Residing on an upper floor can provide a bit more privacy and safety, but also comes with a cost. Recently, my neighbor came knocking to inform me she could hear loud music through the ceiling. Embarrassed, I quickly turned down the volume and began investigating ways to reduce noise from traveling through the floor.
From left to right: Performance, Ultimate, and Premium Carpet Underlay. Another affordable option, 440 Homasote, can be found at Lowe's or Home Depot.
My search landed me on a site specializing in noise isolation solutions. The Sound Isolation Company offers 3 carpet underlay options designed to reduce sound emanating from TVs, stereo systems, and also footsteps (here's a graph illustrating the noise reduction qualities of their 3 models). The prices vary depending on the model and square feet you need to cover, so a phone call is recommended to suit your specific needs.
I also discovered another solution for absorbing noise between apartment floors requiring installation: 440 Homasote is a dense cellulose fiberboard designed to be installed under carpet to
reduce sound transmission (rated for a noise reduction coefficient of 0.20) If you happen to own an upstairs unit or can convince your landlord to split the costs, this material could be an effective long term solution.
Privacy is a two-way street for upstairs and downstairs neighbors, so remember that installing a noise barrier between floors works in both directions. I haven't yet found the right solution within my budget at this time, but you can bet I'm reading the archives for additional ideas like these for acoustic dampening so I don't hear that knock on the door again: