| 摘要 |
986, 520. Indicating extremes of amplitude. INTERNATIONAL BUSINESS MACHINES CORPORATION. Dec. 4, 1962 [Dec. 7, 1961], No. 45737/62. Heading G1U. [Also in Division G4] In speech recognition apparatus an indication of local amplitude extreme in a number of frequency channels is provided by applying each channel to a transistor adapted to respond to a local maximum, the output of any transistor which responds serving also to inhibit response of at least adjacent transistors. The speech signal from microphone 7 is applied to band-pass filters 8a-8n the outputs of which pass to detectors 10a-10n giving D.C. amplitudes proportional to the square of the input amplitudes. These signals are therefore measures of the power in the corresponding frequency band. The curve of Fig. 2 represents the power in the different frequency bands, each maximum being accompanied by smaller peaks on each side, relating to harmonics of the maximum frequency. The circuit is designed to respond only to the main maxima and to ignore all or some of the adjacent peaks. The outputs from detectors 10a- 10n are each applied to comparator transistors 11a-11n which tend to conduct. When the transistor, say 11b of the channel having a maximum, conducts the potential at point 13b increases and exceeds the amplitude of the adjacent peaks. Through resistors 14a and 14b the potential of points 13a and 13c is also raised sufficiently to prevent the transistors 11a and 11c conducting. At more remote points 13d-13n the effect of the conduction of transistor 11b is more attenuated due to the successive resistors 14c-14n and more remote transistors are not affected so that other local maximum may be detected in the same way. Those transistors which conduct energize relays 17a-17n through second transistors 16a-16n The output, Fig. 4 indicates the local maxima. These are called the "formants" of the signal. A modification having two comparator stages for detecting more widely differing maxima such as the one at f6. |
