Acoustic Metamaterials: Are they the wave of the future?

By Rosemarie Szostak, Ph.D., Nerac Analyst

Originally Published January 15, 2021

Merritt & Stubbs, Inc., a firm that provides microperforated panel absorbers (MPP) to the architectural, construction and automotive markets asked Nerac to explore the emerging technology field of acoustic metamaterials, as it may represent a threat to their basic product portfolio or the potential for acquisition/licensing.

Acoustic Metamaterials

A metamaterial is an artificially structured material that is able to exhibit unique electromagnetic properties not seen, or available, in nature. The properties of metamaterials are tailored by manipulating their periodic physical geometry and structure. A metamaterial can be made from any material, metal, plastic, composites, and even paper. Acoustic metamaterials are specifically designed to control, direct, and manipulate sound waves.

Metamaterials carry significant disruption risk to the acoustics field. Acoustic metamaterials can block low-frequency sound, which cannot be accomplished by any other type of material. Once metamaterials can be inexpensively and quickly manufactured, conventional offerings in these areas are likely to become uncompetitive. The two primary technology drivers in the development and potential commercial uses for acoustic metamaterials are computer simulation and additive manufacturing (3D printing).

Both these technologies are at, or reaching, their commercial stage. The advantage of 3D printing of acoustic metamaterials is that they can be completely tailored for specific architectural applications for close to the same price as mass production methods. Unlike traditional mass manufacturing, 3D printing can produce complex geometries that cannot be manufactured by other means. 3D printing can print ten or a million products for essentially the same cost per unit.

Companies that understand metamaterial structures have been devising ways of incorporating acoustic metamaterials into existing material offerings, so that they can be used in new applications. For example, these metamaterials have been augmented with microperforated panels to produce hybrid structures that exhibits superior broadband low-frequency sound absorption as well as excellent mechanical stiffness/strength. A recent example (2019) of a hybrid structure using a MPP sandwiching a coil-channel acoustic metamaterial is shown in Figure 1.

The researchers found that the material works at a frequency greater than 30 times the total thickness. At the resonance frequency (<500 Hz), the sound absorption effect can reach 99%. There are other geometries of the acoustic metamaterial that show extraordinary sound absorption.

The Acoustic Metamaterials Group (AMG), headquartered in Hong Kong, a spin-off company by researchers at HKUST and Aberdeen University, hold two patents (priority dates 2014 and 2016) for hybrid MPP/acoustic metamaterials. Their overall patent portfolio consists of six (6) patent families focused exclusively on acoustic metamaterials. According to their website, they are not focusing on marketing these hybrid structures but on acoustic applications of their other structures.

This is a summary of the results that Nerac found for their client, Merritt & Stubbs, Inc.. Nerac provided a full report of the field of acoustic metamaterials, their market, leading technology, key players and potential competitors, and IP that covers both acoustic metamaterials as well as the hybrid structures, both of which are considered disruptive for their company product line. In the report, the analyst provided insight into this field for the client so that they can make a decision about a) monitoring the progress of this technology, b) building in-house expertise in acoustic metamaterials, or c) acquiring the expertise or licensing the IP and introducing a new product line to their existing portfolio to mitigate the potential of this disruptive technology.

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