Go to the app store on your 4th gen TV, and look for the search key word, "Nature".
About the 2nd or 3rd result over will say Nature Soundscapes.
Now, don't worry, this is not the whole new-agy kind a thing. This is truely soundscapes of things.
The app developer needs to really do a better job at labelling the buttons in this app, as right now, hardly anything is labeled correctly, although I did figure it out. Here is a general walkthrough of the app.
While in navigation mode on the remote, which is what you'll be in by default anyway, move as far to the virtical top left edge of the screen as you can focus yourself. This will be a sleep timer button. If you click this button, you then have options you can click on ranging from 5 minutes, to 2 hours, plus an option to stop the timer, and one to cancel out of the menu. Of corse, you could just also hit the menu key to back your way out.
The next button past the timer, if you flick right once from there is a display off button. So, if you click this, your TV screen will go blank solid black as if it's not even on. This is good for people with sensitive light perception, or for people who may want to sleep in the dark, but have a nice soundscape to chill out to. If you hit this by mistake, don't pannick. Just hit your menu button once on the remote, and your screen will turn back on. No biggy.
To the right of the display off button is a play/stop toggle button, which surprisingly, is! properly labeled.
The next button, I can't quite figure out. I know what it is, but I don't know what it does exactly. Basically it's a button to enable/disable oscillating mode. I thought that would pan the sound around the room, or would oscillate between all the different soundscapes after x amount of time, but that doesn't appear either to be the case. Maybe it's a visual thing?
The final button on the top is a menu button which you can click to rate the app in the app store.
Just to be sure we're correctly oriented, move back to the very very very top left icon, on the sleep timer. Now, if you move down one row, you'll have, well, initially 5 buttons. I say initially as in a sec, you'll see why. These just say copy1 through copy5 button initially as you move to the right across that row. These clearly need to be better labeled. These are the 5 different soundscapes you have by default. I'd just suggest clicking one of them and seeing what plays. Voiceover sometimes after clicking one of them will read what the active soundscape is, but I've found it somewhat inconsistent.
Just below these 5 buttons is an unlock icon you can click to make an in-app purchase for 99 cents which unlocks 3 more soundscapes like the wilderness, waterfalls, etc. I wish it had birdsounds, but it doesn't. I might look for an app though. The purchase process for this bundle is quite straight forward. Once you buy the bundle, you'll have copy6, 7, and 8 buttons to the right of the copy5 button on the last row I spoke of.
Once purchased, I'm pretty sure that icon turns to a restore purchases. If not, then you'll just go like you were gonna buy it again, then it'll tell you you already bought them, and will just restore. I've not hadda need to do that, but that would be my logical guess.
Then, once installed, that in app unlocker thing disappears, making the 8 copy buttons be the last virtical row on the screen. And, that's the whole app for ya, guys