EP3471434A1

EP3471434A1 - Hearing aid having a microphone module with improved ultrasound properties

Info

Publication number: EP3471434A1
Application number: EP18158599.3A
Authority: EP
Inventors: Per Pedersen; Gorm Dannesboe
Original assignee: Oticon AS
Current assignee: Oticon AS
Priority date: 2018-02-26
Filing date: 2018-02-26
Publication date: 2019-04-17

Abstract

A microphone module for use in a hearing aid comprises a PCB, a MEMS microphone mounted on one surface of the PCB, having an acoustic inlet facing the one surface of the PCB, an opening formed in the PCB, which faces the acoustic inlet of the MEMS microphone, a snout element, which is provided opposing the MEMS microphone on the other surface of the PCB, and a passage extending through the snout element, one end thereof facing the opening in the PCB. The passage forms an acoustic channel and is configured to be longer than the length of the opening in the printed circuit board, and at least a part of the passage has a cross-sectional area which is smaller than the opening area in the PCB.

Description

FIELD OF THE INVENTION

The present disclosure refers to a microphone module for use in a hearing aid, a hearing aid, and a method for manufacturing the microphone module for use in a hearing aid.

BACKGROUND

In general, a hearing aid is configured to improve or augment the hearing capability of an individual by receiving acoustic signals from the individuals' surroundings, modifying the acoustic signals electronically and providing audible signals to at least one of the individual's ears.
Hearing aids generally have a frequency bandwidth capable of supporting the user with speech information and a comfortable sound. This means a bandwidth of at a least 5 kHz in most situations. For the lightest hearing losses the bandwidth should be up to 8-9 KHz and slightly beyond. The optimum would be to have a bandwidth like the normal hearing up to 15 kHz to 20 kHz. All frequencies above 20 kHz should be attenuated as much as possible in order to reduce unwanted side effects. Frequencies above 20 kHz are called ultrasound. Ultrasound impacts the working of a hearing aid in that it can become demodulated or cause clipping or attenuation of the main signal both in the microphone and in an amplifier.
Ultrasound problems have been known to be present in hearing aids for some time, and efforts have been taken to find solutions on how to avoid the ultrasound impact. One solution has been to provide first and second chambers as well as first and second pipes formed in a housing of a hearing aid, wherein the first chamber and the first pipe is fluidly connected to form a first conduit leading from a first acoustic inlet to a first transducer, and the second chamber and the second pipe is fluidly connected to form a second conduit leading from a second acoustic inlet to a second transducer. The first and second conduit each form an acoustic resonator with the respective chamber acting primarily as an acoustic compliance and respective pipe acting primarily as an acoustic mass.
Furthermore, a cavity provided into an inlet member for a microphone system, which also has the function of performing filtering of ultrasound in an incoming sound signal from the environment, so as to reduce unwanted artefacts or sounds, in the ultrasound range, in the signal reaching the microphone, has been investigated.
The investigations have generally focused on minimizing ultrasound effect from especially electret type microphones. However, within the field of hearing aids there is an increased focus on using MEMS (microelectromechanical system) microphone rather than electret microphones. This being due to, among other things, the need for smaller devices, easier installation which is achieved by MEMS since they can be surface mounted to a PCB (printed circuit board). However, MEMS microphones tend to be even more sensitive in view of ultrasound, which, if sent through the processing system of the hearing aid, may cause problems like noise and distortion, within the system. Also, miniaturized systems are generally more vulnerable to contamination, which may occur during manufacturing.
Therefore, there is a need to provide a solution that addresses at least some of the above-mentioned problems, or at least provides an alternative to the solutions already known.

