This paper presents the off-line evaluation of scalp EEG signals registered while a potential brain-computer-interface user was hearing unpleasant sounds. The EEG patterns of event-related desynchronization/synchronization are studied during the human perception of sound stimuli, which was given by scraping a sharp knife along the surface of a ridged metal bottle sound. This evaluation was conducted with the purpose of search the correlating EEG signals with emotional state caused by unpleasant stimuli and their influence of brain-computer-interface commands, as motor imagery commands, in order to increase the efficiency of this kind of human-machine-interface performance. It was observed that waveforms in μ and ß frequency bands of Fpl and Fp2 channels present variations that could been caused by neural activity due to the unpleasant sound stimuli. © 2013 IEEE.