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Make it: code it / Sound meter

Activity

Sound meter

Beginner | MakeCode, Python | LED display, Microphone | Data handling, Input/output

Step 1: Make it

What is it?

Measure how noisy it is around you using the new micro:bit's microphone sensor and a simple bar chart display.

Introduction

Coding guide

What you'll learn

  • How to use the new micro:bit's built-in microphone input sensor to measure how loud sounds are around you
  • How to display numerical data from input sensors graphically on the LED display output

How it works

  • The new micro:bit's microphone measures sound levels in numbers between 0 and 255. 0 is the quietest and 255 is the loudest sound measurement it can make.
  • The code uses a forever loop to keep the microphone measuring sound levels and plotting a bar graph on the LED display.
  • The louder the sounds measured, the higher the bar graph gets.

What you need

  • new micro:bit with sound (or MakeCode simulator)
  • MakeCode or Python editor
  • battery pack (optional)

Step 2: Code it

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1from microbit import *
2
3# function to map any range of numbers to another range
4def map(value, fromMin, fromMax, toMin, toMax):
5    fromRange = fromMax - fromMin
6    toRange = toMax - toMin
7    valueScaled = float(value - fromMin) / float(fromRange)
8    return toMin + (valueScaled * toRange)
9
10# set of images for simple bar chart
11graph5 = Image("99999:"
12               "99999:"
13               "99999:"
14               "99999:"
15               "99999")
16
17graph4 = Image("00000:"
18               "99999:"
19               "99999:"
20               "99999:"
21               "99999")
22
23graph3 = Image("00000:"
24               "00000:"
25               "99999:"
26               "99999:"
27               "99999")
28
29graph2 = Image("00000:"
30               "00000:"
31               "00000:"
32               "99999:"
33               "99999")
34
35graph1 = Image("00000:"
36               "00000:"
37               "00000:"
38               "00000:"
39               "99999")
40               
41graph0 = Image("00000:"
42               "00000:"
43               "00000:"
44               "00000:"
45               "00000")
46
47allGraphs = [graph0, graph1, graph2, graph3, graph4, graph5]
48               
49# ignore first sound level reading
50soundLevel = microphone.sound_level()
51sleep(200)
52
53while True:
54    # map sound levels from range 0-255 to range 0-5 for choosing graph image
55    soundLevel = int(map(microphone.sound_level(), 0, 255, 0, 5))
56    display.show(allGraphs[soundLevel])
57
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Step 3: Improve it

  • Create your own ways of displaying how loud a sound is, for example showing different emojis depending on how loud it is
  • Make a visual noise alarm that only flashes when the sound goes over a certain level - you could use this to help keep your classroom peaceful

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This content is published under a Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0) licence.