Noizio is a free Mac app for generating soothing ambient sounds, reducing distractions and helping you get on with your work.
The app offers 10 soundscapes: October Rain, Paris Cafe, Thunderstorm, Campfire, Winter Wind, Sea Waves, River Stream, Summer Night, Sunny Day, Deep Space.
If this isn't enough then you can mix your preferred soundscapes, giving each one a separate volume level, until you produce the feel and atmosphere you're after.
Whatever you choose, the sounds aren't just an endless identical repeats of the same fixed sample. Noizio actually generates new ingredients for the mix you've selected each time, looping them seamlessly, so they can be left running in the background without ever providing any distractions.
If you really like the app then you can even have Noizio start when you log in, leaving nothing more to do: your favourite soundscapes will always be playing when you need them. (Although if you do need to turn them off, it only takes a couple of clicks.)
Many people find this kind of background noise generator can help to reduce distractions and improve their productivity. There are no guarantees, but Noizio does give you plenty of choice and control, and as it's entirely free (no ads or other issues) there's no penalty in giving it a try.