One of the practical consequences of the development of low CO₂
emission cars is that many of the traditional NVH sound engineering
processes no longer apply and must be revisited.
Different and new sound sources, new constraints on vehicle body
design (e.g., due to weight) and new sound perception
characteristics make that the NVH knowledge built on generations of
internal combustion-powered vehicles cannot be simply transferred
to Hybrid and Electric Vehicles (HEV). Hence, the applicability of
tools must be reviewed and extensions need to be developed where
necessary.
This paper focuses on sound synthesis tools as developed for
ICE-powered vehicles. Because of the missing masking effect and the
missing intake and exhaust noise of the Internal Combustion Engine
(ICE) in electric vehicles, on one hand electric vehicles are
quieter than traditional vehicles. On the other hand, other
components such as HVAC system, alternator, vacuum pump,
power-steering pump, cooling systems, transmission systems,
inverter noise, etc., become more important and generate new
complex sound signatures. Typically, their interior noise is
well-defined by high-frequency noise components which can be
subjectively experienced as annoying, hence the increased
importance put to sound quality aspects and perceptual-relevant NVH
studies.
In the paper, a Virtual Car Sound (VCS) synthesis technique for
HEV is designed. This approach turns out to be a very helpful
engineering tool to design a brand specific sound and allows
reproducing typical sound features of HEV during real-time driving
simulation based on a Sound Quality Equivalent Model (SQE). Several
SQE models were constructed for different powertrains of HEV in
various engine conditions. Finally, the results of the sound
metrics and listening tests indicate a comparison between the
synthesized sounds and the original sound recordings.