Raspberry Pi Decibel Meter (Mini Project)

## Situation

> see: https://github.com/dwyl/hq/issues/113
## Design Brief

Build a basic sound-level (decibel) meter using off-the-shelf components.
The unit should have the following functionality:
- [ ] monitor/record the decibel level in real-time on the device (using reliable components).
- [ ] display the level on a screen or set of LEDs (_which ever is quicker to implement_)
- [ ] flash a clear warning when the sound level is too high so people are instantly aware.

Optional "bonus level" features:
- [ ] store the data locally in a time-series database for later analysis. (_This may require larger microSD cards..._) appending to a csv log should be more than enough. One log file per day.
- [ ] Display a _graph_ so we know what times of the day are the most noisy/quiet
## Investigation
- [ ] investigate hardware and component requirements for the project
- [ ] investigate if there are any _existing_ schematics or code we can re-use
- [ ] order required hardware/components
- [ ] play/experiment!
- [ ] write-up findings in the form of an _easy-to-follow-along_ guide e.g: https://github.com/dwyl/learn-tdd
- [ ] install unit(s) in Quiet Space and see if the noise level decreases!
# `tl;dr`
## Why Raspberry Pi?

Raspberry Pi is a "general purpose" micro-computer. There are _many_ other specific-purpose boards we _could_ but for the _prototype_ we just need to get started quickly.

> Raspberry Pi passes 10m sales: http://www.bbc.co.uk/news/technology-37305200

There are over 10 Million Raspberry Pi's in the wild which means this project will be _useful_ to quite a few people. Think about how many school libraries and quiet spaces for reflection, reading and creativity could use one of these!

https://www.amazon.co.uk/gp/product/1119046025/

Yes, we _could_ just buy an Arduino-based kit: https://learn.adafruit.com/adafruit-microphone-amplifier-breakout/measuring-sound-levels but where is the fun in that?