Filter for a microphone system, a microphone system, a miniature electronic device and a method of equipping a printed circuit board

1. A filter ( 34 ; 34 ′, 34 ″) for a microphone system ( 16 ) of a miniature electronic device ( 10 ), said filter ( 34 ; 34 ′, 34 ″) having a sound inlet and a sound outlet, an acoustic tube ( 42 ) for coupling the sound inlet to the sound outlet, wherein the filter ( 34 ; 34 ′, 34 ″) is adapted to be mounted on a surface of a printed circuit board ( 14 ) such that the sound outlet of the filter ( 34 , 34 ′, 34 ″) faces the printed circuit board ( 14 ) in a portion thereof which is formed with a through-hole ( 38 ); and wherein the acoustic tube ( 42 ) is adapted to be mounted on the printed circuit board ( 14 ) such that the longitudinal direction of the acoustic tube ( 42 ) passes through the through-hole ( 38 ) formed into the printed circuit board ( 14 ).

2. The filter ( 34 ; 34 ′, 34 ″) according to claim 1 , wherein the filter ( 34 ; 34 ′, 34 ″) is an acoustical low pass filter or an acoustical band pass filter.

3. The filter ( 34 ; 34 ′, 34 ″) according to claim 1 , wherein the filter ( 34 ; 34 ′, 34 ″) is a SMD component adapted to be machine mounted on the surface of the printed circuit board ( 14 ) by means of a pick and place process.

4. The filter ( 34 ) according to claim 1 , wherein the acoustic tube ( 42 ) comprises a flange ( 44 ) adapted to be mounted on a portion of the printed circuit board ( 14 ) surrounding the through-hole ( 38 ).

5. The filter ( 34 ) according to claim 1 , further comprising a seal ( 45 ) including an elastic material, said seal ( 45 ) surrounding the acoustic tube ( 42 ) in at least a portion of the sound inlet of the filter ( 34 ).

6. The filter ( 34 ) according to claim 5 , wherein the length of the seal ( 45 ), in a direction of the acoustic tube ( 42 ), is dimensioned such to exceed the length of the acoustic tube ( 42 ).

7. The filter ( 34 ) according to claim 5 , wherein the seal ( 45 ) is formed tapered.

8. The filter ( 34 ) according to claim 5 , wherein the seal ( 45 ) is dimensioned such to provide an acoustically tight coupling between a sound entrance channel ( 32 ′, 32 ″) of the miniature electronic device ( 10 ) and the sound inlet.

9. The filter ( 34 ) according to claim 1 , wherein the acoustic tube ( 42 ) is made of plastic.

10. The filter ( 34 ) according to claim 9 , wherein the acoustic tube ( 42 ) is mounted on the printed circuit board ( 14 ) by means of gluing.

11. The filter ( 34 ) according to claim 1 , wherein the acoustic tube ( 42 ) is made of a metal.

12. The filter ( 34 ) according to claim 11 , wherein the acoustic tube ( 42 ) is mounted on the printed circuit board ( 14 ) by means of soldering or gluing.

13. The filter ( 34 ) according to claim 1 , further comprising at least one of an acoustical filter element ( 50 ) and a protective cover ( 52 ) received into at least a portion of the acoustic tube ( 42 ) or at a sound entry or a sound exit of the acoustic tube.

14. The filter ( 34 ; 34 ′, 34 ″) according to claim 1 , wherein the miniature electronic device is a hearing aid ( 10 ).

15. A microphone system ( 16 ) comprising a printed circuit board ( 14 ), a filter ( 34 ′) according to claim 1 mounted on a first surface of the printed circuit board ( 14 ), at least one microphone ( 36 ′) mounted on a second surface of the printed circuit board ( 14 ), wherein an acoustic input of the microphone ( 36 ′) is acoustically coupled to the sound outlet of the filter ( 34 ′) via a through-hole formed into the printed circuit board ( 14 ).

16. The microphone system ( 16 ) according to claim 15 , wherein the microphone system ( 16 ) comprises a further microphone ( 36 ″) and a further filter ( 34 ″) having a sound inlet and a sound outlet, wherein the filter and the further filter are mounted on opposing surfaces of the printed circuit board ( 14 ), wherein the acoustic input of the further microphone ( 36 ″) is acoustically coupled to the sound outlet of the further filter ( 34 ″) via a further through-hole formed into the printed circuit board ( 14 ).

17. The microphone system ( 16 ) according to claim 15 , wherein the microphone ( 36 ; 36 ′, 36 ″) is a dynamic microphone, a condenser microphone, an electret condenser microphone or a MEMS microphone.

18. A miniature electronic device ( 10 ) comprising a housing ( 12 ) formed with at least one sound entrance, a printed circuit board ( 14 ) equipped with at least one processing means ( 18 ) and a microphone system ( 16 ) of claim 15 .

19. The miniature electronic device ( 10 ) according to claim 18 , wherein the filter ( 34 ; 34 ′, 34 ″) comprises a seal ( 45 ) adapted to prevent acoustic leakage.

20. The miniature electronic device ( 10 ) according claim 18 , wherein the miniature electronic device is a hearing aid ( 10 ).

21. A method of equipping a printed circuit board ( 14 ) with a filter ( 34 ; 34 ′, 34 ″) according to claim 1 , said method comprising the step of mounting the filter ( 34 ; 34 ′, 34 ″) to the surface of the printed circuit board ( 14 ) by means of a pick and place process.