Perceived (6)
'perceived' is the definition.
(hearing is a kind of perceiving)
This is all the clue.
(Other definitions for heard that I've seen before include "Tried" , "Detected aurally" , "Examined" , "Received aurally" , "Gathered" .)
(Other definitions for noticed that I've seen before include "Detected" , "Observed or saw" , "Realised" , "Marked" , "Became aware of" .)
'perceived' is the definition.
('sense' can be a synonym of 'perceive')
This is all the clue.
(Other definitions for sensed that I've seen before include "Became aware through mental perception or intuition" , "Felt, tasted, etc" , "Became vaguely aware of (something)" , "Felt, had mental impression" , "'Felt, perceived (6)'" .)