One fairly easy way to bring the outside sounds in is to use a baby
monitor (room monitor) and put the baby unit outside. Also, if the
parent unit is connected to a better speaker, that helps.

I've always somehow known that my cats enjoy listening to the outside
sounds. My most recent rescue is obvious about it. I keep the speaker
on the floor. She frequently lies with her head resting against the
speaker. Even when the volume is louder than you might think
comfortable, she's got her head right there, relaxing. And it's not
just one place, the speaker is moved around.

It's obvious now.