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”
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.”
