Approximately how many times louder is the latter sound?

Question

The sound level measured in a room by a person watching a movie on a home theater system varies from 45 dB

 during a quiet part to 65 dB during a loud part. Approximately how many times louder is the latter sound?

Answer 1

A general rule to remember: a 10 dB increase relates to a 10 times increase in loudness. In this scenario the sound is increased by 20 dB, which means the sound will become 10 times louder, twice. This would result in the 65 dB sound being perceived as 100 times as loud as the 45 dB sound.