Impact of Source Identifiability on Perceived Loudness

In order to disentangle acoustical and non-acoustical factors in sound-quality evaluation, a signal-processing scheme [H. Fastl (2001). Proceedings 17th ICA, Rome] that renders most sounds unrecognizable while preserving their temporal loudness envelopes was employed. Two independent groups of subjects (N=20 each) evaluated a set of 40 environmental and product sounds, either in their original, or in a thus processed version. In contrast to previous investigations using this methodology, the stimuli covered a larger range of sound pressure levels, and additional data were collected on the proportion of correct identifications in the two versions presented. The results show that the identifiability is greatly reduced (from 90 to 13% on the average) by the “neutralization” procedure. Loudness judgments of the original and neutralized sounds are indistinguishable for the majority of sounds. Only very few sounds produce statistically significant discrepancies in the two versions, which may be attributed to effects of the “meaning” of the sounds on the assessment of loudness.