EP4643553A1

EP4643553A1 - Hearing instrument

Info

Publication number: EP4643553A1
Application number: EP23836406.1A
Authority: EP
Inventors: Niels Christian Damgaard Jakobsen; Kevin Bayer; Manuel WEISS; Bernd Meister; Elisabet TIANA-ROIG; Lars Friis; Patrick SCHEEPER; Boris VALNERT
Original assignee: Widex AS; Sivantos Pte Ltd
Current assignee: Ws Audiology AS; Sivantos Pte Ltd
Priority date: 2023-12-19
Filing date: 2023-12-19
Publication date: 2025-11-05
Also published as: WO2025131248A1

Abstract

An inventive hearing instrument (1) comprises - a main housing (2) having an outer wall enclosing an interior from the outside, - a microphone (4) having a mic-housing (16), a membrane (12) being 5 disposed within the mic-housing (16) and defining a membrane plane (32), and a port hole (20) penetrating a first side-wall (22) of the mic-housing (16), the microphone (4) being aligned within the interior of the main housing (2), and - a sound transmission channel (30) being aligned outside an inner volume of the mic-housing (16), ending with a first end at the port hole (20) and fluidically connecting the port hole (20) with the outside through a mic-opening (24) that penetrates the outer wall of the main housing (2). The sound transmission channel (30) is guided in a curved way such that it intersects the membrane plane (32), the sound transmission channel (30) thus being divided in a port-side part (34) and a rear-side part (36) that is located within a rear- side region of the membrane plane (32) with regards to the port hole (20). An air column within the rear-side part (36) of the sound transmission channel (30) has parts that are perpendicular to the membrane plane (32). An effective length (l_eff) of the rear-side part (36) of the sound transmission channel (30) is chosen in dependence on a sensitivity (Smic) to acoustic inertia of the microphone (4). Also, at least a segment of the sound transmission channel (30) is formed within an element (22, 46, 60) that is integral to the microphone (4).

Description

Specification

Hearing instrument

The invention relates to a hearing instrument. More specifically, the invention relates to a hearing instrument serving as a hearing aid.

Hearing instruments are usually used to output a sound signal to the hearing of the wearer of this hearing instrument. The output is generated by means of an output transducer, usually acoustically via airborne sound by means of a loudspeaker (also referred to as "receiver"). Such hearing instruments are often used as so-called hearing aids. For this purpose, the hearing instruments normally comprise an acoustic input transducer (in particular a microphone) and a signal processor which is set up to process the input signal (also: microphone signal) generated by the input transducer from the ambient sound using at least one signal processing algorithm, usually stored in a user-specific manner, in such a way that a hearing loss of the wearer of the hearing instrument is at least partially compensated. In particular in the case of a hearing aid, the output transducer can be, alternatively to a loudspeaker, a so-called bone conduction receiver or a cochlear implant, which are set up for mechanically or electrically stimulating the hearing of the wearer. The term hearing instruments additionally includes in particular devices such as so-called tinnitus maskers, headsets, headphones and the like.

Typical designs of hearing instruments, in particular hearing aids, are behind-the- ear ("BTE") and in-the-ear ("ITE") hearing instruments. These designations refer to the intended wearing position. Behind-the-ear hearing aids have a (main) housing that is worn behind the auricle. A distinction can be made here between models whose loudspeaker is located in this housing - the sound is usually emitted to the ear by means of a sound tube that is worn in the ear canal - and models that have an external loudspeaker that is placed in the ear canal. In-the-ear hearing aids, on the other hand, have a housing that is worn in the pinna or even completely in the ear canal.

Hearing instruments are often sensitive to vibration, be it structure-borne sound from the receiver or vibration due to movements of the hearing device itself. The latter can cause damage to the microphones or the receiver due to excessive mechanical stress, e. g. in case the vibrations are caused by dropping the hearing aid (or another form of strong mechanical impact). That and structure-borne sound is why microphones and receivers are usually supported with compliant material such that these vibrations are damped and/or reduced. However, movement of the hearing instrument (e.g. by turning the head or the like) may also cause movement (vibration in the widest sense) of an air column within an air duct leading to a sound port of the microphone. Such movement is generally the same as a sound wave and would cause noise in the microphone signal.

