Given that a person with normal hearing can barely detect a sound with intensity of 1 db at a frequency of 1 khz (the sensitivity of the human ear peaking near 1 khz), how far away could this person detect another person breathing normally?

Answer = 3.16m

Explanation:

The concept applied here is the relationship between intensity and sound level. the intensity I of a sound wave is the average rate per unit area at which energy is transferred.

I = P/A

I = intensity

A = Area

The intensity of a sound wave can also be expressed in terms of the decibel scale. DB is the abbreviation for decibel which is the unit of sound level this was named after Alexander Graham bell whose work on this aspect was recognized.

The step by step calculation and necessary derivations is a shown in the attachment.

a and b sometimes have a positive value