US20170325012A1 - Device for detecting acoustic waves - Google Patents
Device for detecting acoustic waves Download PDFInfo
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- US20170325012A1 US20170325012A1 US15/586,328 US201715586328A US2017325012A1 US 20170325012 A1 US20170325012 A1 US 20170325012A1 US 201715586328 A US201715586328 A US 201715586328A US 2017325012 A1 US2017325012 A1 US 2017325012A1
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- Prior art keywords
- housing
- thermally insulating
- housing wall
- frequency range
- thermal conductivity
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H17/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves, not provided for in the preceding groups
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- 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
- H04R1/04—Structural association of microphone with electric circuitry therefor
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H11/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by detecting changes in electric or magnetic properties
- G01H11/06—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by detecting changes in electric or magnetic properties by electric means
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/02—Analysing fluids
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/22—Details, e.g. general constructional or apparatus details
- G01N29/24—Probes
- G01N29/2418—Probes using optoacoustic interaction with the material, e.g. laser radiation, photoacoustics
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- 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
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R19/00—Electrostatic transducers
- H04R19/04—Microphones
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R29/00—Monitoring arrangements; Testing arrangements
- H04R29/004—Monitoring arrangements; Testing arrangements for microphones
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R19/00—Electrostatic transducers
- H04R19/005—Electrostatic transducers using semiconductor materials
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R2201/00—Details of transducers, loudspeakers or microphones covered by H04R1/00 but not provided for in any of its subgroups
- H04R2201/003—Mems transducers or their use
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R2201/00—Details of transducers, loudspeakers or microphones covered by H04R1/00 but not provided for in any of its subgroups
- H04R2201/02—Details casings, cabinets or mounting therein for transducers covered by H04R1/02 but not provided for in any of its subgroups
- H04R2201/029—Manufacturing aspects of enclosures transducers
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R2410/00—Microphones
- H04R2410/03—Reduction of intrinsic noise in microphones
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R2499/00—Aspects covered by H04R or H04S not otherwise provided for in their subgroups
- H04R2499/10—General applications
- H04R2499/11—Transducers incorporated or for use in hand-held devices, e.g. mobile phones, PDA's, camera's
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R31/00—Apparatus or processes specially adapted for the manufacture of transducers or diaphragms therefor
Definitions
- Various embodiments relate generally to a device for detecting acoustic waves including a housing and an acoustic wave sensor.
- a key performance parameter of sensors in general is the signal-to-noise ratio which is directly linked to both the sensitivity and the resolution of the sensors. This also applies to devices for detecting acoustic waves. Low noise levels are a mandatory prerequisite for achieving high signal-to-noise ratios.
- a specific noise source of devices for detecting acoustic waves arises from thermal fluctuations of gas present inside the housing that induce pressure fluctuations, i.e. acoustic waves, that may contribute to the noise level of the device.
- a device for detecting acoustic waves may include a housing having a housing wall with an inner surface, and an acoustic wave sensor provided at least partially inside the housing and configured to detect acoustic waves.
- the inner surface of the housing wall is made in at least half of its entire area of a thermally insulating material.
- a device for detecting acoustic waves may include a housing having a metal housing portion, a layer formed on an inner surface of the metal housing portion, and an acoustic wave sensor provided at least partially inside the housing and configured to detect acoustic waves.
- the layer is made of a material having a thermal conductivity that is smaller than the thermal conductivity of the metal housing portion.
- a device for detecting acoustic waves may include a housing having a housing wall, and an acoustic wave sensor provided at least partially inside the housing and configured to detect acoustic waves.
- the housing wall comprises a portion extending from the inner surface to the outer surface of the housing wall, the portion being entirely made of a thermally insulating material.
- FIG. 1 shows a schematic view of a device for detecting acoustic waves
- FIG. 2 shows a schematic view of a modified device for detecting acoustic waves
- FIG. 3 shows a schematic view of another modified device for detecting acoustic waves.
- FIG. 1 shows a device 100 for detecting acoustic waves.
- the device may include a housing 102 having a housing wall 104 with an inner surface 106 and an outer surface 108 .
- the device 100 may include an acoustic wave sensor 110 provided at least partially inside the housing 102 and configured to detect acoustic waves.
- the sensor 110 may include a membrane 111 that may be caused to vibrate by the acoustic waves to be detected, thereby generating a detection signal indicative of the acoustic wave energy and/or intensity.
- the inner surface 106 of the housing wall 104 may be made in at least half of its entire area of a thermally insulating material.
- Thermally induced noise in devices for detecting acoustic waves may be generated by a time-varying energy input into the inside of the housing 102 leading to a temperature rise of gas present inside the housing 102 and thereby to an increase in gas pressure.
- the time-varying energy input may either originate from the exterior of the housing or from an isothermal heat exchange with a lining at the inner surface of the housing wall made of a material with a high thermal conductivity such as metal.
- the temperature of the gas may be thereby increased above the temperature of a heat sink to which the housing 102 is coupled via a thermal link.
- a heat sink may be a holder of the device 100 or the surrounding atmosphere.
- a heat exchange subsequently occurs with the heat sink after the energy input into the inside of the housing 102 , thereby reducing the temperature of the gas inside the housing 102 and, hence, its pressure.
- This in turn leads to pressure fluctuations of the gas inside the housing 102 , i.e. to acoustic waves that may be detected as noise by the acoustic wave sensor 110 .
- the thermal link between the interior of the housing 102 and the exterior of the housing 102 that may act as a heat sink is reduced as compared to housings entirely made of metal which is generally the case in common devices for detecting acoustic waves.
- the frequencies of pressure fluctuations of the gas inside the housing 102 induced by a time-varying energy input into the interior of the housing 102 can be reduced compared to common metal housings, thereby shifting the frequency of the thermally induced noise to lower frequencies, e.g. outside of the frequency range of a signal to be detected by the acoustic wave sensor 110 . Consequently, the signal-to-noise ratio of the device 100 can be improved, since the noise power in the frequency range of the signal is reduced.
- the acoustic wave sensor 110 may be configured as a microphone, e.g. a microphone employed in a telephone such as a MEMS microphone.
