When max's father installed a new ceiling fan in his room, the "whirring" sound initially disturbed max's sleep. after a few nights, however, max was back to sleeping normally, as if the fan did not bother him at all. max's filtering out of the fan's noise is best described as

I believe the answer is habituation.
habituation refers to a standardized psychological response that given to a stimulus that we get over and over again.
Initially, every organism would eventually ignore any repeated stimulus that no longer relevant to our biological and psychological activities (such as the sound of the fan)