Sound acoustic performance required for roof glass

The popularity of electric vehicles, EVs, is growing due to how high-tech and savvy these vehicles are and how much they save energy and protect the planet. In addition, EVs are equipped with panoramic roof glass, which has a larger glass area. As EVs have batteries under the seats, the seats are positioned higher than in engine vehicles, and the tendency is to remove the sunshades to provide headroom for passengers.

Larger roof glass and the removal of sunshades allow more sunlight to enter the vehicle and create an open space. On the other hand, the roof glass is required to have sound acoustic function due to the increase in external noise coming in through the glass.

SEKISUI S-LEC has verified the need for sound acoustic performance in roof glass and the effectiveness of S-LEC™ Sound Acoustic Film through actual vehicle tests.

Driving tests with sunroof open and closed

Does the roof glass need to have sound insulation performance?

As an approach to this question, we conducted a driving test using a model equipped with a sunshade.

We installed a dummy head in the front passenger seat. We measured the sound pressure by driving a fixed distance at 140 km/h with the sunshade open and closed, respectively. A sound pressure difference of up to 4dB was found when the sunshade was open compared to when it was closed. This result proofs opening or removing the sunshade allows more noise to enter the vehicle.

With the increasing popularity of vehicles with panoramic roof glass, there is a need for higher sound acoustic in roof glass.

Wind tunnel test

Using an SUV EV with approximately 2 square meters of roof glass, we had a 140 km/hr wind tunnel test on the same vehicle with a standard laminated roof glass and a sound acoustic roof glass with S-LEC™ Sound Acoustic Film.

We installed dummy heads at four front and rear seat locations and measured sound pressure at the ear positions. The result shows an improvement of up to 3.2dB, particularly significant at ear positions closer to the car’s center. In addition, a significant improvement was also observed in the rear seats as well as in the front seats. When sound pressure is converted into Articulation Index, it’s equivalent to 3.7%, contributing to an improvement in the overall quietness of the car interior.

These results prove roof glass with S-LEC™ Sound Acoustic Film significantly improves the interior’s comfort.

Rain drop test

We carried out laboratory tests with standard laminated glass and acoustic laminated glass with S-LEC™ Sound Acoustic Film to evaluate the effect on rain noise.

A microphone was placed 35cm from the glass, assuming a distance from the roof glass to the ear. We measured sound pressures for each type of laminated glass under a 40mm/h rainfall drop. As a result, we confirmed the acoustic glass improved sound acoustic performance by up to 5.9dB compared to the standard glass.

The result shows laminated glass using S-LEC™ Sound Acoustic Film is highly effective in sound acoustic against rain noise and contributes to a quieter cabin.

Proven sound acoustic performance

From these vehicle and laboratory tests, SEKISUI S-LEC has confirmed the need for a sound acoustic performance in roof glass and the effectiveness of S-LEC™ Sound Acoustic Film.

For more information on evaluation methods and results or any questions about S-LEC™ Sound Acoustic Film, please do not hesitate to contact us.

Solutions for panoramic roof glass

SEKISUI S-LEC’s PVB interlayer laminated glass, S-LEC™ Film, provides a wide range of solutions to needs for panoramic roof glass, not limited to sound acoustic functions.

Adjusting the transmittance provides both a feeling of openness and sunlight control. It also contributes to the safety of the roof glass by preventing its shattering in the case of glass breakage. S-LEC™ Film cuts more than 99% of UV rays, protecting passengers’ skin in vehicles without sunshades. It can be combined with solar control performance, effectively cutting infrared rays as a heat source, providing additional comfort.

You can download more information on the wide range of lineups and technical data here.