How does a seamless acoustic ceiling work?

There are a few different technologies here, but in very general terms, the acoustic ceiling works by converting sound energy into heat. The technology for achieving this varies at different sound frequencies. Few if any sound absorbers are able to absorb sound equally well across the entire audible sound spectrum and it is usually easier to absorb sounds with higher frequencies than with lower frequencies. The best effect is thus achieved by combining different types of absorbents.