Like the sound of (one's) own voice disapproving expression
To get lots of enjoyment from hearing oneself talk because one is pretentious and/or self-centered. (Implying that one is talkative)
I didn't bother to talk to him because I knew he liked the sound of his own voice.
Mary is usually shy and humble, but today she seems to like the sound of his own voice.
This phrase is usually used in simple present or past tense.
The origin of this expression is not clear.