Disclosed in the present specification are a multimedia apparatus for servicing an optimized sound depending on the surrounding environment and a method for processing an audio signal thereof. The method for processing an audio signal of the multimedia apparatus, according to the present invention, comprises the steps of: receiving an external test sound; analyzing the frequency properties of the received test sound; calculating a compensation value of the test sound according to the analyzed frequency properties; compensating an audio signal to be output, according to the calculated compensation value; and outputting the compensated audio signal.