Acoustic Delay Measurement via Impulse Response Thresholding

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Solution Overview

Problem

Existing methods for acoustic propagation delay measurement in noisy and strongly reflective rooms are unreliable due to interference from noise signals and reflections, which corrupt the measurement results and fail to accurately determine the arrival of the direct sound wave.

Innovation Solution

A system and method that includes an impulse response calculation unit to estimate the impulse response of the transmitter-room-receiver system from a measuring signal, and a delay time calculation unit to determine the acoustic propagation delay by identifying the time when the impulse response exceeds a threshold, using an adaptive filter to refine the estimation and account for changing noise conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional acoustic propagation delay measurement methods are used in noisy and strongly reflective rooms, then the measurement process is simple, but the measurement precision deteriorates due to interference from noise signals and reflections

Engineering Contradiction:

Improveacoustic propagation delay measurement precisionVSAvoidinterference from noise signals and reflections

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent segments the acoustic signal processing into distinct stages: receiving the mixed signal containing direct sound, reflections, and noise; estimating the impulse response to separate the direct sound component; and detecting the arrival time threshold. This segmentation allows each stage to address specific aspects of the measurement problem, improving overall precision in noisy environments.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces an impulse response estimation as an intermediary step between receiving the raw acoustic signal and determining the propagation delay. This intermediary processing separates the direct sound wave from reflections and noise, enabling accurate delay measurement even when the direct sound is buried in the mixed signal.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If threshold-based delay detection is used to identify direct sound wave arrival, then the measurement process is straightforward, but reliability deteriorates in strongly reflective rooms where reflections correlate with the direct sound signal

Engineering Contradiction:

Improvemeasurement reliability in reflective roomsVSAvoidsignal processing complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent performs preliminary impulse response estimation before the final delay detection. This preliminary action characterizes the acoustic environment and separates the direct sound component from reflections and noise, making the subsequent threshold-based delay detection reliable even in strongly reflective rooms.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses the estimated impulse response as feedback to inform the delay detection process. By comparing the impulse response characteristics with the received signal, the system can reliably identify direct sound wave arrival times despite the presence of correlated reflections, improving measurement reliability.

Inventive Principle:

Principle #23Feedback

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 allows for reliable measurement of acoustic propagation delay and distance in noisy and reflective environments by distinguishing the direct sound wave from reflections and noise, providing accurate results even in complex acoustic conditions.

Implementation Method 1

Acoustic waves traveling in gaseous media, such as air, propagate with a finite velocity

Methodology Applied

Scientific EffectAcoustic wave propagation: Sound

Implementation Method 2

an impulse response calculation unit configured to estimate the impulse response of the transmitter-room-receiver system from a measuring signal provided by the acoustic receiver and from the forward signal

Methodology Applied

Scientific EffectImpulse response estimation:

Implementation Method 3

a delay time calculation unit coupled to the impulse response calculation unit and configured to calculate the acoustic propagation delay from the estimated impulse response, the acoustic propagation delay being calculated from the time when the impulse response exceeds a threshold for the first time

Methodology Applied

Scientific EffectThreshold-based delay detection:

Data Source

PatentEP2045620B1Acoustic propagation delay measurement

Publication Date: 2015.08.12 HARMAN BECKER AUTOMOTIVE SYST GMBH

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AI summary

A system for measuring the acoustic propagation delay from an acoustic transmitter to an acoustic receiver which form a transmitter-room-receiver system, the system comprising a signal source coupled to the acoustic transmitter for supplying a forward signal thereto, the acoustic transmitter emitting an acoustic signal, an impulse response calculation unit configured to estimate the impulse response of the transmitter-room-receiver system from a measuring signal provided by the acoustic receiver and from the forward signal, the measuring signal representing a superposition of the acoustic signal, echoes thereof and noise and a delay time calculation unit coupled to the impulse response calculation unit and configured to calculate the acoustic propagation delay from the estimated impulse response, the acoustic propagation delay being calculated beginning at the time when the impulse response exceeds a threshold for the first time.