Sound Insulation Performance of Vacuum Glass

The sound insulation performance of vacuum glass refers to its ability, when used as part of a building envelope, to reduce the transmission of airborne sound. Its key technical feature is a vacuum layer maintained at a pressure of ≤0.1 Pa between two glass panes. By replacing the conventional air-filled cavity of insulating glass with a vacuum medium, vacuum glass changes the way sound is transmitted through the glazing structure.

Urban environmental noise, particularly road traffic noise and equipment noise, is primarily concentrated in the low- and mid-frequency ranges, typically below 500 Hz. This frequency range can be a challenging part of the acoustic performance of conventional insulating glass. Vacuum glass therefore represents an important technological approach to improving acoustic performance in building applications.

Q1: Why Is Vacuum Glass Better at Blocking Low-Frequency Noise?

A: The low-frequency sound insulation advantage of vacuum glass comes from its structural design, rather than simply from glass thickness. By maintaining a vacuum layer at a pressure of ≤0.1 Pa between two glass panes, vacuum glass removes the air that acts as an “air spring” in a conventional insulating glass unit.

With virtually no air medium in the cavity, sound transmission and cavity resonance are significantly reduced, helping improve sound insulation performance in the low-frequency range.

According to acoustic test reports, within the 200–500 Hz frequency range, a range relevant to traffic noise, the tested sound reduction values of vacuum glass increased steadily from 30.2 dB to 37.7 dB. The sound insulation curve remained relatively stable, without the pronounced low-frequency dip typically associated with conventional insulating glass.

Q2: Does More Glass or Greater Glass Thickness Always Mean Better Sound Insulation?

A: Not necessarily. The sound insulation performance of glazing depends on how its acoustic characteristics correspond to the frequency spectrum of the noise, rather than simply on the number or thickness of glass layers.

Increasing glass thickness or adding more panes primarily increases the mass of the glazing, but does not necessarily change the fundamental sound transmission path. Vacuum glass uses a vacuum layer to reduce sound transmission through the cavity, enabling high sound insulation performance within a relatively slim glazing profile.

Therefore, the acoustic performance of a glazing system should not be judged solely by specifications such as the number of panes or cavities. When evaluating sound insulation, it is important to refer to the acoustic test report, particularly the Rw (weighted sound reduction index) and the associated spectrum adaptation terms (C; Ctr), which provide additional information about performance across different noise frequency ranges.

Q3: How Much Better Is Vacuum Glass at Sound Insulation Than Insulating Glass?

A: In a comparative test conducted in an architectural acoustics laboratory, 5 + 0.3V + 5 titanium vacuum glass, with a total thickness of 10.3 mm, was compared with 5 + 12A + 5 + 12A + 5 triple insulating glass, with a total thickness of 39 mm.

At 200 Hz, the tested vacuum glass achieved a sound reduction value 15 dB higher than the tested triple insulating glass configuration. Across the low-frequency range below 500 Hz, the vacuum glass also demonstrated higher sound insulation performance than the tested triple-glazing configuration.

This comparison demonstrates that acoustic performance is not determined simply by the number of glass panes or the overall thickness of the glazing. The vacuum structure can provide an effective approach to improving low-frequency sound insulation while maintaining a much slimmer glazing profile.