The concert vs car alarm test
You escuchas a concert (you chose to go). You oyes a car alarm (it invaded your ears uninvited). The distinction is intent: did you choose to receive the sound?
Oiga — a uniquely useful word
The imperative form oiga (formal) or oye (informal) is used constantly in spoken Spanish to get someone's attention — like tapping someone on the shoulder: Oye, ¿tienes un momento? (Hey, do you have a minute?). It also answers the phone in Spain.
Escuchar + que vs oír + que
You can use either with que + clause, but the nuance differs: Oí que te casaste (I heard that you got married — through the grapevine). Escuché que dijiste eso (I heard/was listening when you said that — I was present).