General synonyms:
* Heard
* Attended
* Paid attention
* Took notice
* Heeded
More specific synonyms:
* For sounds: Heard, perceived, detected
* For people: Attended to, observed, watched, followed
* For advice: Heeded, followed, obeyed
* For a request: Complied with, responded to, acceded to
* For a story: Absorbed, engrossed, captivated
More formal synonyms:
* Apprehended
* Discerned
* Perceptively understood
* Attentively observed
The best choice will depend on the specific situation and the tone you want to convey.