Influence of temporal resolution of meteorological and traffic data on long-term average sound levels
A theoretical study is conducted to investigate the impact of different time-averaging approaches with regard to meteorological conditions (influencing sound propagation), traffic intensity patterns, and correlation between them, on calculated noise levels. The indicators Lden and Lnight, prescribed by the European Environmental Noise Directive for noise mapping, are of main interest. Sound propagation over flat ground from a long, straight highway is simulated, for receiver distances ranging from 50 m to 2000 m. Detailed, meteorological data from a tower (located near Mol, Belgium), for a full year, is used. An extended database containing yearly-averaged hourly traffic counts is available. Detailed sound propagation calculations are made with the Green's Function Parabolic Equation method, accounting for the refractive state of the atmosphere and range-dependent ground effect. The imprecision introduced by averaging meteorological conditions and traffic intensities over time, and by not fully accounting for the temporal correlation between them, may result in an underestimation up to 20 dB(A) for one-day Lden values, using this particular meteorological data set. For yearly-averaged values, the imprecision may reach 3 dB(A). For Lnight, very similar conclusions could be drawn. Multiple linear regression analysis is used to rank the factors that contribute to the imprecision. This led to the conclusion that the decrease in accuracy resulting from different averaging approaches is mainly proportional to the variability in the refractive state of the atmosphere over a 24 hour-period. The type of traffic intensity profile may intensify this error up to 10 dB(A). The use of meteorological data, statistically-averaged over the year, results in a small loss in accuracy compared to calculating noise levels for every hour of the year and averaging the result afterwards. The error introduced by the approach used to average meteorological condition and traffic intensity over the day is not affected by this.
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Document Type: Research Article
Publication date: November 1, 2007
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- Acta Acustica united with Acustica, published together with the European Acoustics Association (EAA), is an international, peer-reviewed journal on acoustics. It publishes original articles on all subjects in the field of acoustics, such as general linear acoustics, nonlinear acoustics, macrosonics, flow acoustics, atmospheric sound, underwater sound, ultrasonics, physical acoustics, structural acoustics, noise control, active control, environmental noise, building acoustics, room acoustics, acoustic materials, acoustic signal processing, computational and numerical acoustics, hearing, audiology and psychoacoustics, speech, musical acoustics, electroacoustics, auditory quality of systems. It reports on original scientific research in acoustics and on engineering applications. The journal considers scientific papers, technical and applied papers, book reviews, short communications, doctoral thesis abstracts, etc. In irregular intervals also special issues and review articles are published.
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