Sound wave detector

Abstract

Sound wave detector (100) comprising the following: - an outer casing (102) with an outer casing wall (104); a gas chamber (106) arranged inside the outer casing (102) and configured to hold a gas, wherein the outer casing wall (104) has an opening (108) providing a gas passage between the gas chamber (106) and the outside of the sound wave detector (100); an excitation element (110) configured to selectively excite gas molecules of a specific type in the gas contained in the gas chamber (106) in a time-varying manner, thereby generating sound waves in the gas; and a sound wave sensor (112) configured to detect the sound waves generated in the gas and sound waves generated outside the sound wave detector (100), the sound wave sensor (112) having an acoustic connection (114) that overlaps with the opening (108) in the outer housing wall (104), wherein the sound wave sensor (112) comprises a mechanical structure which can be deflected by the sound waves to be detected, wherein a deflection of the mechanical structure indicates properties of the sound waves to be detected, wherein the mechanical structure is a transducer, and wherein the mechanical structure is arranged within the gas chamber (106).

Description

Technical field

[0001] Different designs generally refer to a sound wave detector. background

[0002] Sound wave detectors have gained significant importance in modern life, either as part of a speech transmission device or as a photoacoustic detector used in a gas analyzer to analyze gases such as ambient air. As the analysis of ambient air composition, for example due to pollution, becomes increasingly important, it is desirable to create a compact sound wave detector that is flexible in its application.

[0003] US 2008 / 0 252 891 A1 discloses a photoacoustic sensor comprising a sensor system for photoacoustic detection. DE 10 2014 114 672 A1 discloses a photoacoustic gas sensor device for analyzing gas. US 2012 / 0 247 183 A1 discloses a photoacoustic detector. US 2013 / 0 027 707 A1 discloses a filter. US 2008 / 0 011 055 A1 discloses a method for analyzing a gas concentration. Summary

[0004] According to various embodiments, a sound wave detector is provided. The sound wave detector comprises the following: an outer housing with an outer housing wall, a gas chamber arranged within the outer housing and configured to hold a gas. The outer housing wall includes an opening that provides a gas passage between the gas chamber and the outside of the sound wave detector. The sound wave detector further comprises: an excitation element configured to selectively excite gas molecules of a specific type in the gas held in the gas chamber over time, thereby generating sound waves in the gas, and a sound wave sensor configured to detect the sound waves generated in the gas and sound waves generated outside the sound wave detector.The sound wave sensor has an acoustic port that overlaps the opening in the outer housing wall. The sensor incorporates a mechanical structure that can be deflected by the sound waves being detected, with any deflection of this structure indicating characteristics of the sound waves. This mechanical structure is a transducer located within the gas chamber. Brief description of the drawings

[0005] In the drawings, the same reference numerals generally refer to the same parts across different views. The drawings are not necessarily to scale; instead, emphasis is generally placed on illustrating the principles of the invention. The following description details various embodiments with reference to the following drawings, wherein: Fig. Figure 1 shows a schematic view of an exemplary sound wave detector; Fig. 2 shows a schematic view of a modified sound wave detector; Fig. Figure 3 shows a schematic view of another modified sound wave detector; Fig. Figure 4 shows a schematic view of yet another modified sound wave detector; Fig. 5 a simplified view of the in Fig. The sound wave detector shown in section 4 is shown; Fig. 6 a fluidic-acoustic surrogate model of the in Fig. 4 and Fig. The sound wave detector shown in section 5 is shown; Fig. 7 the frequency dependence of signal components of a sound wave sensor of the in Fig. 4 and Fig. The pressure signal detected by the sound wave detector shown in section 5 is shown; and Fig. Figures 8A-8H show various example types of mechanical structures that can form part of the sound wave sensor disclosed here; more precisely, they show Fig. 8A-8B an exemplary membrane structure; Fig. 8C-8D an exemplary cantilever structure; Fig. 8E-8F an exemplary comb structure; and Fig. 8G-8H an exemplary rotatable structure. Description

[0006] The following detailed description refers to the accompanying drawings, which show by way of example specific details and embodiments in which the invention can be practiced.

[0007] The word "exemplary" is used here to mean "serving as an example, case, or illustration." Any embodiment or design described herein as "exemplary" is not necessarily to be construed as preferable or advantageous over other embodiments or designs.

[0008] Fig. Figure 1 shows a sound wave detector 100 comprising an outer housing 102 with an outer housing wall 104 and a gas chamber 106 arranged inside the outer housing 102 and configured to hold a gas. The outer housing wall 104 may include an opening 108 providing a gas passage between the gas chamber 106 and the outside of the sound wave detector 100.

[0009] The term “outer housing wall”, used throughout this description, refers to an outer edge of the sound wave detector 100 that is not obscured by other housing parts, i.e., it defines an outer boundary of the sound wave detector 100.

[0010] The sound wave detector 100 can further comprise an excitation element 110 configured to selectively excite gas molecules of a specific type of gas contained in the gas chamber 106 over a period of time. The excitation element 110 can be configured to cause a specific atomic or molecular excitation of a gas molecule in the gas to be analyzed and / or to excite different vibrational and / or rotational modes of these gas molecules. This excitation causes a positive pressure pulse.

