Acoustics - Sound intensity level


In one of the Practice Exam Form 2 there is the following question:
A sound of 30 dB is how many times more intense than a sound of 10 db?
Answer given:
Each increase of 10 dB is a two-fold increase in sound level intensity. Therefor, two two-fold increases would be 10 x 10, which equals 100.

Can you, please explain how this corresponds to the statement from
Mechanical and Electrical Equipment for Buildings 12th ed 2014, page 1028:
“doubling a signal’s intensity raises the intensity level by 3 dB”

Thank you,

Hey Artem,

First off, welcome to the ARE community!

In regard to your question here and in this thread, I’m not sure off hand. Going to reach out and see if I can get you an answer on these.

Hi Artem,

We’ve received questions on this one before - it’s tricky. Here’s the response from our resident architect, Heather Rivera, NCARB, AIA, LEED AP


“The question and answer are correct as shown. I understand the reference material says “doubled;” and we know this is confusing. In actuality, for every 10-decibel increase in the intensity of sound, loudness is 10 times greater. It is a logarithmic equation; and simply saying “doubling” makes it sound linear. I’m including a snapshot below for your reference to help explain.”