The problem underlying the invention is to improve a hearing instrument regarding its vibrational sensitivity.

According to the invention that problem is solved by a hearing instrument with the features of claim 1. Additional embodiments and further developments that may be also inventive for themselves are described in the dependent claims as well as the subsequent specification.

According to the invention the hearing instrument comprises a main housing having an outer wall enclosing an interior from the outside, a microphone having a mic- housing, a membrane being disposed within the mic-housing and defining a membrane plane, and a port hole opening into a first side-wall of the mic-housing adjacent to the membrane. The microphone is aligned within the interior of the main housing. The hearing instrument further comprises a sound transmission channel being aligned outside an inner volume of the mic-housing, ending with a first end at the port hole and fluidically connecting the port hole with the outside through a mic- opening that penetrates the outer wall of the main housing. The sound transmission channel is thereby guided in a curved way such that it intersects the membrane plane. Thus, the sound transmission channel is divided in a port-side part (i. e. particularly a part adjacent to the port hole of the microphone) and a rear-side part that is located within a rear-side region of the membrane plane with regards to the port hole. An air column within the rear-side part of the sound transmission channel has parts that are perpendicular to the membrane plane. Additionally, an effective length of the rear-side part of the sound transmission channel is chosen in dependence on a sensitivity to acoustic inertia of the microphone. Further, at least a segment of the sound transmission channel is formed within an element that is formed integral to the microphone.

“Opening into the first side-wall” adjacent to the membrane is to be understood here and in the following especially in that way that the first side wall of the mic-housing as an opening (the port hole) through which air sound generated by the membrane may enter into or preferably through the first side-wall. Optionally, the port hole may penetrate the first side-wall as a straight bore. Otherwise, the port hole may also be the membrane side opening of a tunnel-like curve bore within the first side-wall, that would exit the first side-wall through another hole at a position not co-axial with the port hole.

“Acoustic inertia” relates especially to the characteristic of microphones that their inertia, especially the inertia of the membrane, further especially in combination with an air mass of a back volume, has an acoustic impact. That is due to the fact that each movement of the membrane creates an electrical output, regardless of the type of microphone (e. g. electret or micro electro-mechanical), that is at first interpreted as due to an acoustic input. The sensitivity of the microphone to the acoustic inertia is a comparative measure that gives information on how strong the acoustic impact of a movement of the microphone is. That “acoustic inertia sensitivity” is given in dB SPL I g (i. e. Decibel sound pressure level per acceleration).

“Curved” is preferably to be understood as not being straight, partially. However, the “curves” the sound transmission channel comprises may be kinked “elbow pieces” as well as smooth (rounded) bendings. The above design of the sound transmission channel may be compared to a typical (diving) snorkel which is usually J-shaped. Since the rear-side part of the sound transmission channel is located on the other side of the membrane plane than the port-side part, the port-side part is preferably the bent-part of the snorkel (or of the “J”) and, thus, there is a balance of the air column within the port-side part regarding its impact on the membrane for movements perpendicular to the membrane plane. Generally, in classic designs, a longer sound transmission channel leading (in a straight way) to a microphone would increase a vibrational sensitivity of the microphone since the longer air column within that channel leads to additional pressure at the membrane. That can be seen from the formula wherein p_pm is the pressure at the port-side of the membrane, pair is the density of air, a is the acceleration, leff is the effective length.

Designing the sound transmission channel in dependence on the acoustic inertia sensitivity advantageously allows to reduce or even cancel impact of mechanical vibrations of the whole hearing instrument upon the output of the microphone, at least in the direction of the effective length. Further, since the inertia of the air in the (comparingly) long sound channels causes a lower resonance frequency, a frequency response of the microphone would be less flat in the frequency range of interest (typically 100 Hz - 10 kHz for hearing aids). Additionally, integrating at least segments of the sound transmission channel into an element integral with the microphones makes up for an easy mounting of the microphone.

In a preferred embodiment, the sound transmission channel, especially its rear-side part is designed under the criterion (i. e. the ideal cancellation condition)

^eff ^mic/ Pair (?) wherein

S ic is the acoustic inertia sensitivity of the microphone. Especially, the sound transmission channel, preferably its rear-side part is chosen such that this criterion (formula 2) is met or at least approximated in a sufficient manner (e. g. by reducing the acoustic inertia sensitivity by at least 20 percent or to about 20 to 10 percent of its nominal value).

