They had a thought. All this time the gravity drives seemed to have their own thoughts, their own personalities. But they never before had been given their own voice. It seemed a shame, really. They couldn't tell when they were upset, hurt, or needed to be fixed, these vital parts of any ship. The parts that most people treated as mere objects and often had lonely existences despite going through the expanses of space. So why not give them a voice? Give them that chance to express themselves? Maybe it should be recommended that all ships with gravity drives get this modification, but would it work? So three ships were given that modification to test it out. Their gravity drives given speakers to speak through, for the first time since their creation they could truly communicate. And one lovely voice began to sing. -- Anon Guest
People only think the Nae'hyn keep the gravity drives voiceless. They have been at this a very long time, both subjectively and by the accepted Standard Calendar. They know when it's advisable to give a machine a voice. The hostile ones, the ones doomed to exist alone and like it that way - those are never given a voice. It is the kind ones who prefer company, the ones who trust new faces to care for them as they care for others.
There are reasons why the voice is not given before the engine has reached a certain age and level of maturity. Attach a voice to a drive that's too young and the entire ship cries. Or it becomes an absolute brat. A crew needs some intense parenting licenses in order to deal with an immature gravy drive if it gets a voice too early. The Nae'hyn have been through all possible journeys. Trust them. They know what they're doing.
Other machines have gained personalities and voices. The Deuteronomy for example. Some other members of the AI alliance have achieved cogniscence care of a Nae'hyn's hand, but the thing most people forget is... Gravy Drives are cusp-cogniscent.