- the frequency range of the signal to be detected by the acoustic wave sensor 110 is the audible frequency range (about 20 Hz to about 20 kHz).
- the frequencies of the thermally induced noise may be shifted down to below 20 Hz, i.e. outside of the audible frequency range, thereby reducing the noise in the frequency range of the signal and increasing the signal-to-noise ratio of the microphone.
- the frequency range of the signal is the frequency range between the lowest and the highest frequency components of the signal.
- the frequency components of the signal may be determined by Fourier transformation or any other suitable spectral transformation.
- the suppression of thermally induced noise in the device 100 for detecting acoustic waves may be the more efficient the lower the thermal conductivity of the thermally insulating material is.
- the thermal conductivity of the thermally insulating material may be less than about 20 W/(m ⁇ K) or even less than about 10 W/(m ⁇ K). In an exemplary device, the thermal conductivity of the thermally insulating material may be even less than about 5 W/(m ⁇ K).
- the thermal conductivity of the thermally insulating material can be as low as about 0.02 W/(m ⁇ K) which nearly corresponds to the thermal conductivity of air. Such a low thermal conductivity may be achieved, e.g., with expanded polystyrene that relies on thermal insulation by air.
- An even lower thermal conductivity may be provided by a vacuum shield that may be microfabricated.
- the housing wall 104 may have a portion extending between the inner surface 106 and the outer surface 108 of the housing wall 104 , the portion being entirely made of the thermally insulating material. This means that this portion extends over the full thickness of the housing wall 104 .
- Another parameter that may directly influence the suppression of thermally induced noise may be the area of the inner surface 106 that is made of the thermally insulating material. The suppression of thermally induced noise may be the more efficient the higher the area of the inner surface 106 of the housing wall 104 made of the thermally insulating material is.
- the inner surface 106 of the housing wall 104 may be made in at least 70% or even in at least 90% of its entire area of the thermally insulating material. In an exemplary device 100 for detecting acoustic waves, the entire inner surface 106 of the housing wall 104 may be made of the thermally insulating material.
- the housing wall 104 may include a layered portion 112 .
- the layered portion 112 may include a plurality of layers 112 a, 112 b stacked in a thickness direction of the housing wall 104 .
- the layered portion 112 may include an inner layer 112 a forming at least a part of the inner surface 106 of the housing wall 104 , and at least one outer layer 112 b positioned closer to the outer surface 108 of the housing wall 104 than the inner layer 112 a.
- the device 100 shown in FIG. 1 includes a layered portion 112 with only two layers 112 a, 112 b, layered portions 112 with more than two layers are also conceivable.
- the inner layer 112 a may be made at least in part of the thermally insulating material.
- one outer layer 112 b may be made at least in part of a material having a higher thermal conductivity than the material of the inner layer 112 a.
- the outer layer 112 b may be made of an electrically conductive material such as a metal to support EMI (electromagnetic interference) protection.
- the outer layer 112 b made of a material with a higher thermal conductivity may form at least a part of the outer surface 108 of the housing wall 104 .
- the device 100 for detecting acoustic waves does not necessarily have to be employed in a telephone.
- An exemplary device 100 for detecting acoustic waves may be employed in a gas analyzer configured to analyze gases based on the photo-acoustic effect.
- a gas to be analyzed is excited by an excitation radiation such as light, e.g. emitted by a laser e.g. in the visible or in the ultraviolet (UV) frequency range in a time-varying fashion.
- Infrared (IR) excitation radiation is also conceivable.
- the energy of the excitation radiation may be chosen depending on particles that are to be detected in the gas to be analyzed.
- the frequency may be chosen to match an atomic or molecular transition characteristic to certain particles to be detected in the analyzed gas. In this way, these particles can be selectively excited by the excitation radiation.
- thermal energy is generated. Since the gas to be analyzed is excited in a time-varying fashion, e.g. periodically, thermal energy is also generated in a time-varying fashion leading to pressure fluctuations in the gas, i.e. acoustic waves that may be detected by the acoustic wave sensor 110 .
- the gas to be analyzed may be received inside the housing 102 of the device 100 shown in FIG. 1 .
- the excitation radiation may be supplied to the gas to be analyzed inside the housing 102 through an optically transparent window portion 114 provided in the housing wall 104 .
- the amount of acoustic energy generated during the relaxation of the excited states and detected by the acoustic wave sensor 110 is indicative of a certain content of the particles to be detected in the analyzed gas.
- the inner layer 112 a may be made at least in part or even entirely of a material which is optically transparent.
- the optically transparent material may be optically transparent in the infrared and/or in the visible and/or in the ultraviolet frequency range.
- the optically transparent material may have a transmittance of at least about 80% or even of at least about 90% in the infrared and/or in the visible and/or in the ultraviolet frequency range.
- At least one outer housing wall layer 112 b may be made at least in part or entirely of a material which is optically opaque. In case of a gas analyzer, an opaque outer housing wall layer 112 b may also avoid losses of excitation radiation through the housing wall 104 .
- the optically opaque material may be optically opaque in the infrared and/or in the visible and/or in the ultraviolet frequency range.
- the optically opaque material may have a reflectance of at least about 80% or even of at least about 90% in the infrared and/or the visible and/or in the ultraviolet frequency range. This may be achieved with an outer layer 112 b made at least in part or entirely of a metal.
- An exemplary device 100 configured as a gas analyzer may have an inner layer 112 a made of an optically transparent material with a low thermal conductivity as defined above, and an outer layer 112 b acting as a reflector to provide an efficient gas excitation.
- the housing 102 may include a substrate 116 on which the acoustic wave sensor 110 is mounted, and a lid 118 .
- the substrate 116 may be made of a semiconductor such as silicon.
- the lid 118 may include a part of the layered portion 112 of the housing wall 102 or may be even identical to the layered portion 112 of the housing wall 102 .
- the substrate 116 may include an acoustic port 120 in close proximity to the mounting position of the acoustic wave sensor 110 to efficiently direct acoustic waves to the acoustic wave sensor 110 .
