Based on the way sound travels, the following are true:
Sound can travel through solids. The music therefore passed through the solids - windows and doors of the car - to get to the boy inside the car which was why he could still hear the music.
When the cars were 100 feet apart, the sound waves produced by the music were able to disperse into the surrounding area such that only a few of those waves reached the boy.
When they entered the tunnel, the waves could no longer disperse into the area as before. They had to travel along to tunnel and as the boy was also in the tunnel, he heard the music.
In conclusion, sound travels through various mediums.
Find out more on sound travelling through solids at https://brainly.com/question/1280585.