Method and an apparatus for processing an audio signal

A method of decoding an audio signal, and which includes extracting spectral data and a loss signal compensation parameter from an audio signal bitstream; detecting a loss signal based on the spectral data; generating first compensation data corresponding to the loss signal using a random signal based on the loss signal compensation parameter; generating a scale factor by adding a scale factor difference value to a scale factor reference value if the scale factor corresponds to a band quantized to zero, and the scale factor reference value is included in the loss signal compensation parameter; and generating second compensation data by applying the scale factor to the first compensation data.