This Stone is a Undercover Sound Level Meter
“There’s a lot of noise. But there is only one silence”, Kurt Tucholsky wrote in 1925 in the “Weltbühne”. Every urban dweller will know what he means. And also that noise is quite a subjective thing. Our surrounding is loud. Every neighbourhood is. Noise is one of the underestimated dangers for modern life. You want to find out how loud the disco really is? What volume level does the open-air concert reach? Or how loud is the horn of the trucks? You need a sound level meter! This one could be the stone of the momentum for a discussion about all the noise in the city.
A sound level meter is a basic noise measurement instrument .Many sound level meters only measure noise in one brief moment. The ingredients for this sensor had been lying around for two years. So I developed this mobile, camouflaged sound level meter.
Better think about it one more time before using a hidden sensor. I use an aquarium stone that is used to hide the pump. The stone protects your sensor from vandalism. And makes an optimal waterproof housing.
Ingredients for the Soundstone
- Particle Argon microcontroller (Wifi) or Boron (3G/LTE)
- Powerbank, 10,000 maH
- Sound sensor “Analog Sound Level Meter”, df robotics
- A small piece of acrylic glass, approx. 12 x 25 cm, 3 mm thickness
- 8 nylon spacers M2.5 x 6 mm with matching screws and nuts
- 3 short Dupont calves male to male
- Aquarium stone with pump cavity
- Drill 3 mm
- Fabric adhesive tape
STEP 1: PROGRAM IT
In order for the noise sensor to know what to do, you must program it. That’s quick, because the program is really simple. I assume that you have already installed your Argon. Otherwise check out Particle.io. Open the development environment of Particle (build.particle.io). In the symbol, which resembles a crosshair, you have to select your Argon or Boron. In my case it is a Boron called “Clara Schumann”. Then you have to go to the symbol “<>”. Now you can copy the code into it. A good start will be the example code of the sensor. Then press the flash symbol to transfer the program to the microcontroller.
STEP 2: Attach the Argon
I designed an acrylic glass plate so that it fits well into the aquarium stone. The template is at the bottom. Then I drilled holes after the template to fix the argon and the sound sensor next to each other. (Unfortunately it has holes for not so common M2.5 screws.) With the spacers you can fix it on it now. You can also put it on a plug-in board.
STEP 3: Connect the sound sensor
The Gravity sound sensor measures the sound on the black microphone capsule on the side opposite the plug socket. It is very sensitive. Do not touch it.
STEP 4: Drill microphone holes
Now drill five to six small holes in the aquarium stone so that the sound arrives at the sound sensor. This is best done at the point where the black microphone capsule of the sound sensor is located. It’s best to protect it a little from the rain. You can stick an insect screen or a loudspeaker screen against it from the inside.
STEP 5: Power up
Connect the power bank and stow everything in the stone. From below, you should stick a piece of acrylic glass or bubble wrap with fabric adhesive tape against it so that the sensor does not get damp.
TIP: Write something like “My name is Measuring Stone Bernard. I am not from the intelligence service, but a sensor for a research project”, your name and phone number under the sensor. This helps to avoid any misunderstandings if someone finds your sensor.
STEP 6: Installation
Find a good place for the sensor. It’s really unobtrusive. It should be dry and not too far from the measuring target. And of course it needs signal reception. Maybe you place it under some plants?
Have fun. More instructions (in German) in my blog Journalism of Things.
