Acoustic energy can be transmitted rather easily through the vehicle's windshield compared with other passenger compartment boundaries. At high operating speeds, strong aerodynamic pressure fluctuations around the windshield cause the glass surface to radiate noise to the vehicle's interior. The transmission of structure borne noise generated by structural vibrations of the car body can contribute to the noise transmission of windshields. A standard laminated glass windshield consists of a 'sandwich' of a tough, polyvinyl butyral (PVB) interlayer bonded between two sheets of glass under heat and pressure. This PVB interlayer, which was first introduced for safety reasons, damps vibrations in the glass and produces a significant reduction in road and wind noise. However, standard windshields have two fundamental problems with regard to sound transmission: vibration at resonance frequency region, where glass transmits structure-borne noise, and the coincidence effect, which occurs at a frequency at which the speed of airborne incident acoustical waves match that of the glass bending wave. This manifests in the sound transmission loss frequency characteristics of the windshield, which shows a dip at the coincidence frequency. Increasing the thickness or weight of the windshield does not noticeably reduce the noise transmission. Using a new acoustical grade interlayer, the new Vanceva Quiet acoustical windshield reduces vehicle interior noise by as much as 6 dB, mostly in the audible frequency range. This results in greater passenger comfort and an improved Articulation Index (AI), which characterizes the intelligibility of speech. Additionally, the acoustical interlayer makes it possible to produce thinner windshields for weight savings.
New windshield improves vehicle interior cabin noise and articulation index
Verringerung des Lärmpegels und Verbesserung der Sprachverständlichkeit in Personenkraftwagen durch eine neue Windschutzscheibe
Sound and Vibration ; 37 , 12 ; 6-12
2003
6 Seiten, 4 Bilder
Aufsatz (Zeitschrift)
Englisch
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