<p>Provided are an audio signal processing apparatus and method. The audio signal processing apparatus includes: a sensing unit for sensing an impedance value of a headphone and adjusting a gain to be applied to an audio signal based on the sensed impedance value; and an amplifier for generating an output audio signal by receiving at least one bias voltage corresponding to the adjusted gain and amplifying the input audio signal according to the adjusted gain. The audio signal processing apparatus is capable of appropriately adjusting the magnitude of an acoustic signal output from a headphone, according to the product specifications of the headphone.</p>
