How does the strength of a sound field 1 meter from its source compare with its strength 4 meters away?

Intensity is defined to be the power per unit area carried by a wave. Power is the rate at which energy is transferred by the wave. In equation form, intensity I is
I
=
P
A
I
=
P
A
, where P is the power through an area A. The SI unit for I is W/m2. The intensity of a sound wave is related to its amplitude squared by the following relationship:

I
=
(
Δ
p
)
2
2
ρ
v
w

The answer is telescope.