A comprehensive community noise prediction model.

摘要

The goal of this research was to develop a comprehensive community noise model that includes transportation and point sources found in a typical community environment. Other goals such as evaluation, development and implementation of acoustic and traffic algorithms and extensive validation of the model were also accomplished. Community sources of noise include automobile traffic, both interrupted and free flow, commuter and freight railway traffic, aircraft flyovers and point sources of noise, such as air conditioning units, pumps and lawn maintenance equipment. Existing models can predict the noise impact from a single transportation source using point, line and area source techniques but very few can model multiple source types. Some of these models use approximate solutions to the wave equation while others use simplified or empirical methods. These models provide adequate accuracy under specific modeling conditions. Most transportation noise models approximate automobile traffic and railway traffic as line sources. The concept of modeling moving sources as line sources can be a good approximation in some cases, such as highways and long trains, but may be error prone when interrupted flow conditions exist. Noise prediction models exist that calculate sound levels from highway traffic, railway traffic, aircraft and point sources individually, however, very few allow all sources to be combined into a single model. These models fall short of completing the total picture of the community environment. It may be possible to use these models individually and to combine their output to estimate the total sound level due to all sources, but this is time consuming and difficult. Also, models often compute different metrics such as L_eq (equivalent sound level representing a time varying level over a specified period of time), CNEL (community noise emission level that applies penalties for nighttime operations), L_max (maximum sound pressure level over a specified period of time) and these are not readily combined. Different models may not utilize a common method of characterizing source reference levels or common modeling methodologies. Some models use infinite line source approximations, while others use stationary point source methods. Some models use sound power reference levels while others use sound pressure levels and these are not equivalent. The Comprehensive Community Noise Model (CCNM) uses a simulation approach to predict sound levels at homes by modeling transportation sources moving point sources of energy. This represents a new approach that combines most community noise sources in a single simulation model. This allows analysts, planners or engineers to assess total community sound levels with a single comprehensive model.