If you do want to change your voice in the Series 5 DynaVox devices and Maestro, then go into the blue triangular Menu button and choose Setup and then select the Speech settings. I have discovered that people often don’t realise that if you change the manufacturer you will get a whole new range of voices to pick from. On the DynaVox you have access to a number of different voices from Acapela, AT&T, the Scansoft Australian voices, Microsoft and Verivox. You could also try playing with speech rate as this can give the voice some character too. The instructions to change voices is here: How do I change my speaking voice?
You could also opt to record someone’s voice onto the device. The Dynavox M3 will only record digitised speech. However, the Dynavox Series 5 devices and Maestro are usually used with synthesised speech, so knowing how to record your own voice can be a little trickier to master.
It could be quite tedious to record speech onto lots of buttons, especially if the user has a lot of pages in their pagesets and significant vocabulary that they are using. But here are the instructions for making a digital recording and then programming a button to play that recording.
I’d also recommend this previous great blog post about how synthesised voices come about and listen to some samples.