1) The sound level measured in a room by a person watching a movie on a home theater system varies from 40 dB during a quiet part to 60 dB during a loud part. Approximately how many times louder is the latter sound?

2) A sound pulse emitted underwater reflects off a school of fish and is detected at the same place 0.03 s later. How far away are the fish?

3) Ultrasound probes can resolve structural details with sizes approximately equal to the wavelength of the ultrasound waves themselves. What is the size of the smallest feature observable in human tissue when examined with 18-MHz ultrasound? The speed of sound in human tissue is 1,540 m/s.