Given the brain's plasticity, it is unknown whether the brain may adapt to such repeated auditory stimuli. Constant auditory stimuli may lead to adaptation, resulting in the stimuli being "ignored." NMTD's stimuli, however, are less likely to lead to significant adaptation since they are intermittent and somewhat random, dependent on apneic or hypopneic events. Subjects will undergo two sequential nights of PSG with NMTD to evaluate if there is any stimulus-response extinction over time. In the future, when more devices are available, we will plan on long-term evaluations.