Another factor might be the extreme chainlines that result from those wide rear cassettes. There is likely more noise from the chain going into the cog and out the lower jockey wheel in some gear combinations. I'm going to guess that the thin large diameter tubing and rims on some bikes tend to telegraph and amplify the sound as well.
By the way, using the term "freewheel" seems to automatically land you in the geezer set these days.
Steve Barner, Bolton, Vermont
> Date: Sun, 14 Mar 2004 21:00:04 -0600
\r?\n> From: Steve Kurt <kurtsj@mtco.com>
\r?\n> To: Classicrendezvous@bikelist.org
\r?\n> Subject: re [CR]lugged steel noise levels
\r?\n>
\r?\n> From: "Greg Brooks" <gregb51@lycos.com>
\r?\n>
\r?\n> "Is it just me, or are lugged steel bikes quieter than the
\r?\n> carbon,aluminum,& titanium varieties?
\r?\n> .......
\r?\n> During these otherwise pleasant rides, I've been surprised at the
\r?\n> amount of squeaks,ticks,whirrs,creaks, & humming noises coming from
\r?\n> the other bikes. My old Masi & Paramount are virtually silent in
\r?\n> comparison."
\r?\n>
\r?\n> Hi Greg,
\r?\n> You're not the only person to notice this! A buddy commented on how
\r?\n> my classic bikes had drivetrains that were so much quieter than the
\r?\n> rest of the group's. My observation is that the quieter drivetrain
\r?\n> is due to better (and less critical) alignment of the jockey pulley
\r?\n> with the rear cog.
\r?\n>
\r?\n> On the average friction set-up, there's a fair amount of distance from
\r?\n> the jockey pulley to the cog. On indexed systems, the jockey pulley
\r?\n> has to be right up against the cog, and this just seems to invite
\r?\n> noise. The most modern drivetrain I own is a SunTour XC Pro rear
\r?\n> derailleur friction shifting with a Winner freewheel, and it's a lot
\r?\n> tougher to keep it quiet simply because the slightest mis-alignment
\r?\n> will cause noise. Makes it more sensitive when shifting too, which is
\r?\n> not such a good thing.
\r?\n>
\r?\n> There may also be a factor related to the limited use of titanium.
\r?\n> Very few opportunities for the little clicks and squeaks that seem to
\r?\n> plague my friends' titanium parts.
\r?\n>
\r?\n> Steve Kurt
\r?\n> Peoria, IL
\r?\n> (it was much too windy here today to hear *any* noises the bike was
\r?\n> making!)