How To Soundproof A Floor

Soundproofing a Floor

Similar to wall soundproofing the sound traveling through floors is dependent on structure-borne and airborne noise. These two transmission mechanisms should be addressed in tandem to ensure that the maximum amount of noise transfer is attenuated. Unlike walls, flooring is often-times a major contributor for structure-borne noise, due to the constant footfall or impact imparted on the floor from moving objects (unless of course, someone is hammering into the wall.) This is particularly problematic in high-rise condos and apartments, and sometimes even in 2-3 story homes.

First, evaluate the flooring system to determine the primary paths of sound transfer. Once identified, we always address the “low hanging fruit” first – those elements that are fixed in the most cost-effective manner. Finally, determine the amount of sound-blocking you need in the floor, and develop a budget that will allow you to meet those goals. Solutions range from decoupling joists from subfloors, adding soundproofing layers below the top floor, and even using localized isolation pads for loudspeakers and dancing areas.

There are 5 primary layers in any floor, as well as two primary contact points, show in the diagram below,:

Soundproofing Floor Diagram

  1. Floor Supports – The rafters or joists running within a floor to support it from caving in or sagging when a load is applied. These are often 2×4, 2×6, or even 2×8 boards of construction lumber, installed so that their greater dimension is vertical to more effectively combat bending moments.
  2. Substrates – also known as a subfloor, this is the layer installed directly onto the underlying floor supports. It is not the aesthetic layer that you can see when walking into a room, but provides support and additional insulation. The most common substrates are plywood or concrete flooring – with plywood used often in residential or small-commercial applications, and concrete used for large commercial and industrial applications, and grade-level flooring. Other substrates include particle board or chipboard (underlayment grade), vinyl ceramic tile (VCT), cement backer board, or even gypsum and terrazzo (stone & glass composite)
  3. Acoustic Layer – the acoustic layer is sometimes included in flooring, especially when there are sound-blocking or absorption requirements. These may range from cork board and carpet cushions to specialized acoustical sound-blocking materials (including our Floor Blokker). While cork board may be effective at reducing some vibration, acoustic floor underlayments provide sound-blocking for structure-borne and airborne noises.
  4. Top Flooring – the top flooring layer is the aesthetic and functional layer that you see when entering a room. This can range from wood (hardwood, engineered wood, parquet mosaic, or bamboo) to concrete, carpet, or tile.

The performance of any flooring assembly depends on the interaction and makeup of each of these layers, and the contact points between them.

There is a contact point between each layer. With 4 layers, that leaves three primary contact points (we have consolidated the substrate-acoustic underlayment-top flooring below), listed as follows.

  1. Floor Support-Substrate Contact: the substrate is typically screwed directly into the supports, ensuring a structural contact directly between the two layers. This contact allows structure-borne noises to flow directly through the assembly, and may be minimized by using a non-hardening caulk or strips of acoustical underlayment between them.
  2. Substrate-Top Flooring Contact: There is also an opportunity to decouple the connection between the substrate and top flooring layers, via use of non-hardening caulk or thin-set adhesive membranes (when the top floor can be adhered, such as in the case of hardwood flooring or tiles).

Floors have a number of unique performance characteristics from other construction elements, implicit in their function to support weight above them. These include:

  1. Thermal: act as a temperature gradient between the room and underlying space
  2. Moisture: this is critical on the 1st floor or at grade-level. Non-permeable, moisture-resistant materials should be used to ensure moisture does not seep into the living space. The primary difference between the Floor Blokker and other wall and ceiling sound-blocking materials is its moisture-resistant properties.
  3. Acoustics: as mentioned below, flooring not only provides a substantial STC from tenants above and below, but is also responsible for IIC (structure-borne). Unlike walls and ceilings, carpeted flooring can also significantly contribute to absorption in an open space.
  4. Structural Support: As we’ve already discussed, the flooring also needs to support weight from above, evenly and uniformly, without excessive deflection. To reduce creaking below, it’s critical to ensure the floor is level (i.e. less than 3/16” vertical change every 10’). Acoustic underlayment or non-hardening caulk may be used to “shim” the floor to approach this level criteria. Furthermore, plywood and other underlayment should be “scored” or “kerfed” during install, to release tension and prevent warping.

