Normative data from seven different studies were collected and the normative references compared. It was demonstrated that the different scaling procedures relate the perceptual categories differently to sound level - e.g. at “comfortable” level a range of about 25 dB HL is found (see Figure 1). Normative data from three studies was used to evaluate the between-subject variance - e.g. at “comfortable” level a 95%-interval of about 35 dB HL is found.
Hearing-impaired data from four different studies were collected and analysed using a novel representation of the data, displaying the normalised, inverse slope of the loudness growth functions versus the hearing threshold level. In this representation the inverse slope varies linearly with the hearing threshold, and the observed variance becomes constant.