SPL Loss Over Distance

[Zing]

What's the formula for determining this?

If a speaker states that its maximum output is, say 110dB, typically that's at 1m. So what would it be at 3m?

 

[Flint]

In free space (no bounderies) it is the Inverse Square Law... look it up, there are a ton of calculators on the net.

 

[Towen7]

FWIW the inverse square law applies to a lot more than SPL loss.

 

[Zing]

^True. When you look it up, you'll find ALL its applications.

 

[Botch]

If you use a flash on a photography subject from 8 feet, and you want to double the brightness, move the flash to 5.6 feet.
If you want to double the brightness again, move to 4 feet.

Sound familiar? :mrgreen:

 

[Towen7]

Especially photography.

Double the distance and you need 4 times the light. It's handy that each full f/stop allows twice the light of the the next smaller aperture.

 

[Deleted member 133]

Inverse square law: the hipper one gets, the less square one is.

 

[Flint]

With SPL it is 6dB loss for every doubling of the distance. So, if 1 meter is 110dB, then 2 meters is 104dB and 4 meters is 98dB. However, in a room with reflective surfaces, the loss per distance is less (depending on reflected wave phase interaction).