SUMMARY

Hence, it is an object to provide an improved microphone module for use in a hearing aid, which can suppress influences on a MEMS microphone caused by ultrasound with a simple structure, as well as a method for manufacturing a microphone module which suppresses accumulation of dirt and residues within the module.
This object is achieved by a microphone module for use in a hearing aid, which microphone module comprises a printed circuit board, a MEMS microphone mounted on one surface of the printed circuit board, the MEMS microphone comprising an acoustic inlet facing the one surface of the printed circuit board, wherein an aperture is formed in the printed circuit board, which faces the acoustic inlet of the MEMS microphone, an interconnecting element, which is provided opposing the MEMS microphone on the other surface of the printed circuit board, and a passage extending through the interconnecting element, one end thereof facing the aperture in the printed circuit board (in the following also referred to as "PCB"). The passage forms an acoustic channel and is configured to be longer than the length of the aperture in the printed circuit board, and at least a part of the passage has a cross-sectional area which is smaller than the area of the aperture in the printed circuit board.
That is, an interconnecting element is provided at the PCB on a surface opposing the surface of the PCB to which the MEMS microphone is connected. A passage forming an acoustic channel is formed within the interconnecting element, wherein the passage connects the inlet of the MEMS microphone through an aperture (i.e. an opening, e.g. a through hole) formed in the PCB with the outside of the microphone module and leads acoustic waves from the outside of the microphone module to the acoustic inlet (also denoted the inlet) of the MEMS microphone.
Thereby, the interconnecting element not only acts an interconnect component, but also as an acoustical damping element which is capable of reducing influences caused by ultra sound. Particularly, since at least a part of the passage has a cross-sectional area which is smaller than the cross-sectional area of the aperture (i.e. area of the opening in the PCB, e.g. a circular area of a through hole), and the length of the passage (i.e. the path from the opening in the PCB opposing the microphone through the interconnect component to the exterior at the opposing end thereof) is longer than the length of the aperture (i.e. the thickness of the PCB), the acoustic channel formed by the passage is a large property for the sound path that may add to the sound path significant acoustical resistance and acoustic mass. That is, a longer and narrower passage enables shifting the microphone resonance peak(s) to lower frequencies as well as damping the peak(s).
Thereby, the interconnecting element may be provided centrally with regard to the MEMS microphone on the other surface of the printed circuit board.
According to certain embodiments, the passage may be formed by an opening extending through an insert element pressed into the interconnecting element.
That is, an insert element through which an opening extends is inserted (e.g. pressed) into the interconnecting element so that the opening connects the inlet of the MEMS microphone through the aperture formed in the PCB with the outside of the microphone module. Due to e.g. flux and solder issues, both an opening in the interconnecting member and the PCB aperture (opening) have preferably a large diameter in order for the dirt to drop out (supported by gravity) rather than falling into the microphone and causing faults. Hence, the insert element may be inserted (e.g. pressed) into an opening (e.g. hole) formed through the interconnect element after the solder work and a cleaning process, so as to suppress accumulation of dirt in the microphone module. In addition, the insert element may glued onto the interconnect element.
Thereby, according to certain embodiments, the opening may be a round hole formed in the center of the insert element or a polygonal (e.g. rectangular) slit extending through the center of the insert element. A slit may have a high amount of resistance (dampens peaks and high frequencies) and increased inductance (shifts peaks towards lower frequencies).
According to certain embodiments, at least a part of the opening extending through the insert element has a diameter in the range of 0.1mm and 0.3mm, and more preferably in the range of 0.1mm and 0.2mm.
The microphone module according to certain embodiments may further comprise an inlet element, wherein a protrusion of the inlet element is accommodated in an opening extending through the center of the interconnecting element with a spacing formed by a gap between the outer circumference of the protrusion and the inner circumference of the opening in the interconnecting element as well as a gap between the top surface of the protrusion and the printed circuit board, wherein the passage is formed by the spacing.
