Unter einer strengen Definition von "Instrument": Pfeifenorgel - sie schütteln Ihre Knochen wie ein Rockkonzert.
Die Behauptung lautet, dass der Atlantik Die Orgel der City Music Hall ist das lauteste Instrument der Welt. Eine der Haltestellen ist lauter als ein Zugpfiff. Mehrere Artikel, einschließlich des Wiki-Artikels, dieses und des obigen Links, weisen darauf hin, dass dies vom Guinness-Buch der Rekorde anerkannt wird, obwohl ich Ich konnte es nicht direkt bestätigen.
Ein anderer Anwärter, der "Instrument" lockerer interpretiert, wären Kirchenglocken, obwohl das Publikum normalerweise nicht richtig mit ihnen ist, wenn sie geschlagen werden.
Loudness is a subjective sensation, so I will talk about an objective measure, which is the acoustic power that different instruments can generate. In contrast to the pipe organ answer, this answer is restricted to instruments that derive all of their power from a single human performer.
This page indicates that drums easily produce more acoustic watts than other instruments, which seems to match experience.
It also indicates that the trombone has the greatest power output of the instruments that can play different notes (not counting tuned drums). Experience also agrees that brass instruments are pretty darn loud.
I've read other sources that are not easy to cite here that closely match the numbers listed on the cited page.
As already said, there are many different ways how this could be judged. Acoustic power is certainly a good criterion, though it should be weighted with the ear's response: bass instruments require much more power to sound loud. That also allows their sound to reach further, though.
Subjectively, I'd name a couple of contenders. I'll not count church bells, these would actually win in all categories, nor instruments that can't be fully human-powered.
Maybe the calliope?
From Wikipedia: A calliope (see below for pronunciation) is a musical instrument that produces sound by sending a gas, originally steam or more recently compressed air, through large whistles—originally locomotive whistles. A calliope is typically very loud. Even some small calliopes are audible for miles.
Another option could be the cannon, as used in the 1812 Overture.