Randy Waldeck, Principal of Acoustics, and Indi Savitala, Director of Acoustics attended the 2019 National Conference on Noise Control Engineering (Noise-Con 2019). The event was co-hosted by the Institute of Noise Control Engineering USA and the Transportation Research Board Committee on Transportation-Related Noise and Vibration in San Diego, CA. Randy presented a paper about aviation noise and Indi presented a paper on high-impact fitness centers. Learn more about the conference here: https://noisecon19.inceusa.org/.
Kickboxing studios in multi-family housing, commercial buildings, and mixed-use developments are creating noise problems for tenants, owners, and developers. The low frequency vibration created from kicking a free-standing bag propagates through structural connections and can be felt in adjacent dwelling units.
Kickboxing classes include a warmup period (light jogging and stretching), punching period (jabs, crosses, hooks, and uppercuts), kicking period (front kick, side kick, and roundhouse kick), combination punching and kicking period, partner training, and cool down period. During a typical 50-minute class, there will be about 10 minutes that involves kicking the bag. The greatest amount of vibration is felt during this 10-minute period.
The installation of a vibration isolation flooring solution (commonly called a “floating floor”) can reduce enough low frequency vibration so that it is not disturbing to adjacent dwelling units. This type of solution goes beyond the standard gym mats that all owners are required to provide. A proper vibration isolated flooring solution should include a product that is at least 2 inches thick with one or two layers of plywood or cement board on top (to assist with compressing the product). Owners should explore products that have been laboratory tested and include Impact Isolation Class (IIC) ratings along with one-third octave band frequency data.
There are a lot of products on the market and they are not all the same. Material composition, density, and thickness are just a few factors that can affect product performance. Additionally, each product reacts differently to the floor structure vibration, so reviewing the laboratory test results is extremely important. Key aspects that acoustical consultants review include: IIC, Delta IIC, one-third octave band transmission loss, and the natural frequency response.
To assess the efficacy of a product, the structural engineer should confirm the frequency response of the structure (known as the resonant frequency). If this cannot be determined, an acoustical consultant can conduct in-field vibration measurements. Once the resonant frequency has been determined, an acoustical consultant will compare the frequency response of the structure and isolated flooring product. Both products should not resonant at the same frequency. The idea is that placing the product on top of the structure will create a dissimilar resonance that will allow for greater damping.
Lastly, the intersection of an isolated flooring solution and surrounding walls is another area where vibration can travel through the structure. An acoustical consultant can evaluate the project details and provide comments on ways to support the construction and retain the isolation.
The installation of a proper vibration isolated flooring solution is a must for kickboxing studios and residences/tenants to coincide harmoniously.