Pickering XV 15 Cartridge question...re: Installing

I just installed the above cartridge on my Technics SL 1600 turntable.
Sounds great...But...when I tap the tonearm and headshell with volume up , 
sound feedback ( not hum ) comes through the speakers.
Why do you think this is occuring?  Is this normal ?
Thanks !
Rocky which stylus do you have on your Pickering?
Which numbers witten on the stylus plastic holder, just curious?

Do you have the manual to understand how the tracking force must be adjusted for use with Brush and Without Brush ?

As for the problem you have described i believe dead quiet plinth and well damped tonearm is not about Technics 1600.

If all of your cartridge pins are connected very well to the headshell wires, if the ground wire is connected and if you don’t have a hum or any problems when you play music (not knocking on the arm and table by hands) then it should be OK.