We tend to assume that fireworks are designed purely for their visual impact. However, for their creators, the sound they make is equally important. We can think of them as highly effective, single-use percussion instruments. Whereas drums make sound by creating pressure waves through the movement of a diaphragm, an explosion is a much more direct and effective source of noise. (The loudest sound in history was created by Krakatoa exploding in 1883. The percussion created was recorded on barometers around the world as it circled the earth four times before fading away. It even briefly shifted global sea levels as the atmosphere rang like a bell.)
The sounds of fireworks are divided into four types: retorts and crackles created by staged explosions; hums created by fireworks spinning as they burn; and whistles created by rapid on/off pulsing of the burning fuel resonating with the surrounding air. Whatever the type, as the distance from a firework increases, its characteristic sound changes. It is modified by wind and temperature gradients and humidity in the air, as well as reverberation caused by multiple reflections between ground and buildings. When we listen to these recordings of fireworks over Newhaven, what we hear carries with it an imprint of the geography of Edinburgh, its hills, streets and buildings, as well as the neighbouring sea.