Originally Posted by Bike N Brew
Oops, I quoted you on the exact time.
Do you mean 30 seconds with a stone? Seems to me that if shaking were that much more efficient than a stone, HBS's would be selling a lot more carboy shakers and a lot fewer 02 stones...
Found the episode -- 11/2/05 Second Interview with Dave Logsdon of WyeYeast. The conversation begins at about 15:30.
The money quote is around 21:10, Dave: "we found that shaking actually works better than an aquarium pump... we did some studies on it and I think it was only about 4 minutes of good heavy shaking gave us enough dissolved oxygen for a typical gravity beer."
you can download all of the episodes (for free, at least it was for me a few months ago) from the itunes podcast list.