The acoustic reflex threshold: not predictive for loudness perception in normally-hearing listeners

The working hypothesis of an ongoing study is that the quick and reliable procedure of acoustic reflex threshold (ART) determination in conjunction with measurements of HTL may yield accurate estimates of loudness. The aim of this study was to investigate whether differences in loudness in normally-hearing subjects are reflected in the ARTs and to collect normal material with respect to pure-tone elicited ART and loudness categories. Categorical loudness scaling (CLS) and ART measurements were performed at frequencies of 0.5, 1, 2 and 4 kHz in 60 normally-hearing subjects (HTL<20 dB HL, 26 males, 34 females, aged 21-63 years) with no history or sequelae of middle ear disease. Subjects reporting disturbing tinnitus were excluded. The results show that the ART is not a predictor of individual loudness perception for normally-hearing subjects. Using a numerical scale (HTL=0, 'very soft'=5, 'soft'=15, 'OK'=25, 'loud'=35, 'very loud'=45 and 'too loud'=50) loudness for pure tones grows almost linearly at approximately 0.4 arbitrary loudness units per dB below the 'loud' category. Above the 'loud' category the slope is around 1 unit per dB. The median ART was 85 dB HL at frequencies of 0.5, 1, 2 and 4 kHz. No differences in loudness perception across frequencies were found.