Hang out anywhere there are people — Amtrak, Burger King, the I.C.U. — and it can feel as if there’s no escape from their noise. A Mets game, the Beyoncé discography, FaceTime conversations about nothing: Thanks to the unfettered use of speakerphones, other people’s business is now yours too, loudly.

To be fair, not using headphones may have nothing to do with disrespect. Many smartphones don’t have traditional headphone jacks. Bluetooth headphones can be pricey. Sometimes you just forgot to bring earbuds and it’s your mom’s birthday.

But on Reddit recently, the second most popular answer to the question “What do you secretly judge people for?” was “when they watch TikToks loud in a quiet room without headphones.”

Cellphones make it easy to aggravate an entire subway car, but this isn’t a 21st-century issue; ask anyone who remembers boombox-era New York City. But there’s a difference between having a conversation on the phone and having your speaker on. For some people, going sans headphones doesn’t register as a problem. For others, it’s an affront — in some cases, debilitatingly so.

According to the etiquette expert Myka Meier, the issue is a clash over what constitutes civic pollution.

“On our phones, we selfishly have interests that we are able to tap into any second of any day, and we are so used to it that we forget other people are around us,” said Ms. Meier, who shares tips on removing tea bags and answering text messages with her 640,000 Instagram followers. “I get embarrassed if I cause somebody to feel uncomfortable or if I take up someone else’s space. A lot of people don’t feel that anymore.”