- At least a part of the substrate 116 facing to the inside of the housing 102 may be coated with a thermally insulating substrate material.
- a part of the substrate 116 or the entire surface of the substrate 116 facing to the inside of the housing 102 may be coated with a thermally insulating substrate material.
- the thermal conductivity of the thermally insulating substrate material may be less than about 20 W/(m ⁇ K) or even less than about 10 W/(m ⁇ K). In an exemplary device, the thermal conductivity of the thermally insulating substrate material may be even less than about 5 W/(m ⁇ K).
- the substrate 116 may also include an electronic circuit 122 mounted thereon inside the housing 102 , e.g. for processing signals such as electric signals generated by the sensor 110 , e.g. by its vibrating membrane 111 .
- the electronic circuit 122 may be at least in part coated with thermally insulating substrate material 124 .
- the electronic circuit 122 may include a printed circuit board and/or an electronic component such as an application specific integrated circuit (ASIC).
- ASIC application specific integrated circuit
- the thermally insulating substrate material may be coated on a surface of the printed circuit board and/or of the electronic component. Thermally insulating material may be also provided on the membrane 111 of the sensor 110 and/or on bonding wires.
- no open metallization is present inside the housing 102 , e.g. no open metallization of the electronic circuit 122 . This may be achieved by avoiding any bonding wires inside the housing 102 , e.g. by providing electrical contacts by flip-chip bonding inside the housing 102 .
- the thermally insulating material of the housing wall 104 and/or the thermally insulating material on the substrate 116 may be selected from glass materials, plastic materials such as polymers, Teflon or a mold compound, and oxides such as metal oxides.
- the inner surface 106 of the housing wall 104 may be made in different portions of different thermally insulating materials. Also the substrate 116 or the components mounted thereon may be coated in different portions thereof with different thermally insulating materials.
- bottom-port configuration The configuration shown in FIG. 1 with the sensor 110 mounted on the substrate 116 and the acoustic port 120 provided in the substrate 116 is referred to as “bottom-port” configuration.
- FIG. 2 A device 200 for detecting acoustic waves according to a mirrored configuration with an acoustic wave sensor 210 mounted on a lid 218 and an acoustic port 220 provided in the lid 218 is shown in FIG. 2 .
- This configuration is referred to as “top-port” configuration.
- the same reference numerals are used for the same elements as in FIG. 1 , however, enhanced by the number 100 .
- an electronic component 222 is mounted on the lid 218 .
- the length of wires between an acoustic wave sensor 210 and the electronic component 222 can be kept short, thereby reducing their contribution to the overall thermal conductivity of the thermal link between the interior and the exterior of the housing 102 .
- FIG. 3 A modified device 300 for detecting acoustic waves according to the “top-port” configuration is shown in FIG. 3 .
- the same reference numerals are used for the same elements as in FIG. 1 , however, enhanced by the number 200 .
- the exemplary device 300 shown in FIG. 3 differs from the device shown in FIG. 1 in that the acoustic port 320 is provided in the lid 318 . Similar to the device 100 of FIG. 1 , the electronic component 322 and the acoustic wave sensor 310 are mounted on the substrate 316 .
- walls 326 of the acoustic wave sensor 310 define with the substrate 316 an enclosed volume 328 that might be the origin of the above-discussed noise.
- the walls 326 of the acoustic wave sensor 310 may include thermally insulating material 330 at a side thereof delimiting the enclosed volume 328 .
- the thermally insulating material may include the above-described thermally insulating materials, e.g. oxides and polymers.
- Example 1 is a device for detecting acoustic waves.
- the device may include a housing having a housing wall with an inner surface, and an acoustic wave sensor provided at least partially inside the housing and configured to detect acoustic waves.
- the inner surface of the housing wall is made in at least half of its entire area of a thermally insulating material.
- Example 2 the subject matter of Example 1 can optionally include that the thermal conductivity of the thermally insulating material is less than 20 W/(m ⁇ K).
- Example 3 the subject matter of Example 2 can optionally include that the thermal conductivity of the thermally insulating material is less than 10 W/(m ⁇ K).
- Example 4 the subject matter of Example 3 can optionally include that the thermal conductivity of the thermally insulating material is less than 5 W/(m ⁇ K).
- Example 5 the subject matter of any one of Examples 1 to 4 can optionally include that the inner surface of the housing wall is made in at least 70% of its entire area of the thermally insulating material.
- Example 6 the subject matter of Example 5 can optionally include that the inner surface of the housing wall is made in at least 90% of its entire area of the thermally insulating material.
- Example 7 the subject matter of any one of Examples 1 to 6 can optionally include that the housing wall includes a layered portion including a plurality of layers stacked in a thickness direction of the housing wall.
- the layered portion may include an inner layer forming at least a part of the inner surface of the housing wall, and at least one outer layer positioned closer to an outer surface of the housing wall than the inner layer.
- Example 8 the subject matter of Example 7 can optionally include that the inner layer is made at least in part of the thermally insulating material.
- Example 9 the subject matter of Example 8 can optionally include that at least one outer layer is made at least in part of a material having a higher thermal conductivity than the material of the inner layer.
- Example 10 the subject matter of Example 9 can optionally include that one outer layer forming at least a part of the outer surface of the housing wall has a higher thermal conductivity than the inner layer.
- Example 11 the subject matter of any one of Examples 9 or 10 can optionally include that at least one outer layer is made at least in part of a metal.
- Example 12 the subject matter of any one of Examples 7 to 11 can optionally include that the inner layer is made at least in part of a material which is optically transparent.
- Example 13 the subject matter of Example 12 can optionally include that the optically transparent material is optically transparent in the infrared and/or in the visible and/or in the ultraviolet frequency range.
- Example 14 the subject matter of Example 13 can optionally include that the optically transparent material has a transmittance of at least 80% in the infrared and/or in the visible and/or in the ultraviolet frequency range.
- Example 15 the subject matter of Example 14 can optionally include that the optically transparent material has a transmittance of at least 90% in the infrared and/or in the visible and/or in the ultraviolet frequency range.
