EP1125471A1

EP1125471A1 - Microphone

Info

Publication number: EP1125471A1
Application number: EP99953865A
Authority: EP
Inventors: Heinz Epping; Manfred Bleichwehl; Arthur Seehafer
Original assignee: Sennheiser Electronic GmbH and Co KG
Current assignee: Sennheiser Electronic GmbH and Co KG
Priority date: 1998-10-30
Filing date: 1999-10-16
Publication date: 2001-08-22
Anticipated expiration: 2019-10-16
Also published as: US7079663B1; DE59903998D1; DE19850298C1; ATE230916T1; WO2000027165A1; EP1125471B1

Abstract

A microphone comprising a diaphragm which has a front diaphragm surface on which sound waves impinge and a rear diaphragm surface which is at least partially acoustically separated from the front diaphragm surface, and a sound inlet, through which sound waves can go to the rear diaphragm surface. In order to improve a strongly frequency-dependent frequency response characteristic in respect of the directional effect of the microphone, the microphone includes at least one damping element and the slot-shaped sound inlet forms substantially an acoustic inductance so that at least a part of the sound waves to be picked up is passed with a delay to the rear diaphragm surface.

Description

microphone

The invention relates to a microphone with a membrane which has a front membrane surface on which sound waves strike and which has an at least partially acoustically separated rear membrane surface from the front membrane surface, and at least one, preferably slit-shaped, sound inlet through which sound waves can reach the rear membrane surface .

Such a microphone is known from DE 22 17 051, in which an acoustic resistance is formed through the slit-shaped sound inlet in order to dampen the sound passing through the slit-shaped sound inlet. The directional effect of the microphone can be influenced by the sound inlet between the air volume behind the membrane and the outside air. So that the slit-shaped sound inlet has the required acoustic resistance, its width is small in relation to the length. The sound inlet is designed as a groove-shaped recess in the magnet system made of sintered material. With such known microphones, the directional effect of the microphone is strongly frequency-dependent and can usually only be used for low frequencies. The production of the corresponding slot-shaped sound inlets in the magnet system from sintered material requires special tools, and a coordination of the directional effect by changing the slot-shaped sound inlets can only be achieved by exchanging the entire magnet system. It is therefore an object of the present invention to develop a microphone of the type mentioned at the outset in such a way that it has a predetermined directional effect essentially over the entire frequency response and enables inexpensive, automated production.

The object is achieved according to the invention in the microphone of the type mentioned at the outset in that the microphone has at least one damping element and the slit-shaped sound inlet essentially forms an acoustic inductance, so that at least some of the sound waves to be recorded are conducted to the rear membrane surface with a delay.

With such a microphone, the directional effect is achieved by delaying the sound that enters through the rear sound inlet. The delay in the sound is achieved with the aid of an acoustic network which essentially has an inductance formed by the slit-shaped sound inlet and a separate damping element which forms an acoustic resistance.

The advantages of the invention are, in particular, that a microphone is implemented with a directional effect that is essentially constant over the entire frequency range. Furthermore, the acoustic network formed by the acoustic inductance and the damping element can be tuned easily and precisely, so that the directional effect of the microphone can be predetermined to a large extent.

A parasitic acoustic resistance occurs in the sound inlet of the microphone according to the invention. However, in order to make the acoustic network essentially dependent on the size of the acoustic inductance and that of the separate damping element, the sound inlet in the microphone according to the invention is preferably designed in such a way that the acoustic resistance occurring in the sound channel is less than the acoustic resistance of the damping element.

In a preferred embodiment of the microphone according to the invention, the damping element is formed by a sound channel provided with acoustic damping material, which connects a cavity with the volume delimited by the rear membrane surface. The tuning of the damping element is essentially determined by the size of the volume and the acoustic response. Status of the sound channel, which connects the cavity with the volume delimited by the rear membrane surface, is specified.

