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Abstract

An optically transparent glazing measures about 3 to 5 mm in total thickness, and has an interlayer film, the interlayer film comprises at least two polymeric film layers: a core film layer having a modulus of at least 25,000 psi (173 MPa) and a surface film layer having a maximum modulus of 15,000 (104 MPa) at 50 to 10,000 Hz and 20.degree. C.; and the glazing is characterized by an acoustical barrier insulating capacity at least equivalent to that of a 3.85 mm thick monolithic pane of glass. The glazing also has an Articulation Index value of less than 64.2% at 50 to 10,000 Hz, a sharpness value of less than 150 at 50 to 10,000 Hz, a penetration resistance of at least 9 meters in test method ECE R43, A6 4.2, and a maximum haze of 4%. The interlayer film has a bending stiffness of at least 0.01 Pa*m.sup.3. The surface film layer has a maximum tan delta of 0.6 at 50 to 10,000 Hz and 20.degree. C. The interlayer film preferably comprises one core film layer of between 1.0 and 1.7 mm in thickness within two surface film layers, each between 0.2 and 0.6 mm in thickness. The glazing preferably comprises a glass/interlayer film glass sandwich having a glass/film thickness ratio from 4.2/0.8 to 1.0/2.8.

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