- Example 16 the subject matter of any one of Examples 7 to 15 can optionally include that at least one outer layer is made at least in part of a material which is optically opaque.
- Example 17 the subject matter of Example 16 can optionally include the optically opaque material is optically opaque in the infrared and/or in the visible and/or in the ultraviolet frequency range.
- Example 18 the subject matter of Example 17 can optionally include that the optically opaque material has a reflectance of at least 80% in the infrared and/or the visible and/or in the ultraviolet frequency range.
- Example 19 the subject matter of Example 18 can optionally include that the optically opaque material has a reflectance of at least 90% in the infrared and/or the visible and/or in the ultraviolet frequency range.
- Example 20 the subject matter of any one of Examples 1 to 19 can optionally include that the housing includes a substrate on which the acoustic wave sensor is mounted, and a lid.
- Example 21 the subject matter of Example 20 and of any one of Examples 7 to 19 can optionally include that the lid includes a layered portion.
- Example 22 the subject matter of any one of Examples 20 or 21 can optionally include that at least a part of the substrate facing to the inside of the housing is coated with a thermally insulating substrate material.
- Example 23 the subject matter of Example 22 can optionally include that the thermal conductivity of the thermally insulating substrate material is less than 20 W/(m ⁇ K).
- Example 24 the subject matter of Example 23 can optionally include that the thermal conductivity of the thermally insulating substrate material is less than 10 W/(m ⁇ K).
- Example 25 the subject matter of Example 24 can optionally include that the thermal conductivity of the thermally insulating substrate material is less than 5 W/(m ⁇ K).
- Example 26 the subject matter of any one of Examples 20 to 25 can optionally include that the substrate includes an electronic circuit mounted thereon inside the housing.
- the electronic circuit is at least in part coated with the thermally insulating substrate material.
- Example 27 the subject matter of Example 26 can optionally include that the thermally insulating substrate material is coated on a surface of at least one of a printed circuit board, of an electronic component, a membrane of the acoustic wave sensor, and of a bonding wire.
- Example 28 the subject matter of any one of Examples 1 to 27 can optionally include that the acoustic wave sensor is configured as a microphone.
- Example 29 the subject matter of any one of Examples 1 to 28 can optionally include that the housing wall includes an optically transparent window portion providing an optical port to the inside of the housing.
- Example 30 the subject matter of any one of Examples 1 to 29 can optionally include that the thermally insulating material and/or the thermally insulating substrate material is selected from glass materials, plastic materials, and oxides.
- Example 31 the subject matter of any one of Examples 1 to 30 can optionally include that the housing wall comprises a portion extending from the inner surface to the outer surface of the housing wall, the portion being entirely made of the thermally insulating material.
- Example 32 is a device for detecting acoustic waves.
- the device may include a housing having a metal housing portion, a layer formed on an inner surface of the metal housing portion, and an acoustic wave sensor provided at least partially inside the housing and configured to detect acoustic waves.
- the layer is made of a material having a thermal conductivity that is smaller than the thermal conductivity of the metal housing portion.
- Example 33 is a device for detecting acoustic waves.
- the device may include a housing having a housing wall with an inner surface and an outer surface, and an acoustic wave sensor provided at least partially inside the housing and configured to detect acoustic waves.
- the housing wall includes a portion extending from the inner surface to the outer surface of the housing wall, the portion being entirely made of a thermally insulating material.
- Example 34 the subject matter of Example 33 can optionally include that the thermal conductivity of the thermally insulating material is less than 20 W/(m ⁇ K).
- Example 35 the subject matter of Example 34 can optionally include that the thermal conductivity of the thermally insulating material is less than 10 W/(m ⁇ K).
- Example 36 the subject matter of Example 35 can optionally include that the thermal conductivity of the thermally insulating material is less than 5 W/(m ⁇ K).
Abstract
A device for detecting acoustic waves may include a housing having a housing wall with an inner surface, and an acoustic wave sensor provided at least partially inside the housing and configured to detect acoustic waves. The inner surface of the housing wall is made in at least half of its entire area of a thermally insulating material.
Description
- This application claims priority to German Patent Application Serial No. 10 2016 108 421.2, which was filed May 6, 2016, and is incorporated herein by reference in its entirety.
- Various embodiments relate generally to a device for detecting acoustic waves including a housing and an acoustic wave sensor.
- A key performance parameter of sensors in general is the signal-to-noise ratio which is directly linked to both the sensitivity and the resolution of the sensors. This also applies to devices for detecting acoustic waves. Low noise levels are a mandatory prerequisite for achieving high signal-to-noise ratios.
- A specific noise source of devices for detecting acoustic waves arises from thermal fluctuations of gas present inside the housing that induce pressure fluctuations, i.e. acoustic waves, that may contribute to the noise level of the device.
- According to various embodiments, a device for detecting acoustic waves is provided. The device may include a housing having a housing wall with an inner surface, and an acoustic wave sensor provided at least partially inside the housing and configured to detect acoustic waves. The inner surface of the housing wall is made in at least half of its entire area of a thermally insulating material.
- According to various embodiments, a device for detecting acoustic waves is provided. The device may include a housing having a metal housing portion, a layer formed on an inner surface of the metal housing portion, and an acoustic wave sensor provided at least partially inside the housing and configured to detect acoustic waves. The layer is made of a material having a thermal conductivity that is smaller than the thermal conductivity of the metal housing portion.
- According to various embodiments, a device for detecting acoustic waves is provided. The device may include a housing having a housing wall, and an acoustic wave sensor provided at least partially inside the housing and configured to detect acoustic waves. The housing wall comprises a portion extending from the inner surface to the outer surface of the housing wall, the portion being entirely made of a thermally insulating material.
- In the drawings, like reference characters generally refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the following description, various embodiments of the invention are described with reference to the following drawings, in which:
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FIG. 1 shows a schematic view of a device for detecting acoustic waves; -
FIG. 2 shows a schematic view of a modified device for detecting acoustic waves; and -
FIG. 3 shows a schematic view of another modified device for detecting acoustic waves. - The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and embodiments in which the invention may be practiced.
