# US 12,183,333 B2 · Speech recognition

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- Number: US 12,183,333 B2
- Document ID: US12183333B2
- Status: Granted
- Kind: B2
- Application number: 17/549,528
- Filed: 2021-12-13
- Published: 2022-03-31
- Granted: 2024-12-31
- Earliest claimed: 2013-06-26
- Assignees: Cirrus Logic, Inc.
- Applicants: Cirrus Logic International Semiconductor Ltd.
- Inventors: John Paul Lesso; Robert James Hatfield
- Web page: https://patentgrep.com/patent/US12183333B2

## CPC

- G10L 15/20: Speech recognition techniques specially adapted for robustness in adverse environments, e.g. in noise, of stress induced speech (G10L21/02 takes precedence)
- G10L 15/28: Constructional details of speech recognition systems
- G10L 17/24: the user being prompted to utter a password or a predefined phrase
- G10L 21/0208: Noise filtering
- G10L 2015/088: {Word spotting}
- G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING

## Abstract

A speech recognition system comprises: an input, for receiving an input signal from at least one microphone; a first buffer, for storing the input signal; a noise reduction block, for receiving the input signal and generating a noise reduced input signal; a speech recognition engine, for receiving either the input signal output from the first buffer or the noise reduced input signal from the noise reduction block; and a selection circuit for directing either the input signal output from the first buffer or the noise reduced input signal from the noise reduction block to the speech recognition engine.

## Claims

### Claim 1

A speech recognition system, comprising:
an input, for receiving an input signal from at least one microphone;
a first buffer, for storing the input signal;
a noise reduction block, for receiving the input signal and generating a noise reduced input signal;
a speech recognition engine, for receiving either the input signal output from the first buffer or the noise reduced input signal from the noise reduction block; and
a selection circuit for selecting between passing either the input signal output from the first buffer or the noise reduced input signal from the noise reduction block to the speech recognition engine;
wherein the speech recognition system has a pass-phrase validation function for determining from the input signal whether a trigger phrase has been spoken by an authorised user of the system, wherein the selection circuit is controlled to select passing the noise reduced input signal from the noise reduction block to the speech recognition engine only after the pass-phrase validation function has determined that the trigger phrase has been spoken by the authorised user of the system.

### Claim 2 (depends on 1)

A speech recognition system as claimed in claim 1, wherein:
the selection circuit is controlled to select the input signal output from the first buffer to be passed to the speech recognition engine when the pass-phrase validation function first determines that the trigger phrase has been spoken by an authorised user of the system; and wherein:
the selection circuit is controlled to select the noise reduced input signal from the noise reduction block to be passed to the speech recognition engine when the speech recognition engine determines that the signal represents a gap in speech.

### Claim 3 (depends on 2)

A speech recognition system as claimed in claim 2, comprising a second buffer, for applying a time delay to the noise reduced input signal so that it is substantially in time alignment with the input signal output from the first buffer.

### Claim 4

An integrated circuit for use in a speech recognition system, comprising:
an input, for receiving an input signal from at least one microphone;
a first buffer, for storing the input signal as a buffered input signal;
a noise reduction block comprising a second buffer, for receiving the input signal and generating a buffered noise reduced input signal; and
a selection circuit for selecting between passing either the buffered input signal or the buffered noise reduced input signal, such that either the stored input signal can be routed from the first buffer to a speech recognition engine, or the buffered noise reduced input signal can be routed from the second buffer to the speech recognition engine;
wherein the speech recognition system has a pass-phrase validation function for determining from the input signal whether a trigger phrase has been spoken by an authorised user of the system, wherein the selection circuit is controlled to select passing the buffered noise reduced input signal from the noise reduction block to the speech recognition engine only after the pass-phrase validation function has determined that the trigger phrase has been spoken by the authorised user of the system.