Hi Anthony
Reading this thread with interest. Living in Glasgow I have a particular interest in Clyde and West highland ferries. I've often looked at the various sound systems on offer and they tend not to suit a large ship with variable pitch props or Voith Schneider units. As an example the Gourock to Dunoon ferry 'Jupiter' has two Voith units, one fore and one aft. The units run continuously and even when berthed are nudging the vessel against the berth. When the ship moves away from the berth there is a tonal change in the engine pitch as the weight goes onto the blades and they 'bite'. This tonal change is the only real change in the exhaust sound that can be heard ( along with a cough of darker exhaust fumes! ).
Jupiter's fleet mate the Arran ferry 'Caledonian Isles' has variable pitch props and when berthed the props don't turn. On preparing to leave the berth the engine revs lift as the props engage and maintain a similar exhaust tone until arrival on end of passage. I expect that the power of her engines means there is no discerable change in engine tone to be heard when under way, just the steady increase in revs for around five minutes into the journey. Caley Isles has a distinct exhaust sound, a reasuring soft 'whistle' a quieter version of some old Diesel railway engines.
Is it possible to have a unit which could mimic the exhast sound changes from a constantly running engine? I guess that Voith powered tugs would have the same characteristics, just more powerful sounding.
I have often listened to the ambience of these ships, outside while at sea, exhaust sounds from the funnel, various vents and fans and the distant rumble of the engine room. I have always meant to record the various elements and have a mixed version running on a CD within a model.
Just thought I would add my tuppence worth , interested if anyone has any other views on the V Pitch and Voith sound issue.
I've posted pictures below of the two Calmac ferries mentioned for those not familiar with them, and also my model of Caledonia, a 1:50 scale model of the ex Arran car ferry.
Keep up the good work Anthony, very best wishes as you get your workshop up and runnng.
Regards
Andrew