Orange County NC Website
Browse       Search
|�� � ^�'/~ ` <br /> � ' - <br /> —~.'---___ <br /> 412-776'3600 <br /> � �r <br /> - it/ . <br /> � } UL/P R. BERGER G. ASSOCIATES, INC, / BOX 193 / BHADFOR0\8/OOOS, PA-16015 <br /> 2LAI;r|mG SBSMOLOGY/GEOLOGY/GEOPHYSICO <br /> Ju7y 11 , 1980 <br /> STONE COMPANY <br /> �. . <br /> Box 720 <br /> Grecnsboro, NC 27402 <br /> 9e; American Stone Company and Orange County Zoning Proposal Standards <br /> Gentlemen: <br /> Following is a discussion of items discussed in your letter of June 5, 1980 and <br /> accompanying material. <br /> i�he noise and vibration effects of quarrying fall generally into four areas. <br /> these re: <br /> 1. The steady-state noise associated with the operation <br /> of machinery and equipment. <br /> with blasting uperatYuns <br /> �, The air concussion associated ^ <br /> 3 The continuous vibration in the ground from operation <br /> ` of plant machinery and equipment (usually perceptible <br /> at distances of a few feet). <br /> 4. The ground vibrations produced by blasting operations. <br /> Before discussing noise limitations, it is useful to review some of the terminology <br /> used to describe noise as it is perceived by humans. Noises are composites of <br /> «oe o d of various frequencies (pitches). A sound is a variation in air <br /> Pure sounds p � �md as a We can perceive sound waves because the <br /> pressure that is propnga m wave. <br /> varlatjon in air pressure caused by the in the vicinity of the eardrum <br /> c <br /> causes wave j js�h by the small bones <br /> of ses tha eardrum to vibrate. This vibration transmitted the "middle ear° tn:a-deTiOte.organ in the "inner ear" that converts the <br /> vibrations' into signal on'nerve9qhers leading to the brain. <br /> Noises may be annoying if they disrupt the pattern of background nund sounda <br /> that are r <br /> e <br /> normally perceived, or if th ey make it difficult to hear sou nds that are receiving <br /> ng <br /> conscious attention,such as speech. The "loudness" of the noise, and thus its <br /> i oo tential to be disruptive or annoying, is determined both by the magnitude of <br /> the pressure variation and by the frequencies of its constituent sounds. <br /> SAN FRANCISCO <br />