Acoustical Ceiling Tiles
How to Design a Quiet Library for Reading and Study
As population centers continue to grow, we have access to fewer quiet spaces in our lives. Peaceful prairies and waterfront properties have been replaced by population centers and industrial zones,which are hardly models for peace and quiet. Libraries are one of the few remaining spaces in densely populated areas where we can quietly read and study. This is why quiet library design is more important than ever.
Libraries are kept quiet through a delicate balance of rules, simple etiquette and acoustical design. They are used as coworking spaces as well as for solitary study. Because keeping everyone silent simply doesn’t always work, acoustically treating these spaces is important. The right treatment will help keep collaborative conversations contained and keep quiet comments from turning into unwanted noise.
Understanding Library Acoustics
Sound waves travel and interact with surfaces in very predictable ways. Sound energy travels in straight lines until it reaches an object, where it is then either reflected or absorbed, or some combination of the two. In a library, especially, the more absorption that we can introduce, the better.
Quiet noises that reflect off of a hard surface do not typically have enough energy to bother other patrons nearby. Considering that a majority of modern building materials are hard, reflective surfaces, most modern libraries are designed deliberately, with specific types and quantities of acoustical panels or absorptive surfaces present in the room. Designing a noise free workspace, or one that has a manageable amount of reflections, allows for better concentration and focus.
When building materials such as wood, concrete and glass make up a significant amount of the surface area in a room, it’s highly probable that the space is too reflective. Sound waves continually bounce around, creating echo and reverberation issues. In spaces with high ceilings, like libraries, these effects are exaggerated. The result is an increase in ambient noise, which reduces speech intelligibility and prompts people to speak more loudly to compensate. By absorbing some of these reflections, you can eliminate acoustical issues and create a more pleasant sounding space.
There is no such thing as too much absorption in spaces like libraries or other rooms where the lower the ambient noise, the better. Most libraries have large rooms with high ceilings as well as an abundance of hard surfaces (desks, chairs, shelves, walls, floors) so over-deadening a library is unlikely. Quiet room design is important for many rooms, but considering the main uses for spaces like this, it is even more so.
Key Acoustic Design Principles for Quiet Study Spaces
Treating a library can be a tricky endeavor since we are usually dealing with airborne noises that are generated in large, fairly open spaces. Because sound travels from a source to a receiver through air, and because there are no physical barriers in large, open rooms, it is very easy for sound to get from point A to point B. Noises created by conversation, walking noises from hard-soled shoes hitting a hard floor, moving furniture, or from rolling book carts all generate airborne noise within a room that has an efficient path to get from the noise source to your ear. Here are the key concepts you need to understand for creating an effective quiet library design.
Sound Absorption: Reducing Echo and Reverberation
Sound absorption is one of the most important principles of managing noise in any space. Since most of our unwanted noise and acoustical issues are compounded by reflections, eliminating a portion of them through the use of absorbent materials delivers both echo and reverberation control.
Professional sound absorption materials for libraries like acoustic panels, ceiling tiles, baffles, and clouds all do a great job of absorbing the types of frequencies generally found in libraries and other similar environments. To determine the absorption characteristic of a product, be sure to research its absorption numbers. The Noise Reduction Coefficient (NRC) of any material will tell you how effective it is at absorbing sound.
NRC values range from 0 to just above 1.0, with decimal values near the low end absorbing a lesser amount of sound, and decimals near the high end absorbing more sound. Due to an anomaly in the testing process, NRC values may fall above 1.0, so don’t be confused if a product has an NRC of 1.15, or higher.
It is important to understand that a product’s NRC value is an average of that material’s absorption properties at 250 Hz, 500 Hz, 1,000 Hz and 2,000 Hz. Just because a certain product has a higher NRC value, that doesn’t mean that it absorbs more sound. It simply means that it has a higher AVERAGE absorption. For instance, if the noise you are trying to absorb is in the 1KHz range, be sure to compare the absorption of that product in a 1” and a 2” thickness, because the values at that frequency might be extremely close.
The best acoustic panels for libraries are ones that look great, absorb a decent amount of sound, and are fairly durable against the occasional bump if they must be installed in areas where they will see contact. Fabric-wrapped panels are a popular option, since they are available in a wide range of sizes, shapes and colors, can be custom printed, and may be mounted to walls or suspended from ceilings to create eye-catching visual art.
Sound Insulation: Blocking External Noise
When the goal is to block external noises from entering a space, we use soundproofing materials. They are designed to either add mass or density to a wall assembly, to seal gaps or cracks in the facade or to decouple a wall assembly. The intent of a decoupled assembly is to reduce or prevent vibrational energy from traveling between one side of the wall and the other. Keep in mind that when a sound travels through the air and hits the outside of a building, some of its sound energy transforms into vibration energy. When the materials used to construct a wall have hard surfaces that touch each other, those surfaces offer an efficient path for the vibration energy to travel from one side of the wall to the other..
STC, or Sound Transmission Class, is a numerical rating that spans from about 20 (very little sound or no reduction) to 65+ (generally considered totally soundproof). STC values measure the ability of a material to reduce sound transmission. Any value over 60 is considered excellent sound insulation, meaning that even speech or loud music will be nearly inaudible. Keep in mind that the lower the frequency, the harder it is to block that noise, and that like NRC values, STC values are also an average.
