Mac plays unexpected running water sound

Water Running Sound on My Mac What Could It Be?

My Mac suddenly started playing a sound similar to running water, even though I had no apps, music, or videos open. Adjusting the volume made the sound louder or quieter, but it wouldn’t stop on its own. The noise only disappeared after I restarted the Mac, and it hasn't returned since.

What could have caused this, and is it something I should be worried about?