1. A method for signal extraction of audio signal, comprising: converting an audio signal into a plurality of frames, wherein the frames are arranged in a chronological order; obtaining spectral data of each of the frames; extracting the spectral data of each of continuous N frames extracted from a current frame to a N th frame in the chronological order by separately using each of the frames as the current frame, and executing a spectral connectivity operation for the N frames, wherein the spectral connectivity operation comprises: obtaining a signal block list of each of the N frames based on the spectral data included in each of the N frames, wherein the signal block list records spectral index range having a signal value; and searching for a spectral connectivity between adjacent frames according to the signal block list of each of the N frames; and determining a signal including the frames having the spectral connectivity between the adjacent frames in each of the frames as an ideal signal.