Preliminary studies of the effect of travelling speed and propulsion type on the sound level in the passenger compartment of a vehicle with a hybrid propulsion system

Hybrid propulsion systems are more and more commonly used in means of transport such as passenger cars. The use of this type of propulsion, in addition to important environmental issues, also affects the acoustic climate in the passenger compartment and may therefore also affect the safe operation of vehicles. The paper presents the results of preliminary studies aimed at assessing the change in the sound level in the passenger compartment of a SUV passenger car with a hybrid propulsion system, depending on whether internal combustion or electric propulsion is being used. The sound level was measured in the entire frequency range and 1/3 octave bands, in the passenger compartment of the vehicle at speeds enabling the use of either the electric or combustion engine for propulsion. The comparison of the recorded sound level values leads to the conclusion that the electric propulsion system, which is used for starting and driving at a low travelling speed corresponding to speed in urban areas with reduced maximum speed, significantly improves the acoustic climate in the passenger compartment. The recorded reduction in the sound level in the passenger compartment, when compared to propulsion provided by an internal combustion engine, ranges from 1.4 to 4.8 dB(A), depending on the travelling speed. Analyses carried out in 1/3 octave bands indicate that changes in the sound level depending on the engine used for propulsion at the given time are strongly dependent on frequency and travelling speed of the vehicle.