[Camilo] built a spectrum analyzer to use with his audio system (translate). The hardware is quite simple, using an op-amp, microcontroller and LCD display. He chose an LMV324M low-voltage op-amp ...

[Ryan] wanted a spectrum ... the analyzer’s output will exactly follow the input signal. In “energy filler” (AKA peak detect) mode, the output will display the signal peaks, with a slow ...

because it can display the signals over a range of frequencies. For example, whereas an oscilloscope would show total noise level, a spectrum analyzer would show the noise as related to frequency.