The majority of all new construction in the Core Program area was classed as acoustically isolated construction and required very specific guidelines for all trades to observe to control outside vibration and sound from transferring beyond the source. Early in the process, it was determined that to achieve complete isolation within the existing structure it would be necessary to begin with a clean building shell. All nonessential structure, conduit, piping and interior walls in the main space were removed and the remaining building sealed as a massive airtight envelope.
To achieve a reasonable ceiling height in the main Tracking Room and provide isolation from exterior noise, the existing metal roof structure and deck were removed during demolition. The concrete masonry walls were extended an additional 8 feet, and a 12-inch-deep concrete-plank roof structure was installed, allowing an attic space to be created above the main studio ceiling to provide acoustic insulation, HVAC distribution and noise control. The existing open-web steel joists were maintained, yet required additional vibration isolation as they were rigidly connected to the existing exterior walls.
Quiet Systems
The nature of the recording studio is one of isolation—figuratively and physically. Quiet mechanical systems with acoustic-specific detailing were employed to achieve adequate noise control where required. Of critical importance was the inclusion of return and supply air Acoustic Expansion Chambers (AECs), where the ducts opened into a much larger cross-sectional volume to create an acoustic muffler that controls duct-borne noise generated by the flow of air. The AECs measured 9-feet long by 6-feet wide by 11-feet high with a continuous 4-inch-thick plenum liner on all interior walls, floor and ceiling of the chamber. Additional AECs were constructed from found architectural space within the built-up wall system. The project anticipated large HVAC duct runs throughout the studio and dedicated space for supply and return AECs to achieve RC-15 to RC-20 (Room Criterion). RC was originally developed as a measure of mechanical system noise as recommended by Atlanta-based ASHRAE. The method can be applied to the rating of room noise from other sources, as well, measuring background noise in a building above the frequency range of 16 Hz to 4000 Hz.
The rigor and research invested in the operation and design of isolated and quiet systems brought an invaluable level of experience to the design team. The end result is an interior acoustic system comprised of three major wrappings (control, isolation and dispersion), which were introduced to address the isolation and sound quality needs of the space.
The interior walls required diffusion and avoidance of an overabundance of low-frequency absorption while reflecting sound, which would inevitably cause coloration (undesirable variations in sound resonance, such as hollow, boxy or shrill sounds) and impede clarity. Increased thickness and inclined walls introduce stiffness and minimize unwanted absorption while providing adequate diffusion of the sound, particularly at high frequencies.