1984.03.14 PC Minutes - Laserfiche WebLink

Home

(3) "Measure of external noise environments" "is determined by the value of day -night average sound level produced as the result of the accumulation of noise from all sources contributing to the external noise environment at the site. Day -night average sound level, abbreviated as DNL and symbolized as Ldn is the 24-hour average sound level." It is interesting to note that: HUD's minimum property standards for urban and rural communities, as developed over the past 44 years are aimed at prohibiting HUD support for new construction, of noise sensitive useson sites having unacceptable noise exposure. (Above information found on page 221 and 222 book 24 C.F.H.) Another item to consider is the type of metering equipment used. The meter used on March 3, 1984, falls into the following category, and I quote from U.S. Bureau of Standards Hand Book 119, page 12, attachment ##5. "The readings of an ordinary sound -level meter will fail to indicate the true level of rapidly peaking sounds because the needle of the meter is too sluggish to follow the sharp pressure changes that occur on impulsive sounds like shots, or even the sounds of a poorly muffled internal combustion engine, which after all, derives its power from the explosions confined in combustion chambers. This makes it difficult to estimate exposure to impulsive noises." In visiting the gun club's noise abatement enclosure on March 3, 1984, I see they have framed in and made previsions for one door and two windows on the south side. This presents a new problem not yet addressed. I have specific pages from a document titled Fundamentals and Abatement of Highway Traffic Noise. The above document and its contents are used by the Minnesota Highway department. In this document they have a section titled "Holes in Barriers," which gives the following example... (Attachment #6) Barrier "A" 80 decibels on noise producing side of a barrier and then 50 decibels on receiver's side, for a 30 decibel reduction. Barrier "B" Same as above except we now have a hole which represents 10'0 of the surface area. We still have 80 decibels on noise pro- ducing side, but now have only a 4 decibel reduction, or a 76 dba reading on the receivers side, due to the 10/ hole in the barrier. Mir. Linnell stated that he thought a 10 dba reduction in sound level will occur this summer when the foliage comes out. I have attachment ##7