Thereby, the protrusion forces the sound into a tiny gap between the interconnecting element and the inlet element, thereby forming a relatively long path. This yields high resistance and inductance, where the higher resistance ensures that the resonance peak is dampened (or suppressed) and wherein the higher inductance ensures that the resonance frequency is reduced.
According to certain embodiments, the aperture may be displaced with respect to the interconnecting element, so as to provide a gap between the interconnecting element and the aperture as part of the passage.
According to still further embodiments, the supporting member is formed so as to engage with the interconnecting element on an inner side thereof, and the aperture is displaced with respect to the interconnecting element, so as to provide a gap between the part of the supporting member engaged with the interconnecting element and the aperture as part of the passage.
Furthermore, according to certain embodiments, the aperture in the printed circuit board may by a through hole extending through the printed circuit board and having a diameter in the range of 0.2mm to 0.5mm, and/or may have a length of 0.5mm to 1mm.
Furthermore, the dimensions of the passage may be set in accordance with preset acoustical damping properties (e.g. a look-up table).
The microphone module may further comprise a first mesh which covers the opening of the passage at the side facing the acoustic inlet, and/or a second mesh which covers the opening of the passage at the side facing away from the acoustic inlet.
According to a further aspect there is provided a hearing aid which comprises a casing, at least one microphone module according to previous described aspect, a sound processing means for processing the sound received by the at least one microphone module, and an outputting means for outputting the processed sound.
According to a still further aspect, there is provided a method for manufacturing a microphone module for a hearing aid, comprising mounting a MEMS microphone on one surface of a printed circuit board, wherein an aperture facing the acoustic inlet of the MEMS microphone is formed in the printed circuit board, providing a passage extending through an interconnecting element, installing the interconnecting element at the printed circuit board, such that the interconnecting element centrally opposes the MEMS microphone on the other surface of the printed circuit board and faces the aperture, wherein the passage forms an acoustic channel and is configured to be longer than the length of the aperture in the printed circuit board, and at least a part of the passage has a cross-sectional area which is smaller than the area of the aperture in the printed circuit board.
Thereby, according to certain embodiments, the method may further comprise pressing an insert element into the interconnecting element, wherein the insert element comprises an opening extending through the center thereof, which forms the passage.
Furthermore, according to certain embodiments, the method may further comprise accommodating a protrusion of an inlet element in an opening extending through the center of the interconnecting element with a spacing formed by a gap between the outer circumference of the protrusion and the inner circumference of the opening in the interconnecting element as well as a gap between the top surface of the protrusion and the printed circuit board, wherein the passage is formed by the spacing.
Additionally, the dimensions of the passage may be set in accordance with preset acoustical damping properties.
The interconnecting element forms an acoustical damping element configured to shift a microphone peak to lower frequencies as well as damping the peak. Thereby, it is possible to provide an improved microphone module for use in a hearing aid, which can suppress influences on a MEMS microphone caused by ultra sound with a simple structure, as well as a method for manufacturing a microphone module which suppresses accumulation of dirt and residues within the module.
In the following, embodiments of the present invention are described in detail by means of the accompanying drawings. Thereby, it is to be noted that like elements are provided with like reference numerals in the drawings and descriptions of the embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The aspects of the disclosure may be best understood from the following detailed description taken in conjunction with the accompanying figures. The figures are schematic and simplified for clarity, and they just show details to improve the understanding of the claims, while other details are left out. Throughout, the same reference numerals are used for identical or corresponding parts. The individual features of each aspect may each be combined with any or all features of the other aspects. These and other aspects, features and/or technical effect will be apparent from and elucidated with reference to the illustrations described hereinafter in which:

