If you talk to yourself, even while earmuffed, you can still hear yourself - so there is no sensory deprivation as far as sound.
If you make yourself day-dream or think about memories in your head, then you won't notice the darkness - so there is no sensory deprivation as far as sight because you see through your imagination.
Can can there be complete sensory deprivation, then, by blindfolding you and earmuffing you? Maybe because we live in a society where people aren't used to silence or some sort of visual stimulation.