[0011] Switching off the excitation source causes the excited gas molecules to relax, resulting in a negative pressure pulse. Since the specific gas molecules to be analyzed are excited in a time-varying, for example, periodic, manner, a time-varying, for example, periodic, pressure fluctuation is generated in the gas being analyzed. More precisely, sound waves are generated that indicate the concentration of gas molecules of a specific type in the gas. The concentration of these gas molecules is proportional to the generated sound pressure.

[0012] The Sound Wave Detector 100 can be used to monitor the composition of ambient air, for example, to detect the CO2 content and / or toxic gases such as CO in the ambient air. Methane and / or water molecules (humidity) in the ambient air can also be detected in this way. Alternatively or additionally, the Sound Wave Detector 100 can be configured as a breath analyzer and used to measure the alcohol and / or acetone content, which indicates blood sugar levels.

[0013] As in Fig. As shown in Figure 1, the sound wave detector 100 can include a sound wave sensor 112 configured to detect sound waves generated in the gas and sound waves generated outside the sound wave detector 100. A method for distinguishing the sound waves generated in the gas by the excitation element 110 from sound waves generated outside the sound wave detector 100 will be discussed later when the operating principle of the excitation element 110 is described in more detail.

[0014] The sound wave sensor 112 can have a diaphragm 112a that can be deflected by sound waves to be detected. A deflection of the diaphragm 112a can indicate properties of the sound waves to be detected, such as the frequency and / or intensity of the sound waves.

[0015] The diaphragm 112a can be positioned in parallel to a fixed reference diaphragm, thereby defining a capacitor whose capacitance can be changed by a displacement of the diaphragm 112a. Consequently, by measuring this capacitance, a signal can be obtained that indicates the properties of the sound waves. Alternatively or additionally, a piezoelectric element can be used to detect a displacement of the diaphragm 112a.

[0016] As in Fig. As shown in Figure 1, the diaphragm 112a of the sound wave sensor 112 can delimit the gas chamber 106 in order to efficiently detect sound waves generated therein. The diaphragm 112a can include at least one opening 113 formed through it, thus creating a gas inlet and / or gas outlet for the gas chamber 106.

[0017] The at least one opening 113 can have a diameter in the range of approximately 10 µm to approximately 50 µm. In various embodiments, the membrane 112a can have an opening 113 with a diameter of approximately 30 µm. Several openings, for example 30 openings, can be formed through it to provide a sufficient flow area in the membrane 112a. In this way, gas can be exchanged between the gas chamber 106 and the outside of the sound wave detector 100 by diffusion through the opening 108 provided in the outer housing wall 104 and through the openings 113 provided in the membrane 112a of the sound wave sensor 112. The gas chamber 106 has a volume of approximately 1 mm³. 3 The associated diffusion time can be approximately 1 minute. Gas chambers 106 with larger volumes up to 10 mm³ 3 are also conceivable.

[0018] As in Fig. As shown in Figure 1, the sound wave sensor 112 can include a sound connection 114 that overlaps with the opening 108 in the outer housing wall 104. In this way, sound waves to be detected from outside the sound wave detector 100 are efficiently delivered to the sound wave sensor 112. In the Fig. In the exemplary sound wave detector 100 shown in Figure 1, the membrane 112a can overlap with the opening 108 provided in the outer housing wall 104. In this way, the sound waves entering the sound wave sensor 112 are efficiently directed to the membrane 112a, thus ensuring highly efficient detection of sound waves from outside the sound wave detector 100.

[0019] In this exemplary sound wave detector 100, the sound wave sensor 112 forms part of the gas passage that connects the gas chamber 106 with the exterior of the sound wave detector 100. Furthermore, the gas chamber 106 is in constant communication with the exterior of the sound wave detector 100 via the gas flow. In this way, changes in composition, for example of the ambient air, can be detected quickly.

[0020] The sound wave detector 100 can be mounted in a mobile device such as a mobile phone. This allows for flexible deployment of the sound wave detector 100. In this case, the sound wave sensor 112 can be configured as a microphone, such as a MEMS microphone, and the gas chamber 106 can be part of the microphone's rear volume. This enables the provision of a phone with a compact structure.

[0021] The excitation element 110 can comprise a radiation source 116 configured to emit radiation into the gas chamber 106. The radiation can be suitable for selectively exciting gas molecules of a specific type in the gas in a time-varying manner, thereby generating sound waves.

[0022] The radiation source 116 can be configured to emit electromagnetic radiation in the infrared, visible, and / or ultraviolet frequency range. Infrared light is suitable for exciting molecular vibrational modes. For example, infrared light with a wavelength of approximately 4.25 µm is suitable for exciting the vibrational modes of CO2. The radiation source 116 can be configured to emit light pulses at predetermined time intervals, for example, periodically. The time intervals at which pulses are emitted by the radiation source 116 can determine the frequency of the sound waves induced in the gas, provided that the relaxation of the gas occurs within a period shorter than the time difference between two immediately successive light pulses emitted by the radiation source 116.

[0023] In an exemplary sound wave detector 100, light pulses can be emitted in time intervals in the range of about 0.01 s to about 0.1 s, inducing sound waves with a frequency of about 10 Hz to about 100 Hz, i.e. with a sound frequency in the low frequency range of the audible frequency range of about 20 Hz to 20 kHz.

[0024] Consequently, the sound waves induced in this way are difficult for humans to hear. Therefore, if the Sound Wave Detector 100 is installed in a mobile phone, it can be operated continuously, even during phone calls, without significantly degrading the voice quality. Alternatively, the operation of a Sound Wave Detector 100 installed in a mobile phone can, of course, be interrupted during a phone call.

