A Measurement-based Statistical Model to Evaluate Uncertainty in Long-range Noise Assessments

Carefully validated long-range sound propagation measurements with extensive meteorological instrumentation were continued for 612 days without interruption, around the clock, resulting in a database with millions of files, terabytes of sound and environmental data, and hundreds of pages of documentation. More than 100 environmental variables were analysed by statistical means, and many statistically highly significant dependencies linked to excess attenuation were found. At a distance of 3 km from the source, excess attenuation was spread over a dynamic range of 80 dB, with differences of 10 dB between individual quarters of the year; also, negative excess attenuation at frequencies below 400 Hz existed. The low frequencies were affected mainly by the stability characteristics of the atmosphere and the lapse rate. Humidity; lapse rate; sensible heat flux; and longitudinal, transverse, and vertical turbulence intensities explain excess attenuation at higher frequencies to a statistically highly significant extent. Through application of a wide range of regression analyses, a set of criteria for frequency-dependent uncertainty in sound propagation was created. These criteria were incorporated into a software module, which, together with a state-of-the-art physical sound propagation calculation module, makes it possible to perform environmental noise assessments with known uncertainty. This approach can be applied to the short term measurements too and it was shown that some of the most complex meteorological variables, among them atmospheric turbulence, can be taken into account. Comparison with two standardized noise modelling methods showed that the statistical model covers well a range of uncertainty not matched with the standardized methods and the measured excess attenuation fit within the limits of predicted uncertainty

Infrasound Does Not Explain Symptoms Related to Wind Turbines

Some individuals have reported various symptoms that they have intuitively associated with infrasound from wind turbines. Scientific evidence on the potential association or studies focusing directly on the health effects of wind turbine infrasound are lacking. This research project aimed at assessing whether wind turbine infrasound has harmful effects on human health. A questionnaire study, sound measurements, and provocation experiments were conducted. In the questionnaire study, symptoms intuitively associated with wind turbine infrasound were relatively common within 2.5 km from the closest wind turbine and symptom spectrum was broad. Many of the symptomatic respondents associated their symptoms also with vibration or electromagnetic field from wind turbines. In measurements, infrasound levels were similar to the levels occurring typically in urban environments. The captured sound samples with the highest infrasound levels and amplitude modulation values were used in the double blinded provocation experiments. The participants who had previously reported wind turbine infrasound related symptoms were not able to perceive infrasound in the noise samples and did not find samples with infrasound more annoying than those without previous wind turbine infrasound related symptoms. Further, wind turbine infrasound exposure did not cause physiological responses in either participant group.This publication is part of the implementation of the Government Plan for Analysis, Assessment and Research (tietokayttoon.fi). The content is the responsibility of the producers of the information and does not necessarily represent the view of the Government

Tuulivoimaloiden tuottaman äänen vaikutukset terveyteen

Tuulivoimalat tuottavat laajakaistaista ääntä, joka sisältää myös pieniä taajuuksia. Alle 20 Hz:n taajuisia ääniä kutsutaan sopimusluonteisesti infraääneksi. Infraääntä esiintyy yhdessä kuultavan äänen kanssa kaikkialla luonnossa ja rakennetuissa ympäristöissä. Infraäänet eivät yleensä ole kuultavissa tavanomaisilla ympäristössä esiintyvillä tasoill

Binauraalinen äänenlaadun arviointijärjestelmä

Tässä diplomityössä on evaluoitu ja dokumentoitu Teknillisen Korkeakoulun akustiikan ja äänenkäsittelytekniikan laboratoriossa äänenlaadun arviointiin kehitetty laitteisto. Laitteisto perustuu binauraaliseen äänitys- ja toistotekniikkaan. Se käsittää välineet ja menetelmät, joilla ääninäyte tallennetaan, muokataan digitaalisen signaalinkäsittelyn keinoin ja esitetään samanaikaisesti usealle koehenkilölle. Eri osien evaluointi tapahtuu sekä perinteisin mittausmenetelmin että kuuntelukokein. Lisäksi työssä on kehitetty tosipäätekniikkaa, jolloin binauraalisia äänityksiä tehdään koehenkilöiden korviin sijoitetuilla mikrofoneilla. Tosipää- ja keinopää- äänitystekniikoita on verrattu keskenään