Subtitles

I originally started watching a couple of television series with the subtitles turned on because my husband was having trouble understanding the names and the British accents on Game of Thrones and Mr Selfridge.  When I happened to be watching an episode of Wolf Hall by myself and the subtitles had been accidentally left on, I discovered that I loved them and I’m pretty sure it’s probably just a matter of time before I let them creep into other things.  Here’s my question:  When there is music playing, the subtitles display a couple of eighth notes in the lower lefthand corner of the screen.  And often there are parentheses saying such things as “birds singing”, “harp music playing in background” or “car horns honking”.  If I had never known the sense of hearing, what would be my interpretation of those things?