[0025] The sound waves generated in the gas by the excitation element 110 can be efficiently distinguished from sound waves generated outside the sound wave detector 100, which do not have a well-defined fixed frequency, because the frequency of the sound waves generated in the gas by the radiation source 116 is determined by the frequency of the excitation pulses. Additionally, the sound wave detector 100 can employ a lock-in discrimination scheme based on the time correlation between the operation of the excitation element 110 and the detection of sound waves of the predetermined frequency.

[0026] The radiation source 116 can comprise at least one group consisting of a black body, a photodiode, and a laser. A black body emits radiation according to Planck's law, which means that the emitted spectrum is determined by its temperature and not by its shape or composition.

[0027] The black body can be designed as an electrically heated membrane. During operation, the membrane can be heated to several hundred degrees Celsius, for example, to about 600 °C.

[0028] To selectively excite only a single type of gas molecules present in the gas to be analyzed, it may be necessary to limit the radiation spectrum of the radiation source 116 to a narrow energy band to guarantee that gas molecules of another type are not unintentionally excited, which could impair the measurement accuracy.

[0029] Radiation of a well-defined energy can be provided by a filter 118, which is configured to selectively allow radiation of a predetermined energy, emitted by the radiation source 116 into the gas chamber 106, to pass through. The filter 118 can also be configured to thermally isolate the excitation source 110 from the gas chamber 106 to prevent a thermostatic effect that could override the photoacoustic signal. Thermal insulation between the mounting section of the excitation source 110 and the gas chamber 106 can be provided regardless of whether a filter is required. This means that a thermally insulating window can be provided that is not configured as a filter.

[0030] In cases where only a single type of gas molecule is to be detected in the gas being analyzed, a filter 118 with fixed transmission properties, i.e., a fixed transmission band at a fixed wavelength, can be used. Alternatively, in cases where gas molecules of different types with different excitation energies are to be detected in the gas, an adjustable filter 118 with more adjustable transmission properties can be used. During operation, the transmission properties can be varied over time, for example, periodically, to individually excite the types of gas molecules of interest.

[0031] The fixed or adjustable filter 118 can include a plasmonic filter and / or a Fabry-Perot interferometer.

[0032] As in Fig. As shown in Figure 1, the filter 118 can divide the interior of the sound wave detector 100 into the gas chamber 106 and a radiation source chamber 120, which houses the radiation source 116.

[0033] The radiation source chamber 120 may be partially bounded by the outer casing wall 104 of the outer casing 102. To dissipate the heat generated by the radiation source 116 during operation and to release the pressure generated as a direct result, for example, if the radiation source 116 includes an electrically heated membrane, the outer casing wall 104 may include a heat exchange or pressure equalization passage 122 between the radiation chamber 120 and the outside of the sound wave detector 100. In this way, a temperature increase, for example of the gas in the gas chamber 106, which could otherwise impair the measurement accuracy, can be avoided.

[0034] In the case where the radiation source 116 comprises an electrically heated membrane 117, the membrane 117 can divide the radiation source 120 into a first and a second subchamber 120a, 120b. In this arrangement, the outer housing wall 104 can include a first and a second heat exchange or pressure equalization passage 122a, 122b, respectively, between the first and second subchamber 120a, 120b and the outside of the sound wave detector 100. In this way, differential pressures generated by the radiation source 116 can be efficiently equalized. Efficient pressure equalization can additionally or alternatively be provided by a pressure equalization hole 117a in the membrane 117.

[0035] As in Fig. As shown in Figure 1, the radiation source chamber 120 can be formed in a recess 124 provided in the outer housing wall 104 and covered by the window (filter) 118. In this way, a gas chamber 106 with a large volume can be provided.

[0036] The filter 118 can cover the recess 124 in the outer housing wall 104 in a gas-tight manner to prevent an undefined gas flow into the radiation source chamber 120.

[0037] The recess 124 can be formed in a section of the outer casing wall 104 that comprises several casing wall layers 104a, 104b. As shown in Fig. As shown in Figure 1, the radiation source 116 can be mounted on a housing wall layer 104b that differs from an inner housing wall layer 104a, which forms part of an inner surface of the outer housing wall 104, for example, on a housing wall layer 104b that forms part of an outer surface of the outer housing wall 104. This arrangement provides a way to thermally decouple the radiation source 116 from the gas contained in the gas chamber 106, for example, by providing a thermally insulating film between the housing wall layer 104b supporting the radiation source 116 and the inner housing wall layer 104a.

[0038] Alternatively or additionally, the housing wall layer 104b, on which the radiation source is mounted, can have a lower thermal conductivity than the inner housing wall layer 104a. The outer housing wall layer 104b can be made of a material having a thermal conductivity of less than about 10 W / (m·K) or even less than about 5 W / (m·K).

[0039] The outer casing wall 104 can comprise a substrate 126 and a lid 128, which define the gas chamber 106 between them. The gas chamber 106 can be configured as shown in Fig. 1 shown is limited by the substrate 126 and the lid 128.

[0040] The substrate 126 can be made, at least in part, of a semiconductor such as silicon. The cover 128 can be made of a material with high thermal conductivity, such as metal, to provide a highly thermally conductive connection to a heat sink outside the sound wave detector 100. A holder of the sound wave detector 100 or a person carrying the sound wave detector 100 can serve as a heat sink.

