Why does Patrick Stewart whisper in "Chain of Command Part I"?

[DS9forever]

There is a scene in "Chain of Command Part I" aboard a shuttlecraft where Picard is telling Worf and Crusher about the information on the Cardassians. Throughout the scene, Patrick Stewart whispers, almost as if the Cardassians could be listening. Anybody else notice?

 

[Ro_Laren]

I never noticed him whispering in that scene.

 

[Tosk]

He doesn't whisper. He just speaks quietly and calmly about a serious topic.

 

[Tiberius]

Cardassian sensors could have detected the vibrations in the shuttle's window caused by his voice. By speaking quietly, he was able to make sure that any vibrations caused by his voice were masked by vibrations from the shuttle's fusion reactor.