In a further preferred embodiment, the sound inlet has a substantially rectangular cross section. This cross-sectional shape is easy to dimension in the construction of a microphone according to the invention and easy to implement in manufacture. The height of the sound inlet is particularly expediently less than its length, the sound flow taking place along the longitudinal direction of the sound inlet, and the length of the sound inlet in turn less than its width. Because the width of the sound inlet is large in relation to the length, the parasitic resistance of the sound inlet is kept low. In an expedient development, the width of the sound inlet essentially corresponds to the circumference of the microphone. The sound inlet is only interrupted by support sections which are provided for the mechanical stability of the microphone and in particular of the sound inlet. In this embodiment, the sound inlet is thus not formed by narrow and long channels, but by an essentially circumferential slot which has only a low parasitic acoustic resistance and a predetermined acoustic inductance.

In a preferred embodiment, the membrane is connected to a membrane fastening section. The membrane fastening section serves to support the membrane and align it via a corresponding magnet system in such a way that a voice coil attached to the membrane plunges into an air gap provided in the magnet system.

In a further embodiment, the microphone comprises a terminating element which is arranged in front of an opening of the sound channel and has an opening which essentially corresponds to the opening of the sound channel and which is provided with the acoustic damping material. The end element essentially serves to carry the acoustic damping material and to hold it in front of the mouth of the sound channel. The acoustic resistance of the damping element can be changed particularly advantageously by merely exchanging the terminating element and replacing it with another terminating element with a different acoustic resistance. In this way, identical microphone housings can also be tuned differently using appropriate terminating elements. In order to form the slit-shaped sound inlet through which sound waves can reach the rear membrane surface, in a preferred embodiment of the microphone according to the invention the membrane fastening section has an opening leading from the outside to the rear membrane surface, which opening is essentially closed by a sealing element. The opening through the sealing element is narrowed to such an extent that the slit-shaped sound inlet is formed between the sealing element and the membrane fastening section.

As a result, the dimensions of the slot-shaped sound inlet can be specified particularly advantageously by the sealing element, which can be manufactured and dimensioned independently of the membrane fastening section. The microphone according to the invention can in turn be tuned in the desired manner by means of an easily manufactured, inexpensive component. Design changes to the housing of the microphone or to other components to be manufactured with complex tools are therefore no longer necessary. In an expedient development, the sealing element consists of a porous, in particular a sintered material. Such material has a high internal attenuation, which improve the acoustic properties of the microphone, and it can be easily brought into a desired shape.

In an expedient development, the cross section of the slot-shaped sound inlet is essentially formed by a recess in the membrane fastening section, the length of the sound inlet being essentially determined by the thickness of the sealing element. The sealing element is preferably of essentially annular design and is seated in an annular groove provided in the membrane fastening section. The cross section of the slit-shaped sound inlet can be specified in a simple manner by the size difference between the inside diameter of the membrane fastening section and the outside diameter of the sealing element, in which case no recesses have to be provided on the membrane fastening section. This makes it possible to realize differently dimensioned slots with the same membrane fastening section, in that only the annular sealing element is replaced by another with a different outer diameter.

However, if the slit-shaped sound inlet is completely closed by the sealing element, only the damping element is effective and the directional character The microphone characteristics approach the spherical shape. It is thus also possible with the microphone according to the invention to implement a microphone with a spherical directional characteristic with the same structure of the microphone capsule. If such a directional characteristic is to be realized, the slot-shaped sound inlet can expediently also be dispensed with entirely, the other advantageous features described here nevertheless being able to be provided in such an embodiment.

The sealing element, which essentially specifies the size of the slot-shaped sound inlet, is particularly expediently formed in one piece with the closing element, which is arranged in front of the mouth of the sound channel and carries the acoustic damping material. As a result, both the acoustic inductance by influencing the dimensions of the slot-shaped sound inlet and the acoustic resistance of the damping element by selection of the acoustic damping material can be specified particularly advantageously by means of a single component.

