Which Instrument is loudest?

trombone is the loudest instrument

Um....factor in the human aspect here.

If someone was playing, you must consider the air speed and pressure from the person playing it, which is different with every single person, and will produce different volumes of sound even if they're on the same instrument.

Secondly, projection of sound is also different because of different instrument shapes. The air direction will be different for each one, so you'll need some sort of equipment to measure the volume of air, because if you rely on humans, it will be different for each spot the person perceives the sound vibrations.

So, to find out this question....you'll have to do a little math and find out the density, velocity, volume, WHATEVER unit of measure is most appropriate, that the instrument is capable of producing with a certain amount of air speed and volume. Then, once you have those answered, you'll have to measure the volume of air produced with those factors.

So do the math and come back to us when you find out.

I believe it is the Alphorn, it was made to be heard across mountain ranges.

Here is a link:

http://en.wikipedia.org/wiki/Alphorn

The loudest in the orchestra is the Trombone.