Fc (cutout freq) = 1/(2* pi* R* C)
15.900 khz for 100 ohm/100nF RC. The resistor and capacitor act like a voltage divider, being low impedance for high frequency signals, taking the least resistance/impedance path and thereby attenuating the signal.
-3DB -> V out is 0,707 * Vin (1/√ 2) but only if the parallel load is high ohm
