How Loud Is a Whisper at 3.5 Meters?

[kristibella]

Homework Statement

A. What is the sound intensity of a whisper at a distance of 3.5 m, in W/m²?
I know that a whisper is approximately 20 dB and P = 10^-10 W/m².

B. What is the corresponding sound intensity level in dB?

Homework Equations

I = Power/[(4pi)(3.5m)²)
dB = 10 log (I/I_o).

The Attempt at a Solution

I = 6.50*10^-13

dB = -1.87 (I used 10^-12 W/m² for I_o)

 

[Redbelly98]

I know that a whisper is approximately 20 dB and P = 10^-10 W/m².

dB level would depend on how far away you are. You know it's 20 dB at what distance from the whisperer?