Quintiles Transnational, which helps pharmaceutical, biotechnology and medical device companies develop and market innovative therapies, recently celebrated the grand opening of its new headquarters in Durham, North Carolina. At 252,000 square feet, the new, 10- story, glass-and-concrete structure, with room for some 1,100 employees, towers above its neighbors and glows at night from the light of more than 3,000 bulbs. Thorburn Associates was commissioned by architect Gensler Associates to provide acoustical and sound masking system design services for the project.
In the 1960s, early sound masking systems simulated the sound of moving air by electronically filtering random noise produced by gas-discharge vacuum tubes, distributing the amplified noise signal throughout the office via ceiling loudspeakers. Modern day sound masking has evolved to utilize digital signal processing (DSP), robust amplifier selection, correct loudspeaker placement and proper system calibration.
The Quintiles project called for sound masking on 9 of 10 office levels. Additional design criteria involved an emergency paging system that employed not only the sound masking loudspeakers but also added dedicated paging zones on three floors as well as paging horn type loudspeakers on all four parking decks. Sound pressure levels for masking systems typically do not exceed 50dB at the low end of the spectrum and slope off to about 20dB at the high end. Paging, on the other hand, was specified at between 55dB and 65dB SPL across the entire spectrum for human speech.
To insure that speech would be intelligible, especially through the sound masking loudspeakers, TA specified enough amplification horsepower to insure that the specified Sound Pressure Levels (SPL) for speech could be achieved. Keep in mind that sound masking loudspeakers are not mounted flush in the ceiling but suspended upside down ABOVE the ceiling. This is optimum for producing the diffuse sound field that makes sound masking work so well but tends to reduce speech intelligibility.
Because this was one of the last contracts to be let in the project funds were limited. Part of our challenge was to value engineer the system to meet the owner’s budget while keeping to the schedule. We took steps to restrict the project scope without compromising the critical systems, and issued the bid package as a performance specification only. After two rounds of bidding, we took the unusual step of awarding to a vendor that was also the manufacturer. TA insured quality control through final testing and calibration of the system following installation.