In the United States, is one's workplace generally considered to be a place where an employee can assume a relative level of privacy from hidden surveillance?
For example, suppose that I had a private office at work. Can I legally assume a reasonable level of privacy in my "private" office. Or can my employer record, without my knowledge, conversations I have with my wife on my personal cell phone during my lunch break? Can my employer just have a live mic hooked up in my office 24-7 to see if I say anything they do not like?
Legal disclaimer: This is a hypothetical question and I am not under the suspicion of my employer recording my conversations with my wife. I am not seeking personal legal advice for me or my agents.