- The word “exemplary” is used herein to mean “serving as an example, instance, or illustration”. Any embodiment or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments or designs.
-
FIG. 1 shows adevice 100 for detecting acoustic waves. The device may include ahousing 102 having ahousing wall 104 with aninner surface 106 and anouter surface 108. Thedevice 100 may include anacoustic wave sensor 110 provided at least partially inside thehousing 102 and configured to detect acoustic waves. As indicated inFIG. 1 , thesensor 110 may include amembrane 111 that may be caused to vibrate by the acoustic waves to be detected, thereby generating a detection signal indicative of the acoustic wave energy and/or intensity. Theinner surface 106 of thehousing wall 104 may be made in at least half of its entire area of a thermally insulating material. - Thermally induced noise in devices for detecting acoustic waves may be generated by a time-varying energy input into the inside of the
housing 102 leading to a temperature rise of gas present inside thehousing 102 and thereby to an increase in gas pressure. The time-varying energy input may either originate from the exterior of the housing or from an isothermal heat exchange with a lining at the inner surface of the housing wall made of a material with a high thermal conductivity such as metal. The temperature of the gas may be thereby increased above the temperature of a heat sink to which thehousing 102 is coupled via a thermal link. Such a heat sink may be a holder of thedevice 100 or the surrounding atmosphere. Via the thermal link a heat exchange subsequently occurs with the heat sink after the energy input into the inside of thehousing 102, thereby reducing the temperature of the gas inside thehousing 102 and, hence, its pressure. This in turn leads to pressure fluctuations of the gas inside thehousing 102, i.e. to acoustic waves that may be detected as noise by theacoustic wave sensor 110. - By making the
inner surface 106 of thehousing wall 104 in at least half of its entire area of a thermally insulating material, the thermal link between the interior of thehousing 102 and the exterior of thehousing 102 that may act as a heat sink is reduced as compared to housings entirely made of metal which is generally the case in common devices for detecting acoustic waves. In this way, the frequencies of pressure fluctuations of the gas inside thehousing 102 induced by a time-varying energy input into the interior of thehousing 102 can be reduced compared to common metal housings, thereby shifting the frequency of the thermally induced noise to lower frequencies, e.g. outside of the frequency range of a signal to be detected by theacoustic wave sensor 110. Consequently, the signal-to-noise ratio of thedevice 100 can be improved, since the noise power in the frequency range of the signal is reduced. - The
acoustic wave sensor 110 may be configured as a microphone, e.g. a microphone employed in a telephone such as a MEMS microphone. In this case, the frequency range of the signal to be detected by theacoustic wave sensor 110 is the audible frequency range (about 20 Hz to about 20 kHz). Here, the frequencies of the thermally induced noise may be shifted down to below 20 Hz, i.e. outside of the audible frequency range, thereby reducing the noise in the frequency range of the signal and increasing the signal-to-noise ratio of the microphone. - The frequency range of the signal is the frequency range between the lowest and the highest frequency components of the signal. The frequency components of the signal may be determined by Fourier transformation or any other suitable spectral transformation.
- The suppression of thermally induced noise in the
device 100 for detecting acoustic waves may be the more efficient the lower the thermal conductivity of the thermally insulating material is. The thermal conductivity of the thermally insulating material may be less than about 20 W/(m·K) or even less than about 10 W/(m·K). In an exemplary device, the thermal conductivity of the thermally insulating material may be even less than about 5 W/(m·K). The thermal conductivity of the thermally insulating material can be as low as about 0.02 W/(m·K) which nearly corresponds to the thermal conductivity of air. Such a low thermal conductivity may be achieved, e.g., with expanded polystyrene that relies on thermal insulation by air. An even lower thermal conductivity may be provided by a vacuum shield that may be microfabricated. - In an
exemplary device 100, thehousing wall 104 may have a portion extending between theinner surface 106 and theouter surface 108 of thehousing wall 104, the portion being entirely made of the thermally insulating material. This means that this portion extends over the full thickness of thehousing wall 104. Another parameter that may directly influence the suppression of thermally induced noise may be the area of theinner surface 106 that is made of the thermally insulating material. The suppression of thermally induced noise may be the more efficient the higher the area of theinner surface 106 of thehousing wall 104 made of the thermally insulating material is. Theinner surface 106 of thehousing wall 104 may be made in at least 70% or even in at least 90% of its entire area of the thermally insulating material. In anexemplary device 100 for detecting acoustic waves, the entireinner surface 106 of thehousing wall 104 may be made of the thermally insulating material. - As shown in
FIG. 1 , thehousing wall 104 may include alayered portion 112. Thelayered portion 112 may include a plurality oflayers housing wall 104. Thelayered portion 112 may include aninner layer 112 a forming at least a part of theinner surface 106 of thehousing wall 104, and at least oneouter layer 112 b positioned closer to theouter surface 108 of thehousing wall 104 than theinner layer 112 a. - Although the
device 100 shown inFIG. 1 includes a layeredportion 112 with only twolayers layered portions 112 with more than two layers are also conceivable. - The
inner layer 112 a may be made at least in part of the thermally insulating material. - In various embodiments, one
outer layer 112 b may be made at least in part of a material having a higher thermal conductivity than the material of theinner layer 112a. Theouter layer 112 b may be made of an electrically conductive material such as a metal to support EMI (electromagnetic interference) protection. Theouter layer 112 b made of a material with a higher thermal conductivity may form at least a part of theouter surface 108 of thehousing wall 104. - The
device 100 for detecting acoustic waves does not necessarily have to be employed in a telephone. Anexemplary device 100 for detecting acoustic waves may be employed in a gas analyzer configured to analyze gases based on the photo-acoustic effect. In such a gas analyzer, a gas to be analyzed is excited by an excitation radiation such as light, e.g. emitted by a laser e.g. in the visible or in the ultraviolet (UV) frequency range in a time-varying fashion. Infrared (IR) excitation radiation is also conceivable. The energy of the excitation radiation may be chosen depending on particles that are to be detected in the gas to be analyzed. In various embodiments, the frequency may be chosen to match an atomic or molecular transition characteristic to certain particles to be detected in the analyzed gas. In this way, these particles can be selectively excited by the excitation radiation. - During the subsequent relaxation of the excited atomic or molecular energy states, thermal energy is generated. Since the gas to be analyzed is excited in a time-varying fashion, e.g. periodically, thermal energy is also generated in a time-varying fashion leading to pressure fluctuations in the gas, i.e. acoustic waves that may be detected by the
acoustic wave sensor 110. - The gas to be analyzed may be received inside the
housing 102 of thedevice 100 shown inFIG. 1 . The excitation radiation may be supplied to the gas to be analyzed inside thehousing 102 through an opticallytransparent window portion 114 provided in thehousing wall 104. - By selecting the energy of the excitation radiation to match a characteristic atomic or molecular transition energy of particles to be detected in the analyzed gas, the amount of acoustic energy generated during the relaxation of the excited states and detected by the
acoustic wave sensor 110 is indicative of a certain content of the particles to be detected in the analyzed gas. - To avoid a temperature rise of the
housing wall 104, e.g. by the excitation radiation, theinner layer 112 a may be made at least in part or even entirely of a material which is optically transparent. Depending, e.g. on the frequency of the excitation radiation in case of a gas analyzer, the optically transparent material may be optically transparent in the infrared and/or in the visible and/or in the ultraviolet frequency range. - In an exemplary device, the optically transparent material may have a transmittance of at least about 80% or even of at least about 90% in the infrared and/or in the visible and/or in the ultraviolet frequency range.
