I would like to tell about the effect of distance to sound pressure level; sound pressure level’s unit is dB. It depends on the fluid pressure, and distance.

Fluid pressure is inversely proportional to the distance (p ≈ 1/r )

When the distance becomes twice, the fluid pressure will be a half.

And the equation of sound pressure level is dB = 20 log (P/P_{ref}).

If

P_{1} = P

r_{1} = r

r_{2} = 2r

Then, P_{2} = 0.5 P

dB_{1} = 20 log (P_{1}/P_{ref})= 20 log (P/P_{ref})

dB_{2} = 20 log (P_{2}/P_{ref}). = 20 log (0.5P/P_{ref}). = dB_{1} + 20 log 0.5 = dB_{1} – 6.

dB_{2} = dB_{1} – 6

It is similar to love, when 2 people are in Long distance relationship (LDR), and the distance is twice larger, The Love will be reduced in 6 values. What are 6 values? I dunno exactly, maybe 6 watt, or 6 meter, or 6 days. So, keep your love and be patient.