Actually my 20 month old boy DID coming running over to the couch see my phone when he heard the pipes... Hahah
That was honestly one of the few reasons why I enjoyed riding my bike.
You'd see kids of all ages react totally differently.
One little boy about 3 years of age, stopped walking with his parents just to see me pull up to a light.
Then when I blipped the throttle, he started doing this vigorous little dance, moving his feet quickly in some strange shuffle motion with a huge grin on his face.
Another time a mother was walking with her daughter (roughly the same age).
As soon as she realized where the sound was coming from, she started bawling her eyes out and tried to hide behind her mother.