Fig. 1 shows a comparison of sound pressure level diagrams regarding a MEMS microphone in an example with no filter (top diagram) and with filter (bottom diagram).
Fig. 2 is a graph showing the behavior of an electret microphone.
Fig. 3 schematically shows a comparative example of a microphone module for use in a hearing aid.
Fig. 4 schematically shows a microphone module according to a first embodiment.
Fig. 5 schematically shows a microphone module according to a second embodiment.
Fig. 6 shows an example of a snout element according to the second embodiment.
Fig. 7 schematically shows a microphone module according to a third embodiment.
Fig. 8 schematically shows a microphone module according to a fourth embodiment.
Fig. 9 schematically shows a microphone module according to a fifth embodiment.
Fig. 10 schematically shows a microphone module according to a modification.
Fig. 11 is a flow chart illustrating a manufacturing method according to certain embodiments.
Fig. 12 schematically illustrates a hearing aid according to certain embodiments.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appended drawings is intended as a description of various configurations. The detailed description includes specific details for the purpose of providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. Several aspects of the apparatus and methods are described by various components or elements, steps and/or processes, collectively referred to as "elements". Depending upon particular application, design constraints or other reasons, these elements may be implemented in different embodiments as described herein.
Generally speaking, a hearing device may include a hearing aid that is adapted to improve or augment the hearing capability of a user by receiving an acoustic signal from a user's surroundings, generating a corresponding audio signal, possibly modifying the audio signal and providing the possibly modified audio signal as an audible signal to at least one of the user's ears. The "hearing device" may further refer to a device such as an earphone or a headset adapted to receive an audio signal electronically, possibly modifying the audio signal and providing the possibly modified audio signals as an audible signal to at least one of the user's ears. Such audible signals may be provided in the form of an acoustic signal radiated into the user's outer ear, or an acoustic signal transferred as mechanical vibrations to the user's inner ears through bone structure of the user's head and/or through parts of middle ear of the user or electric signals transferred directly or indirectly to cochlear nerve and/or to auditory cortex of the user.
The hearing device is adapted to be worn in any known way. This may include i) arranging a unit of the hearing device behind the ear with a tube leading air-borne acoustic signals into the ear canal or with a receiver/ loudspeaker arranged close to or in the ear canal such as in a Behind-the-Ear type hearing aid, and/ or ii) arranging the hearing device entirely or partly in the pinna and/ or in the ear canal of the user such as in an In-the-Ear type hearing aid or In-the-Canal/ Completely-in-Canal type hearing aid, or iii) arranging a unit of the hearing device attached to a fixture implanted into the skull bone such as in Bone Anchored Hearing Aid or Cochlear Implant, or iv) arranging a unit of the hearing device as an entirely or partly implanted unit such as in Bone Anchored Hearing Aid or Cochlear Implant.
A "hearing system" refers to a system comprising one or two hearing devices, and a "binaural hearing system" refers to a system comprising two hearing devices where the devices are adapted to cooperatively provide audible signals to both of the user's ears. The hearing system or binaural hearing system may further include auxiliary device(s) that communicates with at least one hearing device, the auxiliary device affecting the operation of the hearing devices and/or benefitting from the functioning of the hearing devices. A wired or wireless communication link between the at least one hearing device and the auxiliary device is established that allows for exchanging information (e.g. control and status signals, possibly audio signals) between the at least one hearing device and the auxiliary device. Such auxiliary devices may include at least one of remote controls, remote microphones, audio gateway devices, mobile phones, public-address systems, car audio systems or music players or a combination thereof. The audio gateway is adapted to receive a multitude of audio signals such as from an entertainment device like a TV or a music player, a telephone apparatus like a mobile telephone or a computer, a PC. The audio gateway is further adapted to select and/or combine an appropriate one of the received audio signals (or combination of signals) for transmission to the at least one hearing device. The remote control is adapted to control functionality and operation of the at least one hearing devices. The function of the remote control may be implemented in a Smartphone or other electronic device, the Smartphone/electronic device possibly running an application that controls functionality of the at least one hearing device.
In general, a hearing device includes i) an input unit such as a microphone for receiving an acoustic signal from a user's surroundings and providing a corresponding input audio signal, and/or ii) a receiving unit for electronically receiving an input audio signal. The hearing device further includes a signal processing unit for processing the input audio signal and an output unit for providing an audible signal to the user in dependence on the processed audio signal.
