You can make the regular Valk a bit quieter and lower pitched by doing the foam mod (stuff pieces of foam or tissue paper or whatever in the corners). Alternatively, swapping in the Valk Power corners also works, but you obviously need to already have both cubes to do that and you might as well just use the Power.In the valk 3 there are air pockets under the squared off ledges of each corner. This does give the cube a more tactile and structured feel, but it also gives the valk 3 a very high pitched sound that I am sure would annoy someone who wasn't into cubing.
The valk power has fully sealed corners, hence ridding that sound.