Most libraries are designed properly and have fairly thick exterior walls, but the windows and doors can sometimes present opportunities for significant sound intrusion from outside. This is because the windows and doors do not have as much mass as the wall assembly, and because of potential gaps and cracks around the perimeter of operable building materials. Below are some simple and effective soundproofing techniques that will help.
Doors
Relative to a well-built exterior wall, some types of doors are too thin to provide an adequate amount of sound reduction. Upgrading to heavier doors will often reduce excess noise in the library.
If sound is still seeping in through the gaps between the door and frame, adding a standard closed-cell foam gasket or weather stipping to the door stop will provide an airtight seal when the door is closed and reduce a significant amount of sound.
If sound is leaking from room-to-room within the space, we suggest using heavy, solid-core doors with one of our adjustable door seal kits added to make an air-tight seal when the door is closed. These kits can also easily be installed on existing doors as a retrofit soundproofing measure.
Windows
Replacement windows can also offer a significant increase to the sound blocked by an exterior wall, but replacing windows is often prohibitively expensive. As an alternative, consider using something like a magnetic window insert to improve the performance of your existing windows.
Window inserts are designed to fit specifically into or onto existing window frames, providing an additional pane and an air gap that work together to improve thermal efficiency and reduce noise transfer. Window inserts also help to maintain the vintage look of windows in historic buildings, making them a preferable option to replacement windows in many cases.
If you can live with an industrial grade aesthetic, quilted soundproof curtains can also be effective at blocking window noise. Soundproof curtains contain a very dense, heavy, noise-blocking vinyl membrane incorporated as the center layer. Because of the noise barrier at the center, they are too rigid to pleat like a fabric curtain, but roller tracks can be supplied to allow for mobility. If you need to block light out, they do that as well. As an added benefit, they work as sound absorbers for interior noise as well, providing an option for treating tricky windows. If an industrial grade blanket doesn’t work for your aesthetic, introducing dense, heavy, velour or stage curtains may be the best way to go. They have a bit more mass and density than traditional window treatments and will operate like a standard curtain.
Strategic Space Planning for Noise Control
For noise that originates inside the library, strategic space planning can help significantly. Using modular acoustic solutions like partitions and free-standing barriers is a simple option that allows for easy space configuration and reconfiguration, but because these partially enclosed spaces share common air with the surrounding areas, they are not the most effective way to contain noise. If the space allows, creating soundproof study spaces or small, purpose-built rooms within larger rooms is always a better way to go.
These small study, huddle or reading rooms will block more sound simply because they eliminate or significantly reduce the amount of common air space shared with the larger area.
If possible, we also suggest locating collaborative spaces in parts of the building that are more likely to have a higher ambient or background noise level. These would be spaces like front door or entry locations, common areas, or those near exterior walls adjacent to noisy roads. Try to keep the quiet study areas far from noisy exterior walls, bathrooms, common areas or building mechanical rooms to keep them as quiet as possible.
Furniture and Fixtures for Noise Reduction
The types of furniture and fixtures in the library can have a significant impact on the sound quality as well. Choosing more absorptive library furniture can help a lot. It effectively introduces multiple sound absorption solutions throughout the room, reducing the amount of sound energy bouncing back and forth in the space. Furniture is not going to be effective as professional sound absorption products, but it will help. Other possible room treatments that can reduce reflections are rugs, wall tapestries and even honeycomb blinds for windows. Any and all soft, porous or plush surfaces introduced into the space will help.
Read More: Soundproofing a Psychologist’s Office [Case Study]
HVAC and Mechanical Noise Control
Noise originating from mechanical, electrical, and plumbing (MEP) systems may seem insignificant, but all of these services contribute to the overall noise level inside of a building. Reducing HVAC noise is an important part of noise reduction in libraries. Utilizing things like internally lined ductwork and in-line duct silencers are always a good idea when a specific space needs to be extremely quiet.
Advanced Acoustic Solutions for Quiet Library Design
There are some additional solutions that are great for maintaining an acceptable noise level in library common areas. If the realities of how people use your library don’t allow for complete quiet, try some of these solutions.
White Noise
Utilizing sound masking technology like white noise machines can help guests concentrate even when there is moderate conversation. Using white noise machines for study areas adds a subtle background noise that helps mask or cover up distracting sounds to make them less noticeable and distracting.
Noise Cancelling Headphones
Some libraries offer noise cancelling headphones for checkout at the front desk. Using headphones that cancel background noises can help us concentrate and also provide the ability to listen to music while studying without disturbing others.
Conclusion
Reducing library noise levels doesn’t have to be incredibly tricky. Through some careful planning and the inclusion of absorptive materials in your quiet library design, you can effectively mitigate noise issues and create quieter study spaces for your community.
Acoustical Surfaces carries a wide variety of professional sound products and an experienced staff to help you get the most out of your acoustic design. Whether you are looking for the best flooring for libraries or are just beginning to learn about study space acoustics, we would love to provide whatever guidance you need.
