K2645 - light instead of sound

I think this is the first time K2645 is mentioned on the forum, but I hope I can get some help any way. I posted this under Instrument since the GEIGER-MULLER COUNTER is a kind of an instrument.
Upon bilding this kit I am intressed of getting a LED indicating the signal instead of the sound. I hope to get some suggestions on how to do this. Perhaps an ordinary transistor can be driven by the sound otput and force the LED to lighten up? Perhaps someone has a general sollution uton how to convert a sound signal to light?

An LED with series resistor can be used instead of the buzzer…