[0041] In an exemplary sound wave detector 100, the sound wave sensor 112 and the excitation element 110 can be mounted on the substrate 126, for example on a side of the substrate 126 that points towards the interior of the outer housing 102.

[0042] As in Fig. As shown in Figure 1, an electronic component 130 can also be mounted on the substrate 126. The electronic component 130 can be configured to control the radiation source 116, for example, the time intervals in which radiation pulses are emitted, as well as the duration of the individual radiation pulses. The electronic component 130 can also be configured to control the transmission properties of an adjustable filter 118.

[0043] The electronic component 130 can additionally or alternatively be configured to analyze signals output by the sound wave sensor 112 in order to distinguish the concentration of gas molecules of a specific type in the gas from a signal output by the sound wave sensor 112. In various embodiments, it can be configured to distinguish signals induced in the sound wave sensor 112 by sound waves generated in the gas chamber 106 from signals induced in the sound wave sensor 112 by sound waves generated outside the sound wave detector 100. In an exemplary sound wave detector 100, the electronic component 130 can be configured as an application-specific integrated circuit (ASIC).

[0044] The gas chamber 106 can be delimited by a reflector to provide highly efficient excitation of gas molecules that are to be detected in the gas. In an exemplary device, the inner surface of the outer casing 104 can be formed, at least in part, from a material with high reflectivity in the frequency range of the emitted electromagnetic radiation. In the device described in Fig. In the sound wave sensor 100 shown, the inner surfaces of the substrate 126 and / or the lid 128, which define the gas chamber 106, can be designed as reflectors.

[0045] The reflector delimiting gas chamber 106 can have a reflectivity in the infrared and / or visible and / or ultraviolet frequency range of at least 20% or at least 50% or even at least 80%.

[0046] Fig. Figure 2 shows a schematic view of a modified sound wave detector 200. Fig. 2 are elements that correspond to the elements of the in Fig. The sound wave detector shown in Figure 1 corresponds to 100, with the same reference symbols, but increased by 100. The one in Fig. The sound wave detector 200 shown in Figure 2 is described only insofar as it differs from the one shown in Figure 2. Fig. 1 shows a sound wave detector 100 differentiating.

[0047] The in Fig. The sound wave detector 200 shown contains a radiation source 216, which differs from the one in Fig. The sound wave detector 100 shown in Figure 1 is not located in a recess provided in the outer housing wall 204. Instead, the radiation source 216 is mounted on a substantially flat section of the inner surface of the outer housing wall 204. The outer housing wall 204 comprises, similarly to the outer housing wall 104 of the one shown in Figure 1, a recess provided in the outer housing wall 204. Fig. 1 Sound wave detector 100 shown, a substrate 226 and a cover 228. The radiation source 216 is mounted on the substrate 226.

[0048] The sound wave detector 200 includes (a radiation window and / or) a filter 218, which divides the interior of the outer housing 202 into a gas chamber 206 and a radiation source chamber 220. The filter 218 can be arranged between two opposing parts of the inner surface of the outer housing wall 204, e.g., between the inner surfaces of the cover 228 and the substrate 226. The filter 218 can be in physical contact with the inner surface of the outer housing wall 204 over its entire circumference and can provide a gas-tight separation between the gas chamber 206 and the radiation source chamber 220.

[0049] To efficiently compensate for the thermoacoustic pressure differences generated by the radiation source 216, a heat exchange or pressure equalization passage 222 can be provided in a part of the outer casing wall 204 that limits the radiation source chamber 220, e.g. in the lid 228.

[0050] The radiation source chamber 220 can of course be provided with several heat exchange or pressure equalization passages, e.g., in the case where the radiation source 216 is designed as an electrically heated membrane that divides the radiation source chamber 220 into several sub-chambers. In this case, similar to the one described in Fig. 1. The sound wave detector 100 shown has its own pressure equalization passage in the outer casing wall 204 for each sub-chamber.

[0051] The other principles of the present invention, which are referred to in Fig. The explanations given for the sound wave detector 100 shown in section 1 also apply accordingly to the one in Fig. 2 shown sound wave detector 200.

[0052] Fig. Figure 3 shows a schematic view of another modified sound wave detector 300. Fig. 3 are elements that correspond to the elements of the in Fig. The sound wave detector 100 shown corresponds to the same reference symbols, but with the number increased by 200. The sound wave detector 300, which is shown in Fig. Figure 3 is only described insofar as it differs from the one shown in Fig. 1 and Fig. The two sound wave detectors shown, 100 and 200, differ.

[0053] Unlike the ones in Fig. 1 and Fig. The sound wave detector 300, which is located in the two sound wave detectors 100 and 200 shown, is included. Fig. Figure 3 shows a radiation unit 332 comprising a radiation unit housing 334, a radiation source 316, and an exit window 318 for the excitation radiation generated by the radiation source 316. The exit window can be configured as an optical filter.

[0054] The radiation unit housing 334 can be constructed from a material with high thermal conductivity, such as a metal, to efficiently dissipate the heat generated by the radiation source 316 during operation. Additionally or alternatively, a heat exchange or pressure equalization passage 322 can be provided in the portion of the outer housing wall 304 on which the radiation unit 332 is mounted. The heat exchange or pressure equalization passage 322 can be a passage between the interior of the radiation unit housing 334 and the exterior of the sound wave detector 300. The radiation source 316 can comprise an electrically heated membrane 317, which is provided with a pressure equalization hole 317a to compensate for pressure differences between the individual parts of the radiation unit housing 334.

