Paleoclimatology dates back to the 19th century, and the concept of examining varves in lake beds and tree rings to track local climatic changes was suggested in the s. This was the basis of a "schematic diagram" featured in the IPCC First Assessment Report of beside cautions that the medieval warming might not have been global. The report discussed the difficulties with proxy data, "mainly pollen remains, lake varves and ocean sediments, insect and animal remains, glacier termini" but considered tree ring data was "not yet sufficiently easy to assess nor sufficiently integrated with indications from other data to be used in this report.
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Planners, policymakers, and legislators must look at noise damage costs caused by motor vehicles when considering transportation options.
The noise created by traffic normally resides in the range of 50 to 95 dB. The effects of transportation noise are routinely measured using an A-weighted decibel scale designated dBAwhich is useful for measuring the noise impact of a single occurrence but not the impact of continuous noise.
A frequently used measurement for continuous noise is the equivalent sound level Leqknown also as the energy mean sound level. Leq includes both the intensity and length of all sounds occurring during a given period; it indicates "the average acoustic intensity over time and is the equivalent noise energy level of a steady, unvarying tone.
The measure of this day-night sound level, designated DNL or Ldn, is commonly used to evaluate noise impacts on communities and residential areas. One method for calculating noise impact cost is based on an estimating procedure developed in and used in the Federal Highway Cost Allocation Study.
This procedure takes into consideration reduced residential property values caused by noise from vehicles. It operates on the theories that people will pay to avoid high noise levels and that housing values reflect location relative to a noisy roadway.
The procedure for estimating noise damage uses three main components: The number of housing units affected varies by location. The noise emission level of vehicles changes depending on the type of vehicle, its speed, its operating weight, and the volume of traffic on the roadway.
The third component of the calculation is constant for all housing units, based on a survey of studies on residential property values affected by noise. Using these values, the noise damage caused by each vehicle-kilometer can be calculated--subject to the type of vehicle, its speed, the volume of traffic on the roadway, and the type of housing development surrounding the roadway.
Noise emission level estimates of single vehicles are based on two emission equations developed by the FHWA--the first for large trucks and the second for passenger cars and light trucks.
Truck noise levels, which are significantly different from those generated by passenger cars, are converted into noise passenger-car equivalents NPCEs using factors developed through a vehicle emission equation and a total noise level equation.
By combining transportation noise levels across vehicle classes, a composite noise emission level for the roadway is produced.
It should be noted that decibels add logarithmically rather than algebraically. The number of housing units affected by transportation noise depends on the density of the housing population and how close the housing unit is to the roadway.
Noise distance ranges are estimated for each of the land development types shown in Table 1 below. The distance ranges are an estimated number of feet within which houses are subject to a given noise level range.
The noise distance ranges are labeled A, B, and C, where C is closest to the roadway and assumed to begin at 9.
After noise distance ranges are estimated, housing densities are needed to calculate the total number of housing units affected. Based on the noise cost study, Table 1 illustrates the housing densities per acre by land development type and noise distance range.
As noted earlier, previous noise impact studies estimated that housing units lose 0. Using this value annualized at a 10 percent discount rate and multiplied by the 0.Open-plan offices are equipped with barriers such as panels and bookshelves to induce the perception of a private workspace.
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