Datasheet

Playground Sound Meter

Use the microphone on your Circuit Playground Express to measure sound levels and display them on a VU-meter-like

display!

The program is below. There are many settings that you can change to make the readings more or less sensitive and

the display more or less jumpy. Try changing CURVE to be 4 or 1 or 10 or -2 and see what happens.

The program samples audio for a short time and the computes the energy in the sample (corresponding to volume)

using a Root-Mean-Square (https://adafru.it/Bf5) computation (RMS). You could try varying the sample size if you like.

The log_scale() function varies the number of NeoPixels lit in an exponential way, because sound levels can vary by

many factors of 10 between loud and soft. Try varying how it's computed to see what happens.

The program takes one sample when it first starts to set a "quiet" sound level. If that doesn't work for you, set

input_floor to be a fixed number. If the meter seems too sensitive, try changing input_ceiling = input_floor + 500 to

be input_ceiling = input_floor + 2000 or higher. Or go the other way.

You can also change the colors. Try different ways of computing volume_color(i) for more of a rainbow effect, or make it

a constant if you don't like changing colors.

Note: This program will only work with the improved microphone support in CircuitPython 2.2.0 or later.

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