Designing NHPR's Acoustics
May 1, 2009 12:00 PM
Acoustical design for New Hampshire Public Radio started long before the station had even selected a building. "Our first discussions about this project were in 2004," says Richard Schrag, project manager for Russ Berger Design Group (RBDG). "NHPR had started assessing possible facility upgrades back in 2001. At that time, the plan was to add on to the existing station, but the building was landlocked with limited parking and code issues. Once we got into the details of all that the station wanted to do - and considering all the disruption that would accompany a renovation in place - it became clear that it made better sense to look at relocating the entire facility."
"At the start," recalls Schrag, "we helped NHPR develop an architectural program, which basically listed all the rooms the station would need and identified sizes for each of them. Once we totaled it up, the station had a benchmark to use in looking for properties that might be a good fit." RBDG also developed guidelines for the station's property search, including a checklist of issues that would affect the facility's acoustics, such as neighborhood noise sources, structural capacity and optimum clear height. Because this was to be a radio station, properties were also evaluated for other specialty items like a place for uplink and downlink dishes, unobstructed look angles to the satellites, availability of a stand-by generator, and provisions for adding supplementary air conditioning systems.
NHPR looked at a variety of other buildings before selecting its current location. For each, acoustics was considered along with the more obvious issues of location, available space, lease costs and amenities. Other buildings had specific issues to contend with, like adjacent tenants (a movie theater, for example) that might create noise disturbances, and structure-borne vibration from adjacent rail lines. "By taking the time to find a building that was really right for the station," Schrag adds, "NHPR avoided a lot of potential pitfalls and really tailored the project to fit its capital campaign budget."
An important element in finding the right home was the location's ability to accommodate a large multi-purpose space that would serve as a gathering space for the station's community, and would be large enough to handle staff meetings and fundraising phone banks. NHPR also wanted to visually connect the multi-purpose room with the main on-air control room to accommodate recording and broadcast of musical performances and events such as "town hall" meetings.
Because the lease space that NHPR selected was above ground in a multi-story building, RBDG chose to implement a floating floor system. "This building has ceiling height that is less than optimum," Schrag continues. "By incorporating the wire management systems for the broadcast cabling into the floating floors, we were also able to keep the audio wiring physically separate from the power distribution overhead." Structural limitations precluded additional concrete slabs, so the floating floors were constructed of multiple layers of plywood and gypsum board supported by a grid of isolation pads specially designed to match that load.
NHPR is on the building's top floor, so RBDG also paid particular attention to possible noise transmission through the roof, especially from mechanical equipment in the penthouse above. Even noise from water flowing through the roof drains was addressed. According to Schrag, "The results are an extremely low noise floor in the acoustical spaces, even below the target levels we set."
"In a facility like this, the floor plan can be a real challenge," he notes. "Any existing building imposes constraints on the layout, due to the particular shape of the lease space and the location of elevators, stairs, restrooms and electrical service. Also, unlike new construction, where floating floors can be recessed into the structural slab so that the finished surfaces match adjacent spaces, working with an existing structure meant we had to raise the studios above the rest of the surrounding rooms." Transitions were carefully crafted both to meet accessibility codes and to avoid getting in the way of efficient workflow. Ultimately, that led to a plan with the technical spaces grouped together, central to the floor plan. "This gives more windows to the office spaces, but maintains easy connections between the studios and all the different groups that use them," Schrag says.
Designing NHPR's Acoustics
May 1, 2009 12:00 PM
It was important to NHPR that the new facility include capacity for future growth, and the plans included more studios than what the station would need on day one. "Initially, we expected to leave space for a second main control room and talk studio, plus an additional production studio, but to do as little as possible to finish them out," Schrag explains. "Fortunately, the bids came in lower than our conservative estimates, so NHPR was able to add in the work necessary to complete all the rooms. That way, even though some of the spaces are not yet outfitted with equipment, everything is already in place, from the air conditioning to the wiring pathways. The station could literally have a new program stream up and running over a weekend."
Due to the low ceilings, acoustical finishes were applied directly to the underside of the sound isolation ceilings, rather than in a suspended ceiling system. "The goal was to maximize the acoustical performance in the minimum possible depth," Schrag says. "To meet the project budget, we used pre-fabricated acoustical panels, but they were spaced off the wall surfaces to gain additional low-frequency absorption."
"In a tight floor plan like this," he notes, "sound-rated doors and windows are essential to maintain reasonable sound isolation where the rooms cannot be physically separated from each other." In fact, the sound-rated glass turned out to be a hitch in the project schedule when several large sections had to be replaced due to manufacturing flaws. "That's part of what you deal with on every job," Schrag says. "You can't anticipate which material or which subcontractor might end up having problems, but you have to plan the design and the schedule to be able to handle the unexpected."
"We've designed more than 70 public radio stations across the country, and the reason they're such fun projects is that the stations are really passionate about quality, both in terms of the technical performance of the studios and in establishing a work environment that inspires the staff to be more creative," Schrag concludes. "When a radio station is capable of producing high-quality local content like NHPR is, it can continue to be a vital, relevant asset to its community."
Although the timeline for the construction project was to be on the air from the new facility by Dec. 31, 2008, in an almost unheard of turn of events, NHPR originated its first broadcast from the facility at 2 p.m. on Dec. 15....