The Challenge
Bash Boxing is a fitness center that uses a unique water-filled heavy bag in a fitness class setting to provide a physical workout to it clients. Classes range from 10 to 18 users. Instructors use a headset microphone for verbal instructions while high levels of background music are played. Noise levels constantly exceed 100 dBA during a 45-minute session. The heavy bags are suspended from the ceiling overhead.
Knowing that noise may be an issue for its neighbors, Bash Boxing came to Phoenix Noise & Vibration during the planning stages of its new fitness center in Arlington, Virginia. The retail location in Arlington was surrounding on all sides by office and other retail uses. They knew they were loud but didn’t know they produced vibration too!
Our Solution
After reviewing the plans, Phoenix Noise & Vibration engineers knew that the sound of the class instructor and associated music would be a challenge but also determined that the planned heavy bags, suspended from overhead, would potentially transmit structure borne noise to legal office spaces above the studio. Additionally, vibration from footfalls and other fitness impacts would bother the classroom use below. Distinguishing airborne noise (the instructor’s voice and music) from the structure borne noise (heavy bag and footfall vibration) is a critical step in accurately mitigating noise from this unique use. Airborne noise must also be addressed to control noise impact to lateral spaces including bother retail and office uses.
To mitigate the airborne noise to the attorney’s offices one floor above, a custom, spring isolated gypsum board ceiling was installed. Properly constructed, this modification increases the Sound Transmission Class (STC) rating of the concrete structural slab by 28 points in laboratory tests. Mitigation of airborne noise laterally was achieved with multilayer gypsum board walls over double steel stud framework with fiberglass batt insulation in the cavity. In some cases, acoustically engineered gypsum board employing a visco-elastic damping layer was used.
The structure borne noise from the 18 heavy bags presented a unique situation requiring a two-step solution. First, a custom framework was specified which was supported not from the overhead slab but only by structural columns greatly decreasing the rigid connections to the building. Second, each bag was then suspended by a spring isolated mount which isolates the bag from the structure while still maintaining the required lateral stability expected from a heavy bag mount.
To control footfall and floor impacts an isolated plywood floor system was employed which mounted multiple layers of plywood on high density fiberglass pucks spaced 48 inches on center. Again, properly installed, this increases the Impact Insulation Class (IIC) rating of a bare concrete floor by 36 IIC points in laboratory tests, greatly reducing the impact noise. It also increases the STC rating by 10 points, aiding the control of air borne noise to the educational spaces below.
The Results
After months of operation there have been no issues with the sound and vibration produced by the Bash Boxing studio in Arlington. Maximum sound levels within the studio have measured 110 dBA with both music and vocal instruction with multiple “boxers” aggressively bashing away!