Generally speaking, when looking to improve the sound-blocking capability of a floor, we are looking to improve its ability to block structure-borne noises (shown in its IIC rating) and air-borne noises (shown in its STC rating). Floor are unique in that IIC is more important than most other structural elements. This is due to frequent impact noises they endure, from footfall and support moving objects (unlike most walls and ceilings, that do not receive regular impact). To improve the STC of the floor, we increase the mass of the floor by adding additional, functional layers, and the IIC by decoupling adjacent layers and adding impact-resistant materials.

Approach each layer independently, adding thickness to plywood, gypsum board and concrete wherever possible. Add decoupling between joists and subfloor, and then between the subfloor and top floor. Finally, add a reliable acoustic underlayment that will increase both the IIC and STC of the floor. Acoustic underlayment should be installed under framing (if necessary) on the floor above, and should completely cover the floor so that paths of least resistance do not develop.

A typical IIC for high-rise construction is 50, meaning that the floor reduces structure-borne noise by 50 dB on average. By applying the Floor Blokker, decoupling joists and sub-floors, and using other techniques discussed above, you can achieve and exceed IIC values of 60 or more.

How to Manage Acoustics in a Cubicle

office space acoustics

The majority of offices have adopted the concept of cubicles, which are partially encircled workspaces that are separated from neighboring ones by partitions. Initially, their purpose was to isolate employees from sights and noises of an open workspace. Later, they started promoting interactions among employees. Even though the idea behind this architectural structure sounds great, there are some drawbacks related to it.

These environments are associated with being stressed out, distracted, and deprived of privacy. Above all these, the biggest complaints of an open-space: workers relate to hearing, and to being heard, which also leads to wasting more time. Good office acoustics is a key to better work performance and well-being of the employees in the workplace. According to U.S. General Services Administration “Acoustical comfort is achieved when the workplace provides appropriate acoustical support for interaction, confidentiality, and concentrative work.”

How to achieve desired comfort in a cubicle? There are three major types of changes that your office can implement to improve the environment:

  1. Behavior

Changing the patterns of behavior might be the first step towards better office experience. Identifying the right balance of concentration and interaction among the workers is crucial as well as developing working protocols. You should have special guidelines for all employees: zones to print, voice levels, and spaces for communications or breaks. Introducing technology-based devices for employee interaction can also help to reduce noise levels within the office.

  1. Design

Zoning (layout strategy), planning, and furniture are key elements to consider when thinking about solutions for office acoustics. You need to locate different office “functions” separate from each other. For example, conference room should be far from a copier room. Plan supporting facilities such as coffee bars with consideration to the location of the workstations. Moreover, select furniture that satisfies acoustical standards and helps muffling the noises.

  1. Acoustic Treatment

Two major ideas for improvement are sound absorbing materials on the ceilings, walls, and floors, as well as sound masking systems. Some special methods for noise absorption would be: acoustic ceiling tiles, carpeting, furniture finishes, curtains, and acoustical plasters. The more absorptive material you add to the open space, the quieter the environment will become.

Some of the sound masking solutions include ceiling based applications, desktop systems, or even apps for your smartphone or laptop.

Another tip is to always look at the STC (Sound Transmission Class) of the products, as there are some minimum requirements for office spaces. The minimum level of STC required in normal speech privacy is 40.

If the first step is easiest to implement, then for the acoustic design and treatment solutions you will require some specialist knowledge. Commercial Acoustics is willing to help you solve the problem of open space office environment. Check our sound absorbing products here. We would be also glad to offer you personalized consultation if needed.