1. A process for processing a scattered light signal to determine the presence of particles in a scanned measurement volume, said method comprising the steps of: applying a scanning light beam onto a measurement volume; detecting scattered light pulses from particles moving through said measurement volume; and processing the detected light pulses, said processing steps including the step of determining the existence of multiple pulse events representative of a scanned particle in a time domain by generating a corresponding particle pulse envelope (PPE) in order to segregate particles moving in the measurement volume from noise.