the membrane cover may have an airflow across the membrane cover of from 5 cm 3 /cm 2 sec to 30 cm 3 /cm 2 sec.
  • the membrane cover may have an airflow across the membrane cover of from 7 cm 3 /cm 2 sec to 30 cm 3 /cm 2 sec.
  • the membrane cover may have an airflow across the membrane cover of from 10 cm 3 /cm 2 sec to 30 cm 3 /cm 2 sec.
  • the membrane cover may have an airflow across the membrane cover of from 5 cm 3 /cm 2 sec to 20 cm 3 /cm 2 sec.
  • the membrane cover may have an airflow across the membrane cover of from 7 cm 3 /cm 2 sec to 20 cm 3 /cm 2 sec.
  • the membrane cover may have an airflow across the membrane cover of from 10 cm 3 /cm 2 sec to 20 cm 3 /cm 2 sec.
  • the membrane cover may have an airflow across the membrane cover of from 5 cm 3 /cm 2 sec to 20 cm 3 /cm 2 sec.
  • the membrane cover may have an airflow across the membrane cover of from 7 cm 3 /cm 2 sec to 20 cm 3 /cm 2 sec.
  • the membrane cover may have an airflow across the membrane cover of from 10 cm 3 /cm 2 sec to 20 cm 3 /cm 2 sec.
  • the membrane may have a MPA less than about 3.0 g/m 2 .
  • the membrane may have a MPA less than about 2.5 g/m 2 .
  • the membrane may have a MPA less than about 2.0 g/m 2 .
  • the membrane may have a MPA less than about 1.7 g/m 2 .
  • the membrane may have a MPA less than about 1.5 g/m 2 .
  • the membrane may have a MPA from about 1.1 g/m 2 to about 3.0 g/m 2 .
  • the membrane may have a MPA from about 1.1 g/m 2 to about 2.5 g/m 2 .
  • the membrane may have a MPA from about 1.1 g/m 2 to about 2.0 g/m 2 .
  • the membrane may have a MPA from about 1.1 g/m 2 to about 1.7 g/m 2 .
  • the membrane may have a MPA from about 1.1 g/m 2 to about 1.5 g/m 2 .
  • the membrane may have a MPA from about 1.3 g/m 2 to about 3.0 g/m 2 .
  • the membrane may have a MPA from about 1.3 g/m 2 to 2.5 g/m 2 .
  • the membrane may have a MPA from about 1.3 g/m 2 to about 2.0 g/m 2 .
  • the membrane may have a MPA from about 1.3 g/m 2 to about 1.7 g/m 2 .
  • the membrane may have a MPA from about 1.3 g/m 2 to about 1.5 g/m 2 .
  • the membrane may have a MPA from about 1.3 g/m 2 to about 3.0 g/m 2 .
  • the membrane may have a MPA from about 1.5 g/m 2 to about 3.0 g/m 2 .
  • the membrane may have a MPA from about 1.7 g/m 2 to about 3.0 g/m 2 .
  • the membrane may have a MPA from about 2.0 g/m 2 to about 3.0 g/m 2 .
  • the SNR of the acoustic transducer may be reduced by less than about 1.5 dB at 1 kHz compared to the SNR of the acoustic transducer without the membrane cover.
  • the SNR of the acoustic transducer may be reduced by less than about 1.3 dB at 1 kHz compared to the SNR of the acoustic transducer without the membrane cover.
  • the SNR of the acoustic transducer may be reduced by less than about 1.0 dB at 1 kHz compared to the SNR of the acoustic transducer without the membrane cover.
  • the SNR of the acoustic transducer may be reduced by less than about 0.7 dB at 1 kHz compared to the SNR of the acoustic transducer without the membrane cover.
  • the SNR of the acoustic transducer may be reduced by less than about 0.5 dB at 1 kHz compared to the SNR of the acoustic transducer without the membrane cover.
  • the SNR of the acoustic transducer may be reduced by from about 0.1 dB to about 1.5 dB at 1 kHz compared to the SNR of the acoustic transducer without the membrane cover.
  • the SNR of the acoustic transducer may be reduced by from about 0.1 dB to about 1.3 dB at 1 kHz compared to the SNR of the acoustic transducer without the membrane cover.
  • the SNR of the acoustic transducer may be reduced by from about 0.1 dB to about 1.0 dB at 1 kHz compared to the SNR of the acoustic transducer without the membrane cover.
  • the SNR of the acoustic transducer may be reduced by from about 0.1 dB to about 0.7 dB at 1 kHz compared to the SNR of the acoustic transducer without the membrane cover.
