### Description

The distance to someone shooting at you can be estimated from various sounds such as the sound of a bullet's impact and the sound of the gunshot that follows. Many bullets fired from a distance are supersonic.

Background:

(1) The speed of sound at sea level is 340 meters per second. It is affected by temperature and atmospheric pressuer.

(2) The speed of a bullet varies on several factors. A rifle may have a muzzle velocity from 2,300 to 3,200 feet per second (701 to 976 meters per second).

Some rules of thumb:

(1) If a thump of a bullet impacting is heard at the same time as the sound of the shot, then the shooter is within 300 meters.

(2) Multiplying the number of seconds between the sound of impact and the sound of the shot by 300 will give an approximate distance to the shooter in meters.

(bullet velocity in m/s) * (flight time of bullet in seconds) =

= (speed of sound in m/s) * ((flight time of bullet in seconds) + (seconds between sound of impact and gunshot))

flight time of bullet =

= (speed of sound) * (seconds between impact and gunshot) / ((speed of bullet) - (speed of sound))

distance to shooter in meters =

= (bullet velocity) * (flight time of the bullet)