Stasis field glitch
From Halopedia, the Halo wiki
The Stasis Field Glitch is a sound error present in Halo 3's Campaign. The glitch causes the wrong sound to play on specific occasions.
Procedure
In the Halo 3 Campaign level Cortana, after the cutscene where the Master Chief rescues Cortana, melee the pedestal where Cortana was. It should make the 'sizzle' noise that happens when you hit energy shields, but there is no visible stasis field.
Sources