It will not send an actual audio alert to the speaker (except maybe a ding or whatever the device is configured to do when it receives a notification). It just uses "Audio Alert" as a way to send a text based alert to the device. (that said, I do real audio speech notifications as well using an Android device and the LANnouncer device driver that I adapted from the other platform).
I use the Pushbullet driver as a workaround to the limit of 10 SMS per day. I just send all of my notifications to my push bullet devices using the Audio Alert / speak function of the PushBullet device driver. Pushbullet then sends a push notification with text to my phone and other devices that I have configured.
This is basically what the earlier mentioned Pushover notification does as well. I tried Pushover and it was nice, but not free and I already had Pushbullet, so I adapted a driver to work with Hubitat for it.
Anyway, were probably hijacking this topic with discussion solely about Pushbullet. Please PM me or discuss at the custom driver link I posted so we don't hijack this thread.