The silence from Soraka actually prevents Tryn from slowing, healing, spinning, or casting his Ultimate.
I've found that the best counter for Tryn is Rammus. I've been playing Rammus lately (about 7 games, and I just bought him last night) and I've had no problems with Tryndamere. Only one game did I have an issue with him, but we were able to shut him down mid-late game due to good taunts, powerballs, silences, and stuns from my teammates. Tryn isn't as big of an issue for me now, unless he is fed early game then he takes some catching up.
The best way to counter Tryndamere is to out-jungle him. Always take two people into the top jungle. Have one person defending lane, take two people up to top jungle and wipe out/ward the buffs. Tryndamere is always powerful because he always has some sort of buff. Control those and silence his ass; no more Tryndamere problem.