"Greenhouse Effect" is melting the Earth ice core every minute and creating dangerous icebergs. By knowing the exact concentration of CO2(Carbon Dioxide), we can do something to reduce the CO2 and to protect our Earth. Here is the CO2 sensor designed by DFRobot lovely engineer.
This is an Arduino compatible sound level meter(also known as decibel meter, noise meter). It uses instrument circuit and low noise microphone, which enable it to accurately measure the sound level of the surrounding environment. It can be applied to environmental noise testing, such as highway noise monitoring station, bedroom noise monitoring, etc.