Can envelope decay time be calculated based on this circuit diagram excerpts?
A 1 Megohm resistor and 1uf capacitor produce a 1_second time_constant, thus 8.7 db weaker per second.

For 100 Kohm and 0.1uf, the time constant is 100X faster, at 0.01 seconds or 10 milliSeconds.

For 200Kohm and 0.01uf, the time constant is 5X faster, at 0.002 seconds.

For 200Kohm and 0.005uf, the tau (time constant) is 1 millisecond.