Preferably, the effective length of the rear-side part of the sound transmission channel is defined by the sum of all vector values of an inward flow within the rearside part of the sound transmission channel that are perpendicular to the membrane plane. Thus, a syphon like bending of the rear-side part would not add up to the effective length for the whole length of the bending since only parts (or segments) having a flow vector directed to the membrane plane are relevant. In other words, a symmetrical U-shaped structure would - in general - cancel itself out because the length of the part directed to the membrane plane is (usually) the same as in the opposite direction. Figuratively speaking, in the case that the membrane plane is a x-y-plane of a coordinate system and the rear-side part of the sound transmission channel is aligned only along the z-axis, a movement of the hearing instrument in +z-direction will cause a flow within the rear-side part of the sound transmission channel in -z-direction. If now, there is a U-shaped bend in the rear-side part of the sound transmission channel, both legs of the U being aligned also parallel to the z- axis, within each leg a flow in opposite z-direction would be induced that would cancel each other’s effect out. Ideally, the effective length is also the length of the projection of the rear-side part of the sound transmission channel onto the z-axis.

In a preferred embodiment, at least a part of the rear-side part of the sound transmission channel is guided perpendicular to the membrane plane. In that case, the layout of the rear-side part regarding its effective length is quite easy. Also, such alignment of the sound transmission channel is considered to be space saving.

In a further preferred embodiment, the microphone is aligned in a “flipped” orientation with the port hole facing away from an upper side of the main housing, especially from the side wherein the mic-opening is located. In an expedient embodiment as the segment formed within the integral element (of the microphone) at least a part of the port-side part of the sound transmission channel is chosen. Preferably, as that integrated segment a segment attached to the port hole, most preferred the whole port-side part, is chosen.

In an alternative or additional embodiment, as the segment formed within the integral element a part of the rear-side part of the sound transmission channel is chosen, especially integrated into a side wall of the mic-housing.

As an expedient further development of the aforementioned embodiments with the at least partly integrated sound transmission channel, its port-side part (at least a part of that) is integrated into a base plate of the mic-housing. The base plate, thus, makes up for the first side-wall in which the port hole is formed. The base plate is preferably resembled by a (printed) circuit board, especially on which at least one micro electro-mechanical element, preferably a MEMS microphone die (or chip) including the membrane, is mounted.

In an alternative embodiment, the port-side part of the sound transmission channel is integrated into a circuit board element, especially a PCB element, that forms the integral element and that serves as a carrier of the microphone. The port-side part is integrated (formed) into that PCB element by laminating respectively precut layers to form the PCB element with an internal chamber. I.e., the PCB element including the internal chamber is made layer by layer (sheet by sheet). Especially, the portside part is in that case integral (preferably fully) into (or with) that chamber. Expediently, the microphone is coupled fixedly with that PCB element, especially by a soldered connection, and forms, thus, an “extended” or “upgraded” microphone.

In an additional development of the aforementioned laminated PCB element with the internal chamber, at least one metal layer is laminated into the PCB element as a stiffening layer. Thus, that metal layer adds to mechanical stiffness of the PCB element, especially to a well-defined chamber geometry compared to a normal PCB element. This is due to less bending or deformation of the PCB element having the metal layer. Preferably, such metal layer has a thickness of at least 0,1 mm up to 0,5 mm, preferably from 0,25 to 0,4 mm.

In an optional embodiment, a volume of at least a segment of the sound transmission channel is chosen in dependence on ultrasonic filtering. Preferably, such volume is chosen such that ultrasonic frequencies are dampened.

Preferably, the sound transmission channel comprises an enlarged inlet chamber at its mic-opening sided end having aforementioned volume to dampen ultrasonic frequencies.

