[ELI5] Why does a large amount of quiet noises combine to make a loud noise.

Question

[ELI5] Why does a large amount of quiet noises combine to make a loud noise.

In: 2

Answer 1

Sound is made by using some energy to move the air particles (or other medium, but let’s say air for simplicity). If you use more energy, you move it more, and it sounds louder. If two sounds happen at the same time, and work together in sync, the energy is acting together and the combined sound is louder. If the sounds are out of sync, the energy is acting against each other and the sound can be lower.

Now any noise is a mix of different sound frequencies. When you have multiples low energy noises, some part of them will sync up, adding energy and making it louder, and some parts will cancel, making it quieter. On the whole, you will hear louder noise at different intervals and we focus more on that than the intermittent low noise.