Interior Noise of Automotive Vehicles: A Proposition for Objective Characterization 921457

The interior noise of automotive vehicles is basically composed by two portions. The structureborne sound through the elastic moutings, which is characterized by the low frequencies and the airbornesound through the divisory between the engine compartment and passenger compartment. This last path is mainly traveled by the high frequencies. We show the low frequencies, specially those related to the explosion order make the composition of the overall sound level, when the noise is evaluated by a weighting curve, trying to simulated the ear response, as for example the curve “A”, from which originates the well familiar dB(A). The highest frequencies, although almost ever, are neglected by the weighting curve “A”, are very important when we see the communication aspect in the passenger compartment. To solve this, we use another parameter, calculated from physical measurements and named Articulation Index (Al). We show its association with the highest frequencies. We observe that the overall noise dB(A) increases linearly with velocity (rpm) and that Al decreases in the same way. We show examples of a high linear correlation between these two parameters, > 0.90. A proposition is made concerning objective characterization of interior noise, trying to take advantages of the above properties. We consider a index H that is the area ration between dB(A) and Al, between two velocities (V₁,V₂). We apply this concept in several vehicles and so we are able to show a ranking. Finally, we discuss the utilization of a more complete parameter for overall noise, the Loudness, and we present the differences in the composition of such parameter, relative to dB(A).