Absolutely it will impact the sound. Its a whole lot of copper and iron. What do you think many power conditioners are made of. If you purchase a junk transformer, it may sound like junk. It may have very high distortion.
If you get a high quality transformer , it may greatly improve your power. Go to Controlled Power and look around there.
A transformer will do nothing for a unit that was designed for 50 Hertz and your powering it with 60. It may work just fine and see it as extra power. Or it may create issues.
All transformers hum. Your probably going to hear it in your room. A good transformer is around $1,000 for 1 to 2 kVA