b. Where construction projects are of shorter duration than 15 days and within the proerty line and do not require a perimeter barriers and are within 75 feet of a residential receptor, a temporary or portable (i.e. unanchored) noise barrier shall be made in accordance with this section.

c. Construction of temporary barrier. Noise barriers shall be made of noise-resistant material sufficient to achieve a Sound Transmission Class (STC) rating of STC 30 or greater, based on sound transmission loss data taken according to ASTM Test Method E90. Such a barrier may provide as much as a 10 dBA insertion loss, provided it is positioned as close as possible to the noise source or to the receptors. To be at all effective, the barrier must be long and tall enough to completely block the line-of-sight between the noise source and the receptors. The gaps between adjacent panels must be filled-in to avoid having noise penetrate directly through the barrier.