I don't know if this will help, it might be like comparing apples and oranges, but:
I ran a YS 1.10 powered pattern ship with the short Hatori #725 muffler and my current
YS 1.40 powered pattern ship with the long Hatori #699 muffler and the long muffler is
definitely quieter than the short one. I just changed to an ES Composites muffler in my
new plane as it's quieter than either of the Hatori mufflers although all three of them are
quiet enough for pattern competition.

tommy s