Easy listening to sleep recordings: tools and examples.

BACKGROUND AND PURPOSE To specify a simple conversion of neurophysiological signals contained in sleep recordings into standard audio files and to illustrate how our cerebral audio processor can then detect specific signal characteristics. METHODS A software package (freely accessible from the Internet) has been developed that converts signals from standard EDF (or EDF+) format to standard audio (WAV) format, a process usually called audification. The software has been applied to sleep EEG, EOG and ECG. The software is easy to apply. RESULTS A wide range of audified signals is described, stressing the analogy with familiar sounds. Audio properties of EEG in different sleep stages, EOG, ECG and respiration signals are discussed. Auditive presentation of the signals invokes brain processes that differ essentially from the commonly applied visual interpretation, including physiological frequency analysis. CONCLUSIONS Such auditive interpretation may complement the visual one. The widespread use of EDF+ and multimedia computers makes such audification simple and straightforward.