Silence
Like after every battle, Sam found the silence of the small town unsettling. It only served to remind him that the people who should have been driving down these streets, the children who should have been laughing as they raced down the sidewalks, were gone, either killed in the crossfire or forced to flee.
Bumblebee hated it too, and so guardian and charge made it a habit of talking about anything and everything to pull them away from all morbid thoughts. Sam was so grateful his canary yellow Camaro had never been known for keeping quiet.