Why is the "s" in "vois" silent in,"Dans un jardin public, je vois une ovation publique.".

Bonjour Duo,
Generally, when speaking French, the final consonant is always silent, one exception are words ending in the letter «x» which is generally pronounced, i.e. six, dix, etc. If you are not involved in a conversation French class, I suggest that you try to locate one to enroll in so you can have the practice speaking and listening to French as it is meant to be spoken. That being said, the Alliance Française has chapters in many large cities throughout the US, Canada and Europe; also a lot of colleges and universities offer non-credit courses for adults and some of those have French conversation classes. There is also the option of private French lessons with a native French speaker; however, this is by far the most costly on a per hour basis.
Bonne chance