Laminate/hardwood floors - Underpadding types

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
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Pergo used to carry an underlayment they called "Whisper Walk". It's Homosote in disguise and it works quite well to dampen the sound of foot falls on the laminate. It also works quite well to provide extra resilience for the flooring when it's layed on a concrete slab -- as it is in in our home.
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Steve
www.ApacheTrail.com/ww/
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Check out this article (and related ones at the same site):
http://www.fastfloors.com/articles/Underlayment_Types_Uses.asp
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Y.

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Here is a company that i have used in a house for soundproofing it. Goto http://www.acousti-tech.com/en/p3Prod.asp Hope this helps out
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