  • the SNR of the acoustic transducer may be reduced by from about 0.1 dB to about 0.5 dB at 1 kHz compared to the SNR of the acoustic transducer without the membrane cover.
  • the SNR of the acoustic device may be reduced by less than about 0.75 dB at 1 kHz after immersion of the acoustic device in water as measured using the method described herein.
  • the SNR of the acoustic device may be reduced by less than about 0.5 dB at 1 kHz after immersion of the acoustic device in water as measured using the method described herein.
  • the SNR of the acoustic device may be reduced by less than about 0.25 dB at 1 kHz after immersion of the acoustic device in water as measured using the method described herein.
  • the SNR of the acoustic device may be reduced by less than about 0.1 dB at 1 kHz after immersion of the acoustic device in water as measured using the method described herein.
  • the SNR of the acoustic device may be reduced by from about 0.0 to about 1.0 dB at 1 kHz after immersion of the acoustic device in water as measured using the method described herein.
  • the SNR of the acoustic device may be reduced by from about 0.0 to about 0.75 dB at 1 kHz after immersion of the acoustic device in water as measured using the method described herein.
  • the SNR of the acoustic device may be reduced by from about 0.0 to about 0.5 dB at 1 kHz after immersion of the acoustic device in water as measured using the method described herein.
  • the SNR of the acoustic device may be reduced by from about 0.0 to about 0.25 dB at 1 kHz after immersion of the acoustic device in water as measured using the method described herein.
  • the SNR of the acoustic device may be reduced by from about 0.0 to about 0.1 dB at 1 kHz after immersion of the acoustic device in water as measured using the method described herein.
  • the SNR of the acoustic device may be reduced by from about 0.1 to about 1.0 dB at 1 kHz after immersion of the acoustic device in water as measured using the method described herein.
  • the SNR of the acoustic device may be reduced by from about 0.1 to about 0.75 dB at 1 kHz after immersion of the acoustic device in water as measured using the method described herein.
  • the SNR of the acoustic device may be reduced by from about 0.1 to about 0.5 dB at 1 kHz after immersion of the acoustic device in water as measured using the method described herein.
  • the SNR of the acoustic device may be reduced by from about 0.1 to about 0.25 dB at 1 kHz after immersion of the acoustic device in water as measured using the method described herein.
  • the SNR of the acoustic device may be reduced by from about 0.1 to about 0.1 dB at 1 kHz after immersion of the acoustic device in water as measured using the method described herein.
  • the acoustic device may be immersed in water to a specific depth.
  • the acoustic device may be immersed in water to a depth of at least 1 m.
  • the acoustic device may be immersed in water to a depth of at least 1.5 m.
  • the acoustic device may be immersed in water to a depth of at least 2 m.
  • the acoustic device may be immersed in water to a depth of at least 2.5 m.
  • the acoustic device may be immersed in water to a depth of 1 m.
  • the acoustic device may be immersed in water to a depth of 1.5 m.
  • the acoustic device may be immersed in water to a depth of 2 m.
  • the acoustic device may be immersed in water to a depth of 2.5 m.
  • the acoustic device may be immersed in water for a specific period of time.
  • the acoustic device may be immersed in water for a period of 10 minutes.
  • the acoustic device may be immersed in water for a period of 20 minutes.
  • the acoustic device may be immersed in water for a period of 30 minutes.
  • the acoustic device may be immersed in water for a period of at least 10 minutes.
  • the acoustic device may be immersed in water for a period of 20 minutes.
  • the acoustic device may be immersed in water for a period of at least 30 minutes.
  • the SNR of the acoustic device may be reduced by less than 1.0 dB at 1kHz after immersion of the acoustic device in water at a depth of 2 m for a period of 30 minutes. In some embodiments, the SNR of the acoustic device may be reduced by less than 1.0 dB at 1kHz after immersion of the acoustic device in water at a depth of 1.5 m for a period of 30 minutes. In some embodiments, the SNR of the acoustic device may be reduced by less than 1.0 dB at 1kHz after immersion of the acoustic device in water at a depth of 1 m for a period of 30 minutes.
  • water challenge water immersion of the acoustic device
  • the acoustic device comprises an acoustic transducer, an acoustic cavity proximate to the acoustic transducer and a membrane cover spanning the acoustic cavity;
  • an acoustic cover comprising a membrane, the acoustic cover being configured to cover an acoustic transducer to thereby protect the acoustic transducer and to reduce the signal to noise ratio (SNR) of the acoustic transducer by less than 1.5 dB at 1 kHz compared to the SNR of the acoustic transducer without the acoustic cover as measured using the method as described herein.
