Floating Base Vector Sensor for Low-Frequency Directionality
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Solution Overview
Problem
Conventional methods for detecting the direction of arrival (DOA) of acoustic signals, especially low-frequency signals in viscous mediums, face limitations due to large sensor arrays and sensitivity issues with existing micromechanical vector sensors, which require rigid mounting and struggle with achieving an acceptable signal-noise ratio.
Innovation Solution
A vector sensor utilizing a fine mesh structure that measures acoustically induced normal displacement of fibers, exploiting the two-dimensional nature and nano-scale dimensions to enhance sensitivity, allowing for the detection of low-frequency sound waves without rigid anchoring, and employing a floating base vector sensor design that combines acoustic scattering and viscous forces for improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional pressure sensor arrays are used to detect low frequency acoustic signals, then directionality can be achieved, but the array size becomes prohibitively large
Solution Approach 1:
The patent changes the measurement parameter from pressure gradient (conventional method) to particle velocity using a neutrally buoyant accelerometer. This parameter change allows achieving directionality with a single sensor instead of large arrays, as the accelerometer directly measures the velocity vector of water particles in the acoustic wave.
Solution Approach 2:
The patent replaces the mechanical pressure sensor array system with a single accelerometer-based velocity sensor. The accelerometer measures the inertial response of water particles to acoustic waves, substituting the need for spatially distributed pressure sensors with a single point measurement of particle velocity.
2Measurement precision
If accelerometer sensitivity is increased by增大test mass to operate in 10 Hz frequency range, then low frequency detection improves, but the device size becomes prohibitively large
Solution Approach 1:
The patent employs a neutrally buoyant accelerometer where the test mass is suspended in water with buoyant force balancing gravity. This dynamic configuration allows the sensor to operate in the acoustic frequency range without being constrained by the static weight requirements, enabling sensitive low-frequency detection with a compact test mass.
Solution Approach 2:
The patent uses buoyant force as a counterweight to gravity acting on the test mass. The neutral buoyancy condition (where buoyant force equals gravitational force) creates a weightless environment for the test mass, allowing it to respond purely to acoustic acceleration forces without the influence of its own weight, thus enabling sensitive low-frequency operation with small mass.
3Stability of the object's composition
If micromechanical vector sensors are rigidly mounted underwater, then structural stability is maintained, but the sensor cannot achieve acceptable signal-noise ratio due to small deformation measurements
Solution Approach 1:
The patent transitions from rigid mounting to a dynamically floating configuration where the sensor body is neutrally buoyant and free to move with the water particles. This dynamic approach allows the sensor to follow the acoustic particle motion, converting small deformations into measurable displacements of the entire sensor body, thereby achieving acceptable signal-noise ratio while maintaining stability through neutral buoyancy.
Data Source
AI summary
Systems and methods are provided for sensing acoustic signals using a floating base vector sensor. A vector sensor according to an embodiment of the present disclosure can be used to detect and characterize low frequency sound wave(s) in a viscous medium (e.g., air, water, etc.) by detecting a periodic motion of the media particles associated with the sound wave(s). The orientation of the particle velocity deduced from such measurements can provide information regarding the wave vector of the sound wave(s), can define the direction of arrival (DOA) for the acoustic signal, and can assist locating the source of the sound of interest.