Here the Reaktor5 macro I created for sending VU meter values via MIDI. I guess, that it can be easily changed for OSC messages.
It basically consists of a rectifier, amplifier, lin/log-converter, slew limiter (to smooth the waveform), sample&hold stage, step filter (events are only forwarded if there is a difference of >= 1) and CC output unit:
8 of these macros are stacked together, and the S&H stages are clocked at 50 Hz to reduce MIDI traffic:
1-8 are the audio inputs, A is the amplification factor, and should be connected to a constant or knob (typically, 100..1000 are good values for the instruments I tested)
Best Regards, Thorsten.