Noise Levels in the American Sub-Arctic

On the basis of six months' data, a comprehensive study was instituted of the atmospheric static intensity at a frequency of 150 kc in northern and southern Canada. Three noise levels, the average (a measure of the mean atmospheric noise level), quasi peak (a measure of the highest noise bursts indicated by the recorder), and absolute quasi peak (a measure of the maximum value of the highest noise bursts indicated by the recorder) were determined. The average level furnished a record of the average noise caused by bursts and background rumble; the quasi-peak level of atmospherics furnished a record of noise bursts (superimposed upon the usually negligible background); and the absolute quasi-peak level supplied the highest value of the bursts. Various temporal and spatial distribution studies of the intensity of atmospherics were effected, such as diurnal, seasonal, latitudal, and the like. The diurnal trend is absent or small during winter but increases markedly as summer is approached. The familiar rise and decline of noise intensity about sunset and sunrise, respectively, is found. Toward summer the increase in noise level rise occurs earlier and earlier, sometimes taking place shortly after noon, local standard time (LST). The daily cycle usually attains a minimum after sunrise and a maximum after sunset, although exceptions are found. Seasonally, the static intensity is higher in June than January. At southern stations noise increased progressively from January to June.