Pre-processing system for speech recognition
AssigneeHitachi, Ltd.
InventorsAkira Nakajima, Akira Ichikawa
Life of this patent
Estimating the term…
Abstract
A pre-processing system for a speech recognition system nullifies the distortion in a received signal caused by the transmission line by forming a normalized received signal whereby the distortion is cancelled: the received signal is spectrally averaged to form a mean spectrum which is used to adjust a filter to a characteristic inverse to the distortion; this filter then filters the received signal to form the normalized received signal s.sub.j '(.omega.,t)=S.sub.j (.omega.,t)/S.sub.j (.omega.) which is equal to the normalized source signal =S.sub.i (.omega.,t)/S.sub.i (.omega.).
Claims11
A pre-processing system for speech recognition comprising:
- first means for receiving input speech which has been transmitted through a transmission medium, said first means providing an output representative of said input speech;
- second means connected to the output of said first means for determining the mean frequency spectrum of the input speech received by said first means and providing an output representative of said mean frequency spectrum;
- and
- filter means, connected to the outputs of said first and seconds means, having a frequency spectrum response inversely proportional to the mean frequency spectrum determined by said second means, for filtering the input signal received by said first means.
A pre-processing system for speech recognition comprising:
- first means for receiving an input speech signal which is a product of true speech and a distortion signal produced by transmission characteristics of a transmission system over which said speech is transmitted, wherein said first means provides an output representative of said received input speech signal;
- second means connected to the output of said first means for determining the mean frequency spectrum of the received input speech signal and providing an output representative of said mean frequency spectrum;
- and
- filter means, connected to the outputs of said first and second means, for using the mean frequency spectrum determined by the second means to provide a frequency response inversely proportional to the mean frequency spectrum determined by said second means, and for filtering the signal received from the first means representing the received input speech signal with the inversely proportional frequency spectrum to eliminate the distortion signal present in said received input speech signal.
Dependencies are inferred from the claim text.