After being entertained by radios and cassette players in his childhood — and especially the VU meter display present on the front of many audio systems — Shawon Shahryiar has decided to design an audio dB meter himself.
His build uses a Seeed Studio Grove Sound Sensor to pick up on sound pressure levels (SPLs), and thus volume, passing along this data to a Microchip PIC18F242 microcontroller for processing.
How the sensor works, along with the math behind how the PIC turns voltage levels into reliable audio readings is explained in the project write-up. Notably here, the sound sensor is able to increase the gain by around 100 times, and processing-wise, the root-mean-square of 16 raw output samples is taken in order to cancel out any unnecessary noise and glitches.
From there, the data is output to an LCD screen with a resolution of 192 x 64 pixels. Three regions within the screen are selected with a trio of chip select (CS) pins, with two regions used for graphics, and the third used to display text.
You can see the meter demonstrated in the video below, first comparing its regions to that of a smartphone, then playing music to see how it reacts graphically. Whether you want to make a device exactly like this or not, it could serve as a great starting point for your own audio experimentation!