Now... I'm not an expert, but if an atomic bomb went off, even a small one, would it make a loud sound?
We'll need a scientist to answer that one.
Not entirely. As others have remarked, it takes no extraordinary scientific understanding to answer in the affirmative.
However, it is correct to say that you need a scientist to answer the question with such mind-numbing detail that you wish you had never asked. That's where I come in.
Sound is a pressure wave carried in the atmosphere. Atomic explosions are among those phenomena that create an unusual kind of pressure wave, namely a
shock wave. The leading edge of the blast is a shock wave, or a sudden jump in the air pressure. Shock waves can be heard after many kinds of explosions (detonations, but not deflagrations) or as sonic booms created by supersonic aircraft. I've heard numerous shock waves, both at airshows and caused by the
Space Shuttle re-entering the atmosphere. They exhibit a distinctively sharp sound, one that carries over long distances, and are "loud" even from many miles away.
An atomic bomb, by virtue of its extremely powerful shockwave, creates a very loud sound indeed.
Here you will see a chart describing just how big of a pressure shock one would experience if nearby a small atomic explosion, one of 1 kiloton TNT equivalent, for various ranges of horizontal distance and explosion altitude. As you can see for yourself, a 1 kT explosion would create a shock of 1 PSI at roughly 1400 meters distance, and 7 PSI at a distance of over 400 meters.
In other words, the answer is yes. A 1 kT device would create a sound loud enough to be lethal to anyone within nearly half a klick who wasn't inside a specially prepared bunker. This should satisy virtually anyone's definition of "loud."
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