Can one use a noise machine on shabbat if it was set before shabbat (e.g on a shabbat clock)?

A noise machine is a device that produces sounds such as a rushing waterfall, wind blowing through trees, rain, music, or ocean waves, it is usually used in order to relax and fall asleep. The noise machine should not be used on Shabbat, like many other electronic appliances, because of “Uvda Dechol” which means doing things that don’t fit the Shabbat spirit [Tzitz Eliezer vol. 3 16,11]. In a situation where it is extremely necessary for someone who is not well or an elderly person who cannot relax otherwise, it may be used on Shabbat with a Shabbat clock, because our Sages did not apply the rule in a case of suffering.