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

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.

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.