Ultrasonic Equalization for Smart Speaker Presence Detection

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Solution Overview

Problem

Existing ultrasonic presence detection systems face challenges due to the varying frequency response characteristics of speakers and microphones, which hinder the resolution of ultrasonic echoes and limit spatial resolution in presence detection.

Innovation Solution

The implementation of an ultrasonic processing system that includes an ultrasonic burst generator, equalizer, and separation filter to pre-compensate and process ultrasonic signals, improving echo resolution by equalizing the signals according to the frequency response characteristics of speakers and microphones, and determining the delay time of echoes for accurate presence detection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If ultrasonic burst signals are emitted for presence detection, then presence detection capability is enabled, but frequency response variations of speakers and microphones degrade echo resolution and spatial resolution

Engineering Contradiction:

Improvespatial resolutionVSAvoidecho resolution

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent applies preliminary equalization to the ultrasonic burst signal before emission, compensating for the frequency response characteristics of the speaker and microphone. This pre-compensation ensures that the signal maintains its spectral integrity after passing through the transducers, thereby improving echo resolution and spatial resolution in presence detection

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system measures the actual frequency response of the speaker-microphone channel and uses this information to adjust the equalization parameters. This feedback mechanism allows the system to adapt to variations in transducer characteristics, maintaining optimal echo resolution and spatial resolution performance

Inventive Principle:

Principle #23Feedback

2Measurement precision

If frequency response equalization is applied to ultrasonic signals, then echo resolution is improved, but processing complexity and computational resources increase

Engineering Contradiction:

Improveecho resolutionVSAvoidprocessing complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The equalization is applied specifically to the ultrasonic frequency band rather than the entire audio spectrum. By focusing processing resources only on the relevant ultrasonic frequencies, the system achieves improved echo resolution while minimizing unnecessary computational overhead in other frequency ranges

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The system adjusts the equalization parameters based on the measured frequency response characteristics of the specific speaker-microphone pair. By optimizing the equalization filter parameters for the actual hardware being used, the system achieves high echo resolution with computationally efficient parameter sets rather than overly complex universal filters

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach enhances spatial resolution and efficiency in ultrasonic presence detection, allowing for improved detection of objects and motion, while optimizing hardware and computational resources.

Implementation Method 1

emitting ultrasonic acoustic waves from the speakers, and sensing reflections via the built-in microphones to detect the presence of a user

Methodology Applied

Scientific EffectUltrasonic acoustic wave reflection: Echo

Implementation Method 2

transmitting bursts of sinusoidal pulses and an array of receivers that detect reflections of those bursts from objects in the vicinity of the transmitter

Methodology Applied

Scientific EffectAcoustic wave propagation: Sound

Implementation Method 3

the equalization of that ultrasonic burst signal according to frequency response characteristics of the speaker and microphone at those ultrasonic frequencies

Methodology Applied

Scientific EffectFrequency response equalization:

Implementation Method 4

A delay time of an echo corresponding to the ultrasonic burst signal in an ultrasonic portion of a signal received from a microphone is then determined

Methodology Applied

Scientific EffectTime delay measurement: Time of Flight

Data Source

PatentUS11971476B2Ultrasonic equalization and gain control for smart speakers

Publication Date: 2024.04.30 TEXAS INSTRUMENTS INC

AI summary

Ultrasonic audio processing circuitry and a method useful in ultrasonic presence detection. An ultrasonic burst generator produces an ultrasonic burst signal at one or more ultrasonic frequencies, and an equalizer equalizes that ultrasonic burst signal according to frequency response characteristics of the speaker and microphone at those ultrasonic frequencies. Driver circuitry drives a speaker with the ultrasonic burst signal, which may be combined with an audible audio signal. An ultrasonic separation filter separates an ultrasonic portion from a signal received at a microphone, and processing circuitry is provided to determine a delay time of an echo corresponding to the ultrasonic burst signal in that separated ultrasonic portion of the received signal. In another aspect, the equalizer equalizes an ultrasonic portion of the signal received at a microphone, according to frequency response characteristics of the speaker and microphone at the ultrasonic frequencies of the burst.