Interesting. If you're so inclined and have the resources then you are using the very tool that can be what you're after.
Get an oldish PC (laptop even) and using the calender reminder alarm functions with sound choices you can program a computer to execute events by clock / date.. You can even have simple powerpoint type presentations triggered. Record your own sound tracks to play at programmed times. Different alert sounds etc.
Having said that, my mum is now at a stage where when I went to visit her today she immediately approached me very concerned that these voices are telling lies and why are they allowed to do that. The TV was on in her room and she'd just listened to the news and she didn't know the sound came from the TV. She never wants to see or hear the TV again since the news is so full of horrible lies. She adopted some ideations as her own and reacted to them so the simple solution was to agree the TV news is full of lies, which is easy, and instructions are in her file now to not turn the TV on. The point is that she could not come to a knowledge about the source of these sounds and constructed a scenario that made sense to her: people are talking lies and she wants them to stop. When I showed her it was the TV and I turned it off she said the TV shouldn't be allowed to tell such lies and she won't have anything to do with them any more.
So, ... I think it is an interesting idea and it certainly may work, I think it would not work for my mum, at this stage. It would be just another strange thing for her to make sense of.
I hope you find the solution you are looking for, cheers.
