Sound Transmission Loss.

The following graph show the difference between a bare steel panel and the panel with dBk30 adhered to it.

Note the transmission loss is constant from low frequencies (65 is similar to the lowest note on a cello) all the way up to high frequencies. (the highest note on a piano is just over 4000)

Decay of Panel Excitement.

This graph essentially is showing the deadening effect of the steelpanel to vibration, the top graph shows the bare steel.