TrafficMaster 100 sq. ft. 3 ft. x 33.34 ft. x 1/8 in. Acoustical Underlayment with Attached Vapor Barrier for Laminate Flooring QW100N1HD - The Home Depot
QuietWalk Luxury Vinyl Underlayment 360-sq ft Premium 1.4-mm Flooring Underlayment in the Flooring Underlayment department at Lowes.com
Hush: Choosing the right underlay to soundproof floors
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Select Acoustic Underlay – Australian Select Timbers