In an additional or alternative embodiment, measures of the chamber within the aforementioned PCB element are chosen in dependence on ultrasonic filtering (or dampening). Preferably, the cross section of that chamber is about 0,350 x 1 ,5 mm² (+/- 10%), a length of the chamber is about 2,85 mm (+/- 10%) and an inlet to the chamber as well as an (especially port-side) outlet opening from the chamber have a diameter of about 0,3 and 0,2 mm (+/- 10%). Such dimensions help to dampen ultrasonic frequencies.

In a further alternative or even additional embodiment, an ultrasonic dampening element is introduced into the sound transmission channel. The dampening element may be a net-like structure, some kind of open pore foam or something similar.

In a further expedient embodiment, a bypass chamber is fluidically attached to the rear-side part of the sound transmission channel. That bypass chamber is for example a real bypass channel being fluidically connected with both ends to the sound transmission channel or a closed chamber with only one and rather narrow inlet (comparable to a Helmholtz resonator). Such a bypass chamber may expediently be used for attenuation of ultrasonic frequencies and/or for resonance tweaking at higher frequencies (designed e. g. for an acoustic remote-control feature which works around 15 kHz). In a further expedient embodiment, an effective length of the sound transmission channel parallel to the membrane plane is as short as possible. By that, vibrational sensitivity to movements (vibrations) parallel to the membrane plane may be reduced.

Most preferred, however, is, that such effective length of the sound transmission channel parallel to the membrane plane is also chosen in dependence on the sensitivity to acoustic inertia of the microphone. Preferably, the sound transmission channel is, thus, designed on the basis of the inventive concept described before such that vibrational sensitivity in as many directions as possible, at least in two or three directions perpendicular to each other, may be reduced. Figuratively, as described before with reference to the alignment of the sound transmission channel along the z-axis, any course of the port-side part of the sound transmission channel parallel to the membrane plane should be compensated for by a respective parallel course of the rear-side part of the sound transmission channel.

In the following, embodiments of the invention are explained in more detail with reference to a drawing. Therein show:

Fig. 1 in a schematic view a hearing instrument,

Fig. 2 in a schematic side view a detail of the hearing instrument including a microphone and a sound transmission channel,

Fig. 3 in a schematic diagram an acoustic inertia sensitivity in dependence on a length of a sound transmission channel for a state of the art hearing instrument and for a hearing instrument of the present invention,

Fig. 4 in a perspective view schematically an embodiment of the hearing instrument, especially of the microphone and the sound transmission channel,

Fig. 5-10 in perspective or partly cutout views schematically respective embodiments of the hearing instrument,

Fig. 11-13 in detailed cut-out views schematically alternative embodiments of a bypass system for the sound transmission channel. Parts corresponding to each other are always provided with the same reference signs in all figures.

Fig. 1 shows a hearing instrument 1 , specifically a hearing aid. The hearing instrument 1 comprises a (main) housing 2 covering several electronic components from the surroundings. As such electronic components the embodiment according to Fig. 1 comprises two microphones 4, a sound processor 6 and a receiver 8. The microphones 4 are set up to receive sound from the surroundings, convert it to electric signals and provide the latter to the sound processor 6. The sound processor 6 is set up to perform sound processing on the electric microphone signals, specifically frequency dependent filtering, enhancing and/or dampening, and to output the processed signals to the receiver 8 for electro-acoustic conversion and output of sound signals to the hearing of a user via a sound tube 10 attached to the housing 2.

Microphones 4 are per se sensitive to movement, specifically to acceleration, since the microphones 4 are designed to sense sound which is generally movement of an air column resting against a membrane 12 (s. Fig. 2) of the respective microphone 4. Since the membrane 12 has a distinct mass the sensitivity to movement is dependent on inertia. The factors that rule the microphones’ 4 inertia is generally the mass of the membrane 12 as well as of a so called back volume 14 which is the volume of the inside of a microphone housing (short: “mic-housing 16”) which is separated from the outside by the membrane 12. Due to such inertia the microphones 4 will output signals if there is movement with acceleration high enough, e. g. vibration of the hearing instrument 1. Therefore, each microphone 4 has an inertia sensitivity Smic.

