I just had my LBS put a new chain on my road bike. The old one had stretched about a 16th of an inch.
they cut down a 9-speed chain to fit my 8-cog bike. When I rode the bike it worked smoother than before; but, the sound of the chain moving through the drivetrain was very different. It sounded much louder and coarser.

I thought something was wrong. But the wrench took it for a ride and said it was OK. Maybe I'm so tunned into my bike, little things seem like a big deal. Is it common for a new chain to change the sound of the drivetrain?