Acoustic glass partitions - what you need to know
Privacy requirements are becoming increasingly important in the working environment. When the correct acoustic glass partition system is specified and correctly installed, acoustic glass provides privacy and a quiet working environment. There is a lot to consider when installing acoustic office partitions. That's why we've put together this guide which explains what acoustic glass is, how sound and sound reduction is measured, the dangers on flanking transmission and how effective acoustic glass partitions are. We also look at where you may want to consider using acoustic glass partitions, the costs, and what to consider before installation.
What is Acoustic Glass?
Acoustic glass is specifically manufactured to help reduce noise levels (it is sometimes referred to as soundproof glass). An acoustic glass panel has virtually the same appearance and transparency as ordinary glass. However, acoustic glass is different in that it comprises of two or more sheets of glass bonded or laminated together (visible only when viewed from the edge of the panel). You can find out more about other glass types by reading our blog article on float glass, toughened glass and laminated glass. A special interlayer is used between the sheets to form a single laminated glass sheet, this PVB (polyvinyl butyral) interlayer helps reduce the transmission of sound.
Above: Diagram showing the interlayer in an acoustic glass panel and the effect it has on should.
How is sound measured?
Sound energy travels in waves and is created by vibrations that travel through the air or another medium. We hear sound when sound waves reach our ears. Sound has both volume and pitch. But, many factors have an effect on how loud a sound may seem, including how long it lasts, the frequencies (or pitch), the loudness (or volume), the environment in which the sound is heard and persons hearing abilities.
Above: Diagram showing volume and pitch wave lengths
Sound pitch or frequency is the number of vibrations per second; frequency is measured in hertz (Hz). The human ear can pick up sounds with frequencies ranging from 20Hz to 20,000Hz, but it's most sensitive to sounds in the range of 100Hz to 5000Hz.
Volume or loudness (or sound intensity) is measured in decibels (abbreviated dB). The lowest audible sound that the human ear can pick up (near total silence) is 0dB, while a normal conversation is usually measured around 60dB.
The table to the below gives examples of commons sounds with their respective estimated decibel levels:
Type of sound and the decibel level
Watch ticking: 20dB (Faint)
Quite whispering: 30dB (Quite)
Working fridge: 40dB (Quite)
Working dishwasher: 50dB (Moderate)
Normal conversation: 60dB (Moderate)
Street city traffic: 70dB (Loud)
Busy factory: 80dB (Loud)
Diesel truck close-by: 90dB (Very loud)
Loud dog bark: 100dB (Extremely loud)
Car hoot: 110dB (Extremely loud)
Live rock concert: 120dB (Extremely loud)
Jet Engine: 130dB (Unbearable)
Siren: 140dB (Unbearable)
An acoustic double glazed window can reduce exterior noise by up to 40dB - which means with the right window glazing, an interior room can be quiet, even if it's near a city street.
How is sound reduction measured?
In an office environment, sound insulation or reduction is the ability of materials to reduce noise or sounds being transmitted from one room to another. Sound absorption is the ability of the material to absorb sound within a room. So sound insulation affects those in the room next to the sound source. And sound absorption affects those inside a room.
The sound reduction index is the level of sound insulation or reduction provided by a structure such as a glass wall. When sound waves hit the surface of an object, some will be reflected, some will be absorbed, and some will pass through, and be heard on the other side. Sound reduction index is the difference between the sound intensity on one side of a structure or object to the other side of that same structure or object.
Materials are tested in laboratories to determine their sound reduction ratings, shown as Rw dB. However, as ratings measured in a laboratory are usually better than ratings tested on-site once the installation is complete, often due to flanking transmission (explained further in this article), another set of ratings are used. Site ratings are generally shown as DnTw dB.
In essence, when buying or specifying an acoustic product for sound reduction, the Rw rating is used. When checking the sound reduction performance on-site DnTw rating is used.
What is flanking transmission?
Flanking transmission is noise that reaches a room through an indirect path. Sound can leak over the top or under a partition separating two spaces. Thus when considering acoustic glass partition wall, it is essential the surrounding areas are also correctly insulated. Sound can pass through adjoining walls, piping, trunking, ducts, junctions of partitions, ceiling voids, flooring as well as other connecting voids and building components.