The input unit may include multiple input microphones, e.g. for providing direction-dependent audio signal processing. Such directional microphone system is adapted to enhance a target acoustic source among a multitude of acoustic sources in the user's environment. In one aspect, the directional system is adapted to detect (such as adaptively detect) from which direction a particular part of the microphone signal originates. This may be achieved by using conventionally known methods. The signal processing unit may include amplifier that is adapted to apply a frequency dependent gain to the input audio signal. The signal processing unit may further be adapted to provide other relevant functionality such as compression, noise reduction, etc. The output unit may include an output transducer such as a loudspeaker/ receiver for providing an air-borne acoustic signal transcutaneously or percutaneously to the skull bone or a vibrator for providing a structure-borne or liquid-borne acoustic signal. In some hearing devices, the output unit may include one or more output electrodes for providing the electric signals such as in a Cochlear Implant.
A microphone has a frequency response that is naturally flat in most of the frequency range for hearing impaired. At higher frequencies a microphone has a peak where the microphone resonates and thus has increased sensitivity in the region of the resonance frequency. This may I induce saturation in the front end of the hearing aid and/or will enter the sound path where the resonation may become audible for the hearing impaired.
Fig. 1 shows a comparison of sound pressure level diagrams regarding a MEMS microphone in an example with no filter and with filter. In particular, the top end diagram illustrates an output of a MEMS microphone according to the prior art, where no "snout"-construction creating a filter is present in the inlet structure, and the bottom diagram illustrates a measurement where a "snout construction" creating a filtering effect is provided. As becomes apparent from the example of MEMS with snout-insert filtering, the ultrasounds frequencies are "dampened" and shifted. Particularly, 1^st peak amplitudes are shifted to lower frequency with reduced peak amplitude, show reduced amplitude and reduced level in certain frequency ranges.
Fig. 2 is a graph showing the behavior of an electret microphone. The behavior shown for the electret microphone is what is intended to achieve with a MEMS microphone instead. The bottom diagram of Fig. 1 illustrates that a microphone module comprising a snout/inlet construction according to the present disclosure is getting close to having a behavior of the MEMS microphone which corresponds to the electret microphone.
According to a comparative example, these demands may be solved by having a damping element in the PCB formed by providing a plurality of holes (e.g. 7 holes) each of approx. 60-70 µm diameter. The rest of the acoustic channel (inlet, snout) are of such large dimensions that they are considered not to be the determining parameters.
As is shown in Fig. 3, the microphone module according to the comparative example comprises a PCB (Printed Circuit Board) 10 being supported by a supporting member 16, such as the housing of the hearing aid or an inlet member 19 provided in the hearing aid, wherein a MEMS (microelectromechanical system) microphone 12 with an acoustic inlet 13 provided on a side of the MEMS facing the PCB 10 is mounted on the PCB 10 (e.g. by soldering). An interconnecting element 14, which is also referred to as "snout element" in the following, serving as interconnect component. A plurality of holes 21 are formed through the PCB 10, thereby forming an acoustic path with a damping characteristics.
However, when manufacturing and assembling the module, various dirt particles (flux, solder balls, etc.) may block the holes after assembly of components on the PCB. Hence, it is preferred to enlarge the PCB holes. Instead of plural small holes, at least one larger hole may be envisaged. However, one large PCB hole may cause the ultra sound performance to deteriorate.
Therefore, instead of using a plurality of the holes the ultrasound problem has been solved, according to the disclosure, by providing an interconnecting element (i.e. a snout) which functions as an acoustical damping element.
That is, by providing a microphone module with an interconnecting element which is provided opposing the MEMS microphone on the other surface of the printed circuit board and comprises a passage extending through the interconnecting element, one end thereof facing the aperture in the printed circuit board, wherein the passage forms an acoustic channel and is configured to be longer than the length of the aperture in the printed circuit board, and at least a part of the passage has a cross-sectional area which is smaller than the area of the aperture in the printed circuit board, an interconnecting element having acoustical damping properties are provided for. By narrowing the snout hole (i.e the hole or passage in the interconnecting element), it is possible to determine dimensions that can be used to control the MEMS performance, by limiting the sensitivity towards at least ultrasounds entering the microphone inlet. Thereby, the added length of the hole - compared to the PCB holes - is relevant to adjust and/or modify in view of limiting the ultrasound contribution to the MEMS microphone. Accordingly, it has been realized that a longer and narrower hole of the passage of the interconnecting element shifts the microphone peak(s) to lower frequencies as well as dampening the peak(s).
According to a first embodiment, as schematically illustrated in Fig. 4, the microphone module comprises a PCB (printed circuit board) 10 being supported by a supporting member 16, such as supported in a part of the housing of the hearing aid or an inlet member 19 provided in the hearing aid, wherein a MEMS (microelectromechanical system) microphone 12 with an acoustic inlet 13 (i.e. an sound inlet) at the side of the microphone 12 facing the PCB 10 is mounted on the PCB 10 (e.g. by soldering). An aperture (opening, such as a through hole) 11 is formed in the PCB at a position centrally opposing the acoustic inlet 13 of the MEMS microphone 12. An interconnecting element 14 (also referred to as a snout element) is provided abutting at the PCB 10 on the opposing side of the MEMS microphone 12.
A passage 15 is extending through the snout element 14 from the aperture 11 to the exterior on the opposite side of the snout 14, thereby forming an acoustic channel.
