It's important to remember that you're making this up. You're just sort of spontaneously interpreting "reasonable expectation of privacy" off the top of your head.
It's usually simpler than that: if you see them recording you, and if they aren't trespassing (i.e. breaking the law otherwise); or you are on their property or on public property that they are legally permitted to use, which carries a posted sign telling you that you may be recorded, you don't have a reasonable expectation of privacy. Otherwise you do.*
Somebody could possibly hear something has nothing to do with it. Consenting to being heard is not consenting to being recorded. But maintaining your presence in a place where people are allowed to record is. If it's your party, tell them to put it away or leave. If it's their party, you leave. If you are recording surreptitiously and you are not working with law enforcement, it's probably not going to be admissible in court and if you publish it, you're going to get sued. Depending on your state and local laws, you are likely to lose badly.
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[*] All of this depending specifically on how the term is defined in your state and local laws. For example, video has often been separated from audio for pragmatic reasons; security cameras are meant to record physical acts, not conversations. For a second example, many states have decided that sending your voice over a wire to a designated recipient as an electronic signal is already consenting for the person receiving that signal to be able to record it and use it as they please; others have not. For a rationale in the second case, imagine that you didn't have the right to reveal a letter that was sent to you.
It's usually simpler than that: if you see them recording you, and if they aren't trespassing (i.e. breaking the law otherwise); or you are on their property or on public property that they are legally permitted to use, which carries a posted sign telling you that you may be recorded, you don't have a reasonable expectation of privacy. Otherwise you do.*
Somebody could possibly hear something has nothing to do with it. Consenting to being heard is not consenting to being recorded. But maintaining your presence in a place where people are allowed to record is. If it's your party, tell them to put it away or leave. If it's their party, you leave. If you are recording surreptitiously and you are not working with law enforcement, it's probably not going to be admissible in court and if you publish it, you're going to get sued. Depending on your state and local laws, you are likely to lose badly.
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[*] All of this depending specifically on how the term is defined in your state and local laws. For example, video has often been separated from audio for pragmatic reasons; security cameras are meant to record physical acts, not conversations. For a second example, many states have decided that sending your voice over a wire to a designated recipient as an electronic signal is already consenting for the person receiving that signal to be able to record it and use it as they please; others have not. For a rationale in the second case, imagine that you didn't have the right to reveal a letter that was sent to you.