A sound that measures 30 decibels is how many times louder than the theshold of hearing

A sound that measures 30 decibels is 1.5 times louder than the threshold of hearing as normal hearing threshold of human hearing is 20 decibels.

Decibels measure intensity. If you whisper in an empty room it will measure between 0 and 1 db. This indicates the intensity of sound is minimal. This is considered the threshold of hearing.

A sound that measures 30 decibels is a 1000 times louder than the the threshold of hearing. An example of this is the noise of a regular computer produces between 20-40 dB.