[0055] The other principles of the present invention, which were discussed above with reference to the principles set out in Fig. 1 and Fig. The explanations given for the sound wave detectors 100 and 200 shown in the diagram also apply accordingly to the one shown in the diagram. Fig. 3 shown sound wave detector 300.

[0056] Fig. Figure 4 shows a schematic view of yet another modified sound wave detector, the 400. Fig. 4 are elements that correspond to the elements of the in Fig. The 3 sound wave detectors shown correspond to 300, designated with the same reference symbols, but increased by 100. The one in Fig. The sound wave detector 400 shown in Figure 4 is only described insofar as it differs from those shown in Figure 4. Fig. 1, Fig. 2 to Fig. The 3 sound wave detectors shown differ in size: 100, 200 and 300.

[0057] Similar to the one in Fig. The 300 sound wave detector shown comprises the one in Fig. 4. The sound wave detector 400 shown also includes a radiation unit 432 with a radiation unit housing 434 and a radiation source 416 mounted therein. The radiation source 416 can comprise an electrically heated membrane 417, which is provided with at least one pressure equalization hole 417a, which is designed to equalize pressure differences within the radiation unit housing 434.

[0058] As in Fig. As shown in Figure 4, the radiation unit 432 can include a window 418, which can be configured to provide thermal insulation between the interior of the radiation unit housing 434 and the gas chamber 406. The window can be configured as a filter.

[0059] The radiation unit 432 can further comprise a coupling element 419 that connects the window 418 to the radiation unit housing 434. The coupling element 419 can be made of a heat-insulating material with a thermal conductivity of, for example, less than 5 W / m·K. The coupling element 419 can also provide a gas-tight seal between the window 418 and the radiation unit housing 434.

[0060] As in Fig. As shown in Figure 4, the window 418 and the coupling element 419 can also include heat exchange or pressure equalization holes 418a and 419a, respectively.

[0061] The other principles of the present invention, which were discussed above with reference to the principles set out in the Fig. 1, Fig. 2 to Fig. The explanations given for the 3 sound wave detectors 100, 200 and 300 shown also apply accordingly to the one in Fig. 4 shown sound wave detector 400.

[0062] The following is a simplified model of the in Fig. 4 shown sound wave detector 400 with reference to Fig. 4, Fig. 5, Fig. 6 to Fig. 7 described. As in Fig. Figure 4 shows several chambers, including a first chamber V1, a second chamber V2, and a third chamber V3, formed within the sound wave detector 400. The first chamber V1 corresponds to the gas chamber 406. The second chamber V2 is defined between the window 418 and the electrically heated membrane 417 of the radiation source 416. The third chamber V3 is defined within the radiation unit housing 434.

[0063] These chambers V1, V2, and V3 are interconnected via the pressure equalization holes 417a, 418a, and 419a. The first chamber, V1, is connected to the outside of the sound wave detector 400 via the opening 413, which is formed in the diaphragm 412a of the sound wave sensor 412. Therefore, the holes 417a, 418a, and 419a, and the opening 413, form resistances to both gas and heat flow between the individual chambers V1, V2, and V3 and the exterior of the sound wave detector 400.

[0064] The Detector 400 is in Fig. Figure 5 is shown in simplified form. This figure depicts the individual chambers V1, V2, and V3 of the sound wave detector 400 with the respective openings between them. As mentioned above, each of these openings represents a specific resistance R1 to R4.

[0065] The effect of each of these resistors R1 to R4, as well as the volumes of the first to third chambers V1 to V3, can be determined by reference to Fig. 6. better understood, which is a fluidic-acoustic surrogate model of the in Fig. 4 and Fig. Figure 5 shows the sound wave detector 400. The frequency dependencies of the signal components of a signal detectable by the sound wave sensor 412 are shown schematically in the power-frequency diagram (Pf diagram) shown in Figure 5. Fig. Figure 7 shows the following. Each of these components can be influenced by changing the resistances R1 to R4, the volumes of the chambers V1 to V3, and the heat capacity of the sound wave detector 400.

[0066] In Fig. 6 designates Q1 as the source of the desired signal, which is generated by the radiation source 416 in the gas chamber 406 or introduced from the outside of the sound wave detector 400. The frequency profile of this signal is mainly determined by the resistance R1 of the opening 413 in the membrane 412a, by the volume of the first chamber V1, and by the heat capacity of the sound wave detector 400, which is essentially a given in Fig. The system specified in section 6 is affected.

[0067] The frequency dependence of the desired signal is shown by curve C1 in Fig. Figure 7 is shown. As shown in this figure, the power of the desired signal decreases with decreasing frequencies due to the resistance R1 of the opening 413 and the volume of the first chamber V1, which together act as a low-pass filter on this signal.

[0068] In Fig. 6 designates Q2 as a signal source equivalent to the electrically heated membrane 417. The signal generated by this source is primarily influenced by the volumes of the second and third chambers V2 and V3, as well as by the resistances R2, R3, and R4 of holes 417a, 418a, and 419a. Here, R2 accounts for the combined resistance of holes 418a and 419a in window 418 and coupling element 419, respectively.

[0069] R3 and R4 denote the resistance that is to be attributed to the hole 417a, which is formed in the electrically heated membrane 417, with respect to the second chamber V2 and the third chamber V3, respectively.