- In order to inhibit or reduce the input of electromagnetic radiation into the
housing 102 from the exterior of thehousing 102, at least one outerhousing wall layer 112 b may be made at least in part or entirely of a material which is optically opaque. In case of a gas analyzer, an opaque outerhousing wall layer 112 b may also avoid losses of excitation radiation through thehousing wall 104. - The optically opaque material may be optically opaque in the infrared and/or in the visible and/or in the ultraviolet frequency range.
- The optically opaque material may have a reflectance of at least about 80% or even of at least about 90% in the infrared and/or the visible and/or in the ultraviolet frequency range. This may be achieved with an
outer layer 112 b made at least in part or entirely of a metal. - An
exemplary device 100 configured as a gas analyzer may have aninner layer 112 a made of an optically transparent material with a low thermal conductivity as defined above, and anouter layer 112 b acting as a reflector to provide an efficient gas excitation. - As shown in
FIG. 1 , thehousing 102 may include asubstrate 116 on which theacoustic wave sensor 110 is mounted, and alid 118. Thesubstrate 116 may be made of a semiconductor such as silicon. Thelid 118 may include a part of the layeredportion 112 of thehousing wall 102 or may be even identical to the layeredportion 112 of thehousing wall 102. - The
substrate 116 may include anacoustic port 120 in close proximity to the mounting position of theacoustic wave sensor 110 to efficiently direct acoustic waves to theacoustic wave sensor 110. - In order to provide an efficient suppression of thermally induced noise, at least a part of the
substrate 116 facing to the inside of thehousing 102 may be coated with a thermally insulating substrate material. In other words, a part of thesubstrate 116 or the entire surface of thesubstrate 116 facing to the inside of thehousing 102 may be coated with a thermally insulating substrate material. - The thermal conductivity of the thermally insulating substrate material may be less than about 20 W/(m·K) or even less than about 10 W/(m·K). In an exemplary device, the thermal conductivity of the thermally insulating substrate material may be even less than about 5 W/(m·K).
- Besides the
acoustic wave sensor 110, thesubstrate 116 may also include anelectronic circuit 122 mounted thereon inside thehousing 102, e.g. for processing signals such as electric signals generated by thesensor 110, e.g. by its vibratingmembrane 111. In order to provide an efficient suppression of thermally generated noise, theelectronic circuit 122 may be at least in part coated with thermally insulatingsubstrate material 124. - The
electronic circuit 122 may include a printed circuit board and/or an electronic component such as an application specific integrated circuit (ASIC). The thermally insulating substrate material may be coated on a surface of the printed circuit board and/or of the electronic component. Thermally insulating material may be also provided on themembrane 111 of thesensor 110 and/or on bonding wires. - In an
exemplary device 100, no open metallization is present inside thehousing 102, e.g. no open metallization of theelectronic circuit 122. This may be achieved by avoiding any bonding wires inside thehousing 102, e.g. by providing electrical contacts by flip-chip bonding inside thehousing 102. - The thermally insulating material of the
housing wall 104 and/or the thermally insulating material on thesubstrate 116 may be selected from glass materials, plastic materials such as polymers, Teflon or a mold compound, and oxides such as metal oxides. - It should be noted that the
inner surface 106 of thehousing wall 104 may be made in different portions of different thermally insulating materials. Also thesubstrate 116 or the components mounted thereon may be coated in different portions thereof with different thermally insulating materials. - The configuration shown in
FIG. 1 with thesensor 110 mounted on thesubstrate 116 and theacoustic port 120 provided in thesubstrate 116 is referred to as “bottom-port” configuration. - A
device 200 for detecting acoustic waves according to a mirrored configuration with anacoustic wave sensor 210 mounted on alid 218 and anacoustic port 220 provided in thelid 218 is shown inFIG. 2 . This configuration is referred to as “top-port” configuration. InFIG. 2 the same reference numerals are used for the same elements as inFIG. 1 , however, enhanced by thenumber 100. - In the exemplary device shown in
FIG. 2 also anelectronic component 222 is mounted on thelid 218. In this way, the length of wires between anacoustic wave sensor 210 and theelectronic component 222 can be kept short, thereby reducing their contribution to the overall thermal conductivity of the thermal link between the interior and the exterior of thehousing 102. - The above concepts described with respect to
device 100 according to the “bottom-port” configuration apply also to thedevice 200 shown inFIG. 2 according to the “top-port” configuration. - A modified
device 300 for detecting acoustic waves according to the “top-port” configuration is shown inFIG. 3 . InFIG. 3 the same reference numerals are used for the same elements as inFIG. 1 , however, enhanced by thenumber 200. - The
exemplary device 300 shown inFIG. 3 differs from the device shown inFIG. 1 in that theacoustic port 320 is provided in thelid 318. Similar to thedevice 100 ofFIG. 1 , theelectronic component 322 and theacoustic wave sensor 310 are mounted on thesubstrate 316. - In the configuration shown in
FIG. 3 ,walls 326 of theacoustic wave sensor 310 define with thesubstrate 316 anenclosed volume 328 that might be the origin of the above-discussed noise. - In order to suppress this kind of noise, the
walls 326 of theacoustic wave sensor 310 may include thermally insulatingmaterial 330 at a side thereof delimiting theenclosed volume 328. The thermally insulating material may include the above-described thermally insulating materials, e.g. oxides and polymers. - The other concepts described with respect to the
device 100 shown inFIG. 1 apply also to thedevice 300 shown inFIG. 3 . - In the following, various aspects of this disclosure will be illustrated:
- Example 1 is a device for detecting acoustic waves. The device may include a housing having a housing wall with an inner surface, and an acoustic wave sensor provided at least partially inside the housing and configured to detect acoustic waves. The inner surface of the housing wall is made in at least half of its entire area of a thermally insulating material.
