A method for processing an audio signal, comprising: discriminating a stationary interval and a transient interval from each other for a current frame of the audio signal by an audio processing apparatus by analyzing an energy of the audio signal, wherein the stationary interval is an interval having a flat energy interval, and wherein the transient interval is an interval where the energy of the audio signal varies abruptly; determining a particular band extension scheme for the current frame among a plurality of band extension schemes including a first band extension scheme and a second band extension scheme, wherein the particular band extension scheme for the current frame is temporarily determined based on a coding scheme of the audio signal, and the particular band extension scheme for the current frame is finally determined based on whether the audio signal is in the transient interval; generating type information indicating the particular band extension scheme; when the particular band extension scheme is the first band extension scheme for the current frame, generating a spectral data of higher band in the current frame using the spectral data of lower band by performing the first band extension scheme; when the particular band extension scheme is the second band extension scheme for the current frame, generating the spectral data of higher band in the current frame using the spectral data of lower band by performing the second band extension scheme; and transferring the type information and the spectral data of lower band, wherein the first band extension scheme is based on a first data area of the spectral data of lower band, and wherein the second band extension scheme is based on a second data area of the spectral data of lower band. discriminating a stationary interval and a transient interval from each other for a current frame of the audio signal by an audio processing apparatus by analyzing an energy of the audio signal, wherein the stationary interval is an interval having a flat energy interval, and wherein the transient interval is an interval where the energy of the audio signal varies abruptly; determining a particular band extension scheme for the current frame among a plurality of band extension schemes including a first band extension scheme and a second band extension scheme, wherein the particular band extension scheme for the current frame is temporarily determined based on a coding scheme of the audio signal, and the particular band extension scheme for the current frame is finally determined based on whether the audio signal is in the transient interval; generating type information indicating the particular band extension scheme; when the particular band extension scheme is the first band extension scheme for the current frame, generating a spectral data of higher band in the current frame using the spectral data of lower band by performing the first band extension scheme; when the particular band extension scheme is the second band extension scheme for the current frame, generating the spectral data of higher band in the current frame using the spectral data of lower band by performing the second band extension scheme; and transferring the type information and the spectral data of lower band, wherein the first band extension scheme is based on a first data area of the spectral data of lower band, and wherein the second band extension scheme is based on a second data area of the spectral data of lower band.