[Elecraft] [K3] APF and Pitch

[Pierfrancesco Caci]

Someone mentioned that APF rings less when pitch tone is set to 440 Hz
instead of 800 Hz. So, I'm trying and it indeed seems to ring less. 
Anyone else hearing this?
Is this some DSP effect or a psychoacustic effect? 

Condition of test: 
200Hz 5-pole filter
DSP BW 50Hz
RF gain backed so that signal is barely audible with no APF
RX Audio EQ bands 4 and 5 set to 0, all rest down -6

Pf

-- 
Pierfrancesco Caci, ik5pvx