Acoustic System for Noncontact Sediment Shear Strength Mapping
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Solution Overview
Problem
Existing methods for determining seafloor sediment properties are limited by the need for direct sampling and are time-consuming, especially in vast areas, and do not efficiently infer geotechnical properties from acoustic returns.
Innovation Solution
A non-contact method using high-frequency acoustic beams to interact with sediments, generating a low-frequency difference tone that allows for the determination of the quadratic nonlinearity coefficient (β), correlating it with sediment shear strength to create lookup tables for rapid and extensive sediment property mapping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct sampling and analysis methods are used to determine sediment properties, then measurement precision is improved, but productivity deteriorates due to time-consuming sampling and interpolation requirements
Solution Approach 1:
The patent replaces mechanical sampling systems with an acoustic field-based measurement system. Two acoustic beams interact nonlinearly within the sediment to generate a difference frequency signal that directly probes sediment properties, eliminating the need for physical sampling, transportation, and laboratory analysis while maintaining measurement precision and enabling rapid area-wide mapping.
2Productivity
If acoustic beams interact nonlinearly in sediment to generate difference frequency, then productivity is improved through rapid mapping, but device complexity increases due to multi-frequency beam generation and interaction requirements
Solution Approach 1:
The patent introduces the sediment itself as an intermediary medium that facilitates the interaction between two acoustic beams. The sediment's nonlinear properties enable the generation of difference frequency signals, converting a complex multi-frequency generation problem into a simpler two-beam interaction problem where the medium performs the frequency mixing function.
Solution Approach 2:
The system employs periodic modulation of acoustic beam parameters (frequency, intensity, or direction) to encode sediment property information into the difference frequency signal characteristics. This periodic action enables systematic extraction of multiple sediment parameters through controlled variation of input conditions.
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
Enables rapid and extensive mapping of sediment properties, including shear strength and transport potential, facilitating decisions on mine burial, unexploded ordnance detection, and trafficability without the need for extensive sampling.
Implementation Method 1
the first and second primary signals combine in a nonlinear fashion in the target granular media to produce low frequency acoustic tone that is a difference between the first and primary signals
Implementation Method 2
a quadratic nonlinearity coefficient and an acoustic pressure field are determined based on the acoustic pulse
Data Source
AI summary
Embodiments relate to noncontact determination of nonlinearities. Initially, a first and second primary signal are preconditioned to produce a first and second tone capable of reaching a target granular media. Using a sound source, the first and second primary signals are emitted such that the first and second primary signals combine in a nonlinear fashion in the target granular media to produce low frequency acoustic tone that is a difference between the first and primary signals. An acoustic pulse is received by an acoustic receiver, and a quadratic nonlinearity coefficient and an acoustic pressure field are determined based on the acoustic pulse. At this stage, a sediment shear strength of the granular media is correlated to the quadratic nonlinearity coefficient to generate a shear strength lookup table.