# Geiger Counter?

Hi:

I have been using Audacity for general audio editing and recording for several years now, but I need it to do something a bit more specialized and was wondering how this feature might be added…or if Audacity might be tricked into doing it as-is.

I need a cross-platform tool for recording the “counts” from an analogue Geiger counter. The counts come from particles of ionizing radiation penetrating a vacuum tube that is loaded with high voltage. When the particle passes through, it causes the high voltage in the tube to arc momentarily. This gets passed through some circuitry and typically produces two things: a needle on a meter to swing to the relevant reading on a dial, and an audible “click” coming through the speaker or headphones.

Audacity can of course record and chart the “clicks” as abrupt spikes, but what is missing is the counting part of a Geiger counter. An analogue Geiger counter has a circuit that averages the number of clicks over a given interval and sends a signal to the meter so that it will read an approximation of the number of pulses. How could Audacity be used to automatically count and generate a number corresponding to the number of counts recorded over a given interval?

An odd question, I know, but Audacity has solved so many problems for me in the past, why not his one?

Thanks

I can’t think of a way of doing it with the normal tools in Audacity, but you could write a Nyquist plug-in for the job.

Depending on what the clicks are like, you may first need to process the clicks so that they are square pulses of equal amplitude and equal width.
You could then plot the RMS signal level which will increase as the density of clicks increases. This could be reasonably accurate up to the point where the clicks start to overlap.

If you prefer a numerical output, you could read samples sequentially and detect each time the waveform rises over a threshold.

The mathematics for this is going to be fairly complicated.

Nyquist is based on the XLISP programming language. The starting point for Nyquist programming is here http://audacityteam.org/help/nyquist