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Threshold Control for Speech Analyzer

IP.com Disclosure Number: IPCOM000073830D
Original Publication Date: 1971-Feb-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Clapper, GL: AUTHOR

Abstract

In speech analyzers, it is necessary to provide a preamplifier with an automatic gain control having a wide control range so that the low intensity parts of speech are adequately amplified. Such an amplifier must, however, be insensitive to interword noise of the same intensity as the intraword low levels. In this circuit, not only is the interword background noise suppressed but a delayed start circuit is also provided to prevent the start of a word analysis cycle by a noise pulse of a substantial amplitude.

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Threshold Control for Speech Analyzer

In speech analyzers, it is necessary to provide a preamplifier with an automatic gain control having a wide control range so that the low intensity parts of speech are adequately amplified. Such an amplifier must, however, be insensitive to interword noise of the same intensity as the intraword low levels. In this circuit, not only is the interword background noise suppressed but a delayed start circuit is also provided to prevent the start of a word analysis cycle by a noise pulse of a substantial amplitude.

In the drawing, a microphone 1 picks up speech and background noise and transmits its signal to a preamplifier 2. Preamplifier 2 will normally be set to attenuate an input signal by a lead 3 having a smoothing capacitor 4 and connected to an adjustable point of a resistor 5 between a negative source and a reset switch 6. The attenuated input signal from preamplifier 2 goes to an automatic gain controlled amplifier 7 acting to bring all input signals to a common output level. The signal is then divided into frequency bands by bandpass filters 8 with frequency band outputs on lines 9. The signals on lines 9 are ORed in OR 10 to provide an output at the maximum signal level on any one of the lines 9 and the output is fed back to AGC 7 as an amplitude control signal. A set of amplitude analyzers 11, essentially an amplifier for each line and a voltage divider network, also have their output lines 12 connected to OR 13. The o...