Abstract: An audio signal processing method is provided. The method separates a left and a right channel audio signal to a center-left and center-right channel audio signals, and a side-left and side-right channel audio signals, and processes the center and side channel audio signals by a Head Related Transfer Function (HRTF) so as to simulate the audio signals into several audio source positions related to a user, then synthesizes the processed audio signals into dual channel audio signals according to the user's hearing characteristics by a frequency compensation process. The invention further provides an audio signal processing apparatus to perform the audio signal processing method.

Abstract: The invention discloses an earphone device comprising a first case, a first speaker unit, a first recording unit, and a second recording unit. The first speaker unit, disposed inside the first case, emits a first testing sound signal according to a test command. The first recording unit, disposed inside the first case, records a first environment sound signal according to a record command or a noise cancelling command. The second recording unit, disposed inside the first case, records a first feedback sound signal, related to the first testing sound signal, according to the test command.