Is speech data streaming?

Just got my iphone 4 and downloaded Gospel Library from the App Store. Works fine, but yesterday I noticed a speech button that, when pressed, reads the document (magazine) while it is being displayed. Since the downloaded magazine is only about 1MB, I would like to ask if the speech is being streamed, and therefore costing me money to listen to it.

Not an issue at home (WiFi) but this might cost me big bucks if I were to do it while outside or on the road.

Can someone enlighten me about this? Thanks.

Something you can try is put your phone in "airplane mode" and see if speech still works.

Turned off the cell data connection and there was no speech, so I think it's streaming the data. Whoever designed the App might like to include this in the installation notes. Thanks.