Is there a formula/way to know how far away a noise is?

Question

My sister said she learned a way to tell how far away a noise is in principales of tech, is there?

Answer 1

If you can see when the sound is made (light travels so fast from the source to your eye it is effectly instantaneous), but you hear the sound at a later time, you can measure the delay in the sound and calculate a distance.  Lightning and thunder are a classic example of this.

We can see lightning very easily, and can hear the thunder too.  For every five seconds it takes the thunder to reach your ear, it has traveled one mile.  For every three seconds it takes the thunder to reach your ear, it has traveled one kilometer.

You can use this same method for things like echoes.  In high school marching band we could hear our music echo off the side of the gym, which was far from the football field.  In that case, we would count the seconds and then take half that amount since the sound was traveling both ways (thunder travels only one way).  The gym was about a quarter mile from the football field.

If you need EXACT measurements, then with scientific equipment you can calculate such things as sound volume, air density, and attenuation to determine distance to the nearest foot or meter or whatever measurement unit you're using.

Answer 2

The sound intensity for a spherical source of sound falls down inversely with the square of the distance.

Answer 3

There are several ways that can be used, depending on the information you have to start with.

1. If you know the exact time the noise was created, you can measure the time it takes to reach your ears and multiply by the speed of sound in air, which is 1100 feet per second.  This is how you tell how far away a thunderstorm is.  Thunder is created by lightning.  When you see a flash of lightning, you know a thunder clap is also created, and you can measure the time until you hear it.

2.  Sound intensity decreases with the square of the distance.  If you know the loudness of a sound at the initiation point, you can write a formula for the intensity at any distance.  Then you can measure the loudness of the sound at your location and solve the equation for the distance.

3.  If you can't use either of the above, you can use triangulation, but you need three microphones at known locations relative to each other, and a precise timing system.  By measuring the difference in time between the sound detection at the microphones, you can use some trigonometry to calculate the location of the sound origin.  The math is a little complicated, but of course there are computer programs to do this.

Answer 4

If you can see the source of the sound (such as lightening) then the answer is, YES.

The speed of sound is, at sea level:

In miles per hour:

761 mph

In kilometers per hour:

1225 kph

In feet per second:

1116 ft/sec.

In meters per second:

340 m/sec.

So, when you see the flash of lightening and start counting seconds until you start to hear the thunder, every 4.73 seconds is equal to one mile away.  If you're metric, every 2.9 seconds would put the lightening 1km away.