How exactly do soundproof windows work?

There is a lot of noise in our homes.

These external noises mainly include:

The sound of traffic on the street outside

The sound of the speakers used by the square dancing aunties

(No matter how hard I try, I can't escape this colorful world)

The sounds of dogs barking and people talking outside...

All of the above noises are related to the noise level in the residential area.

And there was the sound of the neighbor cooking next door.

The sound of a couple arguing upstairs

...

These noises all enter your ears through airborne transmission. Most of the noise entering the room from exterior walls and windows is transmitted through the air, so what is the main reason for poor sound insulation in your home?

What's causing the noise at home?

If the thickness of the floor slab has been ruled out as the cause, then the problem must be found in the weakest point of the front wall.

--window

Windows, due to their opening mechanism and the need for sealing, become a bottleneck for overall sound insulation. Ordinary windows use single-layer glass only 3-5mm thick, about 1/30 to 1/50th the thickness of the wall, providing approximately 5-7 decibels of sound insulation. Therefore, the primary consideration for soundproof windows is using suitable soundproof glass. While the glass itself is sufficient to prevent noise from entering the room, the metal window frame, due to its limited thickness and weight, easily resonates with airborne sound, making it difficult to block noise transmission. Furthermore, windows act as almost all the "air leakage points" in a residence; if airtightness is not ensured, gaps will appear between the tracks and the window frame, allowing noise to easily enter the room along with the air.

Several problems with ordinary aluminum alloy windows include: thin glass with poor sound insulation, window frame prone to resonance, and insufficient airtightness. If you don't have high requirements for window lifespan and quality, but are more concerned about price, PVC windows with double (or triple) vacuum glass are also a good choice. Below are four different types of soundproof window measures; which one is suitable for a home environment with high external noise levels?

Four types of soundproof window measures

● Double-glazed soundproof windows:

Sound insulation performance is mainly determined by the actual thickness of the two panes of glass (e.g., for double-glazed windows: 5+9Air+5, the actual thickness of the glass is 10mm) and the distance between the two panes of glass.

All insulated glass structures exhibit standing wave resonance, resulting in a matching effect between sound waves of a certain frequency band and the insulated glass. This means that sound waves of a certain frequency band can easily penetrate the insulated glass. Practical engineering applications have yielded the following empirical data: the sound insulation matching effect frequency band of commonly used insulated glass (5+9A+5, 6+12A+6, 5+6A+5+6A+5), or insulated + laminated glass, is concentrated between 250Hz and 500Hz, while the frequency band of traffic noise that causes discomfort is concentrated between 125Hz and 750Hz.

Conclusion: Insulating glass exhibits a coincidence effect in low-frequency sound insulation during traffic, allowing low-frequency noise (humming) to easily penetrate the glass and enter the room, making it unsuitable for use on main traffic arteries.

●Vacuum glass:

1. Currently, the vacuum glass available on the market consists of two pieces of glass, each 5-10mm thick, with numerous small support points placed between them to support the glass. This ensures that the two pieces of glass will not be crushed or stuck together under pressure of several tons per square meter of atmospheric pressure. Furthermore, current technology cannot create a complete vacuum; there must be enough support points between the two pieces of glass to further extract air.

2. Sound propagation relies on gases, liquids, and solids as mediums. Currently, vacuum glass available on the market has a large number of support points between the glass panes, forming a solid sound transmission structure (sound bridge effect), which greatly reduces the sound insulation. Its sound insulation performance is equivalent to that of single-pane glass with actual glass thickness.

3. Vacuum glass is more difficult to seal between two panes of glass after vacuuming. Affected by weather and air pressure, many vacuum glass panes will leak air after 3 to 5 years, causing the glass to fog up and turn white. Its sound insulation performance is the same as that of double-glazed glass, forming a low-to-mid frequency matching effect similar to that of double-glazed glass.

●Laminated glass soundproof windows:

Sound insulation performance is mainly determined by the actual thickness of the glass, the thickness of the laminated film, and the flexible vibration damping performance of the laminated film;

1. The sound insulation of all materials generally follows the law of mass, that is: the surface density (the product of the material density and the thickness) determines the overall sound insulation.

2. Each sound insulation material has a matching effect in sound insulation performance. The purpose of noise reduction and vibration control is to find that the sound wave frequency of the matching effect is not in the frequency range where noise reduction is needed.

3. The fit effect of laminated glass appears around 3000Hz, which keeps away from low- and mid-frequency traffic noise, making it the most ideal soundproof glass for busy traffic arteries.

4. Sound waves propagate noise by impacting glass, causing it to vibrate. Single-pane glass, insulated glass, vacuum glass, and laminated glass all vibrate when impacted by sound waves, producing sound. The interlayer in laminated glass acts as a damping layer, effectively suppressing glass vibration and thus improving its sound insulation performance.

5. The better the vibration damping performance of the laminated film, the better the overall sound insulation performance of the laminated glass (increasing by 1-3 decibels); especially for the sound insulation performance of mid-to-low frequencies.

