A detailed analysis of this circuit is beyond the scope of his paper but there have been several articles written on this circuit, including Demystifying Analog Circuits in Professional Audio ...

1. By using the LM555’s reset pin as the input, the timer can serve as a buffer circuit driven by standard logic levels from 1.8 to 5 V. In the inverting configuration, the trigger line is used ...

One of these areas is interfacing to the sampling networks of analog-to-digital-converters. Today's high-performance A/D converters are based on highly oversampled multi-bit delta-sigma conversion ...