Research paper Relationship between loudness growth function and auditory steady-state response in normal-hearing subjects Mikae ¨l Me ´nard a,b,c,e,f, * , Ste ´phane Galle ´go d , Christian Berger-Vachon a,b,c,d,e , Lionel Collet a,b,c,d,e , Hung Thai-Van a,b,c,d,e a Universite ´ de Lyon, Lyon F-69003, France b Universite ´ Lyon 1, Lyon F-69003, France c CNRS, UMR 5020, Neurosciences Sensorielles, Comportement, Cognition, Lyon F-69007, France d Hospices Civils de Lyon, Service d’Audiologie et d’Explorations Orofaciales, Ho ˆpital Edouard Herriot, Lyon F-69003, France e Institut Fe ´de ´ratif des Neurosciences de Lyon, Lyon-Bron F-69677, France f Laboratoire MXM, 2720 Chemin Saint-Bernard, 06224 Vallauris, France Received 20 July 2007; received in revised form 10 October 2007; accepted 20 October 2007 Available online 13 November 2007 Abstract The present study investigates the relationship between auditory steady-state responses (ASSRs) and loudness growth function. ASSR amplitudes were compared to the perceived loudness level at frequencies of 500 and 2000 Hz in 11 normal-hearing subjects. As a first step, loudness growth function was estimated for the two test frequencies. Then ASSR amplitude was recorded for each of the two frequencies at different stimulus intensities, each corresponding to a loudness level as given by the first part of the study. Normalized results show that the ASSR amplitude correlates well with the loudness function (R 2 = 0.81). A stepwise multiple linear regression confirmed these results with loudness explaining almost all the ASSR amplitude (loudness R 2 = 0.81, p < 0.001, f = 562 and for intensity f = 1.1, p = 0.29). The non-linearity of the ASSR amplitude for low loudness levels can be explained by both the active amplification in the cochlea and the noise in the recording. The results suggest that ASSRs can be used for ‘‘objective” loudness measurement. Ó 2007 Elsevier B.V. All rights reserved. Keywords: Objective responses; Psychoacoustic measures; Loudness level 1. Introduction The development and enhancement of physiological measurements of hearing is a principal research domain in audiology. Subjective methods are of little or no value for the assessment of very young children, older patients or those with attention-deficient. Therefore accurate, reliable and precise objective measures are needed. Electrophysiological response methods are already available, including auditory brainstem responses (ABRs) or otoacoustic emissions (OAEs). However, these methods are limited because they require fre- quency-by-frequency and/or ear-by-ear testing, as in conventional audiometry. Auditory steady-state responses (ASSRs) seem promis- ing for estimating the physiological threshold and for more complex auditory exploration. ASSRs are electrophysio- logical responses evoked by one or more carrier frequencies (Fc) presented simultaneously and amplitude-modulated at a specific frequency (Fm). The carrier is the specific test fre- quency, as in classical audiometry. The activity of the spe- cific area in the cochlea stimulated by the Fc ‘‘follows” the 0378-5955/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.heares.2007.10.007 Abbreviations: ASSR, auditory steady-state responses; ABR, auditory brainstem responses; OAE, otoacoustic emissions; DPOAE, distortion product otoacoustic emissions; OHC, outer hair cell; Fc, carrier frequency; Fm, modulation frequency. * Corresponding author. Address: CNRS UMR 5020, Pavillon U, Ho ˆ pital Edouard Herriot, Place d’Arsonval 69437 Lyon Cedex 03, France. Tel.: +33 472110526. E-mail address: mmenard@olfac.univ-lyon1.fr (M. Me ´nard). www.elsevier.com/locate/heares Available online at www.sciencedirect.com Hearing Research 235 (2008) 105–113 Hearing Research