In classical set ups of hearing instruments 1 a connection channel from the surroundings of the hearing instrument 1 leads in a more or less direct line to the membrane 12. Thus, the mass of the air column within that channel adds to the inertia mass and increases the value of inertia sensitivity Smic. Fig. 2 shows a general design of the hearing instrument 1 that is used to decrease the inertia sensitivity Smic of the respective microphone 4. The respective microphone 4 is mounted to a printed circuit board (short: PCB 18) that serves as a carrier for the microphones 4 and other electronic components. The respective microphone 4 comprises a port hole 20 within a first sidewall (here: port-side wall or the “baseplate 22”). The baseplate 22 is resembled by a PCB, on which a MEMS microphone die including the membrane 12 (which in this case is made from silicon) is mounted. The port hole 20, in that embodiment, penetrates the baseplate 22 in a straight manner. The respective microphone 4 is mounted “upside-down”, i.e. with its port hole 20 facing away from an inlet opening 24 (also: “microphone opening” or “mic-opening”) within the housing 2 of the hearing instrument 1. To deliver airborne sound to the port hole 20 of the respective microphone 4 the hearing instrument 1 comprises (for each microphone 4) a sound transmission channel 30 that leads from the inlet opening 24 to the port hole 20.

For the following description a membrane plane 32 is introduced which is defined by the membrane 12. In particular, the membrane’s 12 flat extension is within that membrane plane 32. The sound transmission channel 30 is aligned such that it intersects the membrane plane 32 and is by that divided in a port-side part 34 that is connected with the port hole 20 and ends at the membrane 12, as well as in a rear-side part 36 that is located within a rear-side region of the membrane plane 32 with regards to the port hole 20.

The port-side part 34 of the sound transmission channel 30 resembles a flat and wide U-shape and, in the embodiment according to Fig. 2, a 180 degree turn. The rear-side part 36 is aligned such that an air column within has parts that are perpendicular to the membrane plane 32. According to the embodiment of Fig. 2 the rear-side part 36 comprises a chimney-like subpart 38 that runs perpendicularly to the membrane plane 32 and that opens up to a chamber 40 that in turn is connected to the inlet opening 24. An effective length left of the rear-side part 36 of the sound transmission channel 30 is chosen in dependence on the inertia sensitivity Smic of the microphone 4. The effective length left of the sound transmission channel 30 is the sum of all vector values of an inward flow (i.e. from the inlet opening 24 to the port hole 20) within the rear-side part 36 of the sound transmission channel 30 that are perpendicular to the membrane plane 12.

An example of a relation of the effective length left to the inertia sensitivity Smic is shown in Fig. 3 for a “classic” assembly wherein the sound transmission channel 30 leads in a direct way to the membrane 12 (dashed line) and for the sound transmission channel 30 of Fig. 2 (dashed and dotted line). At a specific value of the effective length left the inertia sensitivity Smic and, therefore, the sensitivity to vibration of the microphone 4 is compensated. At shorter values of the effective length left the inertia of the air column within the rear-side part 36 is smaller than that of the microphone 4 and, therefore, has less effect to the inertia sensitivity Smic. At bigger values the inertia of the rear-side air column is bigger than that of the microphone 4 and, thus, overcompensates the inertia of the microphone 4.

Fig. 4 shows an optional embodiment of the hearing instrument 1 . To realize at least the port-side part 34 and a segment of the rear-side part 38 of the sound transmission channel 30 a chimney-like construction 41 resembled at least partially by a rectangular pipe 42 is attached integrally to the microphone 4. The chimneylike construction 41 comprises a bottom part 44 attached to the pipe 42. The bottom part 44 is resembled by a box-like structure having an open upper side with which the bottom part 44 is attached to the baseplate 22 of the microphone 4 covering the port hole 20. The chimney-like construction 41 is made of metal. Alternatively, it may be made of plastics.

Fig. 5 and 6 show an alternative embodiment of the hearing instrument 1. Here, the port-side part 34 of the sound transmission channel 30 is integrated into a PCB element 46 that is an integral part of the microphone 4. However, the PCB element 46 is additional to the baseplate 22 of the microphone. The port-side part 34 is integrated as a chamber 48 into that PCB element 46 by laminating layers that have cutouts to realize the chamber 48. The PCB element 46 may, as in Fig. 5 and 6, overlap with the baseplate 22 only in parts or may also resemble a carrier plate that contacts the baseplate 22 over its full area. The chamber 48 has a length l_c of 2,85 mm, a height he of 0,35 mm and a width (not shown) of 1 ,50 mm. The diameter do of an outlet 50 is 0,20 mm and the diameter di of an inlet 52 to the chamber 48 is 0,30 mm. These dimensions foster ultrasonic filtering or at least dampening of ultrasonic resonance.

