CLAIMS 1. Behind the ear hearing aid (3) with a frontal sound inlet (1,1 a,lb) and a rear sound inlet (2,2a,2b) for receiving the sound input and at least one microphone in acoustical connection with the frontal and rear sound inlets (1,1a,lb;,2,2a,2b) and an electronic signal path from the microphone to a receiver, which delivers a sound signal to the ear wherein the hearing aid (3) has a geometrically defined centre-line (4) which divides the hearing aid (3) into a first half facing the head of the user and a second half facing away from the user when the hearing aid is placed on or at the ear, whereby the frontal sound inlet (1,1 a,lb) is positioned at the geometrical centre-line (4) or in the first half of the hearing aid and the rear sound inlet (2,2a,2b) is positioned in the second half of the hearing aid (3). 2. Behind the ear hearing aid as claimed in claim 1, wherein a first omnidirectional microphone in acoustic connection with the front inlet port (1,1a,lb) is provided and a second omnidirectional microphone in acoustic connection with the rear sound inlet port (2,2a,2b) is provided. 3. Behind the ear hearing aid as claimed in claim 1, wherein the front inlet port (1,1a,lb) and the rear inlet port (2,2a,2b) are acoustically connected to each their port of a directional microphone. 4. Behind the ear hearing aid as claimed in one of the above claims wherein the distance between the two sound inlet openings perpendicular to the centerline is at least 2.5 mm. 5. Behind the ear hearing aid as claimed in one or more of the above claims, wherein the front sound inlet port (1,1a,lb) is placed at least partially at the side of the hearing aid (3) and facing the head of the user, and the rear sound inlet port (2,2a,2b) is placed at least partially at the side of the hearing aid (3) and facing away from the head of the user. 6. Behind the ear hearing aid as claimed in one or more of claimes 1-4, wherein at least a part the front sound inlet port (1,1 a,lb) and a part of the rear sound inlet port (2,2a,2b) is placed facing upwards. 7. Behind the ear hearing aid as claimed in one or more of claims 1-4, wherein the microphones used are formed using MEMS technology and located on one ore more chips, wherein the chips further comprise integrated circuits. 8. Behind the ear hearing aid as claimed in one of claims 1-4, wherein the front inlet port comprises two openings (la,lb) such that at least one opening is placed at each half of the hearing aid and whereby the opening in the second half is blocked, and wherein the rear inlet port comprises two opening (2a,2b) such that at least one opening is placed at each half of the hearing aid and whereby the opening in the first half is blocked. 9. Method of producing a hearing aid of the kind claimed in claim 1, whereby a hearing aid shell is produced with front and rear openings (la,lb,2a,2b) in each half of the hearing aid, and whereby the frontal inlet opening in the second half of the hearing aid and the rear inlet opening in the first half of the hearing aid are blocked before providing the hearing aid to the end user.CLAIMS 1. Behind the ear hearing aid (3) with a frontal sound inlet (1,1 a, lb) and a rear sound inlet (2,2a, 2b) for receiving the sound input and at least one microphone in acoustical connection with the frontal and rear sound inlets (1,1a, lb ;, 2,2a, 2b) and an electronic signal path from the microphone to a receiver, which delivers a sound signal to the ear where the hearing aid (3) has a geometrically defined center-line (4) which divides the hearing aid (3) into a first half facing the head of the user and a second half facing away from the user when the hearing aid is placed on or at the ear, whereby the frontal sound inlet (1,1 a, lb) is positioned at the geometrical center-line (4) or in the first half of the hearing aid and the rear sound inlet (2,2a, 2b) is positioned in the second half of the hearing aid (3). Behind the ear hearing aid as claimed in claim 1, where a first omnidirectional microphone in acoustic connection with the front inlet port (1,1a, lb) is provided and a second omnidirectional microphone in acoustic connection with the rear sound inlet port ( 2,2a, 2b) is provided. Behind the ear hearing aid as claimed in claim 1, wherein the front inlet port (1,1a, lb) and the rear inlet port (2,2a, 2b) are acoustically connected to each their port of a directional microphone. Behind the ear hearing aid as claimed in one of the above claims where the distance between the two sound inlet openings perpendicular to the centerline is at least 2.5 mm. 5. Behind the ear hearing aid as claimed in one or more of the above claims, wherein the front sound inlet port (1,1a, lb) is placed at least partially at the side of the hearing aid (3) and facing the head of the user, and the rear sound inlet port (2,2a, 2b) is placed at least partially at the side of the hearing aid (3) and facing away from the head of the user. Behind the ear hearing aid as claimed in one or more of claims 1-4, where at least a part the front sound inlet port (1,1 a, lb) and a part of the rear sound inlet port (2,2a , 2b) is placed facing upwards. Behind the ear hearing aid as claimed in one or more of claims 1-4, where the microphones used are formed using MEMS technology and located on one ore more chips, where the chips further comprise integrated circuits. 8. Behind the ear hearing aid as claimed in one of claims 1-4, wherein the front inlet port comprises two openings (la, lb) such that at least one opening is placed at each half of the hearing aid and whereby the opening in the second half is blocked, and where the rear inlet port comprises two opening (2a, 2b) such that at least one opening is placed at each half of the hearing aid and whereby the opening in the first half is blocked. 9. Method of producing a hearing aid of the kind claimed in claim 1, whereby a hearing aid shell is produced with front and rear openings (la, lb, 2a, 2b) in each half of the hearing aid, and whereby the frontal inlet opening in the second half of the hearing aid and the rear inlet opening in the first half of the hearing aid are blocked before providing the hearing aid to the end user.