nuvi 2797 LMT direction voice

I expect you're using Michelle, one of the probable two English language voices that came with your 2797. Switching to Samantha will return street names and more.

If you add the extra English language voices with Garmin Express or the myGarmine website, you'll have a choice of seven voices that speak street names. When choosing a voice, look for "Speaks Garmin Real Directions."

http://www.poi-factory.com/node/42708

With other GPSs?

As far as I know, Garmin "on the road" GPS units use three voice engines and voices for each are incompatible with the other two. See:

http://www.poi-factory.com/node/42708

Note that for the newer nuvis that have less than the full complement of English language voices, WebUpdater will not offer the new voices. You will need to use the myGarmin website or Garmin Express to install all available English voices to your unit. Once installed, WebUpdater will offer updates to any of the voices that are offered. Your 3590 and 3790 should be able to use all the TTS3 and some non-TTs voices, your 855 uses the TTS (and some non-TTS) voices, and I'm not sure which voices your 2595 can accept—but myGarmin and Garmin Express will know and offer you whatever will work for your devices.

thanks to everyone, i was able to download all the English voices [my favorite is Samantha] easy to understand, i used to like Jack, but he sounds more like a synthesized robot
i did the update as follows:
Garmin express
device
optional updates
English
add to update

Good to hear you got the additional voices. You may now want to go into the voice folder and delete those voices you don't need since those TTS3 voices are quite large and take up internal memory.
You now have the option to use Webupdater to upgrade the voices you do like without downloading the whole English package.