| 摘要 |
1310265 Speech recognition RCA CORPORATION 22 April 1970 [30 July 1969] 19354/70 Heading G4R In a speech recognition system, spectrum analysis is followed by slope identification and energy comparison of the spectrum, the slope identification being followed by slope comparison. The speech signal, after passage through a pre-amplifier/equalizer, feeds 15 fullwave rectifier and low-pass filter units (to remove unwanted phase information) directly (total energy signal) and via 14 bandpass filters (providing the frequency spectrum) respectively. The 15 outputs from the units are time-divisionmultiplexed through a log amplifier and demultiplexed into respective sample-and-hold circuits which feed a broad slope identification network and an energy comparison network. The broad slope identification network uses operational amplifiers to detect broad positive and negative slopes in respective parts of the frequency spectrum. Each operational amplifier produces an analogue output representing the difference of two sums of adjacent inputs, providing this difference is positive. The energy comparison network uses operational amplifiers in a similar way except that a thresholded bit output is produced from each amplifier. The outputs from the broad slope identification network feed a slope comparison network which has a similar construction to the energy comparison network. The summing and differencing are equivalent to multiplying and dividing because of the logging. The broad slope identification network, slope comparison network, and energy comparison network, feed recognition logic. The total energy signal mentioned can be used to detect work beginnings, endings and pauses. |
