I've been struggling to understand this issue for a while. It's come to my attention that it's forbidden (according to some opinions, at least) to start a laundry / dryer load on erev shabbos, and let it go by itself into shabbos. I would like some clarification as to why this is the case. If you're allowed to leave the lights on through shabbos, which are constantly being powered, why should we not be able to leave our laundry machine going into shabbos, which will run for far less time than will the lights? I am aware that certain groups allow a laundry machine to be going into shabbos, my question only related to those groups who hold that this is forbidden.
Probably the issue is hashmaat kol (leaving a noisy device running on shabbos that is considered a profanation of it's sanctity). - https://www.naaleh.com/hashmaat-kol-noise-on-shabbat-v5n9