[Wolf] sent in this site a while back, and I thought that this frequency meter how-to looked pretty useful. It’s based on an Atmel AT89C52 and a gutted multi-meter. The circuit isn’t too bad.

[mircemk] had previously built a frequency counter using an Arduino, with a useful range up to 6 MHz. Now, they’ve implemented a new design on a far more powerful STM32 chip that boosts the ...

Such measurements are designated dBA (see NOISE LEVEL). The sound level meter, however, does not take into account the predominant frequency region of the noise, or other factors which may cause ...