Warning: The L272M is listed as obsolete! For an updated version, please see https://www.pcbway.com/project/shareproject/Loudness_Indicator_Updates_Version_42179be8.html

A simple traffic light indicator that shows green if it is silent and switches to yellow and red if it is loud. The circuit is based on simple analog circuits. No microcontrollers are involved.

The PCB is designed as a double-layer populated only on the front side with through-hole components. It makes building simple, and even beginners can use that project as a soldering exercise.

It is not designed for accurate loudness measurements; therefore, it shall not be used in critical environments or for accurate loudness assessments.

The design and documentation are shared under the CC BY 4.0 license. It comes as-is without warranties of any kind.

The images show a previous revision of the circuit board. The documentation can be found in the attached PDF file.