Metamaterials R&D Targets NVH Abatement

May 1, 2021

Lindsay Brooke

Nissan’s 2022 Ariya luxury electric SUV is expected to be the automaker’s first production use of the new metamaterial for NVH attenutation. (Nissan)

Acoustics engineers have a broad variety of materials from which to choose for reducing noise, vibration and harshness (NVH) in vehicles. But their selection often comes with a measurable downside: added mass. It’s not uncommon for a new vehicle to gain 100 lb (45 kg) or more during development as various absorbers, reflective barriers and absorber-barrier combinations – typically baked-on mastics, blankets, injected foams and acoustic glazing – are brought to bear.

Nissan advanced-materials researcher Susumu Miura with a metamaterial sheet. (Nissan)

In an era where “lightweighting rules” and engineers are rewarded on a per-gram basis for cutting vehicle weight, materials researchers are betting on new developments to win the NVH-vs.-mass battle. So-called metamaterials offer significant promise here, with a potential added benefit of being less costly than the traditional NVH solutions used by OEMs.

“Meta” comes from the Greek word μετα – “to go beyond.” Metamaterial mediums are man-made, macroscopic composites. Their three-dimensional cellular honeycomb-like architecture is such that local interaction between the cell assemblies gives them excellent properties for curbing or redirecting unwanted sound waves.

Nissan has been extensively studying metamaterials since 2008, when its scientists began using it on highly sensitive antennae used to study electromagnetic waves. The OEM is now vectoring its development toward production. Nissan first revealed the metamaterial at the 2020 CES and indicated that it will be used for NVH attenuation in the new 2022 Ariya luxury EV.

Susumu Miura, an advanced-materials engineer at Nissan, said the metamaterial offers the sound isolation of traditional solutions weighing four times as much. He described it as a simple lattice structure wrapped in a plastic film and capable of reducing 500-1,200-Hz wide-frequency-band noise typically originating from road or powertrain. A Nissan video indicates the metamaterial can reduce cabin background noise from more than 70 dB to less than 60 dB. The company claims material cost parity, if not a cost reduction, compared with incumbent NVH mitigation. Nissan has not revealed suppliers for the production of its metamaterials.

Hyundai materials researchers, along with colleagues at South Korea’s Gwangju Institute of Science and Technology, are also keenly focused on metamaterials opportunities. Hyundai, among other vehicle applications, has focused its research on using metamaterials to reduce the vibration and noise transfer of a firewall panel. See SAE Technical Paper, An Application of Acoustic Metamaterial for Reducing Noise Transfer through Car Body Panels . The study showed that the suggested metamaterial structure was effective in reducing noise transfer through the bodyshell.