The word soundproofing is playable in Words With Friends™, no blanks required. Because it is longer than 7 letters, you would have to play off an existing word or do it in several moves.
Words With Friends™ Letter Score: 25
Highest Scoring Words With Friends™ Play In The Letters soundproofing
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Seven Letter Word Alert: (35 words)
dooring, dousing, droning, funding, fungoid, gonopod, grounds, indoors, infusor, nondrip, nondrug, nonfood, nongods, nonpros, noosing, nursing, odorous, poofing, pouring, pronoun, pruning, pursing, roofing, rousing, snoring, souping, souring, spongin, sporing, sunroof, surfing, undoing, unipods, unspoof, uropods