An arrangement for calibrating feedforward-type ambient noise-cancelling, ANC, headphones and earphones, the arrangement comprising: a housing bearing a loudspeaker having a diaphragm with a first diaphragm surface coupled to a first volume of air bounded by and coupled to a user's ear, and with a second diaphragm surface bounding a cavity within the housing so as to define a second volume of air, B, , rearward of the diaphragm, in which the sound pressure level, SPL, is defined to be SPL B ; an acoustic coupling arrangement , comprising: a conduit provided in the housing; a first port (310, 410, A) in the housing acoustically connecting the conduit to the ambient air in which the sound pressure level is defined to be SPL AMB ; a second port (306, 406, B) in the housing for acoustically connecting the conduit to the second volume of air , the second port being spaced apart from the first port; a microphone having an inlet provided at a predetermined location, Q, within the conduit at which the sound pressure level is defined to be SPL Q , said predetermined location, Q, being provided between the first port and the second port and spaced apart from the first port; wherein the first port defines a first acoustic couple means having a first characteristic acoustic impedance, R x , and the second port defines a second acoustic couple means having a second characteristic acoustic impedance, R y , whereby the sound pressure at the microphone inlet, SPL Q , includes a pre-determined fraction of an acoustic signal from the loudspeaker according to the relationship: SPL Q = R y R y + R x SPL AMB − SPL B + SPL B . a housing bearing a loudspeaker having a diaphragm with a first diaphragm surface coupled to a first volume of air bounded by and coupled to a user's ear, and with a second diaphragm surface bounding a cavity within the housing so as to define a second volume of air, B, , rearward of the diaphragm, in which the sound pressure level, SPL, is defined to be SPL B ; an acoustic coupling arrangement , comprising: a conduit provided in the housing; a first port (310, 410, A) in the housing acoustically connecting the conduit to the ambient air in which the sound pressure level is defined to be SPL AMB ; a second port (306, 406, B) in the housing for acoustically connecting the conduit to the second volume of air , the second port being spaced apart from the first port; a microphone having an inlet provided at a predetermined location, Q, within the conduit at which the sound pressure level is defined to be SPL Q , said predetermined location, Q, being provided between the first port and the second port and spaced apart from the first port; a conduit provided in the housing; a first port (310, 410, A) in the housing acoustically connecting the conduit to the ambient air in which the sound pressure level is defined to be SPL AMB ; a second port (306, 406, B) in the housing for acoustically connecting the conduit to the second volume of air , the second port being spaced apart from the first port; a microphone having an inlet provided at a predetermined location, Q, within the conduit at which the sound pressure level is defined to be SPL Q , said predetermined location, Q, being provided between the first port and the second port and spaced apart from the first port; wherein the first port defines a first acoustic couple means having a first characteristic acoustic impedance, R x , and the second port defines a second acoustic couple means having a second characteristic acoustic impedance, R y , whereby the sound pressure at the microphone inlet, SPL Q , includes a pre-determined fraction of an acoustic signal from the loudspeaker according to the relationship: SPL Q = R y R y + R x SPL AMB − SPL B + SPL B . <EOS>