Acoustic ceiling tiles are panels that are attached directly to a ceiling or placed into a supportive drop ceiling grid assembly. These types of ceilings are commonly found in commercial office spaces and less commonly in residential construction. They are easy to install, cost-effective, and offer thermal and acoustical properties. The panels come in a wide range of colors, textures, shapes, and patterns.
Acoustic ceiling tiles do absorb sound better than other types of materials, such as thin sheetrock, concrete, plywood, or other wood products. However, there are other acoustical treatments that can offer more sound absorption if you need better acoustics in your space.
Let’s take a look at how acoustic ceiling tiles work, why they absorb sound, as well as other types of acoustical treatments that are available.
Basics of Acoustic Ceiling Tiles
Acoustical ceiling tiles are commonly manufactured from high-density fiberglass boards. Some manufacturers use polyester or acoustical foam while others even apply PVC coatings to their tiles so that the tiles can be installed in high moisture areas. Because there are so many options for acoustic ceiling tiles, they are a popular choice for flexibility in design and future changes.
Acoustic ceiling tiles do absorb some sound, but how well it does depends on its material. The material of the panel affects its ability to absorb sound to keep it from bouncing back to other people in the space, or from being transmitted to the space on the other side of the panel.
Some panels even have shapes or textures that can increase the amount of sound that can be absorbed. Ceiling tiles that absorb the most sound will have special cores, composed of fiberglass, cotton fibers, or other materials, that are then sandwiched or wrapped with a decorative material.
Characteristics that Affect Sound Absorption
When reviewing different types of ceiling tiles, a rating called the “NRC” rating may be provided to indicate how well the tile performs acoustically. NRC stands for Noise Reduction Coefficient.
Tiles with higher NRC ratings will absorb more sound and therefore reduce more noise than tiles with lower ratings. The average ceiling tile will have an NRC rating of 0.55. A material must have an NRC rating over 0.40 before it can be called a true sound absorber.
How the panels are installed can also impact the overall performance of the ceiling. To install an acoustic drop ceiling, an angle support will be secured around the perimeter of the room. This angle will later support the perimeter edges of the tiles. The rest of the ceiling grid is then suspended from wires that hang from the structural elements above, such as joists or floor slabs.
The material of the grid usually absorbs less sound than the tile. Thicker grids between tiles may allow additional sound to transmit through or bounce back into the space. Thin grids allow the tiles to be placed closer together, therefore improving the overall sound quality of the space.
Once the grid is installed, the ceiling panels can be laid into each square or rectangle in the grid. To accommodate light fixtures, fire sprinklers, speakers, or other ceiling elements, the contractor will cut holes in the middle of the tiles with the correct dimensions of the device. These holes in the tile are also sources of sound transmission or reflection.
To prevent sound from penetrating through these sources, any gaps between the fixture and the ceiling can be packed or lined with a sealant or sound-absorbing material, or acoustical insulation wrapped around the device.
How Sound Absorption Works
To better understand how acoustic ceiling panels absorb sound, you need to know how sound is transmitted and how it can be absorbed. Acoustical consultant ABD indicates that when a sound wave travels through space and hits a material, the sound wave will do one of three things: be absorbed by the material, transmit through the material, or bounce back from the material.
Porous materials absorb sound better than non-porous materials. Many will describe porous, sound-absorbing materials as soft, but describe surfaces that bounce sound back as hard. Lightweight or very porous materials will allow sound to be transmitted through them, like thin walls, fabrics, or meshes and screens.
When sound hits a surface, some of its energy is converted to heat as the sound is absorbed. Therefore, the next time the sound hits another material, the sound wave will have less energy, causing the sound to fade over time. The amount of time it takes for the sound to fade is called reverberation. A room that has a lot of reverberation will sound more lively.
Acoustic ceiling types typically absorb sound well due to their composition of materials. Even though the panels are usually under an inch thick, the fiberglass board has many air pockets that traps sound waves, preventing them from being transmitted or bounced back into the occupied space.
Thin, hard acoustic ceiling panels will have fairly low sound absorption properties. If you are concerned about sound being transmitted out of a space, or your space will have high reverberation or echoes, consider better-performing panels. Higher sound-absorbing panels will be thicker, have a deeper texture, or have special cores, such as foam.
While acoustic ceiling tiles are a cost-effective way to absorb some sound throughout large spaces, they do not perform as well for spaces with specific acoustic needs, such as theaters, recording studios, or areas with privacy concerns. Here are a few ways to improve sound absorption in a space:
Acoustical Batt Insulation
Acoustical insulation looks and acts much like normal batt insulation used to insulate walls. This fiberglass material has a low density and is normally several inches thick. This insulation can be laid on top of an acoustic ceiling to help improve the overall sound quality in the space.
Another option includes adding this insulation to the walls in-between spaces to prevent sound from being transmitted through the walls as well. Some batt insulations may have an NRC of 0.95-1.00.
Acoustical Foam or Pads
Acoustical forms or pads can be hung from ceilings or walls, on top of the finished surfaces. Some acoustical foams may look like an egg crate mattress pad, but this material has high sound-absorbing properties.
However, versions of these products may have an attractive surface that provides sound-absorbing properties without compromising the appearance of the space. Some foams may have an NRC rating of 0.95-1.00 or even exceed 1.00.
Where the aesthetic of a space is paramount, baffles can help absorb sound or strategically deflect sound into other spaces. These baffles are typically hung at an angle compared to the space, or staggered in height. As the sound bounces from material to material, the wave loses energy until it is finally absorbed.
A trick that utilizes psychology rather than combating the physical characteristics of sound waves, sound masking works by covering up sounds rather than absorbing them.
When people hear a constant or consistent sound, their brains become accustomed to it and filter the sound out. Other sounds that are around the same dynamic range become mostly imperceptible, and other sounds that are outside the range become less distracting and disruptive.