An active noise reduction system comprising: an earphone to be acoustically coupled to a listener's ear which is exposed to noise, the earphone comprises a cup-like housing with an aperture; a transmitting transducer (16, 21, 38) which converts electrical signals into acoustical signals to be radiated to the listener's ear and which is arranged at the aperture of the cup-like housing thereby defining an earphone cavity located behind the transmitting transducer (16, 22, 38); and a receiving transducer (18, 23, 35) which converts acoustical signals into electrical signals; a sound-guiding tube-like duct having two ends; one end is acoustically coupled to the receiving transducer (18, 23, 35); a first acoustical path which extends from the transmitting transducer (16, 22, 38) to the ear and which has a first transfer characteristic; a second acoustical path which extends from the transmitting transducer through the tube-like member to the receiving transducer (18, 23, 35) and which has a second transfer characteristic; and a control unit (7, 9) which is electrically connected to the receiving transducer (18, 23, 35) and the transmitting transducer (16, 22, 38) and which compensates for the ambient noise at the ear by generating a noise reducing electrical signal supplied to the transmitting transducer (16, 22, 38), in which the noise reducing electrical signal is derived from the receiving-transducer signal (18, 23, 35) filtered with a third transfer characteristic and in which the second and third transfer characteristics together model the first transfer characteristic; characterized in that the receiving transducer (18, 23, 35) is arranged within the earphone cavity and the other end of the sound-guiding tube-like duct is arranged in another cavity between the front portion of the housing and an outer portion of the ear. an earphone to be acoustically coupled to a listener's ear which is exposed to noise, the earphone comprises a cup-like housing with an aperture; a transmitting transducer (16, 21, 38) which converts electrical signals into acoustical signals to be radiated to the listener's ear and which is arranged at the aperture of the cup-like housing thereby defining an earphone cavity located behind the transmitting transducer (16, 22, 38); and a receiving transducer (18, 23, 35) which converts acoustical signals into electrical signals; a sound-guiding tube-like duct having two ends; one end is acoustically coupled to the receiving transducer (18, 23, 35); a first acoustical path which extends from the transmitting transducer (16, 22, 38) to the ear and which has a first transfer characteristic; a second acoustical path which extends from the transmitting transducer through the tube-like member to the receiving transducer (18, 23, 35) and which has a second transfer characteristic; and a control unit (7, 9) which is electrically connected to the receiving transducer (18, 23, 35) and the transmitting transducer (16, 22, 38) and which compensates for the ambient noise at the ear by generating a noise reducing electrical signal supplied to the transmitting transducer (16, 22, 38), in which the noise reducing electrical signal is derived from the receiving-transducer signal (18, 23, 35) filtered with a third transfer characteristic and in which the second and third transfer characteristics together model the first transfer characteristic; characterized in that the receiving transducer (18, 23, 35) is arranged within the earphone cavity and the other end of the sound-guiding tube-like duct is arranged in another cavity between the front portion of the housing and an outer portion of the ear.