Signal classifying method and device, and audio encoding method and device using same

An audio encoding method in an encoding device for an audio signal, the audio encoding method comprising:

• classifying, performed by at least one processor, a current frame as one from among a plurality of classes including a speech class and a music class, based on a signal characteristic of an audio signal;
• evaluating a condition, based on one or more parameter among a plurality of parameters, wherein the plurality of parameters include a parameter obtained from a plurality of frames;
• first determining whether one of the plurality of conditions corresponds to a first threshold value;
• second determining whether a hangover parameter corresponds to a second threshold value;
• and
• correcting a classification result of the current frame, based on a first result of the first determining and a second result of the second determining;
• and
• encoding the current frame based on the classification result or the corrected classification result,
• wherein the plurality of parameters include tonalities in a plurality of frequency regions, a long term tonality in a low band, a difference between the tonalities in the plurality of frequency regions, a linear prediction error, and a difference between a scaled voicing feature and a scaled correlation map feature.