Arts and Entertainment What is a whisper step? What is a whisper step? Whisper step is a high-density support underlayment for luxury vinyl flooring. It provides a significant reduction in impact noise and can be used over most substrates. Related Posts:What is the flooring that looks like wood but isn t?How thick should underlayment be for vinyl plank flooring?Which direction should hardwood floors be laid in the hallway?A basic guide to t-shirt vinyl and heat transfer film is available on Amazon.