Automotive Engineering - August 2022 - 4

TECHNOLOGY
REPORT
NVH
Electrification forces fresh perspectives on vehicle NVH
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BOARD OF DIRECTORS
Srinivasa (Sri) Srinath, Ph.D
President
Jeff Hemphill
2021 President
Todd Zarfos
2023 President Elect
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The increasingly common " skateboard " architectures of EVs create unique NVH challenges; here, the chassis of a
Rivian R1T pickup is married to the bodyshell at Rivian's assembly plant in Normal, Illinois.
The quietness of EVs is, for many, a compelling
selling point. But vehicles becoming inherently
quieter overall hasn't translated into making the
job of noise abatement any easier - the job's
just different, asserted several NVH engineering
experts at the Autotech conference in Detroit in
early June. These NVH experts underlined a primary
point of what's now understood about the
" new " quietness of EVs: the drastic reduction of
powertrain-related noise, vibration and harshness
(NVH) largely means vehicle occupants
now can hear and feel other NVH sources.
" A little squeak becomes more prominent " in
EVs, said Jian Pan, senior director of engineering
at Auria Solutions. And although this seems
self-evident, Pan added that EVs can open up
new or unfamiliar frequencies to occupants -
and some of those frequencies can be particularly
displeasing. Certain frequencies emanating
from EV drive motors, for one, can be distinctly
annoying, Pan said, and are quite different from
the " noise signatures " of combustion engines.
Meanwhile, those relatively minor squeaks and
squeals coming from seat-adjustment motors
and power windows, in the absence of " masking "
noise from an IC powertrain, now are prominent
noise sources, he added.
Building on those points, Brent Dreher, CAE
engineer - NVH & Durability at Faraday Future,
pointed out that many current and coming EVs
are built on " skateboard " chassis architectures
4 August 2022
that tend to use hollow extrusions as their primary
structural elements, rather than conventional
steel unibodies or body-on-frame architectures
of most all internal-combustion vehicles.
Hollow structural elements tend to
transmit and augment noise more readily than
cast steel structures, Dreher stressed.
Mirrors to gears
Structural challenges are just the beginning.
Because of EVs' comparative general quietness,
conventional vehicle components are under
fresh NVH scrutiny. Jeff Hodgkins, senior
application NVH tech expert at VI-Grade, a
Germany-based developer of software simulation
tools, told conference attendees that sideview
mirrors may become a flashpoint for NVH
in EVs. Side-view mirrors have recently been
the focus of aerodynamicists seeking to reduce
vehicle wind resistance by replacing bulky conventional
mirror assemblies with sleeker units
housing cameras. But Hodgkins said the silence
of EVs has made the wind rushing around side
mirrors markedly more noticeable in the cabin.
" It's right around the driver's ear, " he added,
advocating for camera mirrors that would help
reduce wind noise in this vital area.
A related solution could be increased use of
specially laminated " acoustic " glass, many on
the panel agreed. Already seeing increased use
in IC-powered upscale vehicles or as part of
David L. Schutt, Ph.D
Chief Executive Officer
Gregory L. Bradley, Esq.
Secretary
Judy Curran
Rhonda Walthall
Joan Wills
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AUTOMOTIVE ENGINEERING
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Automotive Engineering - August 2022

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