Did you do this work yourself?What type of floor was installed, EXACTLY?Do you know if the flooring was glued to EACH OTHER?What room(s) is the flooring installed in?
The 'hollow' sound is usually due to either a 'light' underlayment/subfloor or a loosely attached floor. What layer(s) of subfloor/underlayment do you have on the joists?
Glue-down floors will, by nature, have a different look, sound, and feel than a 3/4" hardwood floor anyway. Post up some info and we'll go from there.
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