Time-based frequency tuning of analog-to-information feature extraction
First Claim
1. An audio recognition circuit, comprising:
- a first analog filter for filtering an analog signal using a first frequency characteristic over a first interval of a particular duration;
a second analog filter for filtering the analog signal using a second frequency characteristic different from the first frequency characteristic over a second interval of the particular duration differing from the first interval of the particular duration;
first feature extraction circuitry for extracting a first analog signal feature from the analog signal filtered by the first analog filter and corresponding to the first interval;
second feature extraction circuitry for extracting a second analog signal feature from the analog signal filtered by the second analog filter and corresponding to the second interval;
a multiplexer for outputting a feature sequence comprising the extracted first and second analog signal features;
an analog-to-digital converter for digitizing the feature sequence; and
an event trigger for issuing an event trigger signal responsive to the feature sequence matching a particular feature sequence according to a matching criterion.
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Accused Products
Abstract
A sound recognition system including time-dependent analog filtered feature extraction and sequencing. An analog front end (AFE) in the system receives input analog signals, such as signals representing an audio input to a microphone. Features in the input signal are extracted, by measuring such attributes as zero crossing events and total energy in filtered versions of the signal with different frequency characteristics at different times during the audio event. In one embodiment, a tunable analog filter is controlled to change its frequency characteristics at different times during the event. In another embodiment, multiple analog filters with different filter characteristics filter the input signal in parallel, and signal features are extracted from each filtered signal; a multiplexer selects the desired features at different times during the event.
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Citations
8 Claims
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1. An audio recognition circuit, comprising:
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a first analog filter for filtering an analog signal using a first frequency characteristic over a first interval of a particular duration; a second analog filter for filtering the analog signal using a second frequency characteristic different from the first frequency characteristic over a second interval of the particular duration differing from the first interval of the particular duration; first feature extraction circuitry for extracting a first analog signal feature from the analog signal filtered by the first analog filter and corresponding to the first interval; second feature extraction circuitry for extracting a second analog signal feature from the analog signal filtered by the second analog filter and corresponding to the second interval; a multiplexer for outputting a feature sequence comprising the extracted first and second analog signal features; an analog-to-digital converter for digitizing the feature sequence; and an event trigger for issuing an event trigger signal responsive to the feature sequence matching a particular feature sequence according to a matching criterion. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification