Chan School of Public Health, Boston, MA Cardiovascular Epidemiology Research Unit, Division of Cardiology (W.L., K.S.D., E.H.W., P.L.L., M.A.M.) and Division of Pulmonary, Critical Care and Sleep Medicine (M.B.R.), Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden (P.L.L.) Channing Division of Network Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA (D.R.G.) Division of Cardiovascular Medicine, University of Massachusetts Medical School, Worcester (J.F.K.) National Heart, Lung, and Blood Institute's and Boston University's Framingham Heart Study, MA (R.S.V., E.J.B.) Preventive Medicine and Cardiology Sections, Department of Medicine, Boston University School of Medicine, MA (R.S.V., E.J.B.) and Department of Epidemiology, Boston University School of Public Health, MA (R.S.V., E.J.B.). 1 From the Departments of Epidemiology (W.L., K.S.D., E.H.W., J.D.S., M.A.M.), Environmental Health (J.D.S., P.K., D.R.G.), and Biostatistics (B.A.C.), Harvard T.H.This article incorporates public domain material from the General Services Administration document: "Federal Standard 1037C". ^ "PRESSURE Units Conversion micropascals to newton-per-square-meter".^ a b "What does dBA mean when someone talks about noise levels?".Environmental Engineering & Management Journal. "Analytical Noise Contour Construction Using Inverse Square Law of Sound Propagation". ^ Celik, Cahit Tagi Guremen, Lale (2008).SCHOOL OF ENVIRONMENTAL TECHNOLOGY, FUT MINNA. Environmental Technology & Science Journal. "SPATIAL ANALYSIS AND GEOGRAPHICAL INFORMATION SYSTEM (GIS) MAPPING OF NOISE POLLUTION IN BOSSO LOCAL GOVERNMENT COUNCIL, NIGER STATE, NIGERIA". ^ Jonah, S.A Baba-Kutigi, A.N Uno, U.E Dangana, M.L Kolo, M.T Ofor, N.P Unuevho, C.I Abba, F.M Alhassan, D.U Amadi, A.N Umar, M.O Kimpa, M.I (2011).^ "Sound and Vibration Instrument Hire and Calibration Background Noise Measurement".
Most frequently ambient noise levels are measured using a frequency weighting filter, the most common being the A-weighting scale, such that resulting measurements are denoted dB(A), or decibels on the A-weighting scale. The centimeter-gram-second system of units, the reference sound pressure for measuring ambient noise level is 0.0002 dyn/cm 2, or 0.00002 N/m 2. This is because 20 μPa is the faintest sound the human ear can detect. It is usually measured in dB relative to a reference pressure of 0.00002 Pa, i.e., 20 μPa (micropascals) in SI units. Or roadway noise is measured as ambient sound, prior to introducing a hypothetical noise barrier intended to reduce that ambient noise level.Īmbient noise level is measured with a sound level meter. For example, sometimes aircraft noise is studied by measuring ambient sound without presence of any overflights, and then studying the noise addition by measurement or computer simulation of overflight events. Alternatively ambient noise levels may be measured to provide a reference point for analyzing an intrusive sound to a given environment. In this case the product of the investigation is a sound level contour map. Īmbient sound levels are often measured in order to map sound conditions over a spatial regime to understand their variation with locale. In atmospheric sounding and noise pollution, ambient noise level (sometimes called background noise level, reference sound level, or room noise level) is the background sound pressure level at a given location, normally specified as a reference level to study a new intrusive sound source.
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