From one of many sites extolling the virtues of "acoustic" glass in cars:
Noise Reduction
"A significant purpose of an acoustic windshield is to improve a vehicle’s acoustics, hence the name. The PVB membrane between layers of windshield glass absorbs sound waves from the outside world, reducing the amount of sound that enters a car. For this reason, acoustic glass is also used in many buildings, such as schools and hospitals, where quiet environments are necessary. The Federal Highway Administration estimates that highway traffic noise is around 70 – 80 decibels loud, which can cause ear damage over a prolonged period. Noise reduction is a vital feature of acoustic windshields, making car rides safer and more pleasant for passengers and drivers. However, the effectiveness of this feature is dependent on the glass’ thickness."
- Dependent on the thickness, hummmmm...
Crash Safety
"In mitigating noise, windshields reduce the pervasiveness of distracting sounds from the road, such as horns, collisions, and general disturbances. According to the Rhode Island Division of Motor Vehicles, auditory distractions are “any noise that takes away our attention from driving” that, when combined with other factors, can increase the likelihood of car accidents. Reducing distractions keeps drivers more focused on the road, improving road safety."
- Yeah, all those "exterior" distractions that keep the typical American driver from focusing on the road. I can think of more than a few "interior" distractions keeping drivers less focused on the road, that if reduced or eliminated would certainly go further in reducing accidents.
Of course, this B.S. is from sites trying to sell you on the concept. Haven't seen one yet, who will state "our replacement glass will shrug off road gravel like invisible armor."
My money is still on cheap, thin, light weight, barely meeting spec windshields. I'll be replacing this OEM one next month, so will see if an aftermarket is any thicker and or noisier.