a. Where there is a dedicated lane for such barrier, temporary or portable (i.e. unanchored) noise barriers shall be used for street work lasting longer than 15 days as set forth in this section. All such barriers shall be placed as close as possible to the noise source in order to maximize noise attenuation.
b. Where construction projects are of shorter duration than 15 days and within the property line and do not require 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 E 90. 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.
i. Temporary or portable noise barriers, where required, may be made, for example, of concrete jersey bases with 3/4-inch plywood panels attached to fence posts extending upwards to an overall height of 15 feet and must be in accordance with DOB and FDNY rules and regulations. This shall be the maximum height for a free-standing barrier in order to avoid it tipping over from wind load. Multiple jersey bases and plywood panels may be positioned adjacent to one another to form a barrier of any desired length. The gaps between adjacent sections shall be filled-in to form a continuous solid barrier surface.
ii. Wherever practicable, a pitched panel shall be built on top of the barrier in order to provide better shielding for multi-story receptor buildings; however care must be taken to avoid having the barrier tip over from unbalanced loading. Further, the barrier shall not exceed 15 feet in height including the pitched panel.
d. Noise curtains. Noise curtain material may be mounted or hung over perimeter chain link fences, or draped over small noise sources, to form a flexible noise barrier. The chain link fences can also be attached to the top of jersey bases.
i. Noise curtains shall be made of a 1/4-inch thick heavy vinyl material, with a noise absorptive quilt attached to one side (the side facing the noise source).
ii. Noise control curtains shall have a Sound Transmission Class (STC) rating of STC 30 or greater, based on sound transmission loss data according to ASTM Test Method E 90. The noise absorptive face of the curtains shall have a Noise Reduction Coefficient (NRC) rating of 0.85 or greater, based on sound absorption coefficient data taken according to ASTM Test Method C 423.
iii. Noise curtains of this sort, such as SoundSeal model BBC-13-2, or equivalently rated material, generally weigh about 1.5 lbs/sq. ft. They come in 4-foot wide sheets complete with grommets and Velcro edges to aid in hanging the curtains and sealing the sheets side-by-side.
e. Noise Tents. A noise tent may be used within the property line.
i. Noise curtain material may be attached to a metal frame to form a portable enclosure (known as a "noise tent"). The noise tent shall have noise curtain material attached on three sides and on top of the frame, with the remaining side of the frame left open for work access and ventilation.
ii. A frame size of 8 feet tall by 6 feet wide by 6 feet deep shall allow the tent to be positioned over small noise sources, such as pumps, generators or compressors. The tent may also be used to cover a laborer using hand-held power tools, such as jackhammers, saws or grinders. Caster wheels may be placed under the frame for mobility, or the tent may be picked up and moved with the arm of a backhoe, for example.