An arrangement for calibrating feedforward-type ambient noise-cancelling, ANC, headphones and earphones, the arrangement comprising: a housing (304, 404, 604, 906) 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, (308, 408, 616, 912), rearward of the diaphragm, in which the sound pressure level, SPL, is defined to be SPL B; an acoustic coupling arrangement (300, 400, 600, 908), comprising: a conduit (302, 402, 608, 910) provided in the housing; a first port (310, 410, A) in the housing acoustically connecting the conduit to the ambient air (312, 412, 618, 918) 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 (308, 408, 616, 912), the second port being spaced apart from the first port; a microphone (316, 416, 606, 922) 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 (304, 404, 604, 906) 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, (308, 408, 616, 912), rearward of the diaphragm, in which the sound pressure level, SPL, is defined to be SPL B; an acoustic coupling arrangement (300, 400, 600, 908), comprising: a conduit (302, 402, 608, 910) provided in the housing; a first port (310, 410, A) in the housing acoustically connecting the conduit to the ambient air (312, 412, 618, 918) 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 (308, 408, 616, 912), the second port being spaced apart from the first port; a microphone (316, 416, 606, 922) 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 (302, 402, 608, 910) provided in the housing; a first port (310, 410, A) in the housing acoustically connecting the conduit to the ambient air (312, 412, 618, 918) 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 (308, 408, 616, 912), the second port being spaced apart from the first port; a microphone (316, 416, 606, 922) 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.