The real author:

Trofimov Evgeniy Vitalyevich

The indicator displays the market activity. Average line is the aggressiveness percentage (rate of price change). Red is a volatility percentage (corridor value).

The Silence indicator demonstrated one of the variants of normalization of any indicators. I.e. bringing the indicator that changes in an unlimited interval to the form when it starts changing in an limited range. In this case the interval is from 0 and to 100.

This indicator was first implemented in MQL4 and published in Code Base at mql4.com on 06.02.2009. 

Fig.1 The Silence indicator