This is a paid asset, but now you can download 3D Volume Meter and Spectrum Meter Free.
Detail this asset from Unity Store: Original Link
3D Volume Meter and Spectrum Meter v3.0
Display the volume and frequencies of any sound in 3D meters. Super easy setup, drop the prefab, attach audio and ready! You can resize, move, rotate even animate each meter.
Web demo
3D Volume Meter and Spectrum Analysis in real time. Two prefabs ready to use in any scene. Simply drop the prefab where you wish and attach an audio source. The Volume Meter will display the volume level of the sound in real time and the Spetrum Analysis will sow the different frequency levels also in real time. Both prefabs are resizable and animable. It also meters volume and spectrum from the microphone.
You can configure many display options, there are six different leds shapes to choose, two color schemas, you can set the total number of leds in each column, the number of columns in the spectrum analysis and many many options.