Physics Sound, Decibels and distance...

[MCAT guy]

---

Members don't see this ad.

BR has a question: A 50 dB noise is how much further away from its sound source than a 100 dB noise?

Answer: 316 times further away

I understand the difference in intensity is 10^5 but not this concept. BR then refers to an equation that relates I is proportional to 1/r^2 ...

I searched through all my BR equations and then through all of the TPR equations, and I don't see an equation relating the distance of the source to the Intensity. Am I missing something here?

 

[Pulsar]

Well, the 100dB sound is 100,000x more intense than the 50dB sound, and intensity follows the inverse square law. So if something is twice as far away, it's 1/4 as intense, if it's 8 times further away, it's 1/64 as intense. Working in reverse, if it's 1/100,000 times as intense, it must be sqrt(100,000) times as far away (or 316x).

 

[MCAT guy]

Well, the 100dB sound is 100,000x more intense than the 50dB sound, and intensity follows the inverse square law. So if something is twice as far away, it's 1/4 as intense, if it's 8 times further away, it's 1/64 as intense. Working in reverse, if it's 1/100,000 times as intense, it must be sqrt(100,000) times as far away (or 316x).

thx bro.

So I guess it is I = power/area