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Zero Crossing Voice Detection Using Digital Sampling

IP.com Disclosure Number: IPCOM000088991D
Original Publication Date: 1977-Sep-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 45K

Publishing Venue

IBM

Related People

Frankeny, RF: AUTHOR

Abstract

Described is a digital voice detector which uses as a parameter the number of zero crossings of an audio signal in a fixed time interval.

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Zero Crossing Voice Detection Using Digital Sampling

Described is a digital voice detector which uses as a parameter the number of zero crossings of an audio signal in a fixed time interval.

The zero crossings of an input signal are detected by zero crossing detector 1 and converted into crosses which are fed into single shots 2 and 3 which react to pulses having opposite transitions. The outputs of single shots 2 and 3 are gated into the clock input of up/down counter 5 by OR gate 4. When the Q output of free-running clock 6 goes positive, OR gate 7 sets flip-flop 8 to a "one" output which sets the "up" control of up/down counter 5. Up/down counter 5 then counts up for each transition gated into its clock input from OR gate 4.

When the Q output of clock 6 goes positive, flip-flop 8 is reset which activates the "down" control of up/down counter 5. During this transition the up/down counter 5 counts down for each transition gated to its clock input by OR gate 4. An underflow of the up/down counter 5 on the down count indicates that the input signal is of increasing frequency and it is, therefore, possibly a voice signal.

The underflow output causes OR gate 7 to set flip-flop 8 to a positive output which once again triggers up control of the up/down counter 5, and up/down counter 5 counts up for the remainder of the clock cycle.

The next positive transition on the Q output of clock 6 sets single shot 11 to a "one" output to AND gate 12. Simultaneously, the count fr...