Document Procedure, Measure and Correlate Sound Pressure Levels at Krake Development Locations LB, UK, Maryville, Austin

Is your feature request related to a problem? Please describe.
A clear and concise description of what the problem is. Ex. I'm always frustrated when [...]

I am always frustrated when talking about sound without quantifying the conversation.

Describe the solution you'd like
A clear and concise description of what you want to happen.

All Krake developers need a SPL (Sound Pressure Level) meter. Lets try to use our smart phones.

A standard (described and documented) test setup at all locations for which we compare / correlate measurements of SPL.

Audio Files
We need useful test files to put on the SD card in Krake Mini MP3 player.

1. Audio sweep at full (and possibly reduced amplitude),
2. Steady test tones at a set of frequencies which are TBD.
3. White noise, pink noise.
4. Music.
5. The sound of Crake (loud, repetitive krek-krek of the male corn crake or the high-pitched "kee-krrrrr" of the dot-winged crake)
6. Alarm sounds

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Lee documented some SPL Measurement Details in issue #124