Development of sound quality indices for vehicle acoustic comfort based on the correlation between customer perception and objective NVH measurements

The acoustic comfort in vehicle cabins significantly affects customer satisfaction and purchasing decisions. Tests and jury evaluations conducted during the vehicle development process show that traditional Noise Vibration Harshness (NVH) measurement metrics such as A-weighted sound pressure level or Articulation Index level often fail to reflect subjective customer perceptions. This creates the risk of a mismatch between NVH design and user expectations. This can lead to costly solutions being implemented to meet customer expectations at later stages of the vehicle development process. In this study, the Sound Quality (SQ) parameters that better reflect the customer’s perception and preference regarding vehicle acoustic comfort were determined under representative driving maneuvers reflecting the driving characteristics of customers. A third gear full throttle acceleration maneuver was conducted to replicate engine noise, as this maneuver is representative of typical city driving conditions. The interior noise of six vehicles was objectively measured and then, the sound samples were subjectively evaluated by 50 jurors in a listening room using high precision audio system and headphones with a specially designed user interface. Psychoacoustic parameters with high correlation to subjective ratings were used to develop a new sound quality metric via multivariable regression analysis. The validity of this new metric was also proven by studies conducted on nine different vehicles not included in the study pool.