That’s an extremely high bar to clear. If two people are screaming at each other on a street corner with a crowd of onlookers it’s surely fine to record them. But if those same two people are quietly speaking to each other while you stand nearby with a microphone running, you’re violating the Wiretap Act. Same for recording the patrons behind you at a restaurant, the guy on a phone call on the bus, etc.

There are surprising edge cases to this. People have been found in violation of the Wiretap Act for putting microphones on their walls to collect proof that their neighbors are screaming too often. A loud argument in an apartment still has an expectation of privacy even if you can make out the words with your ear to the wall.