Do you really think you'd hear the noise from the dynamotors in an airplane cockpit? I have some dynamotors and I'd never hear one running in the cockpit of my 85 HP airplane without holding it in my lap. The tanks used them, too, and had them right there in the compartment.
The transmitter dynamotors were generally more voltage and more amperage but they usually only cranked them up when the pilot hit the transmit button.
One thing I wonder about is that for at least the receivers a vibrator power supply should have been cheaper to build, at least as reliable, and well within the technology capabilities. Yet there does not seem to be any mention of them in general until around the end of the war.