In an alternative embodiment, the membrane fastening section essentially encloses the rear membrane surface, and the shell is formed between a holding section provided on the membrane and the membrane fastening section. The membrane fastening section is essentially the section of the membrane with which it is connected to the membrane fastening section. In an expedient development, the holding section is formed by a membrane ring connected to the membrane. Such a membrane ring advantageously increases the stability of the membrane and is easy to manufacture. This proves to be particularly advantageous for the reason that, in an expedient development of the invention, recesses are provided in the membrane ring which essentially form the slot-shaped sound inlet. The membrane fastening section can therefore have an essentially flat bearing surface for the membrane ring, the dimensions of the slot-shaped sound inlet being predetermined by the recesses provided in the membrane ring. In this embodiment, too, the size of the slit-shaped sound inlet is formed by a component which can be produced cheaply, so that, in the case of identical membrane fastening sections, the microphone can be tuned by changing the membrane ring. In a further alternative embodiment, the microphone according to the invention has a housing part which is connected to the membrane fastening section and essentially surrounds the rear membrane surface, the sound inlet being formed between the membrane fastening section and the housing part.

Advantageous developments of the invention are characterized by the features of the subclaims.

In the following the invention is explained by way of example with reference to the drawings. Show it:

1 shows a cross section through a first embodiment of a microphone according to the invention;

FIG. 2 shows an enlarged detail from FIG. 1;

FIG. 3 shows a plan view of a sealing element which is used in the embodiment according to FIG. 1;

Figure 4 shows a cross section through the sealing element along the line IV-IV of Figure 3;

Figure 5 shows a second embodiment of the invention

Microphones;

6 shows an enlarged detail of FIG. 5;

Figure 7 is a plan view of a membrane ring, which in the

Embodiment according to Figure 5 is used;

Figure 8 shows a cross section of the membrane ring along the line

Vlll-Vlll from Figure 7;

Figure 9 shows a third embodiment of the invention

Microphones; and

Figure 10 is an enlarged detail of Figure 9.

Figure 1 shows a first embodiment of a microphone according to the invention in cross section with a membrane 3, a membrane mounting section 5, a magnet system 7 and a microphone cover 9. The membrane 3 is connected with its outer edge to the membrane mounting section 5 and thereby centered over the magnet system 7. A voice coil 1 1 attached to the diaphragm 3 extends essentially transversely to the diaphragm 3 into an air gap 1 3 provided in the magnet system 7. The microphone cover 9 on its side facing the diaphragm 3 is essentially adapted to the contour of the diaphragm 3 and has a plurality of sound inlet openings 1 5, through which sound can be incident on the outer surface of the membrane 3. The sound inlet openings 15 are covered by a sound-permeable material 17 in order to protect the membrane from dirt, in particular from dust and moisture.

Also shown in FIG. 1 and in detail in FIG. 2 is the membrane fastening section 5, which has an opening 19 leading from the outside to the rear surface of the membrane 3. An annular groove 21 is provided in the membrane attachment section, the opening 19 being provided in the annular groove 21 in the region of the edge between the floor and the wall. In the annular groove 21 there is a corresponding annular sealing element 23 which essentially closes the opening 19 except for a slot-shaped sound inlet 25.

By changing the geometric dimensions of the slit-shaped sound inlet 25, the acoustic properties of the microphone can be predefined to a large extent. In the described embodiments, the length 28 denotes the dimension of the sound inlet 25 along which the sound foot essentially runs. The width is essentially determined along the circumference of the microphone, and the height 26 of the sound inlet results from the distance between two complementary components (5, 23; 5, 37; 5, 51) which limit the sound inlet 25. In principle, in the illustrated embodiments of the invention, the height 26 of the sound inlet 25 is less than its length 28 and the length 28 of the sound inlet 25 is again less than its width.

The height 26 (defined in the radial direction) of the slot-shaped sound inlet 25 according to FIGS. 1 and 2 is essentially determined by a recess 27 provided in the membrane fastening section 5 and the length 28 is determined by the thickness of the annular sealing element 23.

On the ring-shaped sealing element 23, sections 29 are formed, each forming a sound channel, which are provided with an acoustic damping material 31. The openings 29 in the sealing element 23 connect the volume 32 delimited by the rear surface of the membrane 3 to a cavity 33 which is closed to the outside (not shown).

The cavity 33, together with the acoustic damping material 31 arranged in the openings 29 of the sealing element 23, forms a damping element, the acoustic damping value on the one hand depending on the size of the cavity 33 and on the other hand on the acoustic properties of the openings 29 and the damping material 31 depends. The slit-shaped sound inlet 25 forms an acoustic inductance, the size of which can essentially be predetermined by the geometric dimensions. The acoustic inductance of the slit-shaped sound inlet 25, together with the damping element, forms an acoustic network which conducts a portion of the sound waves to be recorded to the rear membrane surface with a delay.

