The prequel to the ‘A Quiet Place’ saga got me thinking.
spoiler alert!
There is a scene in which many humans march towards a safety point. Each individual human would have been relatively quiet, but because there are a lot of them (potentially hundreds), they end up being, as a whole, loud enough to alert the monsters so they get all killed.
This would suggest that many sources of noise which are near to each other and generate more or less the same amount of noise end up adding up so that the end result in dB is more or less the sum of the individual dB levels.
But then again, it’s fiction.
Back to reality, I work in a room full of different servers which have also very different levels of noise. I have noticed that from my standpoint, the noise of the quietest server seems to disappear whenever the loudest is running, so it kind of does blow my mind how our perception of noise works…
Actually it happens all the time, because of reflection/ refraction from a single source. Say you’ve got a table saw running in a shop. The sound coming from the saw is a (fairly) constant oscillator.
A shop has hard surfaces and that sound will bounce all over the shop the saw is in. Because it still takes time for the sound to travel and bounce all over, there will be places where standing waves of constructive or destructive interference form. Now there is also a shit ton of other sound bouncing all over the place, so it might not be as noticeable, but standing waves/ regions of constructive/ destructive interference don’t require a lab setting.
Modern phased array antenna are effectively taking advantage of this phenomena.