It's also important to ensure that not only the glass meets the sound reduction requirements, but all parts of the glazing system (frames, gaskets, etc.) and doors must also achieve the required performance. Equally important, to ensure effect sound reduction glass and partitions must be correctly installed using sound insulation and components such as acoustic mastic on abutments, acoustic foam to tracks and thresholds to doors.
How effective are acoustic glass partitions?
As mentioned above, sound insulation is dependant on many factors. However, when installed correctly and ensuring surrounding areas are also correctly insulated, can reduce noise and increase privacy significantly.
As general guidance, the table below shows the levels at which conversations will be audible and not audible through the use of sound insulation or sound reduction partition, shown in RwdB:
Type of Sound Sound reduction: RwdB
Normal speech: 20 (normal speech is clearly audible
Loud conversation: 30 (conversation is audible)
Loud conversation: 40 (talking is heard, but is not clear)
Shouting 50: (shouting is barely audible)
A single glazed 12mm glass partition can achieve around 30Rw while a double glazed 12mm glass partition with an acoustic laminate can reach around 50Rw. This can increase or decrease depending on the glass system, sound insulation of surrounding areas and other factors.
Are acoustic glass partitions expensive?
Acoustic glass partitions are more expensive than standard glass partitions. This is due to materials requiring additional processes. Acoustic glass, for example, requires two sheets glass, that needs to be cut, toughened, an acoustic interlay and lamination. Installation can also be costly, also due to the time required to perform additional processes and install components such as acoustic mastic, foam to tracks and insulated doors. Double glazed partitioning systems are more expensive than a single glaze, both in terms of materials and installation.
Where should acoustic glass be used?
Acoustic glass has many external and internal applications, both domestically in homes and commercially. External uses include windows, glass doors, skylights, conservatories, glass facades and office fronts.
An internal working environment with comfortable or low levels of noise help employees concentrate, focus and provides a healthy working environment. Certain interior areas and rooms used to discuss confidential matters may also require glass walls with reduced levels of sound transmission to ensure privacy. Acoustic glass may also be required to comply with building regulations.
Installing acoustic glass panels in a double glazed partitioning system will improve sound resistance. Resistance will further improve by increasing the gap between the two glass faces of a double glaze acoustic partition system. As acoustic glass is laminated, there is a reduced risk of people cutting themselves if the glass panel breaks.
What should I consider when specifying acoustic glass?
When specifying acoustic glass and partitions, there are many things to consider, including:
Building regulations and requirements
General wellbeing and comfort
Areas workers will need to focus and concentration
Meeting room privacy and other sound-sensitive office areas
Potentially noisy that will need sound isolation such as canteens and eating areas
Common areas where conversations may occur, including corridors and walkways
Number of doors (doors are often areas of weakness when it comes to sound insulation)
Levels of privacy needed
Your budget or costs
Also, make sure the surrounding areas are sound insulated, remember flanking transmission. As mentioned before, sound can pass through adjoining walls, piping, trunking, ducts, junctions, ceiling voids and flooring.
Glass does not naturally have sound absorption properties, so you may also want to think about how other areas in an office can be changed to increase sound absorption to reduce noise and increase privacy. This can be done in a number of ways, including using thicker carpets, ceiling tiles with good sound absorptions properties and lining walls.
There is a lot to think about when specifying acoustic glass and office partitions. It's impossible to cover all scenarios and all you need to know in one guide, so it's vital that you use an experienced supplier and acoustic glass fitters to ensure your glass installation project achieves the required standards and is within budget.
We at Prism Glass have been in the glass construction and partitioning industry for over ten years. You can see examples of our glass installation projects on our projects page. If you need help with you acoustic glass office partition project or if you need a free no-obligation for a glass, mirror or balustrade install, please write to us today or call 0208 947 8428.
About the author: Paulo Ferreira is a guest writer. He has extensive experience in project management, marketing and design. He worked for Prism Glass for nearly two years, managing glass installation projects and day to day operations.