You can get real fancy and install an aux button. A saber I have is rigged with a petit crouton and by holding the aux button down for 3 seconds before igniting the saber, it beeps (letting me know it will be soundless), and I simply hit the activation button and ta-da, silent saber. I imagine you could do something very similar with a US and your obsidian card if you look into it.
There's no aux sound font on the Obsidian, so it won't work that way, (but I love the aux button on the PC). Quick disconnects, or even a small toggle switch (that would be far easier to wire in and use) definitely works though.
I just stuff tightly rolled up paper towel in the pommel and barely a sound is made. Gotta love cheap, easy, and effective!