Product Code:SAE J2934 Title:Laboratory Measurement of Tortuosity and Characteristic Lengths of Acoustical Materials Issuing Committee:Acoustical Materials Committee Scope: This SAE Recommended Practice describes a laboratory test procedure for measuring tortuosity , thermal and viscous characteristic lengths of acoustical materials for automotive and other ground transportation applications. The materials may consists of natural fibers, synthetic fibers or cellular foam materials. This method is based on measurement of acoustical quantities of the materials. Tortuosity , thermal and viscous characteristic lengths of the materials are then derived mathematically from the measured acoustical quantities. Rationale: This SAE Recommended Practice describes a laboratory test procedure for measuring tortuosity , thermal and viscous characteristic lengths of acoustical materials for automotive and other ground transportation applications. The materials may consists of natural fibers, synthetic fibers or cellular foam materials. This method is based on measurement of acoustical quantities of the materials. Tortuosity , thermal and viscous characteristic lengths of the materials are then derived mathematically from the measured acoustical quantities.