If I play a consistent sound for 8 hours on my iPhone 5s will it damage the speaker?

I want to use my iPhone 5s as a noise maker. If I play it all night every night, what will it do to the phone's speaker?

You will run down the battery. A speaker running at volume consumes a LOT of electrical power. I have never heard of "wearing a speaker out" although since they are mechanical, it must be possible.