A click is one electrical pulse
Inside a Geiger–Müller tube, a thin wire runs through gas held at low pressure. A voltage between the wire and the tube’s outer wall creates a strong electric field. When radiation knocks an electron loose from a gas atom, that electron accelerates toward the wire and can knock loose more electrons along the way. The resulting brief cascade makes the gas conduct and produces a pulse of electricity.
The instrument’s electronics turn each pulse into a short sound. The click is therefore not the radiation itself making a noise; it is the detector announcing that the tube registered an event.
Why separate events sound like separate clicks
After a pulse, the tube must stop conducting before it can register another event. A gas additive helps quench the discharge, and the detector’s circuit allows the tube to recover. This brief recovery period means that events arriving too close together may not produce distinct clicks.
In ordinary use, a faster stream of clicks generally means the tube is detecting more radiation events per unit of time. But the sound is a count, not a direct measure of how harmful the radiation is: different radiation types and energies are detected with different efficiencies. The familiar clicking is a practical way to make otherwise invisible events audible, one electrical pulse at a time.