Optionally, a metal layer 53 (indicated by a dashed line in Fig. 6) of about 0,3 mm thickness may be laminated between the layers of the PCB element 46. That metal layer 53 may e.g. form a top layer for the chamber 48 on the side facing away from the microphone 4 (not shown in detail). Especially, that metal layer 53 serves for stiffening the PCB element 46.

In Fig. 5 a gasket 54 is attached to the PCB element 46 around the inlet 52 such that a tube, a pipe or the like resembling the rear-side part 36 of the sound transmission channel 30 may be attached in a fluid tight manner.

Fig. 7 shows yet another embodiment of the hearing instrument 1 . Here, the sound transmission channel 30 is partly made up by an attachment 60 of the microphone’s 4 construction. That attachment 60 comprises a PCB base 62 and a three-sided wall element 64. The PCB base 62 has a cutout 66 that in combination with the aforementioned PCB 18 encases the port-side part 34. Therefore, the PCB base 62 comprises a solder track 68 by which fluid tight fixation to the PCB 18 via soldering may be realized. The PCB case 62 is integrally attached to the microphone 4 such that the three-sided wall element 64 encloses together with the mic-housing 16 parts of the rear-side part 36 of the sound transmission channel 30.

Fig. 8 shows an alternative embodiment of the hearing instrument 1 . Here, the sound transmission channel 30 is integrated with all or at least most parts into the microphone 4. In that case, the microphone 4 comprises a (second) outer wall 70. The rear-side part 36 of the sound transmission channel 30 runs between the mic- housing 16 and the outer wall 70. The port-side part 34 is integrated into the baseplate 22 just like explained before for the PCB element 46. Fig. 9 shows an embodiment that is a combination of embodiments of Fig. 7 and 8. The sound transmission channel 30 is, again, integrated into the microphone 4. Hereby, the port-side part 34 integrated into the baseplate 22 is open to the surroundings. For fluid tight fixation to the PCB 18 the port-side part 34 is outlined by the solder track 68, as before.

Fig. 10 shows a principle sketch of an ultrasonic dampening element 80 introduced into the sound transmission channel 30.

Ultrasonic dampening can also be realized by enlarging a distinct volume within the sound transmission channel 30, just as in Fig. 5 and 6. Also, the chamber 40 shown in Fig. 2 is used for providing ultrasonic dampening.

Fig. 11 to 13 show some sketches of further measures for ultrasonic filtering. Here, bypasses 90 of different structures are attached to the sound transmission channel 30. Fig. 12 shows the basic principle of a Helmholtz resonator which in general is no Teal” bypass since it has no separate outlet. However, such structure is understood as a bypass, also, in this context.

The object of the invention is not limited to the embodiments described above. Rather, further embodiments of the invention may be derived by the skilled person from the foregoing description. In particular, the individual features of the invention described on the basis of the various embodiment and the variants thereof can also be combined with one another in other ways.

List of reference signs

1 hearing instrument

2 housing

4 microphone

6 sound processor

8 receiver

10 sound tube

12 membrane

14 back volume

16 mic-housing

18 PCB

20 port hole

22 baseplate

24 inlet opening

30 sound transmission channel

32 membrane plane

34 port-side part

36 rear-side part

38 subpart

40 chamber

41 construction

42 Pipe

44 bottom part

46 PCB element

48 chamber

50 outlet

52 inlet

53 metal layer

54 gasket

60 attachment

62 PCB base

64 wall element 66 cutout

68 solder track

70 outer wall

80 ultrasonic dampening element 90 bypass

Smic inertia sensitivity leff effective length lc length he height do, di diameter

Claims

1. Hearing instrument (1 ), comprising

- a main housing (2) having an outer wall enclosing an interior from the outside,

