Automotive Engineering - April 2023 - 11

TECHNOLOGY REPORT
SENSORS
Transforming the vehicle into a microphone
When an emergency vehicle is approaching
but its blaring siren isn't
heard by nearby motorists, all are at
risk. Engineers at Harman International
have developed novel sensor technology
that detects both the sound and its
direction, in effect piping that screaming
siren into vehicles so-equipped, to
alert the driver.
" What we're in essence doing is turning
the vehicle into a giant microphone, "
Mitul Jhala, senior director of automotive
embedded audio for Harman, explained
in an SAE Media interview.
Harman's sound and vibration sensor
functions as a vehicle's external " listening
ear " to detect sound frequencies from 20
Hz up to 6 kHz. The sensor can " distinguish
siren tones via post-processing algorithms,
so it can tell whether the sound
is a police, fire, or ambulance siren, " Jhala
said. He noted specific tones vary for the
U.S., European and Asian markets. This
sensor can be used alone or alongside
Harman's new external microphones.
600-m range
Using multiple external microphones to
create a multi-element array, post-signal
processing algorithms, such as
beam forming, can be used to determine
the siren's direction.
Harman's external microphone was
designed to function in all environmental
conditions, here in rain.
" Localization is very useful when it's
not possible to see the emergency vehicle
because it's behind a building or
there's another visibility obstruction, "
Jhala said. The distance range for siren
detection is approximately 1968 ft (600
m), depending on factors such as
whether the emergency vehicle is stationary
or moving.
To prevent wind interference, a single
sound and vibration sensor would be
mounted on the B-side of the exterior
panel between the interior panel trim
and the exterior panel. The optimal
placement location for external
microphone(s) depends on the vehicle
type, as different vehicle profiles mean
different aerodynamics, which equates
to different noise profiles. " We've done
testing on small cars, hatchbacks, minivans
and SUVs with microphones integrated
on different locations, such as
the rooftop's shark-fin antenna or the
front bumper, with single- and multiarrays, "
Jhala said.
Exposure to harsh conditions, especially
wind turbulence and water, required
a microphone design unlike
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AUTOMOTIVE ENGINEERING
April 2023 11
HARMAN

http://info.hotims.com/84493-707

Automotive Engineering - April 2023

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