TTSimple

Plays a sound when TTS fires - set volume to 0 in settings and turn off all alerts to 'off' other than 'Say if Targeted'

All this addon does is... play a bell sound when TTS fires.

You need to set volume in TTS to 0, and choose which alert you want the bell to sound on.

Why?

So that you can get an alert when a mob is casting a spell at you - to interrupt it, use a defensive, shadowmeld ... without hearing the TTS voice.

If you want configuration & and a lot more ... I'd recommend https://www.curseforge.com/wow/addons/targetedspells

The TTSimple Team