Polyurethane foams formed under vacuum (below atmospheric pressure) conditions using primarily graft polyether polyols reacted with primarily toluene diisocyanate have lower densities (up to 1.3 lb/ft.sup.3), lower hardness (IFD.sub.25=up to 50 lbs), and exhibit superb thermoformability and fire retardance while retaining good sound insulating characteristics. The foam-forming ingredients are mixed together and foamed under controlled pressures in the range 0.5 to 0.95 bar (absolute). Such foams taken alone, or in combination with a barrier layer to form a laminate, are thermoformed to create a sound insulator for a motor vehicle instrument panel.