My quess there is the road grader is a new sound causing an alert, the school bus is a repetitive none threatening sound.
My father ran a huge boreing mill and a lot of the.cuts were up to an hour long and my dad would sleep through the whole cut waking up just as the bit cleared the cut. This was a machine spinning a huge piece of cast iron, it wasn't quiet. Let the bit hit a sand pocket in the casting and dad was awake before the casting finished the revolution.
When I was going to school nights I ran an 80 ton overhead crane and caught up on my sleep at work. The boss came by and yelled my name and cussed me out till he was horse, my control cage was three stories off the ground. He finally went over to one of the guys and asked how they ever get me to do anything. The guy let out one "WHOOP" and I was awake and ready to go, just shook his head and walked away and never said a word.
Animals and humans can sort sounds, some are meaningless some convey danger or importance.
My father ran a huge boreing mill and a lot of the.cuts were up to an hour long and my dad would sleep through the whole cut waking up just as the bit cleared the cut. This was a machine spinning a huge piece of cast iron, it wasn't quiet. Let the bit hit a sand pocket in the casting and dad was awake before the casting finished the revolution.
When I was going to school nights I ran an 80 ton overhead crane and caught up on my sleep at work. The boss came by and yelled my name and cussed me out till he was horse, my control cage was three stories off the ground. He finally went over to one of the guys and asked how they ever get me to do anything. The guy let out one "WHOOP" and I was awake and ready to go, just shook his head and walked away and never said a word.
Animals and humans can sort sounds, some are meaningless some convey danger or importance.