FIG. 3 shows an annular sealing element which is used, for example, in the first embodiment of the microphone shown in FIGS. 1 and 2. FIG. 4 shows the ring-shaped sealing element in cross section along the line IV-IV of FIG. 3. The ring-shaped sealing element has an essentially rectangular cross section, circumferential grooves 35 lying opposite one another on both sides being provided in the sealing element 23. In sections, openings 29 are made in the grooves 35 of the sealing element 23, which have the same width as the circumferential grooves 35 and essentially have the shape of an elongated hole. An acoustic damping material 31 is arranged within the openings 29, with which the acoustic resistance of the openings 29 provided in the sealing element 23 can be predetermined.

FIGS. 5 and 6 show a second embodiment of a microphone according to the invention, FIG. 5 being a cross-sectional view and FIG. 6 being an enlarged detail from FIG. 5. The microphone shown in FIGS. 5 and 6, like the microphone 1 according to the first embodiment, also has a membrane 3, a membrane fastening section 5 which supports the membrane 3, a magnet system 7, a micron cover 9, a voice coil 11, one in the magnet system 7 provided air gap 1 3, in which the voice coil 1 1 attached to the membrane 3 is at least partially immersed, and a sound inlet opening 1 5, which is covered by a sound-permeable material 1 7. In contrast to the first embodiment, in the microphone 1 according to the second embodiment, the rear surface of the membrane 3 is essentially enclosed by the membrane fastening section 5. The membrane fastening section 5 has, in a volume 32 delimited by the rear surface of the membrane 3, an annular groove 21 in which an annular sealing element 23 is arranged. The sealing element 23 is provided with openings 29, which lie opposite adjacent sound channels formed in the membrane fastening section 5, which connect a cavity 33 (not completely shown) also enclosed by the membrane fastening section 5 to the volume delimited by the rear membrane surface. The ring-shaped sealing element carries acoustic damping material 31, with which the acoustic resistance of the damping element formed by the cavity 33 and the acoustic damping material 31 can be predetermined.

A membrane ring 37 with an essentially rectangular cross section is fastened to the outer, peripheral edge of the membrane 3. A slit-shaped sound inlet 25 is formed in sections between the membrane ring 37 and the membrane fastening section 5, through which sound waves can reach the rear membrane surface. The slot-shaped sound inlet 25 is formed in that the membrane ring 37 has flat recesses 39 on its surface facing the membrane fastening section 5. The length 28 of the slot-shaped sound inlet 25 is determined by the section of the membrane fastening section 5 opposite the flat recess 39 of the membrane ring 37. The height 26 of the slot-shaped sound inlet 25 can be predetermined by the thickness of the recess 39.

A membrane ring according to the invention is shown in detail in FIGS. 7 and 8, specifically in FIG. 7 in a view from below and in FIG. 8 in a cross section along the lines VIII-VIII. In the illustrated embodiment of the membrane ring 37, eight recesses 39 are provided which are arranged uniformly on the circumference. The recesses 39 extend radially outwards from the inner circumferential edge on the lower surface of the membrane ring, the outer, lower edge of the membrane ring 37 being retained throughout.

In the microphone in a third embodiment, which is shown in FIG. 9 in a cross-section and in FIG. 10 in an enlarged detail, a separate housing part 51 is provided, which is connected to the membrane attachment section 5 is connected and essentially encloses the rear membrane surface. Also provided in the housing part 51 is the cavity 33, which is connected to the volume 32 connected by the rear membrane surface by means of a sound channel provided with acoustic damping material 31. The sound channel is formed by mutually opposite openings 53 and 55 in the membrane fastening section 5 and in the housing part 51, the acoustic damping material 31 being arranged and held between the membrane fastening section 5 and the housing part 51.

The slot-shaped sound inlet, which represents the acoustic inductance, is formed between the membrane fastening section 5 and the housing part 51. The height 26 (defined in the axial direction) and the length 28 of the slit-shaped sound inlet are specified by the membrane fastening section 5 and / or the housing part 51.

