My hypnogogia are usually auditory, not visual, although I do get the 'Tetris effect' visual ones when I've been doing a repetitive visual task like playing Tetris.

The auditory ones are usually in the voices of people I've heard in real life that day (whether friends or strangers on public transport) but not saying things they actually said, or often even anything comprehensible.

I get auditory hypnogogia markedly more often and longer if I've had a very people-heavy day. I talked with my psychiatrist about that, and he confirmed that that's because the auditory hallucinations while I go to sleep really are like the Tetris effect: my brain is practising a skill it was working on that day (talking with people) in the moments before sleep. It's part of the learning process.