You can channel the power of your bardic music to deafen your foes.
Prerequisites: Bardic music, Perform 9 ranks.
Benefit: As a standard action, you can expend two daily uses of your bardic music ability to deafen a single target for 3 rounds. A successful Will save (using your Perform check result as the DC) negates the effect. The target must be within 30 feet of you and be able to hear you.
Source: Complete Scoundrel, page 81.