Automotive Engineering - May 2021 - 26

Metamaterials R&D

MATERIALS FEATURE

TARGETS NVH ABATEMENT
Nissan readies its lightweight
acoustic solution for 2022
production - will Hyundai follow?
by Lindsay Brooke

26 May 2021

Nissan advanced-materials researcher Susumu Miura with metamaterial sheet and
inset close-up.

The metamaterial offers the sound
isolation of traditional solutions
weighing four times as much.
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 metamaterial.
Hyundai materials researchers, along with colleagues at South
Korea's Gwangju Institute of Science and Technology, also are 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: https://www.sae.
org/publications/technical-papers/content/2018-01-1566/. The study
showed that the suggested metamaterial structure was effective in
reducing noise transfer through the bodyshell.
AUTOMOTIVE ENGINEERING

NISSAN

coustics 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 bakedon mastics, blankets, injected foams and acoustic glazing - are brought to bear.
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-versus-mass battle. Socalled 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's extensive interest in metamaterial began in
2008, when its scientists began using it on highly sensitive antennae used to study electromagnetic waves.
The OEM now is vectoring its development toward
production. Nissan first revealed the metamaterial at
CES 2020 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 5001,200-Hz wide-frequency-band noise typically originating from the road or powertrain. A Nissan video
shows the metamaterial can reduce cabin background
noise from more than 70 dB to less than 60 dB.

https://www.sae.org/publications/technical-papers/content/2018-01-1566/

Automotive Engineering - May 2021

Table of Contents for the Digital Edition of Automotive Engineering - May 2021