[0070] Source Q2 has different effects on the signal detectable by the sound wave sensor 412, resulting in different signal components represented by curves C2, C3 and C4 in Fig. 7 are displayed.

[0071] First, the membrane 417 in the first chamber V1 can act as an optical source. The signal component associated with this effect is in Fig. 7 is represented by curve C2. This signal component should be located at frequencies above the high-pass cutoff frequency of the sound wave sensor 412, above the low-pass cutoff frequency of the window 418, and above the thermal cutoff frequency of the system.

[0072] Secondly, the membrane 417 can influence the signal through heat conduction via the detector walls. More precisely, during operation of the radiation source 416, the detector walls are heated by the electrically heated membrane 417 and conduct the heat to the first chamber V1, which houses the sound wave sensor 412. This effect of the membrane 417 must be suppressed, as it can overdrive the sound wave sensor 412. It can be suppressed by thermally decoupling the electrically heated membrane 417 from the detector walls and by providing detector walls with low thermal conductivity and / or high heat capacity. In an ideal case, which in Fig. If 7 is displayed, the signal component C3 lies below the corner frequencies of signals C1 and C2 at low frequencies.

[0073] Thirdly, the diaphragm 417 can influence the signal through sound waves generated outside the first chamber V1, which then propagate into the first chamber V1 through the holes 418a, 419a provided in the window 418 or the coupling element 419. The signal component associated with this effect is shown in Fig. 7 is shown by curve C4. This signal component can be shifted towards lower frequencies by increasing the resistance R2 of the passage between the first and second chambers V1, V2, i.e., the resistance of the holes 418a, 419a provided in window 418 and coupling element 419 respectively.

[0074] According to the exemplary embodiments of the present disclosure, the outer casing walls disclosed herein, for example the outer casing wall 104 of the in Fig. The outer casing 102 shown in Figure 1 may contain two or more layers. In other words, the outer wall can consist of several nested layers. For example, the outer casing walls disclosed in the present disclosure can be divided into layers 112a and 112b of the outer casing wall 104, as shown in Figure 1. Fig. 1 of US patent application No. 15 / 586328 entitled “Device For Detecting Acoustic Waves”, which is incorporated herein by reference in its entirety, are shown, or similar layers are divided or comprise them.

[0075] In embodiments of the present disclosure in which the outer wall of the present disclosure has several layers, the different layers may consist of the same material or of different materials. The innermost layer may consist of a heat-insulating layer that contributes to the suppression of thermally induced noise generated by the radiation source, for example, the radiation source 116. In embodiments of the present disclosure, the radiation source may be located in a recess 124 of the substrate 126, as shown in Fig. 1 is shown (or as it is in Fig. 3 is shown, within the radiation unit housing 334 mounted on substrate 326). In contrast, in Fig. 1 of the above-mentioned application, which is incorporated by reference, the radiation source is shown as entering through window 114.

[0076] According to exemplary embodiments of the present disclosure, a mechanical structure other than a membrane 112a can be used. In particular, any mechanical structure implemented as a transducer capable of converting electrical signals into and from acoustic signals can be used. Examples include, but are not limited to, membranes, resonators, piezoelectric elements, mass spring systems, cantilever structures, comb structures, and rotatable structures. Accordingly, the sound wave sensors described in the present disclosure can comprise a mechanical structure that is deflectable by sound waves to be detected, wherein a deflection of the mechanical structure indicates properties of the sound waves to be detected. Furthermore, the mechanical structure can be located within the gas chamber. The sound wave sensor can also be contained within the gas chamber.Additionally, the mechanical structure can delimit the gas chamber and have at least one opening formed through it, wherein the at least one opening provides a gas inlet and / or a gas outlet of the gas chamber.

[0077] Fig. Figures 8A-8H each show different example types of mechanical structures that can form part of the sound wave sensors disclosed here. Fig. Figures 8A-8B show an exemplary membrane structure. Fig. 8C-8D show an exemplary boom structure. Fig. 8E-8F show an exemplary comb structure. Fig.Figures 8G-8H show an exemplary rotatable structure. For example, cantilever and comb structures can be functionally similar to diaphragm structures in that the deflection of a cantilever arm or comb tine, like the deflection of a diaphragm, can be directly proportional to a sound wave or signal. Additionally, a comb structure with tines of different lengths can be used. Each tine of such a comb can have its own structural resonant frequency. Therefore, a comb structure can be used to transform a sound wave or acoustic signal into a signal in the frequency domain (e.g., using FFT). In various embodiments, a rotatable structure can also be used instead of a diaphragm structure. For example, the rotational speed or angular velocity of a rotating blade of a rotatable structure can correspond to, or be proportional to, a sound wave or acoustic signal.

[0078] The following explains various aspects of this revelation:

[0079] Example 1 is a sound wave detector. The sound wave detector can comprise an outer housing with an outer housing wall and a gas chamber located inside the outer housing and configured to hold a gas. The outer housing wall can include an opening that provides a gas passage between the gas chamber and the outside of the sound wave detector. The sound wave detector can further comprise an excitation element configured to selectively excite gas molecules of a specific type in the gas held in the gas chamber over time, thereby generating sound waves in the gas, and a sound wave sensor configured to detect sound waves generated in the gas and sound waves generated outside the sound wave detector. The sound wave sensor can have an acoustic port that overlaps with the opening in the outer housing wall.The sound wave sensor can have a mechanical structure that can be deflected by the sound waves to be detected, whereby a deflection of the mechanical structure indicates properties of the sound waves to be detected.

