Ask Experts Questions for FREE Help !
Ask
    Rubentheran's Avatar
    Rubentheran Posts: 35, Reputation: 1
    Junior Member
    		  
    #1

    Jan 18, 2011, 04:53 AM
    Physics:Intensity
    17.Two sources have sound levels of 75 dB and 80 dB. If they are sounding simultaneously, what is the combined sound level ?

    Ans:81.2 db

    How am I supposed to this? What is the formula.I really don't know.Can someone show me the solution.The given answer is 81.2 db.Thanks
    jcaron2's Avatar
    jcaron2 Posts: 986, Reputation: 204
    Senior Member
    		  
    #2

    Jan 18, 2011, 06:13 AM
    Since dB's are a logarithmic scale, you can't add them directly. It's easiest to convert from dB into W/m^2, add the two intensities, and then convert back into dB.

    To go from W/m^2 to dB, the formula is:

    ,

    where is the intensity in dB, is the intensity in W/m^2, and is the reference intensity (which is equal to W/m^2 by definition.

    So can you solve the above formula for so you can calculate the intensity in W/m^2? Just do it for both sources, then do as I said and add them together, then convert back to dB with the above formula.
    jcaron2's Avatar
    jcaron2 Posts: 986, Reputation: 204
    Senior Member
    		  
    #3

    Jan 18, 2011, 06:14 AM
    Comment on jcaron2's post
    Remember, it's log base 10, so to "undo" the log when solving the equation for I, you need to raise 10 to the power of each side of the equation.
Not your question? Ask your question View similar questions
 

Question Tools Search this Question
Search this Question:

Advanced Search

Add your answer here.


Check out some similar questions!

Intensity of sound waves [ 2 Answers ]

Could some one please tell me the relation between the intensity of a sound wave and its frequency and amplitude?

Intensity of sound; decibels [ 1 Answers ]

At a rock concert, a dB meter registered 130dB when placed 2.8m in front of a loudspeaker on the stage. A.) What was the power output of the speaker assuming uniform spherical spreading of sound and neglecting absorption in the air? B.) How far away would the sound level be a somewhat resonable...

Pre calculus intensity and inverses [ 3 Answers ]

The noise level, N, of a sound in decibels is given by N=f(I)= 10log(I/I0) <---the 0 in the (I/I0) is a sub 0 where I is the intensity of the sound and I0 (sub 0) is a constant. Find and interpret f-1(N) the inverse I don't know how to even go about doing this??

Luminous intensity [ 1 Answers ]

Is luminous intensity also basic quanties?

View more questions Search