- a microphone (4) having a mic-housing (16), a membrane (12) being disposed within the mic-housing (16) and defining a membrane plane (32), and a port hole (20) opening into a first side-wall (22) of the mic-housing (16) adjacent to the membrane (12), the microphone (4) being aligned within the interior of the main housing (2), and

- a sound transmission channel (30) being aligned outside an inner volume of the mic-housing (16), ending with a first end at the port hole (20) and fluidically connecting the port hole (20) with the outside through a mic- opening (24) that penetrates the outer wall of the main housing (2), wherein the sound transmission channel (30) is guided in a curved way such that it intersects the membrane plane (32), the sound transmission channel (30) thus being divided in a port-side part (34) and a rear-side part (36) that is located within a rear-side region of the membrane plane (32) with regards to the port hole (20), wherein an air column within the rear-side part (36) of the sound transmission channel (30) has parts that are perpendicular to the membrane plane (32), wherein an effective length (left) of the rear-side part (36) of the sound transmission channel (30) is chosen in dependence on a sensitivity (Smic) to acoustic inertia of the microphone (4), and wherein at least a segment of the sound transmission channel (30) is formed within an element (22, 46, 60) that is integral to the microphone (4).

2. Hearing instrument (1 ) according to claim 1 , wherein the effective length (left) is defined by the sum of all vector values of an inward flow within the rear-side part (36) of the sound transmission channel (30) that are perpendicular to the membrane plane (32).

3. Hearing instrument (1 ) according to claim 1 or 2, wherein at least a part of the rear-side part (36) of the sound transmission channel (30) is guided perpendicular to the membrane plane (32).

4. Hearing instrument (1 ) according to one of claims 1 to 3, wherein as the segment formed within the integral element (22, 46, 60) a part of the port-side part (34), preferably the segment attached to the port hole (20) is chosen.

5. Hearing instrument (1 ) according to one of claims 1 to 4, wherein as the segment formed within the integral element (22, 46, 60) a part of the rear-side part (36) of the sound transmission channel (30) is chosen.

6. Hearing instrument (1 ) according to claim 4 or 5, wherein at least a part of the port-side part (34) of the sound transmission channel (30) is integrated into a base plate (22) forming the first side-wall of the mic-housing (16).

7. Hearing instrument (1 ) according to claim 4 or 5, wherein the port-side part (34) of the sound transmission channel (30) is integrated into a PCB element (46) forming the integral element, wherein that circuit board (46) serves as a carrier of the microphone (4), especially wherein the port-side part (34) is formed within the circuit board (46) by laminating respectively precut layers to form the PCB element (46) with an internal chamber (48), the port-side part (34) being integral with the chamber (48).

8. Hearing instrument (1 ) according to claim 7, wherein a metal layer (53) is laminated into the PCB element (46) as a stiffening layer.

9. Hearing instrument (1 ) according to one of claims 1 to 8, wherein a volume of at least a segment of the sound transmission channel (30) is chosen in dependence on ultrasonic filtering.

10. Hearing instrument (1 ) according to claim 9, wherein the sound transmission channel (30) comprises an enlarged inlet chamber (40) at its mic-opening sided end.

11 . Hearing instrument (1 ) according to one of claims 7 to 10, wherein measures of the chamber (40, 48) are chosen in dependence on ultrasonic filtering, especially wherein the cross section of the chamber (40, 48) is about 0,350 x 1 ,5 mm², a length of the chamber (48) is about 2,85 mm and an inlet as well as an outlet opening (52, 50) to respectively from the chamber (48) has a diameter of about 0,3 and 0,2 mm.

12. Hearing instrument (1 ) according to one of claims 1 to 11 , wherein an ultrasonic dampening element (80) is introduced into the sound transmission channel (30).

13. Hearing instrument (1 ) according to one of claims 1 to 12, wherein a bypass chamber (90) is fluidically attached to the rear-side part (36) of the sound transmission channel (30).

14. Hearing instrument (1 ) according to one of claims 1 to 13, wherein an effective length of the sound transmission channel (30) parallel to the membrane plane (32) is as short as possible.

15. Hearing instrument (1 ) according to one of claims 1 to 14, wherein an effective length of the sound transmission channel (30) parallel to the membrane plane (32) is chosen in dependence on the sensitivity (Smic) to acoustic inertia of the microphone (4).