What no siren????

Stukas were sporadically using sirens into 1943, depending on the unit. They could by turned on/off by disengaging/engaging a cable operated band brake. There were at least a few pilots/gunners who rather disliked the sirens and who, though their aircraft may have been required (by the CO) to carry one or both of them, may not have actually remembered to release the brake(s) during attacks.