Is it just the noise of the machines? It sounds like a heartbeat... is it yours, or the one of something lurking in the shadows? More recordings on my channel! Feel free to request another one by sending a message or just adding a comment.
To listen while using other apps, switch the player to Picture-in-Picture (PiP) during playback — it keeps playing in a small floating window (the screen stays on).
To listen with the screen fully off, in-browser playback stops by YouTube's design. Open the video in the YouTube app to keep listening where background playback is supported (e.g. with YouTube Premium).
Open in YouTube app