Decibels homework help

You are at a rock concert, standing 9.8 m from one of the loudspeakers. Based on the pain in your ears, you estimate the decibel level to be about 112 dB at this location. You are worried that this intensity level may be harmful to your ears and result in a degradation of your hearing in years to come, so you want to move farther away from the loudspeaker to reduce the sound to a "dull roar" at a decibel level of 86.1 dB. From your present location, how much farther away from the loudspeaker would you have to move to reach this reduced decibel level?

Can someone show me how to solve for r?

Help: "Damping of sound level with distance":
http://www.sengpielaudio.com/calculator-…

Sound level Lp1 = 112 dB.
Distance r1 = 9.8 m.
Sound Level Lp2 = 86.1 dB.
Answer: Distance r2 = 193 m you have to move away from the speaker
to reach this reduced decibel level.

Reference sound pressure po = 20 µPa = 2×10^−5 Pa (Threshold of hearing)
Reference sound pressure level Lpo = 0 dB-SPL (Threshold of hearing level)

Get sound pressure p1 when entering sound pressure level Lp1 = 112 dB.
p1 = po×10^(Lp1/20) Pa (= N/m²) = 2×10^−5×10^(112/20) Pa = 7.96 Pa.
Get sound pressure p2 when entering sound pressure level Lp2 = 86.1 dB.
p2 = po×10^(Lp2/20) Pa (= N/m²) = 2×10^−5×10^(86.1/20) Pa = 0.40367 dB


Get sound pressure level Lp in dB when entering sound pressure p in Pa:
Lp = 20×log (p / po) in dB = 20×log (p / 2×10^−5) in dB.



Cheers ebs

what are the SI units for decibal, then u could use that nd rearrange the equation