Men står det "ping"? (Monty Python reference, in case you were wondering.)
The machine that goes ping? You need a different verb, talking would be better ("standing" is not correct). And the masculine den as it points back to the machine, en maskin, "the machine that...". It wouldn't necessarily be wrong with det but then you are generally waiting for the ping to sound, making the sound itself the cue (versus the entity of "the machine that goes ping").
Men sier den "ping"?