[0080] In Example 2, the subject of Example 1 can optionally include an excitation element comprising a radiation source configured to emit radiation into the gas chamber. The radiation can be adjusted to selectively excite gas molecules of a specific type in the gas over time, thereby generating sound waves.

[0081] In Example 3, the subject of Example 2 may optionally include the fact that the radiation source is configured to emit electromagnetic radiation.

[0082] In Example 4, the subject of Example 3 may optionally include the fact that the radiation source is configured to emit electromagnetic radiation in the infrared and / or visible and / or ultraviolet frequency range.

[0083] In Example 5, the subject of Example 4 may optionally include that the radiation source comprises at least one element from the following group: a black body, a photodiode, and a laser.

[0084] In Example 6, the object from Example 5 can optionally include a black body designed as an electrically heated membrane.

[0085] In Example 7, the object of one of Examples 2 to 6 may optionally include a window designed to transmit radiation emitted by the radiation source into the gas chamber and to thermally isolate the radiation source from the gas in the gas chamber.

[0086] In Example 8, the subject of Example 7 may optionally include the window being configured as a filter designed to selectively transmit radiation of a predetermined energy emitted by the radiation source into the gas chamber.

[0087] In Example 9, the subject of Example 8 may optionally include the filter being designed as an adjustable filter whose transmission properties are adjustable.

[0088] In Example 10, the subject of one of Examples 8 or 9 may optionally include that the filter comprises a plasmonic filter and / or a Fabry-Pérot interferometer.

[0089] In Example 11, the subject of one of Examples 7 to 10 may optionally include the window dividing the interior of the sound wave detector into the gas chamber and a radiation source chamber that houses the radiation source.

[0090] In Example 12, the subject of Example 11 may optionally include the radiation source chamber being partially bounded by the outer casing wall of the outer housing. The outer casing wall may include a pressure equalization passage between the radiation source chamber and the outside of the sound wave detector.

[0091] In Example 13, the subject matter of Examples 6 and 12 may optionally include the mechanical structure dividing the radiation source chamber into a first and a second subchamber. The outer casing wall may include a first and a second pressure equalization passage between the first and second subchambers, respectively, and the outside of the sound wave detector.

[0092] In Example 14, the subject of one of Examples 11 to 13 may optionally include the radiation source chamber being formed in a recess in the outer casing wall. The recess may be covered by the window.

[0093] In Example 15, the subject of Example 14 may optionally include the recess being formed in a section of the outer casing wall that has multiple casing wall layers.

[0094] In Example 16, the subject of Example 15 may optionally include the radiation source being mounted on a housing wall layer that is different from an inner housing wall layer that forms part of an inner surface of the outer housing wall.

[0095] In Example 17, the subject of Example 16 may optionally include the radiation source being mounted on a housing wall layer that forms part of an outer surface of the outer housing wall.

[0096] In Example 18, the subject of one of Examples 16 or 17 may optionally include the fact that the casing wall layer on which the radiation source is mounted has a lower thermal conductivity than the inner casing wall layer.

[0097] In Example 19, the subject of one of Examples 7 to 18 may optionally include a radiation unit comprising a radiation unit housing, the radiation source housed in the radiation unit housing, and the window forming an exit window of the radiation unit housing.

[0098] In Example 20, the subject of one of Examples 1 to 19 may optionally include the sound wave sensor being located inside the outer casing.

[0099] In Example 21, the subject of one of Examples 2 to 19 may optionally include the radiation source being located inside the outer casing.

[0100] In Example 22, the subject of Example 21 may optionally include the fact that the mechanical structure is located inside the gas chamber.

[0101] In Example 23, the subject of Example 22 may optionally include the fact that the sound wave sensor is located inside the gas chamber.

[0102] In Example 24, the subject of one of Examples 21 to 23 may optionally include a mechanical structure that delimits the gas chamber and has at least one opening through it. The at least one opening may provide a gas inlet and / or a gas outlet for the gas chamber.

[0103] In Example 25, the subject of one of Examples 1 to 24 may optionally include the sound wave sensor being configured as a microphone.

[0104] In Example 26, the subject of Example 25 may optionally include the sound wave sensor being configured as a microphone for a mobile phone. The gas chamber may be located in the rear volume of the microphone.

[0105] In Example 27, the subject of one of Examples 1 to 26 may optionally include that the gas chamber has a volume in the range of about 1 to about 10 mm³. 3 exhibits.

[0106] In Example 28, the subject of one of Examples 1 to 27 may optionally include that the outer casing comprises a substrate and a lid that define the gas chamber between them.

[0107] In Example 29, the subject of Example 28 may optionally include the sound wave sensor and / or the excitation element being mounted on the substrate.

[0108] In Example 30, the subject of one of Examples 28 or 29 may optionally include an electronic component mounted on the substrate and configured to process signals output by the sound wave sensor and / or to control the excitation element.

[0109] In Example 31, the subject of one of Examples 1 to 30 may optionally include that the gas chamber is limited by a reflector.

[0110] In Example 32, the subject of Example 31 may optionally include the fact that the reflector has a reflectivity in the infrared and / or visible and / or ultraviolet frequency range of at least 20% or at least 50% or even at least 80%.