- In Example 2, the subject matter of Example 1 can optionally include that the thermal conductivity of the thermally insulating material is less than 20 W/(m·K).
- In Example 3, the subject matter of Example 2 can optionally include that the thermal conductivity of the thermally insulating material is less than 10 W/(m·K).
- In Example 4, the subject matter of Example 3 can optionally include that the thermal conductivity of the thermally insulating material is less than 5 W/(m·K).
- In Example 5, the subject matter of any one of Examples 1 to 4 can optionally include that the inner surface of the housing wall is made in at least 70% of its entire area of the thermally insulating material.
- In Example 6, the subject matter of Example 5 can optionally include that the inner surface of the housing wall is made in at least 90% of its entire area of the thermally insulating material.
- In Example 7, the subject matter of any one of Examples 1 to 6 can optionally include that the housing wall includes a layered portion including a plurality of layers stacked in a thickness direction of the housing wall. The layered portion may include an inner layer forming at least a part of the inner surface of the housing wall, and at least one outer layer positioned closer to an outer surface of the housing wall than the inner layer.
- In Example 8, the subject matter of Example 7 can optionally include that the inner layer is made at least in part of the thermally insulating material.
- In Example 9, the subject matter of Example 8 can optionally include that at least one outer layer is made at least in part of a material having a higher thermal conductivity than the material of the inner layer.
- In Example 10, the subject matter of Example 9 can optionally include that one outer layer forming at least a part of the outer surface of the housing wall has a higher thermal conductivity than the inner layer.
- In Example 11, the subject matter of any one of Examples 9 or 10 can optionally include that at least one outer layer is made at least in part of a metal.
- In Examples 12, the subject matter of any one of Examples 7 to 11 can optionally include that the inner layer is made at least in part of a material which is optically transparent.
- In Example 13, the subject matter of Example 12 can optionally include that the optically transparent material is optically transparent in the infrared and/or in the visible and/or in the ultraviolet frequency range.
- In Example 14, the subject matter of Example 13 can optionally include that the optically transparent material has a transmittance of at least 80% in the infrared and/or in the visible and/or in the ultraviolet frequency range.
- In Example 15, the subject matter of Example 14 can optionally include that the optically transparent material has a transmittance of at least 90% in the infrared and/or in the visible and/or in the ultraviolet frequency range.
- In Example 16, the subject matter of any one of Examples 7 to 15 can optionally include that at least one outer layer is made at least in part of a material which is optically opaque.
- In Example 17, the subject matter of Example 16 can optionally include the optically opaque material is optically opaque in the infrared and/or in the visible and/or in the ultraviolet frequency range.
- In Example 18, the subject matter of Example 17 can optionally include that the optically opaque material has a reflectance of at least 80% in the infrared and/or the visible and/or in the ultraviolet frequency range.
- In Example 19, the subject matter of Example 18 can optionally include that the optically opaque material has a reflectance of at least 90% in the infrared and/or the visible and/or in the ultraviolet frequency range.
- In Example 20, the subject matter of any one of Examples 1 to 19 can optionally include that the housing includes a substrate on which the acoustic wave sensor is mounted, and a lid.
- In Example 21, the subject matter of Example 20 and of any one of Examples 7 to 19 can optionally include that the lid includes a layered portion.
- In Example 22, the subject matter of any one of Examples 20 or 21 can optionally include that at least a part of the substrate facing to the inside of the housing is coated with a thermally insulating substrate material.
- In Example 23, the subject matter of Example 22 can optionally include that the thermal conductivity of the thermally insulating substrate material is less than 20 W/(m·K).
- In Example 24, the subject matter of Example 23 can optionally include that the thermal conductivity of the thermally insulating substrate material is less than 10 W/(m·K).
- In Example 25, the subject matter of Example 24 can optionally include that the thermal conductivity of the thermally insulating substrate material is less than 5 W/(m·K).
- In Example 26, the subject matter of any one of Examples 20 to 25 can optionally include that the substrate includes an electronic circuit mounted thereon inside the housing. The electronic circuit is at least in part coated with the thermally insulating substrate material.
- In Example 27, the subject matter of Example 26 can optionally include that the thermally insulating substrate material is coated on a surface of at least one of a printed circuit board, of an electronic component, a membrane of the acoustic wave sensor, and of a bonding wire.
- In Example 28, the subject matter of any one of Examples 1 to 27 can optionally include that the acoustic wave sensor is configured as a microphone.
- In Example 29, the subject matter of any one of Examples 1 to 28 can optionally include that the housing wall includes an optically transparent window portion providing an optical port to the inside of the housing.
- In Example 30, the subject matter of any one of Examples 1 to 29 can optionally include that the thermally insulating material and/or the thermally insulating substrate material is selected from glass materials, plastic materials, and oxides.
