Does a true hallucination need to go away while plugging one's ears? Can an auditory hallucination be true hallucination even if the person clàims that it doesnot reduces in volume when he plugs his ears. Similarly can a visual hallucination still be a true hallucination even when it doesn't disappear when person closes his eyes??
A hallucination is a perception in the absence of external stimulus that has qualities of real perception and hallucinations can occur in different ways.

Visual hallucinations can occur with the eyes open or closed (see also).  Visual hallucinations can also occur with people who have lost their sight

Just like visual hallucinations, auditory hallucinations can also occur with the ears open or plugged.  To highlight the point, I suffer with tinnitus and I hear the noise with my ears plugged or open. Auditory hallucinations can also occur in people with hearing loss