There are many choices when choosing glass, such as how thick the glass should be. Is laminated glass sound better than a single piece? How wide is the hollow layer? Should it be filled with gas? There is no standard answer to these questions, and the personalized needs of the space should have their own set of selection references.
First, explore the needs. Where is this window used? Bedroom? Balcony? Or outdoors? What is the surrounding environment like? Is it close to the elevated road or inside the community? Is it close to the airport or the high-speed rail station? After confirming it, follow the selection method below to get the glass configuration with the best sound insulation effect.
1. The influence of glass thickness
The sound attenuation of any material depends on its mass, stiffness and damping characteristics. For a single piece of glass, the only effective way to improve the sound insulation performance is to increase its thickness, because stiffness and damping cannot be changed. The sound transmission loss of a piece of glass measured within a frequency range will vary with the thickness of the glass.
Thicker glass tends to isolate more sound, even though it may transmit more sound of certain specific frequencies. Each thickness of the glass has its weak frequency value, and the glass's "sound absorption" ability for this frequency sound is weaker than other frequencies. This value is called the critical frequency. Please see the figure below:
Sound insulation (dB) is measured by different thicknesses of glass in different frequency bands
The original 4mm thick glass is almost transparent to the sound in the high-frequency range of 3500 Hz; the 6mm thick glass has a poor sound insulation effect for frequencies around 2000 Hz; and the 10mm thick glass performs poorly at 1300 Hz. The greater the mass, the smaller the critical frequency at which problems occur. As can be seen from the above chart, 25mm thick glass has no weaknesses.
Therefore, for insulating glass, 6+12A+4mm insulating glass will absorb more sound in the high-frequency range of 2000 Hz (such as a high-pitched whistle or electric horn) than 6+12A+6mm insulating glass, even though the mass of 6+12A+4mm insulating glass is smaller. But for sounds in the 125-250 Hz range (such as traffic noise), 6+12A+6mm insulating glass can achieve more effective sound insulation. For low-frequency sounds, the sound insulation is proportional to the quality of the glass.
2. Laminated glass and single-piece glass
Laminated glass can reduce the transmission of sound better than single glass of the same quality, as shown in the figure:
The original 2+2mm laminated glass can better isolate high-frequency sounds than 4mm thick single-piece glass (can reduce an additional 8 to 10 decibels). Why is this? Because the sound damping provided by polyvinyl butyral eliminates the critical frequency effect (the soft interlayer used to permanently connect the glass dissipates energy through vibration). The same applies to the comparison between 3+3mm laminated glass and 6mm single-piece glass. In contrast, butyral's effect on low-frequency sounds (traffic noise) is not so obvious, but it still has a positive effect on sound insulation.
3. Influence of hollow layer thickness
Surprisingly, the sound insulation of common hollow layer thickness hollow glass units is not much greater than that of single-piece glass. The thickness of the hollow layer does have a significant impact on sound insulation, but it will only be reflected when the hollow layer is increased to a large size.
The influence of hollow layer thickness on the acoustic performance of hollow glass
The sound insulation effect of the original 6+12A+6 mm hollow glass is generally better than that of the 6mm single-piece glass, but the difference is only 2 or 3dB, and the performance of hollow glass in the low-frequency band may be poor. Of course, the sound insulation performance of 6mm single-piece glass will be much worse than that of 12+6A+10mm hollow glass.
The thickness of the hollow layer is important, but increasing the thickness of the hollow layer in a small range has no significant effect on sound insulation. Compared with the hollow glass with a hollow layer thickness of 10mm and the hollow glass with a hollow layer thickness of 20mm, there is no difference in the sound insulation performance of the two.
4. The influence of the gas in the hollow layer
What will happen if argon or krypton is used instead of air? In theory, the higher density of gas between the glass has a positive effect on the sound insulation performance. Comparative tests have shown that argon, which is often used to fill the hollow layer, has almost no additional help for sound insulation. Although there is some improvement at some frequencies, the resonance effect becomes more obvious.
The best sound insulation configuration of glass cannot be generalized. The contribution of glass thickness, hollow layer thickness, filling gas, and interlayer film must be considered comprehensively. Improving only one of them may have little effect. For high-frequency noise and medium- and low-frequency noise, the right medicine must be used. If your home is close to the airport or there is a construction site nearby, and you are affected by sharp noises such as close-range aircraft all day long, you should mainly consider the glass configuration that reduces the impact of high-frequency noise. If you are close to the road and are troubled by traffic noise, you should mainly consider the glass configuration that reduces medium- and low-frequency noise.