The passage is configured to be longer than the length of the aperture 11 in the PCB 10 (the length of the opening extending through the PCB 10), and at least a part of the passage 15 has a cross-sectional area which is smaller than the cross-sectional area of the aperture 11 in the PCB.
Thereby, a longer and narrower hole configured as a passage shifts the microphone peak(s) to lower frequencies as well as dampening the peak(s).
The second embodiment basically differs from the first embodiment in that an insert element is inserted (e.g. pressed) into the snout element (e.g. in an opening, such as a through hole, formed therein), and the passage constituting an acoustic channel is formed in the insert element.
Fig. 5 schematically illustrates the second embodiment. The microphone module comprises a PCB (Printed Circuit Board) 10 being supported by a supporting member 16, such as the housing of the hearing aid or an inlet member 19 provided in the hearing aid, wherein a MEMS (microelectromechanical system) microphone 12 with a acoustic inlet 13 at the side of the MEMS microphone facing the PCB 10 is mounted on the PCB 10 (e.g. by soldering). An aperture (opening, such as a through hole) 11 is formed in the PCB at a position centrally opposing the acoustic inlet 13 of the MEMS microphone 12. An interconnecting element 14 (snout element) is provided abutting at the PCB 10 on the opposing side of the MEMS microphone 12.
An insert element 17 is inserted (e.g. pressed) into the snout element 14. The insert element may have the same length as the snout element, or may be longer or shorter. An opening, which forms the passage 15, is extending through the insert element 17 from the aperture 11 to the exterior on the opposite side of the snout 14 is formed, thereby defining an acoustic channel.
The passage is configured to be longer than the length of the aperture 11 in the PCB 10 (the length of the opening extending through the PCB 10), and at least a part of the passage 15 has a cross-sectional area which is smaller than the area of the aperture 11 in the PCB.
The opening in the insert element may be a round hole formed in the center thereof. However, the hole in the insert element can also be realized differently than a round hole, e.g. a polygonal slit (i.e. an opening with a polygonal (e.g. rectangular cross-section) extending through the center of the insert element. Further, at least a part of the opening extending through the insert element has a diameter in the range of 0.1mm and 0.3mm, preferably in the range of 0.1mm to 0.2mm.
With regard to a rectangular insert hole, it is possible to realize very small dimensions, something tending to an approximation of a slit. A slit will have a high amount of resistance (damps peaks and high frequencies) and increased inductance (shifts peaks towards lower frequencies).
In Fig. 6, an example of an insert element according to the second embodiment is shown. The opening has minimum diameter of 0.2 mm and length of 0.6 mm. The "cone shape" which is made in the PCB as is indicated in Fig. 6 may be beneficial in practice, since the through hole may be made in this way.
The hole can be mechanically scaled to other dimensions and give the same intended acoustical damping, by adjusting height and diameter.
It is assumed that the PCB aperture (hole) dimension (length and diameter; cross-sectional area) has an insignificant contribution to the acoustical peak height and ultra sound damping.
According to the second embodiment, the realization of the snout hole is made by means of an insert, which is pressed into the snout. Due to the flux and solder issues, both the snout hole and the PCB hole need to be having a "large" diameter in order for the dirt to drop out (supported by gravity) rather than falling into the microphone and cause the same fault as caused this change in the beginning.
According to the third embodiment, a protrusion of an inlet element (e.g. an inlet member 19 to be placed within the hearing aid) is accommodated in an opening extending through the center of the interconnecting element (snout element) with a spacing formed by a gap between the outer circumference of the protrusion and the inner circumference of the opening in the interconnecting element as well as a gap between the top surface of the protrusion and the PCB, wherein the passage is formed by the spacing.
As is shown in Fig. 7, the microphone module comprises a PCB (Printed Circuit Board) 10 being supported by a supporting member 16, such as the housing of the hearing aid or an inlet member 19 provided in the hearing aid, wherein a MEMS (microelectromechanical system) microphone 12 with a acoustic inlet 13 at the side facing the PCB 10 is mounted on the PCB 10 (e.g. by soldering). An aperture (opening, such as a through hole) 11 is formed in the PCT at a position centrally opposing the acoustic inlet 13 of the MEMS microphone 12. An interconnecting element 14 (snout element) is provided abutting at the PCB 10 on the opposing side of the MEMS microphone 12.
A protrusion 18 of the inlet element 17 is accommodated in the opening extending through the snout element 14 with a spacing 15 formed by a gap between the outer circumference of the protrusion and the inner circumference of the opening in the interconnecting element as well as a gap between the top surface of the protrusion and the PCB, wherein the passage is formed by the spacing 15.
In the third embodiment, an inlet element with male extrusion is accommodated into the snout. The idea is that rather than a through hole in the center of the insert element, it is possible to make a part that forces the sound into a tiny gap between the snout and insert element. Same principle like a slit, with an extra-long path. This yields higher resistance and inductance as previously explained.