● Double-glazed window structure:

1. The distance between the two panes of glass in an insulated glass unit is only 6~24mm. If this distance is increased, the matching frequency band of the insulated glass unit will shift to a lower frequency. When the distance is greater than 80mm, the matching frequency is close to 125Hz. If the distance between the two panes of glass is further increased, the matching frequency will be far away from the low-to-mid frequency band of traffic noise, making it difficult for annoying noise waves to penetrate the glass.

2. Double-glazed window structure: The original windows of a typical building are sliding windows with medium-glazed glass or outward-opening windows. If a sliding window with laminated glass or an inward-opening window is added, and the distance between the two windows is greater than 80mm, a double-glazed soundproof window structure is formed.

3. The sound insulation principle of double-glazed windows: When sound waves hit the first window, the first window vibrates, causing the air between the two windows to vibrate, which in turn causes the second window to vibrate. The greater the distance between the two windows, the greater the energy of the vibrating air that is attenuated by the air spring when the sound waves reach the second window after penetrating the first window.

Conclusion: For buildings located next to busy traffic arteries, the best choice for soundproof doors and windows is:

① Select triple-laminated glass + extra-thick profile + complete sealing; to achieve a measured sound insulation of 30 decibels for a single-pane window;

② Choose to install double-glazed windows, with a regular medium-glazed outer window and a professional laminated glass inner window. The distance between the two windows is greater than 80mm, and the double-glazed window has an air spring sound insulation structure to achieve a measured sound insulation of more than 40 decibels.

Note: Single-pane windows can never surpass the sound insulation performance of double-pane windows, no matter what. The above references mainly provide explanations on glass selection. The overall sound insulation of a window also depends on a combination of factors such as the frame material and sealing. The principle of sound insulation is similar to the barrel principle, where the weakest link determines the quality of sound insulation performance.

In addition to glass, windows also have metal frames, and there are details about the frames that require attention:

What does "broken bridge" mean in the context of a window frame?

The "bridge" in thermally broken aluminum windows refers to the metal bridge that controls heat and sound transmission. As we know, metal is a poor conductor of heat, much like bricks and cement blocks. As mentioned above, because metal is thin, if it's not broken, it can cause resonance, becoming a major "sound leakage point" in the exterior wall. Thermally broken aluminum windows add a layer of hard plastic between two metal frames, effectively breaking this bridge and blocking heat and sound transmission. This hard plastic layer is usually made of PA66, a fire-retardant material. Conversely, if it's not fire-retardant, it poses a significant safety hazard. When choosing thermally broken windows, you can test its properties by burning it with a lighter. Double thermal break windows are easy to understand; they involve adding two layers of hard plastic between three metal frames. This allows heat and sound waves that would normally pass through the first thermal break to be intercepted by the second layer, further enhancing sound insulation and heat insulation.

In conclusion, choosing soundproof windows is a complex and meticulous task. A lack of knowledge or the perceived complexity of reinstallation can deter many from undertaking the project. As the best partner for windows, curtains are essential. If you feel that the soundproofing performance of your windows is insufficient, you can further enhance it with soundproof curtains.

Sound Doctor soundproof curtains: 15 decibels of sound insulation, true sound absorption, ensuring a healthy and "sound-free" life.

Sound Doctor "Soundproof Curtains"

True sound insulation

"15-20"

decibel

Soundproof curtains versus extensive whole-house soundproofing renovations

For most people

It is the simplest soundproofing measure

However, opinions on its actual sound insulation capabilities are always divided.

This makes consumers suspicious.

To dispel such doubts

Soundproof curtains developed by Dr. Sound

In terms of sound insulation

Its performance has proven that it truly lives up to its reputation.

Its sound insulation ability is mainly reflected in sound absorption.

The curtain uses Bayer acoustic cotton as the inner lining for sound absorption.

Bayer's acoustic cotton technology originates from Sound Doctor's independent research and development.

Its sound absorption coefficient is as shown in the figure.

(The higher the coefficient, the better the sound absorption)

Easy to disassemble and clean

Sound Doctor soundproof curtains use

Double-layer curtain design

Inner liner: Filled with Bayer acoustic cotton for sound absorption.

Outer liner: Customizable curtain fabric according to personal preferences

The two are connected as a whole by hooks.

Then hang it in the window

The inner liner should not be cleaned, but the outer liner can be replaced and cleaned at any time.

Sound Doctor Soundproof Curtains

It offers certain guarantees in terms of environmental protection and health.

Our acoustic cotton itself has an E1 environmental protection certificate.

Formaldehyde-free and odorless

To the greatest extent possible, ensure the health of consumers.

Style Selection

Incorporating acoustics

Our curtains must also meet aesthetic standards.

Regardless of whether it's Western style or Chinese style

Dark and sophisticated style that men like

A lady's elegant and gentle style

There will be one you love.

References: "Noise and Vibration Control Handbook", Fissbo soundproof windows