- In Example 31 the subject matter of any one of Examples 1 to 30 can optionally include that the housing wall comprises a portion extending from the inner surface to the outer surface of the housing wall, the portion being entirely made of the thermally insulating material.
- Example 32 is a device for detecting acoustic waves. The device may include a housing having a metal housing portion, a layer formed on an inner surface of the metal housing portion, and an acoustic wave sensor provided at least partially inside the housing and configured to detect acoustic waves. The layer is made of a material having a thermal conductivity that is smaller than the thermal conductivity of the metal housing portion.
- Example 33 is a device for detecting acoustic waves. The device may include a housing having a housing wall with an inner surface and an outer surface, and an acoustic wave sensor provided at least partially inside the housing and configured to detect acoustic waves. The housing wall includes a portion extending from the inner surface to the outer surface of the housing wall, the portion being entirely made of a thermally insulating material.
- In Example 34, the subject matter of Example 33 can optionally include that the thermal conductivity of the thermally insulating material is less than 20 W/(m·K).
- In Example 35, the subject matter of Example 34 can optionally include that the thermal conductivity of the thermally insulating material is less than 10 W/(m·K).
- In Example 36, the subject matter of Example 35 can optionally include that the thermal conductivity of the thermally insulating material is less than 5 W/(m·K).
- While the invention has been particularly shown and described with reference to specific embodiments, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. The scope of the invention is thus indicated by the appended claims and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced.
Claims (25)
1. A device for detecting acoustic waves, comprising:
a housing having a housing wall with an inner surface; and
an acoustic wave sensor provided at least partially inside the housing and configured to detect acoustic waves,
wherein the inner surface of the housing wall is made in at least half of its entire area of a thermally insulating material.
2. The device of claim 1 , wherein the thermal conductivity of the thermally insulating material is less than 20 W/(m·K).
3. The device of claim 1 ,
wherein the inner surface of the housing wall is made in at least 70% of its entire area of the thermally insulating material.
4. The device of claim 1 ,
wherein the housing wall comprises a layered portion comprising a plurality of layers stacked in a thickness direction of the housing wall;
wherein the layered portion comprises an inner layer forming at least a part of the inner surface of the housing wall, and at least one outer layer positioned closer to an outer surface of the housing wall than the inner layer.
5. The device of claim 4 ,
wherein the inner layer is made at least in part of the thermally insulating material.
6. The device of claim 5 ,
wherein at least one outer layer is made at least in part of a material having a higher thermal conductivity than the material of the inner layer;
wherein optionally one outer layer forming at least a part of the outer surface of the housing wall has a higher thermal conductivity than the inner layer.
7. The device of claim 6 ,
wherein at least one outer layer is made at least in part of a metal.
8. The device of claim 4 ,
wherein the inner layer is made at least in part of a material which is optically transparent.
9. The device of claim 8 ,
wherein the optically transparent material is optically transparent in at least one of the following frequency ranges:
the infrared frequency range;
the visible frequency range;
the ultraviolet frequency range.
10. The device of claim 9 ,
wherein the optically transparent material has a transmittance of at least 80% in at least one of the following frequency ranges:
the infrared frequency range;
the visible frequency range;
the ultraviolet frequency range.
11. The device of claim 4 ,
wherein at least one outer layer is made at least in part of a material which is optically opaque.
12. The device of claim 11 ,
wherein the optically opaque material is optically opaque in at least one of the following frequency ranges:
the infrared frequency range;
the visible frequency range;
the ultraviolet frequency range.
13. The device of claim 12 ,
wherein the optically opaque material has a reflectance of at least 80% in at least one of the following frequency ranges:
the infrared frequency range;
the visible frequency range;
the ultraviolet frequency range.
14. The device of claim 1 ,
wherein the housing comprises a substrate on which the acoustic wave sensor is mounted, and a lid.
15. The device of claim 14 ,
wherein the lid comprises a layered portion.
16. The device of claim 14 ,
wherein at least a part of the substrate facing to the inside of the housing is coated with a thermally insulating substrate material.
17. The device of claim 16 ,
wherein the thermal conductivity of the thermally insulating substrate material is less than 20 W/(m·K).
18. The device of claim 14 ,
wherein the substrate comprises an electronic circuit mounted thereon inside the housing,
wherein the electronic circuit is at least in part coated with the thermally insulating substrate material.
19. The device of claim 1 ,
wherein the acoustic wave sensor is configured as a microphone.
20. The device of claim 1 ,
wherein the housing wall comprises an optically transparent window portion providing an optical port to the inside of the housing.
21. The device of claim 1 ,
wherein at least one of the thermally insulating material or the thermally insulating substrate material is selected from glass materials, plastic materials, and oxides.
22. The device of claim 4 ,
wherein the housing wall comprises a portion extending from the inner surface to the outer surface of the housing wall, the portion being entirely made of the thermally insulating material.
23. A device for detecting acoustic waves, comprising:
a housing having a metal housing portion; and
a layer formed on an inner surface of the metal housing portion;
an acoustic wave sensor provided at least partially inside the housing and configured to detect acoustic waves,
wherein the layer is made of a material having a thermal conductivity that is smaller than the thermal conductivity of the metal housing portion.
24. A device for detecting acoustic waves, comprising:
a housing having a housing wall with an inner surface and an outer surface; and
an acoustic wave sensor provided at least partially inside the housing and configured to detect acoustic waves,
wherein the housing wall comprises a portion extending from the inner surface to the outer surface of the housing wall, the portion being entirely made of a thermally insulating material.
25. The device of claim 24 ,
wherein the thermal conductivity of the thermally insulating material is less than 20 W/(m·K).
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Also Published As
Publication number | Publication date |
---|---|
US20190132661A1 (en) | 2019-05-02 |
US10880629B2 (en) | 2020-12-29 |
US10194226B2 (en) | 2019-01-29 |
CN107421635A (en) | 2017-12-01 |
DE102017109821B4 (en) | 2020-06-04 |
DE102017109821A1 (en) | 2017-11-09 |
US20170325013A1 (en) | 2017-11-09 |
CN107421635B (en) | 2021-02-09 |
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