I use an app (iOS, Android, Windows, web) by TMSoft called White Noise. I think it was like $2.99. It has a bunch of pre-programmed sounds (waves, chimes, birds, traffic, etc) that you can use. You can also import sounds, change existing sounds (alter pitch, make slower, etc), create your own mixes, etc.

My current “sleep sound” is a mix. The base is pink noise, which nicely muffles many sounds. Since a constant hiss can be annoying on it’s own, I topped it with a pitch-lowered heavy rain (the regular pitch was a little annoying). To avoid being woken up by bass noises (lawnmowers, vacuum cleaners, delivery trucks), I added in a slowed-down heavy thunderstorm: it has intermittent peals of thunder that rumble on and then fade away; any base noises that I hear, my sleeping mind interprets as a long peal of thunder and doesn’t bother waking me up. Underneath all that, I have a very slowed-down heartbeat; my heart will tend to try to match it, prepping me for sleep. And I’ve added in some very intermittent birdsong and frogs croaking to make it a little more cheerful, and a kitten purring because that’s relaxing too so why not?

I tinker with it occasionally, but it really helps me sleep through any disturbances at night.