Male ringneck dove cooing

[GuineaGirl]

Hello,
My boyfriend and I are long-time duplex-dwellers and we have a delightful, much-loved male ringneck dove named Boo.
The problem is that Boo coos a LOT and loves to do really loud bow coos (he is absolutely silent at night though). This hasn't been a problem until just recently, because our neighbours downstairs loved Boo as well and actually enjoyed his voice. However, they recently moved out and a new couple moved in. They're employed on shift-work and so they don't look as kindly upon Boo's noise during the daytime.
Is there any way to diminish the frequency of a ringneck's cooing? Putting his cage in a dark room helps, but I can't leave him there for long periods because that really seems cruel. I certainly don't want to torture our neighbours, but our bird is a part of the family and we're willing to try every option before re-homing him, especially as we're hoping to be in our own home within the next year. As an example of how serious we are, we have several large walk-in closets and we're considering putting sound-proofing in one of them to be "Boo's room" during critical daytime hours. Before something so drastic, though, I wanted to see if anyone had any tips that might help.
Thanks very much!!