In a quiet apartment you can hear when neighbours are talking on their phones. I thought that with a change in neighbours that noise pollution would end but my hopes are now dashed. It's a frustrating type of noise pollution because there is nothing you can do about it. You can't tell someone not to speak on their phone so you need to find a way of making white noise to cover it.
Sometimes phone calls are over fast, so it doesn't matter but sometimes they last for minutes, or tens of minutes or longer so for that duration your privacy is invaded by the phone talker.
This is not just an apartment problem. It is also an open office problem. People feel the need to make calls and talk loud. In an ideal world text would be enough. In an ideal world you would send an e-mail with three sentences, and within a few minutes you'd get an answer and the issue would be dealt with.
When you're writing you're sensitive to noise. It's a distraction so you need white noise. I just told Roomba to do some hoovering to provide me with a source of white noise. That white noise returns that sense of privacy.