I live about a mile outside of town, in the country. There is a train track that runs through the town with quite a few railroad crossings. Every time the train approaches a crossing it blows its whistle. This morning, about 5:30, I was outside and a train was going through. It’s all fields and woods between me and town. Every time the train would blow its whistle it would set the coyotes off. Something about the whistle really made them yip and howl. It must have been a pretty good sized pack because there was an awful amount of yipping. It was kind of fun to listen to.

6:00 o'clock whistle in my town sets em' off good.
But only if it's dusk or dark then.

Fire/ambulance sirens set them off right here in the neighborhood...gotta pack right close to the grade school.

Train…

Getting close to a den in the spring will set a female off.