  • SNR signal to noise ratio
  • the membrane may comprise a polymer.
  • 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.
  • PTFE polytetrafluoroethylene
  • PE polyethylene
  • ETFE poly(ethylene-co-tetrafluoroethylene)
  • UHMWPE ultra-high molecular weight polyethylene
  • PPX polyparaxylylene
  • PLLA polylactic acid
  • the polymer may be PTFE.
  • 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.
  • PTFE polytetrafluoroethylene
  • ETFE poly(ethylene-co-tetrafluoroethylene)
  • PPX polyparaxylylene
  • the polymer may be PTFE.
  • the polymer may be an expanded polymer.
  • the polymer may be selected from expanded PTFE (ePTFE) and expanded polyethylene (ePE) and combinations and blends thereof.
  • ePTFE expanded PTFE
  • ePE expanded polyethylene
  • the polymer may be ePTFE.
  • the PTFE membrane may have a mass per area (MPA) of less than 3.5 g/m 2 .
  • the PTFE membrane may have a MPA of less than 3.0 g/m 2 .
  • the PTFE membrane may have a MPA of less than 2.5 g/m 2 .
  • the PTFE membrane may have a MPA less than 2.0 g/m 2 .
  • the PTFE membrane may have a MPA less than 1.7 g/m 2 .
  • the PTFE membrane may have a MPA less than 1.5 g/m 2 .
  • the PTFE membrane may have a MPA from 1.1 g/m 2 to 3.0 g/m 2 .
  • the PTFE membrane may have a MPA from 1.1 g/m 2 to 2.5 g/m 2 .
  • the PTFE membrane may have a MPA from 1.1 g/m 2 to 2.0 g/m 2 .
  • the PTFE membrane may have a MPA from 1.1 g/m 2 to 1.7 g/m 2 .
  • the PTFE membrane may have a MPA from 1.1 g/m 2 to 1.5 g/m 2 .
  • the PTFE membrane may have a MPA from 1.3 g/m 2 to 3.0 g/m 2 .
  • the PTFE membrane may have a MPA from 1.3 g/m 2 to 2.5 g/m 2 .
  • the PTFE membrane may have a MPA from 1.3 g/m 2 to 2.0 g/m 2 .
  • the PTFE membrane may have a MPA from 1.3 g/m 2 to 1.7 g/m 2 .
  • the PTFE membrane may have a MPA from 1.3 g/m 2 to 1.5 g/m 2 .
  • the PTFE membrane may have a MPA from 1.3 g/m 2 to 3.0 g/m 2 .
  • the PTFE membrane may have a MPA from 1.5 g/m 2 to 3.0 g/m 2 .
  • the PTFE membrane may have a MPA from 1.7 g/m 2 to 3.0 g/m 2 .
  • the PTFE membrane may have a MPA from 2.0 g/m 2 to 3.0 g/m 2 .
  • the acoustic cover may have a water entry pressure (WEP) of at least 15 kPa.
  • the acoustic cover may have a WEP of at least 20 kPa.
  • the acoustic cover may have a WEP of at least 25 kPa.
  • the acoustic cover may have a WEP of at least 30 kPa.
  • the acoustic cover may have a WEP of at least 35 kPa.
  • the acoustic cover may have a WEP of at least 40 kPa.
  • the acoustic cover may have a WEP of at least 45 kPa.
  • the acoustic cover may have a WEP of at least 50 kPa.
  • the acoustic cover may be configured when installed in an acoustic device to reduce the SNR of the acoustic transducer of the acoustic device by less than 1.0 dB at 1 kHz compared to the SNR of the acoustic transducer without the acoustic cover after the acoustic cover has been contacted with water.
  • the acoustic cover may be the membrane cover in the acoustic device of the first aspect.
  • the acoustic cover may have an airflow across the membrane cover of at least 5 cm 3 /cm 2 sec (F).
  • the membrane cover may have an airflow across the membrane cover of at least 7 cm 3 /cm 2 sec (F).
  • the membrane cover may have an airflow across the membrane cover of at least 10 cm 3 /cm 2 sec (F).
  • Preferred and optional features of the membrane cover of the first aspect are preferred and optional features of the acoustic cover of the second aspect.
  • the following method was used to measure the SNR of the acoustic device, including the microphone (corresponding to an acoustic transducer), before installation of a membrane cover, after installation of the membrane cover, and after the acoustic transducer has was put through a water challenge as described below.
