Perceptual Test on Annoyance Threshold Linked to Vibrations and Sounds of a Modified Car Engine

New drivetrains are currently worked on with a goal of constant improvement of engine performance and reducing vehicle gas consumption. Vibro-acoustic environment in the car cabin is in certain case considerately modified and could be annoying for drivers or passengers. We focus here on a specific modified 3-cylinders engine whose properties are changed from those of a usual engine. With such a configuration, new engine harmonics are present in addition of already existing 3-cylinders engine harmonics. Those harmonics are perceived as well as sound than as vibrations through the seat leading to particularly annoying low frequencies.A previous perceptual experiment conduced on a naïve panel showed that softer horizontal suspensions should lead to a lowering of the annoyance due to longitudinal high magnitude vibrations at low engine speed around 1500 rpm. In the experiment presented here, we investigated the notion of acceptability threshold between usual vibrations and those due to this particular engine. Moreover, several sonifications are added to the original engine sound in each vibrating configuration. The aim of this test is to evaluate the impact of sound quality on vibration perception and overall annoyance in the car.