Consideration of the Age Related Hearing Ability (Presbycusis) in the Definition of Vehicle Interior Noise Targets

Over recent years MIRA has conducted a large number of vehicle noise appraisals and listening experiments. Their results have highlighted significant differences in people's perception of vehicle noise which can partially be attributed to the age of the participating individuals. Initial investigations suggest that this is primarily due to natural loss in hearing sensitivity especially at high frequencies, resulting from the physiological changes that occur with age (presbycusis). Its effect on subjects' vehicle noise assessments can be highly significant, potentially causing total disagreement between individuals of different ages. This is particularly pertinent in the case of vehicle NVH development, where young NVH engineers may be developing vehicles targeted at the luxury vehicle sector with a relatively older customer base. The Composite Rating of Preference Index (CRP) and related neural network developments are ideal for articulating this phenomenon, with a focus on broad band spectral balance and low frequency noise components. The indices have highlighted objectively the observed subject disagreements and provide a statistical approach defining the relationship between the broad band frequency issues and age related subjective response. Given the variation in age distribution for the different market sectors and vehicle classes, this phenomenon now provides an opportunity to differentiate between these sectors in respect of unique vehicle model noise characteristics.