  • a MEMS Microphone system (acoustic device) was placed in an Anechoic Box and separated from the Acoustic Source by a distance of 10 cm.
  • the Source was first driven with a Single Frequency excitation of 1Pa at 1 kHz to acquire the Signal Level Power of the MEMS Microphone.
  • the Microphone Noise Power was acquired without any signal excitation to capture the noise floor of the MEMS Microphone.
  • A-Weighting Filter was applied for both the Signal Level Power and the Microphone Noise Power measurements.
  • the MEMS microphone used in the following examples was a commercial top port microphone from Knowles - SPH1642HT5H-1 and the membrane cover was attached onto the device to cover the microphone.
  • the SNR of the microphone without the membrane cover was 65 dB.
  • the SNR of the microphone in the acoustic device was measured before the membrane cover of each example was installed (SNR i ).
  • the membrane cover was installed over the microphone and the SNR of the acoustic device was measured again (SNR f ).
  • the change in SNR ( ⁇ SNR) was determined as the SNR of the acoustic device before installation of the membrane cover minus the SNR of the acoustic device after installation of the membrane cover.
  • the acoustic device to which the membranes in the examples were mounted were immersed in water to a depth of 2 m for a period of 30 minutes.
  • the acoustic device was then retrieved and dried and the SNR of the acoustic device was measured again.
  • the difference between the SNR of the device before it was immersed in water and the SNR of the device after it was immersed was determined (SNRwc).
  • the thickness of the membranes was measured using a non-contact method using an optical digital micrometer (controller LS-7600, laser LS-7010MR, target LS-7010MT as provided by Keyence (UK) Ltd, UK).
  • a sample of the membranes was arranged over a cylindrical stem with a hemispherical head. Minimal tension was applied to the membrane to ensure that the membrane was not stretched.
  • the cylindrical stem was positioned between the laser and target/sensor. The tangential point of the laser beam height is recorded and this delta gives the thickness of the membrane.
  • WEP relates to water intrusion through a material. WEP values were determined according to the following procedure. The test sample (1.5 mm diameter circular membrane sample) was held on a sample holder by means of a clamp. The sample was then pressurized with water. The pressure at which water breaks through via the membrane occurs was recorded as the Water Entry Pressure (WEP).
  • WEP Water Entry Pressure
  • Air permeability was measured by clamping a test sample in a circular gasketed flanged fixture 14 cm in diameter.
  • the upstream side of the sample fixture was connected to a flow meter in line with a source of dry compressed air.
  • the downstream side of the sample fixture was open to the atmosphere.
  • Testing was accomplished by applying an air pressure of 1.3 cm of water to the upstream side of the sample and recording the flow rate of air passing through the in-line flow meter (a ball-float rotameter).
  • Results are reported in terms of Frazier Number which has units of cubic cm per square cm per s.
  • Rayl is a measure of the resistance of the sample to air flow.
  • the pressure drop ( ⁇ P) through the sample was measured at a fixed air flow rate of 10 standard cubic feet per minute (scfh).
  • air flow resistance correlates directly to acoustic resistivity.
  • Expanded polytetrafluoroethylene (ePTFE) membranes were produced according to the teaching of US patent 5,814,405 to Branca et al. and of US patent US 7,306,729 to Bacino et al. which are incorporated herein by reference in their entirety.
  • the prepared dried precursor tape was expanded at modified expansion ratios to produce the ePTFE membranes according the examples provided below.
  • an acoustic device 1 comprises a device body 2, a cavity 4, an acoustic channel 6, and a membrane cover 8.
  • the acoustic channel 6 extends into the device body 2 to the cavity 4.
  • a microphone 10 is provided in the cavity 4 and the membrane cover 8 spans the cavity 4.
  • the cavity had an inner diameter (ID) of 1.2 mm. Accordingly, the membrane cover 8 occludes the acoustic channel 6 to ensure that the microphone 10 is protected from foreign material.
  • the membrane cover 8 comprises an ePTFE membrane made according the method described above expanded at a modified expansion ratio to produce a membrane having a thickness of 50.6 ⁇ m and is adhered to the device body 2.
  • the ePTFE membrane had a mass per area of 1.5 g/m 2 .
  • the acoustic device 1 was then subject to a water challenge by submersion of the acoustic device in water to a depth of 2 meters for 30 minutes.
  • the SNR of the acoustic device 1 after the water challenge, SNR wc was measured and compared to the ⁇ SNR.
  • An acoustic device as described above for example 1 was prepared and provided with a membrane cover 12.
