Method of determining variable-length frame for speech signal preprocessing and speech signal preprocessing method and device using the same

A speech signal preprocessing method for extracting a feature vector of a speech signal, the method comprising the steps of:

• (1) converting an input speech signal into a digital signal;
• (2) performing pre-emphasis filtering for emphasizing a high-frequency band of the speech signal;
• (3) varying a frame length of the speech signal and simultaneously calculating a Linear Prediction Coefficient (LPC) residual error from frame length to frame length;
• (4) determining a length of each frame by taking a frame length at which the LPC residual error is minimal;
• and
• (5) extracting a feature vector of the speech signal from each frame.

A speech signal preprocessing device comprising:

• an analog-to-digital converter for converting an input speech signal into a digital signal;
• a pre-emphasis filter for performing pre-emphasis filtering which emphasizes a high-frequency band of the speech signal;
• a framing processor for varying a frame length of the speech signal and simultaneously calculating a Linear Prediction Coefficient (LPC) residual error from frame length to frame length, and determining a length of each frame by taking a frame length at which the LPC residual error is minimal;
• and
• a feature vector extractor for extracting a feature vector from each frame.