A binaural hearing aid system comprising: a first hearing aid (10L, 10R) for placement at, or in, a user's left or right ear, said first hearing aid comprising a first microphone arrangement (20L, 20R), a first wireless communications unit (14L, 14R), a first receiver (24L, 24R), and a first sound channel (26L, 26R) comprising a first valve (28L, 28R) which is movable from an open state to a closed state and from a closed state to an open state, the first sound channel being configured to allow for ambient sound from outside the first hearing aid to reach the ear canal of the user; a second hearing aid (10L, 10R) for placement at, or in, the user's opposite ear, said second hearing aid comprising a second microphone arrangement (20L, 20R), a second wireless communications unit (14L, 14R), and a second sound channel (26L, 26R) comprising a second valve (28L, 28R) which is movable from an open state to a closed state and from a closed state to an open state, the second sound channel being configured to allow for ambient sound from outside the second hearing aid to reach the ear canal of the user; a signal processing arrangement (22L, 22R) adapted for generating a beamformed signal based on microphone signals supplied by the first and/or second microphone arrangement(s) and for applying the beamformed signal to the first and/or second receiver(s), wherein the signal processing arrangement is adapted for generating an omnidirectional signal based on microphone signals supplied by the first and/or second microphone arrangement(s), and wherein the signal processing arrangement is adapted for applying the beamformed signal to one of the first or the second receiver and applying the omnidirectional signal to the other one of the first or the second receiver; and a valve control arrangement which has an asymmetric mode, in which asymmetric mode the valve control arrangement is configured to asymmetrically control the first and second valves by moving the first and second valves into positions wherein one of the first or second valves is opened more than the other of the first or second valves, and wherein the valve control arrangement is further configured to open the valve, which is comprised in the hearing aid comprising the receiver to which the omnidirectional signal is applied, more than the valve, which is comprised in the hearing aid comprising the receiver to which the beamformed signal is applied, when in the asymmetric mode. a first hearing aid (10L, 10R) for placement at, or in, a user's left or right ear, said first hearing aid comprising a first microphone arrangement (20L, 20R), a first wireless communications unit (14L, 14R), a first receiver (24L, 24R), and a first sound channel (26L, 26R) comprising a first valve (28L, 28R) which is movable from an open state to a closed state and from a closed state to an open state, the first sound channel being configured to allow for ambient sound from outside the first hearing aid to reach the ear canal of the user; a second hearing aid (10L, 10R) for placement at, or in, the user's opposite ear, said second hearing aid comprising a second microphone arrangement (20L, 20R), a second wireless communications unit (14L, 14R), and a second sound channel (26L, 26R) comprising a second valve (28L, 28R) which is movable from an open state to a closed state and from a closed state to an open state, the second sound channel being configured to allow for ambient sound from outside the second hearing aid to reach the ear canal of the user; a signal processing arrangement (22L, 22R) adapted for generating a beamformed signal based on microphone signals supplied by the first and/or second microphone arrangement(s) and for applying the beamformed signal to the first and/or second receiver(s), wherein the signal processing arrangement is adapted for generating an omnidirectional signal based on microphone signals supplied by the first and/or second microphone arrangement(s), and wherein the signal processing arrangement is adapted for applying the beamformed signal to one of the first or the second receiver and applying the omnidirectional signal to the other one of the first or the second receiver; and a valve control arrangement which has an asymmetric mode, in which asymmetric mode the valve control arrangement is configured to asymmetrically control the first and second valves by moving the first and second valves into positions wherein one of the first or second valves is opened more than the other of the first or second valves, and wherein the valve control arrangement is further configured to open the valve, which is comprised in the hearing aid comprising the receiver to which the omnidirectional signal is applied, more than the valve, which is comprised in the hearing aid comprising the receiver to which the beamformed signal is applied, when in the asymmetric mode.