  • the membrane cover 12 comprises an ePTFE membrane made according the method described above expanded at a modified expansion ratio to produce a membrane having a thickness of 96.3 ⁇ m and is adhered to the device body 2.
  • the ePTFE membrane had a mass per area of 2.9 g/m 2 .
  • a comparative example acoustic device comprises the device as described above with a membrane cover 14.
  • the membrane cover 14 comprises an ePTFE membrane made according the method described above expanded at a modified expansion ratio to produce a membrane having a thickness of 125.8 ⁇ m and is adhered to the device body 2.
  • the membrane cover 14 comprised an ePTFE membrane that had a mass per area of 4.3 g/m 2 .
  • a comparative example acoustic device comprises the device as described above with a membrane cover 16.
  • the membrane cover 16 comprises an ePTFE membrane commercially available from W.L.Gore & Associates, Inc. under part number PE13.
  • the commercial example had a MPA of 5.3 g/m 2 with an air permeability of 7.4 cm 3 /cm 2 sec and was found to have a ⁇ SNR of -4.0 dB.
  • ⁇ SNR and SNR wc for the examples and comparative example are provided in Table 1 below: Table 1: Parameters for acoustic devices comprising membrane covers according to examples 1 and 2 and comparative example 1.
  • Example 1 Example 2 Comparative Example 1 ⁇ SNR (dB) -0.8 -1.39 -1.54 SNRwc (dB) 0.3 0.1 -0.1 Air permeability (F) 13.25 10.9 9.97 MPA (g/m 2 ) 1.5 2.9 4.3 Thickness ( ⁇ m) 50.6 96.3 125.8
  • Figure 2 A shows data for ⁇ SNR and SNR wc for the examples 1 and 2 and comparative example 1
  • Figure 2B shows similar data for corresponding examples where the internal diameter of the aperture across which the membrane cover spans were 1.0 mm and 1.6 mm.
  • Predominantly reactive membranes typically have very good SNR (see Figure 4 "Before WEP"). However, the acoustic performance of typical "reactive membranes” are significantly impaired by water challenges, whereas predominantly resistive membranes are not. This is shown in Figure 5 and Figure 4 (After eWEP(1h)).
  • Figure 4 shows the change in SNR for a typical reactive membrane compared to the SNR of the microphone before installation of the membrane cover or vent ( ⁇ SNR, "Before WEP"), and the change in SNR of the acoustic device including the membrane cover or vent after water challenge (SNR wc "after eWEP (1h)").
  • ⁇ SNR is very low for reactive membranes but the SNR wc is very poor.
  • the acoustic devices of examples 1-2 provide good acoustic performance ( ⁇ SNR) whilst also maintaining good acoustic performance after water challenge (SNR wc ).
  • Figure 3 shows the acoustic impedance as a function of frequency for the membranes of example 1 and comparative example 1.
  • the comparative example displays predominantly resistive characteristics, whilst the membrane for example 1 shows reactive and resistive characteristics.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Details Of Audible-Bandwidth Transducers (AREA)
EP22181676.2A 2022-04-04 2022-06-28 Geschützter schallwandler Pending EP4258683A1 (de)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5814405A (en) 1995-08-04 1998-09-29 W. L. Gore & Associates, Inc. Strong, air permeable membranes of polytetrafluoroethylene
US7306729B2 (en) 2005-07-18 2007-12-11 Gore Enterprise Holdings, Inc. Porous PTFE materials and articles produced therefrom
WO2017004331A1 (en) * 2015-06-30 2017-01-05 W. L. Gore & Associates, Inc. Vibro acoustic cover using expanded ptfe composite
WO2017134479A1 (en) * 2016-02-04 2017-08-10 Saati S.P.A. Composite multilayer filtering construction for use as a subcomponent in acoustic and electronic products in general

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5814405A (en) 1995-08-04 1998-09-29 W. L. Gore & Associates, Inc. Strong, air permeable membranes of polytetrafluoroethylene
US7306729B2 (en) 2005-07-18 2007-12-11 Gore Enterprise Holdings, Inc. Porous PTFE materials and articles produced therefrom
WO2017004331A1 (en) * 2015-06-30 2017-01-05 W. L. Gore & Associates, Inc. Vibro acoustic cover using expanded ptfe composite
WO2017134479A1 (en) * 2016-02-04 2017-08-10 Saati S.P.A. Composite multilayer filtering construction for use as a subcomponent in acoustic and electronic products in general

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
KINSLER ET AL., INTERNATIONAL ORGANIZATION FOR STANDARDIZATION, 1999

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