1. Institute of Physiology and Pathology of Hearing, ul. Zgrupowania AK 'Kampinos' 1, 01-943 Warszawa, Poland
2. Department of Communicative Disorders, East Tennessee State University, Box 70643, Johnson City, TN 37614, USA
3. Department of Biomedical Physics, Institute of Experimental Physics, Warsaw University, ul. Hoza 69, 00-681 Warszawa, Poland