The test was anonymous and was conducted online via the Internet using Questionpro Professional. This program was chosen because enables uncompressed and high quality audio to be presented. Moreover, before the experiment was made available to the participants, the quality of the signals in this software was subjectively verified by two experienced acousticians (sound engineers) independently (without hearing loss) in terms of distortions and possible artifacts. No difference was found between direct and on-line listening. In addition, to minimize the possibility of a layperson completing the survey, the survey was distributed among the academic medical community and in hospitals. It was also passed on to interested people through lecturers at medical universities and through direct contact with doctors asking them to complete the test.
The experiment consisted of two parts.