A hearing assistance system comprising • a first part adapted for being mounted fully or partially at a first ear or in an ear canal of the first ear of a user, the first part comprising ∘ a first housing, ∘ a number of first electrodes (EEGe1) located at a surface of said first housing to allow said first electrodes to contact the skin (SKIN) of the user when said first part is operationally mounted on the user, each of the first electrodes being adapted to pick up a low-voltage electric signal from the user's brain, • a second part adapted for being mounted on the body spatially separated from said first part, the second part comprising ∘ a number of second electrodes (REFe2) arranged to allow said second electrodes to contact the skin of the user when second said part is operationally mounted on the user, ∘ at least one of the second electrodes of the second part being configured as a reference electrode (REFe2) and adapted to pick up a reference voltage (V REF2) intended to constitute a reference voltage for the low-voltage electric signal(s) from the user's brain picked up by the first electrodes thereby allowing a voltage difference signal (ΔV EEGi) to be determined for each of said first electrodes (EEGe1), wherein the hearing assistance system comprises a comparison unit (COMPU) for determining said voltage difference signal(s), and an electric interface allowing said reference voltage (V REF2) or a measure representative thereof to be transferred from said second part to said comparison unit (COMPU), and characterized in that the electric interface comprises a body-network. • a first part adapted for being mounted fully or partially at a first ear or in an ear canal of the first ear of a user, the first part comprising ∘ a first housing, ∘ a number of first electrodes (EEGe1) located at a surface of said first housing to allow said first electrodes to contact the skin (SKIN) of the user when said first part is operationally mounted on the user, each of the first electrodes being adapted to pick up a low-voltage electric signal from the user's brain, ∘ a first housing, ∘ a number of first electrodes (EEGe1) located at a surface of said first housing to allow said first electrodes to contact the skin (SKIN) of the user when said first part is operationally mounted on the user, each of the first electrodes being adapted to pick up a low-voltage electric signal from the user's brain, • a second part adapted for being mounted on the body spatially separated from said first part, the second part comprising ∘ a number of second electrodes (REFe2) arranged to allow said second electrodes to contact the skin of the user when second said part is operationally mounted on the user, ∘ at least one of the second electrodes of the second part being configured as a reference electrode (REFe2) and adapted to pick up a reference voltage (V REF2) intended to constitute a reference voltage for the low-voltage electric signal(s) from the user's brain picked up by the first electrodes thereby allowing a voltage difference signal (ΔV EEGi) to be determined for each of said first electrodes (EEGe1), wherein the hearing assistance system comprises a comparison unit (COMPU) for determining said voltage difference signal(s), and an electric interface allowing said reference voltage (V REF2) or a measure representative thereof to be transferred from said second part to said comparison unit (COMPU), and characterized in that the electric interface comprises a body-network. ∘ a number of second electrodes (REFe2) arranged to allow said second electrodes to contact the skin of the user when second said part is operationally mounted on the user, ∘ at least one of the second electrodes of the second part being configured as a reference electrode (REFe2) and adapted to pick up a reference voltage (V REF2) intended to constitute a reference voltage for the low-voltage electric signal(s) from the user's brain picked up by the first electrodes thereby allowing a voltage difference signal (ΔV EEGi) to be determined for each of said first electrodes (EEGe1), wherein the hearing assistance system comprises a comparison unit (COMPU) for determining said voltage difference signal(s), and an electric interface allowing said reference voltage (V REF2) or a measure representative thereof to be transferred from said second part to said comparison unit (COMPU), and characterized in that the electric interface comprises a body-network.