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Why do Geiger counters make clicking sounds during radiation detection?

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detector output connected to a measuring circuit — radiation measurement Figure 1: (A) A simple equivalent circuit for the development of a voltage pulse at the output of a detector. R represents the resistance and C the capacitance of the circuit; V(t) is the time (t)-dependent voltage produced. (B) A representative current pulse due to the interaction of a single quantum in the detector. The total charge Q is obtained by integrating the area of the current, i(t), over the collection time, t_c. (C) The resulting voltage pulse that is developed across the circuit of (A) for the case of a long circuit time constant. The amplitude (V_max) of the pulse is equal to the charge Q divided by the capacitance C.

Geiger counters produce their characteristic clicking sound because they are designed to detect individual particles of radiation by generating an electrical pulse for each event.12

When a charged particle or photon enters the Geiger-Müller tube, it triggers a "Geiger discharge"—an uncontrolled spread of gas multiplication that creates a large output pulse, often as high as one volt. Because these pulses are so significant, they require very little amplification to be processed.1

Portable Geiger survey meters are frequently equipped with a loudspeaker that converts each of these individual electrical pulses into an audible sound. This audible output serves as a real-time indicator of the radiation detected, which is the origin of the stereotypical clicking sound associated with these devices.13