what's the meaning of this sentence in "Billie Eilish - She's Broken": "You see them talking but hear no sound to hit the ground"
The full verse, for context, is:
So picture perfect
It can't be real
And all you feel is numb
You see them talking
But hear no sound
To hit the ground
"Hit the ground" is an idiomatic way of ordering someone to deliberately throw themselves to the ground for safety, for example, to avoid gunfire.
The song is a broken love song. This verse appears to be describing a relationship that looks perfect ("picture perfect") but perhaps is not. At a guess, I'd say that "[you] hear no sound to hit the ground" might metaphorically mean that, to an onlooker, they only see a perfect-looking couple and hear no reason to think that there is any trouble in the relationship.
Lyrics, like poetry, may not always stand up to grammatical scrutiny. This expression "hit the ground" may have just been chosen because it rhymes with "hear no sound".