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By Sara Hart

The engineers took detailed on-site measurements and used SoundPLAN—computer software that analyzes noise to predict levels ranging from the bottom of the proposed building to the penthouse. SM&W found that the sound levels intermittently peaked at 96 dBA due primarily to a train passing every few minutes at what would be the fifth floor. [Decibel is abbreviated by dB; the A stands for A-weighting, a measurement for approximating loudness and annoyance of sounds. See sidebar, page 150.] Since the New York zoning code requires an inside noise level not to exceed 40 dBA, the engineers had to propose a design that would reduce the noise level by 56 dBA.

 

The charts were created using SoundPLAN, software that analyzes complex noise scenarios and predicts the level of noise at various locations. The numbers on the left are the sound levels; those on the bottom are the frequencies, measured in units of Hertz (Hz), which correspond to one cycle per second.