To activate a Bankai or its ability, is the user required to perform some verbal command activation?
For example, Ichigo often yells
Bankai: Tensa Zangetsu
However, I'm pretty sure that I've read some silent activations, but I can't remember for sure.
So has a Bankai ever been activated without a vocal command?
Note that this is not a duplicate of Can a mute activate a zanpakutou, as that question asks whether it is possible. And this question asks if a silent activation has ever happened in the series.