Acoustic Glass Explained (How Does It Work?)

What Is Acoustic Glass?

Acoustic glass, also known as soundproof glass, or noise reduction glass is specialist glass installed in noise reduction windows that can reduce the amount of noise that is transmitted through the glass and a window (or door).

Acoustic glass is a double glazed unit that includes a pane of laminated glass. The effect of the laminate is to disrupt the soundwaves and to help dampen sound.

To understand how acoustic glass works, first we need to understand how sound travels and can pass through objects such as glass.

How Does Sound Work?

Sound is a vibration created (for example, a loud bang of two objects colliding) at a frequency that travels through molecules of air, water or any other solid object such as a brick wall until it reaches your ear. The vibration resonates on the eardrum, which translates the frequency of the sound so that you can interpret and ‘hear’ the distinct noise.

The vibrations look like waves (hence soundwave) with different frequencies having different lengths of waves. High-pitched sounds have more oscillations looking like a tighter wave and lower-frequency sounds look like a longer wave with less oscillation.

The human ear has the ability to perceive a pitch range of between 20 Hz to 20 kHz. But as it deteriorates with age, the average adult can usually detect up to 15–17 kHz, depending on their hearing ability.

The strength of the transmitted waves is called Amplitude, which reflects the intensity and physical pressure of the sound waves. This is measured in decibels (dB).

Two people speaking at home have a level of about 50 decibels.

The increase of decibels is measured using a logarithmic scale and this means that an increase of 10dB is equal to a ten-fold increase of sound. Basically, each 10dB doubles the perceived loudness of noise – 60dB would sound twice as loud as 50 dB.

Because high-pitched sounds have more oscillations, they are perceived by the eardrum as louder than a lower pitch sound at the same level of Amplitude. This is why noise from children is especially difficult to ignore, compared to an adult speaking. Lower-frequency noises also travel farther. This is why you can hear the deep thud of bass from a nightclub from miles away.

Try putting your ear to a wall when there is sound on the other side and you can hear much more clearly. This illustrates how solid objects absorb the vibration of the sound and then amplify the sound.

It’s important to understand these differences when considering how acoustic glass works and how you can improve your windows.

How Does Acoustic Glass Work?

When sound waves hit glass, the vibration is absorbed by the glass and is transmitted out of the other side. Every time sound travels through a solid object, some of the vibrations are absorbed into the object and reduced as they pass through, but a single thin pane of glass can only absorb a small amount.

Double glazing works because there are two panes of glass absorbing the sound vibrations and the Argon gas between the panes also helps to slow and dampen the transmission of sound waves.

Specialist acoustic glass goes one step further by disrupting the soundwave, which is the most effective way to reduce noise (apart from having a solid structure so thick it can absorb all of the vibrations). Acoustic glass uses two thicknesses of panes and also has a laminate PVB sound dampening core between one of the panes. This combined effect of different surfaces and thicknesses disrupts the energy of the soundwave and reduces noise transference.

Everest does not currently offer noise reduction glass:

• The thickness of the glass
• Asymmetric thicknesses of glass to disrupt the soundwaves
• Argon gas between the panes
• Depth of gap between the panes
• Sound dampening laminate between panes

How Effective Is Acoustic Glass at Reducing Sound?

Glass can only reduce noise so much and it's not possible to 'soundproof' the glass of windows and block all noise transmitting through the glass.

Standard panes of glass have different levels of noise reduction dependent on their thickness:

• 4 mm single pane - 29 dB*
• 12 mm single pane - 34 dB*

*Pilkington technical bulletin.

Using different thicknesses combined with a PVB laminate fused between the glass will make a combined effect on sound reduction:

A window with specialist acoustic laminated glass can reduce noise by:

• A standard double glazed window will reduce noise by up to 33dB**
• A window with acoustic glass will reduce noise by up to 40db**

**Everest independent testing.

Don’t forget, the 10dB difference is relative to halving/doubling the perceived noise level. So, a difference of 7dB is a notable difference in noise reduction.

In the real world, a 40dB reduction of noise means:

• Two people talking outside your window reduces to a whisper
• Heavy road traffic reduces to a quiet library
• Construction noise reduces to background music
• A jet plane taking off from an airport (305 metres) reduces to a restaurant or office.

Acoustic glass will reduce noise, but cannot make a city centre home completely silent. However, they will make a considerable difference to the quality of your life in your home.

Range of Everyday Sounds and Noise Tolerance

Everyone has their own tolerance for noise levels. What is reasonable for one person may be annoying for another. But, some noises are harmful to health over a sustained period and some can cause permanent damage to eardrums.

Data source

Employers in the UK must provide ear protection for employees at 85 decibels and above.

How Do Windows Let Noise into a Home?

Windows usually cover a large surface area in a wall and have three main points of weakness to allow sound leakage into a room:

• The window pane is a large surface area vulnerable to sound transmission which is variable depending on the type of glazing used. Everest offers specialist noise reducing windows that can help to make a big difference.
• The window frame might have trickle vents, more window openers or could have micro gaps in the seals around the glass. This is where a solid frame with limited openers and high-quality seals and construction will make all the difference. Trickle vents are required by building regulations.
• The window installation is critical. Ideally, a frame should fit as snugly as possible in the wall with minimal use of fillers and packers that can create micro gaps. If your specialist noise reduction window isn’t fitted correctly, you won't benefit from the best noise reduction it can achieve.

Noise is personal and everyone has their own level of tolerance. Once you're annoyed by a certain sound, you can become hypersensitive so that even the slightest noise will be an issue.

It is possible to significantly reduce noise intrusion in your home, but you will have to address all the different factors that contribute to this. Your windows are just one part that can help. Read more about how to soundproof your windows and how to soundproof a room.