The Transducer "is a device that is wired directly into the brain and translates non-vocalized mental impulses into words and vice versa. An external version of this device also exists, creating the same effect when linked between a datajack and a radio.

...This unit can also convert spoken words into text for a display link or other linked device." --pg19 M&M

So, since this lets a user receive the output of radio "mentally" (including, presumably, non-verbal sounds) does that mean it can serve as an entirely "mental," more expensive set of subdermal speakers?

Yep, and it can act as the microphone array as well, all without requiring you to add any detectable vibrations to the air.
My question is, what does someone's voice sound like through a transducer?

~J

My guess would be the same as over normal radio. For something like this to work they'd have to wire it directly into the areas of the brain that deal with oral communication and hearing. So in effect it'd just be bypassing you're ears and the nerves and going straight to the brain.

although over a transducer you would probably sound to others as you sound to yourself...

You know how people think they sound funny when they hear a recording of themselves? What they hear inside their head is different to what everyone else hears. That being the case, what they "think out" through the transducers will be what "listeners" are forced to perceive. Kinda like the Matrix (movie)'s "residual self-image" I guess...

It is also mentionned that 2 users communicating each through a transducer effectively communicate mind-to-mind. Pretty heavy stuff.