I have been doing some testing with the new Aweber “Thank You” page to see if it helps convert more double opt in subscribers.
On a niche site of mine I kept my normal “Thanks” page where it provides instructions on how to confirm their opt in as well as graphics showing the process. The 50/50 split test was against Awebers new default thank you page where a professional sounding recording automatically plays and gives verbal directions on how to confirm their opt in.
The results are
My Page: Displays-98 Subscribes-26 Conversion-26.5%
Aweber Page: Displays-184 Subscribers 44 Conversion- 23.9%
While it’s too early to make any conclusions I have made one…
Aweber can’t divide by 2 very well. 
Michael, I’d recommend putting the audio on your already customized thank you page and testing. Something that’s been personalized is almost always going to perform better than a 1 line generic thank you page. The true head to head comparison would be adding audio to your customized thank you page.
We recommend all customers use a customized thank you page, we provide the generic one as a placeholder until they do so.