Wiktionary
hear the grass grow
vb. 1 (context idiomatic English) To have an extremely sensitive sense of hearing. 2 (context idiomatic English) To hear very well due to being in an exceptionally quiet environment. 3 (context idiomatic English) To be very aware or discerning; to pay attention to every small detail.
Usage examples of "hear the grass grow".
His previous job had qualified him as a man who could hear the grass grow and read tea-leaves with the best of them.