Common methods to determine the quality of media rely on conscious ratings of a subject's opinion about the quality of presented stimuli. While such methods provide a reliable and valid means of determining quality, they provide little insight into the physiological processes preceding the quality judgment, which, however, may affect the subjective behavior, e.g., in terms of alertness or media usage duration. In this paper we used a non-intrusive physiological method, elec-troencephalography, to assess the cognitive state of subjects related to the quality of auditory speech stimuli. We show that users listening to degraded audio rated the quality lower in comparison to an undisturbed stimulus as expected and, in addition, got more fatigued during the 20 minute presentation. Indicators of the increased fatigue were Theta and Alpha frequencies of the electroencephalogram data. The results show that the perception of degraded media has long-term influences on physiological processes at the time scale of minutes which may immediately influence customer behavior.