Acoustic Cloaking Metamaterials Using Pentamode Hexagonal Cells
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current acoustic metamaterials struggle to effectively mimic the acoustic properties of water, particularly in controlling and manipulating sound waves, due to limitations in replicating its density and bulk modulus, which are essential for emulating sound propagation in gases, liquids, and solids.
Innovation Solution
The development of acoustically transparent materials with two-dimensional metamaterial structures, specifically designed to emulate the elastic properties of water, using machined metal structures with regular hexagonal cells and protruding lobes, and the application of pentamode elastic theory to create materials that can steer and cloak acoustic waves, mimicking the behavior of water.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional acoustic metamaterials are used to control sound waves, then some level of acoustic manipulation is achieved, but the ability to effectively mimic water's acoustic properties (density and bulk modulus) is insufficient
Solution Approach 1:
The material is segmented into repeating unit cells with specific geometric configurations. Each unit cell contains strategically placed holes that, when arranged in a periodic pattern, collectively produce the desired effective acoustic properties of water without requiring the material to be homogeneous at the macro scale.
Solution Approach 2:
The patent systematically varies key geometric parameters of the unit cells (hole size, hole shape, wall thickness, cell dimensions) to tune the effective density and bulk modulus. By changing these parameters, the material can be optimized to match water's acoustic properties across different frequency ranges and application requirements.
2Reliability
If the material structure is made more complex to better mimic water's acoustic properties, then acoustic transparency improves, but manufacturing difficulty increases
Solution Approach 1:
The complex acoustic functionality is achieved through segmentation into simple, repeating unit cells rather than a continuously complex structure. This modular approach allows standard manufacturing techniques to produce each identical cell, reducing overall fabrication complexity while achieving sophisticated acoustic behavior at the effective level.
Solution Approach 2:
The patent employs porous unit cell structures with strategically placed holes and voids. These porous configurations can be manufactured using established techniques for creating porous materials (such as foam extrusion, selective laser sintering, or precision drilling patterns), balancing acoustic performance with manufacturing feasibility.
3Manufacturing precision
If the material is designed to precisely control acoustic wave propagation, then wave steering capability improves, but the material becomes more sensitive to manufacturing tolerances
Solution Approach 1:
The acoustic control function is distributed across many identical segmented unit cells rather than relying on a single complex structure. This segmentation means that minor manufacturing variations in individual cells average out, and the collective behavior of the periodic structure maintains consistent wave propagation control even with small tolerances.
Solution Approach 2:
The patent identifies and optimizes which geometric parameters have the most significant impact on acoustic performance versus those with minimal effect. By focusing manufacturing precision on the critical parameters and allowing tolerances on less sensitive dimensions, the material achieves reliable wave steering capability without requiring extreme precision across all features.
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
These materials allow for the control and redirection of acoustic energy, enabling sound to travel around objects undisturbed, with minimal reflection or backscatter, effectively creating acoustic cloaking devices for underwater applications.
Implementation Method 1
machining out of a solid piece of metal a plurality of adjacent regular hexagonal cells having effective elastic properties of water, wherein each regular hexagonal cell includes a plurality of protruding lobes extending inwardly from the vertices of the hexagonal cell
Implementation Method 2
The metamaterial structures are two-dimensional, intended to propagate acoustic waves in the plane in a manner which closely emulates the propagation of waves in water
Data Source
AI summary
Disclosed an acoustically transparent material including an acoustic wave steering material, and methods for fabrication and use thereof. The materials are specially designed structures of homogenous isotropic metals. These structures are constructed to propagate waves according to Pentamode elastic theory. The metamaterial structures are two-dimensional, intended to propagate acoustic waves in the plane in a manner which closely emulates the propagation of waves in water. The acoustically transparent materials described herein have particular utility as acoustic wave steering materials and acoustic cloaks.