Fig. 8 schematically shows a microphone module according to a fourth embodiment. The microphone module differs from the first embodiment in that the aperture 11 is displaced with respect to the interconnecting element (snout) 14, so as to provide a gap 22 between the snout element 14 and the aperture 11 as part of the passage 15. Here, the 'gap 22' functioning as the ultrasound filter is displaced in relation to the inlet 13 to the microphone. Thus, a tiny gap 22 is created through which sound may enter. Thereby, the ultrasound filtering occurs through this "tiny" gap 22 in combination with the snout having the passage therein.
Fig. 9 schematically shows a microphone module according to a fourth embodiment. The microphone module differs from the first embodiment in that the supporting member 16 is formed so as to engage with the interconnecting element (snout) 14 on an inner side thereof, e.g. by clicking, snapping, etc. into the snout 14. Further, the aperture 11 is displaced with respect to the snout 14, so as to provide a gap 22 between the part of the supporting member 16 engaged with the snout 14 and the aperture 11 as part of the passage 15.
According to a modification of the above-mentioned embodiments, as schematically shown in Fig. 10, a first mesh 20a which covers the opening of the passage 15 at the side facing the acoustic inlet 13, and/or a second mesh 20b which covers the opening of the passage 15 at the side facing away from the acoustic inlet 13 may be provided. Such mesh 20a, 20b may also aid in dampening ultrasound, but also ensures that dust, moist or other dirt is prohibited from entering the inlet 13 to the microphone 12.
In all embodiments, the aperture in the printed circuit board may by a through hole having a diameter in the range of 0.2mm to 0.7mm, and/or may have a length of 0.5mm to 1mm. Furthermore, the dimensions of the passage may be set in accordance with preset acoustical damping properties (e.g. a look-up table).
According to the disclosure, there is provided a method for manufacturing a microphone module for a hearing aid, as is illustrated in Fig. 11.
In Step S71 a MEMS microphone is mounted (e.g. soldered) on one surface of a PCB, wherein an aperture (opening) facing the acoustic inlet of the MEMS microphone is formed in the PCB.
In step S72, a passage extending through an interconnecting element is provided.
Then, in step S73, the interconnecting element is installed at the PCB, such that the interconnecting element (snout element) opposes the MEMS microphone on the other surface of the PCB and faces the aperture, wherein the passage forms an acoustic channel and is configured to be longer than the length of the aperture in the printed circuit board, and at least a part of the passage has a cross-sectional area which is smaller than the area of the aperture in the PCB.
Thereby, according to certain embodiments, the method may further comprise pressing an insert element into the interconnecting element, wherein the insert element comprises an opening extending through the center thereof, which forms the passage.
Furthermore, according to certain embodiments, the method may further comprise accommodating a protrusion of an inlet element in an opening extending through the center of the interconnecting element with a spacing formed by a gap between the outer circumference of the protrusion and the inner circumference of the opening in the interconnecting element as well as a gap between the top surface of the protrusion and the printed circuit board, wherein the passage is formed by the spacing.
According to a further embodiment as shown in Fig. 12, there is provided a hearing aid which comprises a casing 80, at least one microphone module 81, a sound processing means 82 for processing the sound received by the at least one microphone module 81, and an outputting means 83 for outputting the processed sound.
According to the present disclosure, the interconnecting element forms an acoustical damping element configured to shift a microphone peak to lower frequencies as well as damping the peak. Thereby, it is possible to provide an improved microphone module for use in a hearing aid, which can suppress influences on a MEMS microphone caused by ultra sound with a simple structure, as well as a method for manufacturing a microphone module which suppresses accumulation of dirt and residues within the module.
As used, the singular forms "a," "an," and "the" are intended to include the plural forms as well (i.e. to have the meaning "at least one"), unless expressly stated otherwise. It will be further understood that the terms "includes," "comprises," "including," and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will also be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element but an intervening elements may also be present, unless expressly stated otherwise. Furthermore, "connected" or "coupled" as used herein may include wirelessly connected or coupled. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items. The steps of any disclosed method is not limited to the exact order stated herein, unless expressly stated otherwise.
It should be appreciated that reference throughout this specification to "one embodiment" or "an embodiment" or "an aspect" or features included as "may" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. Furthermore, the particular features, structures or characteristics may be combined as suitable in one or more embodiments of the disclosure. The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects.
The claims are not intended to be limited to the aspects and specific embodiments shown herein, but several modifications can be carried out within scope of the invention, which is defined by the accompanying claims.
A microphone module for use in a hearing aid comprises a PCB, a MEMS microphone mounted on one surface of the PCB, having an acoustic inlet facing the one surface of the PCB, an opening formed in the PCB, which faces the acoustic inlet of the MEMS microphone, a snout element, which is provided opposing the MEMS microphone on the other surface of the PCB, and a passage extending through the snout element, one end thereof facing the opening in the PCB. The passage forms an acoustic channel and is configured to be longer than the length of the opening in the printed circuit board, and at least a part of the passage has a cross-sectional area which is smaller than the opening area in the PCB.

