Understood but you still have to nail through so are creating a solid
connection which isn't there with laminate? I'm probably completely awry
here! Thanks

No, correct.

Even soundproofing enclosures is very difficult - floors much more so.

o Yes foam under laminate floor will create a reduction in noise
o However far less so if the edges of the laminate touch the walls
---- better to use a flexible sealant and covering wood-profile there

However, there are proper sound-insulatory mats available to go under
both laminate & carpet. They are a thick mass-loaded rubber or a composite
of foam & rubber. Remember mass takes out low-frequency, absorbive
closed-cell-only foam takes out high-frequency. Physical contact thro
any soundproofer short-circuits the sound-proofer benefit out.

Realise soundproofing is slight unless a combination of several methods,
which becomes expensive for most applications. For general sound proofing
laminate over foam over flooring is reasonable. Some would replace the
flooring with fresh T&G interlocking high density boards, if the old boards
are the "usual U warped gap-opening" type re noise & dust kick-back.

Soundproofing is an exercise in physical exersion which can be great at
burning calories, but often depressingly ineffective acoustically :-)

Be clear on what you want to achieve & how important sound insulation is.
Aside, re laminate flooring, remember the surfaces are not indestructible.
o They are easily damaged by older beds with tiny castors
o They conversely are easily cleaned or partly-replaced unlike carpets
---- various make-ups can never be removed from carpet re oil-base

"Warped-U" floorboards should always be replaced if you fit a carpet,
since they can frequently cause rippling in the carpet hessian/base.
That rippling is usually parallel to weave of hessian backing, and so
creates a point ridge that will wear terribly very quickly indeed.

So there is a sound :-) reason for fixing creaking floorboards.
--
Dorothy Bradbury
www.stores.ebay.co.uk/panaflofan