[0111] In Example 33, the subject matter of one of Examples 28 to 30 and one of Claims 31 or 32 may optionally include the substrate and / or the lid being configured as reflectors.

[0112] Example 34 is a mobile device comprising a sound wave detector according to one of Examples 1 to 33.

[0113] In Example 35, the subject matter of Example 34 includes the mobile device being designed as a mobile phone.

[0114] Example 36 is a microphone device. The microphone device can comprise a microphone configured to detect sound waves and a radiation source arranged within a rear volume of the microphone and configured to emit modulated radiation, which is configured to excite a gas in the rear volume of the microphone, thereby generating sound waves detectable by the microphone, wherein the microphone comprises a mechanical structure that can be deflected by the sound waves to be detected, wherein a deflection of the mechanical structure indicates properties of the sound waves to be detected.

[0115] In Example 37, the subject of one of Examples 1 to 33 may optionally include that the mechanical structure is a converter.

[0116] In Example 38, the subject of one of Examples 1 to 33 may optionally include that the mechanical structure is either a membrane structure, a cantilever structure, a comb structure, or a rotatable structure.

Claims

[1] Sound wave detector (100) comprising the following: - an outer casing (102) with an outer casing wall (104); a gas chamber (106) arranged inside the outer casing (102) and configured to hold a gas, wherein the outer casing wall (104) has an opening (108) providing a gas passage between the gas chamber (106) and the outside of the sound wave detector (100); an excitation element (110) configured to selectively excite gas molecules of a specific type in the gas contained in the gas chamber (106) in a time-varying manner, thereby generating sound waves in the gas; and a sound wave sensor (112) configured to detect the sound waves generated in the gas and sound waves generated outside the sound wave detector (100), the sound wave sensor (112) having an acoustic connection (114) that overlaps with the opening (108) in the outer housing wall (104), wherein the sound wave sensor (112) comprises a mechanical structure which can be deflected by the sound waves to be detected, wherein a deflection of the mechanical structure indicates properties of the sound waves to be detected, wherein the mechanical structure is a transducer, and wherein the mechanical structure is arranged within the gas chamber (106). [2] Sound wave detector (100) according to claim 1, wherein the excitation element (110) comprises a radiation source (116) which is configured to emit radiation into the gas chamber (106), wherein the radiation is configured to selectively excite gas molecules of a specific type in the gas in a time-varying manner, thereby generating sound waves. [3] Sound wave detector (100) according to claim 2, wherein the radiation source (116) is configured to emit electromagnetic radiation; wherein the radiation source (116) is optionally configured to emit electromagnetic radiation in the infrared and / or visible and / or ultraviolet frequency range. [4] Sound wave detector (100) according to one of claims 2 or 3, further comprising: a window designed to transmit radiation emitted from the radiation source (116) into the gas chamber (106) and to thermally insulate the radiation source (116) from the gas in the gas chamber (106). [5] Sound wave detector (100) according to claim 4, wherein the window is configured as a filter (118) which is configured to selectively transmit radiation of a predetermined energy emitted by the radiation source (116) into the gas chamber (106); wherein the filter (118) is optionally configured as an adjustable filter whose transmission properties are adjustable. [6] Sound wave detector (100) according to one of claims 4 or 5, wherein the window divides an interior of the sound wave detector (100) into the gas chamber (106) and a radiation source chamber (120) which houses the radiation source (116). [7] Sound wave detector (100) according to claim 6, wherein the radiation source chamber (120) is formed in a recess (124) in the outer housing wall (104), wherein the recess (124) is covered by the window. [8] Sound wave detector (100) according to claim 7, wherein the recess (124) is formed in a section of the outer housing wall (104) which has several housing wall layers. [9] Sound wave detector (100) according to claim 8, wherein the radiation source (116) is mounted on a housing wall layer which differs from an inner housing wall layer which forms part of an inner surface of the outer housing wall (104). [10] Sound wave detector (100) according to any one of claims 4 to 9, further comprising: a radiation unit comprising a radiation unit housing, the radiation source (116) housed within the radiation unit housing, and the window forming an exit window of the radiation unit housing. [11] Sound wave detector (100) according to one of claims 1 to 10, wherein the sound wave sensor (112) is arranged inside the outer housing (102). [12] Sound wave detector (100) according to one of claims 1 to 11, wherein the sound wave sensor (112) is arranged inside the gas chamber (106). [13] Sound wave detector (100) according to any one of claims 1 to 12, wherein the mechanical structure limits the gas chamber (106) and has at least one opening formed through it, wherein the at least one opening provides a gas inlet and / or a gas outlet of the gas chamber (106). [14] Sound wave detector (100) according to one of claims 1 to 13, wherein the sound wave sensor (112) is designed as a microphone. [15] Sound wave detector (100) according to one of claims 1 to 14, wherein the gas chamber (106) has a volume in the range of about 1 to about 10 mm 3 exhibits. [16] Sound wave detector (100) according to any one of claims 1 to 15, wherein the outer housing (102) comprises a substrate (126) and a lid (128) defining the gas chamber (106) between them. [17] Sound wave detector (100) according to any one of claims 1 to 16, wherein the gas chamber (106) is limited by a reflector. [18] Sound wave detector (100) according to any one of claims 1 to 17, wherein the mechanical structure is either a membrane structure, a cantilever structure, a comb structure or a rotatable structure. [19] Sound wave detector (100) according to one of claims 2 to 18, wherein the radiation source (116) is arranged inside the outer housing (102).

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