1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Decibel Question

  1. Oct 28, 2008 #1
    Preface

    This question proves my ignorance. You have been warned.

    Background

    - I am building a new "near silent" computer and I am looking at different types of fans.
    - The case requires 3 fans.
    - I am looking to purchase and install 3 Identical fans that have a rating of 10 dB.

    Question

    - One fan will obviously produce 10 dB of "noise"
    - How many dB of "noise" will all three fans produce?

    - The answer I assume is only 10 dB, however I could be wrong if dB can "accumulate" (meaning 3 fans would produce 30 dB). Furthermore, I may be completely off base and it is neither 10 dB or 30 dB.

    I have been thinking about this too much and it is driving me crazy. Please enlighten me!

    Thanks
     
  2. jcsd
  3. Oct 28, 2008 #2

    atyy

    User Avatar
    Science Advisor

    Let's suppose 10 dB corresponds to a pressure amplitude P, and you want to find Y dB corresponding to 3P.
    Po is the reference pressure in both cases.

    10 = 20log10(P/Po)

    Y= 20log10(3P/Po)

    Y-10
    =20log10(3P/Po)-20log10(P/Po)
    =20log10(3P/P)=20log10(3)=20(0.5)=10 dB

    So if 1 fan produced 10 dB, 3 fans would produce (10+10)=20 dB, and 10 fans would produce 30 dB.

    http://trace.wisc.edu/docs/2004-About-dB/ [Broken]
     
    Last edited by a moderator: May 3, 2017
  4. Oct 28, 2008 #3
    Genius.

    Thanks so much! It makes perfect sense.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Decibel Question
  1. Bels and Decibels (Replies: 9)

  2. The sound of Decibels (Replies: 7)

Loading...