A sound system comprising: a headphone including a transducer and at least one microphone ; an equalization filter adapted to equalize an audio input signal (V) based on at least one predetermined coefficient; a loop filter circuit including a leaky integrator circuit adapted to generate a filtered audio signal (V filt ) based on the equalized audio input signal (V) and a feedback signal indicative of sound received by the at least one microphone , and to provide the filtered audio signal (V filt ) to the transducer ; a controller ; and a switch (S) adapted to switch between a first position , in which the equalization filter is connected to an audio source for receiving a first audio input signal (V), and a second position , in which the equalization filter is connected to the controller for receiving a second audio input signal; wherein the controller is programmed to calibrate the headphone by updating the at least one coefficient of the equalization filter , and wherein the controller is further programmed to: control the switch (S) to be arranged in the second position ; generate the second audio input signal which is indicative of a test signal; receive a second feedback signal indicative of a test sound received by the at least one microphone ; update the at least one coefficient of the equalization filter based on the second feedback signal; and control the switch (S) to be arranged in the first position . a headphone including a transducer and at least one microphone ; an equalization filter adapted to equalize an audio input signal (V) based on at least one predetermined coefficient; a loop filter circuit including a leaky integrator circuit adapted to generate a filtered audio signal (V filt ) based on the equalized audio input signal (V) and a feedback signal indicative of sound received by the at least one microphone , and to provide the filtered audio signal (V filt ) to the transducer ; a controller ; and a switch (S) adapted to switch between a first position , in which the equalization filter is connected to an audio source for receiving a first audio input signal (V), and a second position , in which the equalization filter is connected to the controller for receiving a second audio input signal; wherein the controller is programmed to calibrate the headphone by updating the at least one coefficient of the equalization filter , and wherein the controller is further programmed to: control the switch (S) to be arranged in the second position ; generate the second audio input signal which is indicative of a test signal; receive a second feedback signal indicative of a test sound received by the at least one microphone ; update the at least one coefficient of the equalization filter based on the second feedback signal; and control the switch (S) to be arranged in the first position . control the switch (S) to be arranged in the second position ; generate the second audio input signal which is indicative of a test signal; receive a second feedback signal indicative of a test sound received by the at least one microphone ; update the at least one coefficient of the equalization filter based on the second feedback signal; and control the switch (S) to be arranged in the first position . <EOS>