Claims

_ 1 - | _Expectations

1 . Microphone (1) with a membrane (3), which has a front membrane surface on which sound waves strike, and an at least partially acoustically separated rear membrane surface from the front membrane surface, and at least one, preferably slit-shaped, sound inlet (25) through the sound waves can reach the rear membrane surface, characterized in that the microphone (1) has at least one damping element (29, 31, 33) and the slot-shaped sound inlet (25) essentially forms an acoustic inductance, so that at least some of the sound waves to be recorded are delayed rear membrane surface is directed.

2. Microphone according to claim 1, characterized in that the acoustic resistance occurring in the sound inlet (25) is smaller than the acoustic resistance of the damping element.

3. Microphone according to claim 1 or 2, characterized in that the damping element is formed by an acoustic damping material (31) provided sound channel (29) which connects a cavity (33) with the volume delimited by the rear membrane surface (32).

4. Microphone according to one of the preceding claims, characterized in that the sound inlet (25) has a substantially rectangular cross section.

5. Microphone according to claim 4, characterized in that the height (26) of the sound inlet (25) is less than its length (28), the sound flow taking place along the longitudinal direction of the sound inlet (25), and the length (28) of the Sound inlets (25) is in turn less than its width.

6. Microphone according to claim 5, characterized in that the width of the sound inlet (25) corresponds substantially to the circumference of the microphone (1).

7. Microphone according to claim 6, characterized in that the sound inlet (25) is interrupted only by support sections.

8. Microphone according to one of the preceding claims, characterized in that the membrane (3) is connected to a membrane fastening section (5)

9. Microphone according to claims 3 and 8, characterized by a closure element, which is arranged in front of an opening of the sound channel (29) and one of the opening of the sound channel (29) has substantially corresponding openings, which are provided with the acoustic damping material (31) is.

10. Microphone according to claim 8 or 9, characterized in that the membrane fastening section (5) has an opening leading from the outside to the rear membrane surface (19) which is essentially closed by a sealing element (23), between the sealing element (23) and the slit-shaped sound inlet (25) is formed in the membrane fastening section (5).

1 1. Microphone according to claim 10, characterized in that the sealing element (23) consists of a porous material, in particular a sintered material.

1 2. Microphone according to claim 10 or 1 1, characterized in that the cross section of the slit-shaped sound inlet (25) is essentially formed by a recess (27) in the membrane fastening section (5), the length (28) of the sound inlet (25) is essentially determined by the thickness of the sealing element (23).

1 3. Microphone according to one of claims 8 to 1 2, characterized in that the sealing element (23) is substantially annular.

14. Microphone according to claim 1 3, characterized in that the membrane fastening section (5) has an annular groove (21) in which the sealing element (23) is arranged.

1 5. Microphone according to claim 13 or 14, characterized in that the cross section of the slit-shaped sound inlet (25) by the size difference between the inner diameter of the membrane fastening portion (5) and the outer diameter of the sealing element (23) is predetermined.

1 6. Microphone according to one of claims 8 to 1 5, characterized in that the sealing element (23) is integrally formed with the end element.

17. Microphone according to claim 8 or 9, characterized in that the membrane fastening section (5) essentially surrounds the rear membrane surface, and the sound inlet (25) is formed between a holding section provided on the membrane (37) and the membrane fastening section (5).

18. Microphone according to claim 1 7, characterized in that the holding section (37) is a membrane ring (37) connected to the membrane (3).

19. Microphone according to claim 18, characterized in that the slit-shaped sound inlet (25) is essentially formed by recesses (39) in the membrane ring (37).

20. Microphone according to claim 8, characterized by a housing part (51) which is connected to the membrane fastening section (5) and substantially surrounds the rear membrane surface, the sound inlet (25) between the membrane fastening section (5) and the housing part (51) is trained.

21. Microphone (1) with a membrane (3), which has a front membrane surface on which sound waves strike, and a rear membrane surface acoustically separated from the front membrane surface, characterized in that the microphone (1) has at least one damping element (29, 31, 33) which is formed by a sound channel (29) provided with acoustic damping material (31) which connects a cavity (33) with the volume (32) delimited by the rear membrane surface.