Thanks, Matt, that's the term I was looking for, and yes, that was also the design. I've just checked, and the JU87 (early model, and not all.) incorporated this device within the generator.
On the model, the 'prop' is a bit overscale.
On the JU88, the 'scream' was naturally generated by airflow, mainly through the 'venitian blind' type, slatted dive brakes under the wings. (more accurately, speed brakes, or spoilers). Although the '88 is very often denegrated as a 'dive bomber', it was, in fact, quite good in that role, although the dive angle used was nowhere near as steep as the '87.
When used in this role, the angle was more of a steep approach, around 45 degrees. There was a red line, painted down the side of the canopy, to assist the pilot in achieving the desired angle. This line was aligned with the horizon (to one side), thereby giving a simple indication of angle of attack. When the bombs were releasd, and the aircraft pulled up, the effect was not unlike what we would now call 'loft bombing', where the ordance is 'tossed' at the target. Must have been successful, as it was JU88's that took out Ventnor radar, and one or two other Chain Home sites, during the BoB.
Overall, the '88 was better as a (relatively) low-level, fast attack bomber, and enjoyed quite a bit of success in this role.
When I find the drawings I'm looking for, I'll post the part showing the '87's 'siren'/generator.
