We can't explain how loud this is. You really need to see one live to understand. Let me tell you that your ears will hurt at the last 20 seconds of a mascleta...The other 5 minutes you will just be amazing by the feeling on your chest from the big explosions.
I`ve been to a few Spanish Festivals - Las Fallas twice. The first time I went to Las Fallas I had no idea what to expect and considered that I might be a witness to something like an English Carnival. It turned up to be more like a controlled explosion of a FireWork Factory. The only difference is that no buildings are wrecked and no lives are lost. Though I did see many people being taken away to have their hearing checked in ambulances. The second time I went to Las Fallas I was a little more cautious and stood about a quarter of a mile away from El Ayuntamiento ( the town square where the action occured ). I still had bits of wood dropping on top of my head..... Spanish Festivals are seriously mental ! My wife galloped.....