Few things are more distracting than the sound of a lone human voice, in an otherwise quiet room.
Some people block out distractions in office environments, coffee shops, libraries, and on public transportation by listening to music through headphones, but others find music, even jazz, to be distracting. It was designed to be catchy, what can they do ?
One option, is to consider listening to recordings of large crowds. The sound of a crowd, can more effectively obfuscate the sound of a lone human voice, and do so at a lower volume, than sounds like ocean waves, which do not resemble human speech.
Distractions are a bad thing, but fortunately there are many people who do not find noise, even when it is loud, to be distracting in and of itself, as long as it is meaningless, in other words, devoid of interesting patterns.
The sound of a human crowd is such a noise.
Furthermore, a crowd can be energizing. Restaurants, hotel lobbies, airports, and trading floors can be wonderful places to work, as long as there is enough noise to keep you from inadvertently understanding what is being said around you. A recording of a large crowd, played through headphones, can help you create such an atmosphere without resorting to ear shattering decibel levels.