Claims

Microphone module for use in a hearing aid, comprising:
a printed circuit board;

a MEMS microphone mounted on one surface of the printed circuit board, the MEMS microphone comprising an acoustic inlet facing the one surface of the printed circuit board;

an aperture formed in the printed circuit board, which faces the acoustic inlet of the MEMS microphone;

an interconnecting element, which is provided opposing the MEMS microphone on the other surface of the printed circuit board; and

a passage extending through the interconnecting element, one end thereof facing the aperture in the printed circuit board,

wherein the passage forms an acoustic channel and is configured to be longer than the length of the aperture in the printed circuit board, and at least a part of the passage has a cross-sectional area which is smaller than the area of the aperture in the printed circuit board.
Microphone module according to claim 1, wherein the interconnecting element is provided centrally with regard to the MEMS microphone on the other surface of the printed circuit board.
Microphone module according to claim 1 or 2, wherein the passage is formed by an opening extending through an insert element pressed into the interconnecting element.
Microphone module according to claim 3, wherein the opening is a round hole formed in the center of the insert element or a polygonal slit extending through the center of the insert element.
Microphone module according to claim 3 or 4, wherein at least a part of the opening extending through the insert element has a diameter in the range of 0.1mm and 0.3mm.
Microphone module according to claim 2, further comprising an inlet element, wherein a protrusion of the inlet element is accommodated in an opening extending through the center of the interconnecting element with a spacing formed by a gap between the outer circumference of the protrusion and the inner circumference of the opening in the interconnecting element as well as a gap between the top surface of the protrusion and the printed circuit board, wherein the passage is formed by the spacing.
Microphone module according to claim 1, wherein the aperture is displaced with respect to the interconnecting element, so as to provide a gap between the interconnecting element and the aperture as part of the passage.
Microphone module according to claim 1, wherein
the supporting member is formed so as to engage with the interconnecting element on an inner side thereof, and

the aperture is displaced with respect to the interconnecting element, so as to provide a gap between the part of the supporting member engaged with the interconnecting element and the aperture as part of the passage.
Microphone module according to and of claims 1 to 8, wherein the aperture in the printed circuit board is a through hole extending through the printed circuit board and having a diameter in the range of 0.2mm to 0.5mm.
Microphone module according to and of claims 1 to 9, wherein the aperture in the printed circuit board has a length of 0.5mm to 1mm.
Microphone module according to and of claims 1 to 10, wherein the interconnecting element forms an acoustical damping element configured to shift a microphone peak to lower frequencies as well as damping the peak.
Microphone module according to any of claims 1 to 11, wherein the dimensions of the passage are set in accordance with preset acoustical damping properties.
Microphone module according to any of claims 1 to 12, further comprising a first mesh which covers the opening of the passage at the side facing the acoustic inlet, and/or a second mesh which covers the opening of the passage at the side facing away from the acoustic inlet.
Hearing aid, comprising
a casing;

at least one microphone module according to any of claims 1 to 13;

a sound processing means for processing the sound received by the at least one microphone module; and

an outputting means for outputting the processed sound.
Method for manufacturing a microphone module for a hearing aid, comprising
mounting a MEMS microphone on one surface of a printed circuit board, wherein an aperture facing the acoustic inlet of the MEMS microphone is formed in the printed circuit board,

providing a passage extending through an interconnecting element,

installing the interconnecting element at the printed circuit board, such that the interconnecting element opposes the MEMS microphone on the other surface of the printed circuit board and faces the aperture,

wherein the passage forms an acoustic channel and is configured to be longer than the length of the aperture in the printed circuit board, and at least a part of the passage has a cross-sectional area which is smaller than the area of the aperture in the printed circuit board.
The method according to claim 15, further comprising pressing an insert element into the interconnecting element, wherein the insert element comprises an opening extending through the center thereof, which forms the passage.
The method according to claim 15, further comprising accommodating a protrusion of an inlet element in an opening extending through the center of the interconnecting element with a spacing formed by a gap between the outer circumference of the protrusion and the inner circumference of the opening in the interconnecting element as well as a gap between the top surface of the protrusion and the printed circuit board, wherein the passage is formed by the spacing.
The method according to any of claims 15 to 17, wherein the dimensions of the passage are set in accordance with preset acoustical damping properties.