Yep, that’s the knocker. Invented decades ago and all the machines since then have had that feature.
I’m not sure about NGG specifically but I just checked my World Cup Soccer, and there is no way to disable the knocker in software.
Two options: in the menu, change the replay to Fixed, and then set a really high value that you’ll never reach. You may also be able to change the match feature.
Or, with the power off, clip one of the wires to the knocker, which is a solenoid in the cabinet that fires a plunger right into the wall to produce the sound. Use a wire nut or electrical tape to cover the exposed part of the wire. Say something like “that’s the last we’ll be hearing from you” as you do it. Then give your best maniacal laugh.
Edit: read below for some different advice specific to NGG.