There's a friendly debate going on in our condominium about the
soundproofing effectiveness of underpadding for laminate and/or
hardwood floors applied on top of existing concrete-over-plywood
subfloors.

Can anyone provide information on the following assertions?

1. Underpaddings of any type prevent the new floor from squeaking, but
are of little value in dampening air-borne and structural sound
transmission.

2. When first installed, heavier underpaddings dampen sound better
than lighter ones. However, they compress over time, and end up being
no better than the lighter/cheaper underpaddings.

3. Heavier underpaddings are promoted by laminate/hardwood floor
sellers because they're more profitable, not because they offer
superior sound-dampening performance over the long term.

Any other information on underpaddings would also be appreciated.

Thanks in advance,
Darro