- healthy volunteers aged 18 to 60, currently French-speaking and able to answer questionnaires, BMI 19 to 30 kg/m2, free from any medication since 7 days before each study session, covered by the French welfare health system. Exclusion criteria are : risk of pregnancy, any medical history or condition likely to impair participation or quality of outcome measurement, any ongoing relevant disease, any cutaneous lesion at nondominant forearm, any ocular, neurological or acoustic contra-indication to the tests, spontaneous tinnitus or disease with hyperacusia, anxiety or depression with score >11 on HAD, addiction to drugs or alcohol abuse, inclusion in a concomitant trial, French legal protection