Abstract
Transmission of vibroacoustic energy from an internal combustion engine
(ICE) to its surroundings largely depends on how it is mounted, on
available transmission paths and on the construction of the vehicle body
and/or its surrounding structures. This is especially true in low speed
engines in enclosed areas which generate perceptually weak noise, but
strong low-frequency waves which energy has a negative impact on human
health, comfort and driving safety especially in prolonged exposure to the
source. The primary aim of the article was to analyse components of the
ICE unit which had a determining impact on the reduction of low-frequency
waves. Thus, the structurally transmitted noise from the ICE to its
surrounding structure (body of the passenger vehicle) was analysed. The
results of the vibroacoustic measurements were compared to modal analysis
in order to determine possible resonance sources in the vehicle body
and/or for assessing the influence of the vehicles safety gear on the
generated vibroacoustic energy transfer into the cabin area of the
passenger vehicle. Measurements were made for a passenger vehicle at rest
and operating in its most common operational speed as well as for the
stationary ICE of a cogenerate unit (CGU). Measurements and FFT analysis
were used for the detection of the vibroacoustic energy sound pressure
level (noise) and mechanical vibration. Firstly, the low-frequency noise
sources were determined and their direct effects on the human body were
investigated. Finally, this paper suggests some measures which may
contribute to the reduction of undesirable vibroacoustic energy in
enclosed areas.
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