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Experimental investigation of ambient electromagnetic noise from 1.0 to 4.0 kHz in Italy and Norway
Author(s) -
Dinger Robert J.,
Meyers William D.,
Davis John R.
Publication year - 1982
Publication title -
radio science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.371
H-Index - 84
eISSN - 1944-799X
pISSN - 0048-6604
DOI - 10.1029/rs017i001p00285
Subject(s) - noise (video) , attenuation , ambient noise level , environmental science , atmospheric noise , noise floor , amplitude , noise spectral density , physics , noise measurement , noise reduction , optics , infrasound , acoustics , noise figure , sound (geography) , artificial intelligence , computer science , image (mathematics) , amplifier , optoelectronics , cmos
Measurements have been made at sites in Italy and Norway of the spectral noise density, amplitude probability distribution (APD), and spectral content of ambient noise from 1.0 to 4.0 kHz. Analysis of the 120 days of recorded data included investigation of the noise diurnal variation, comparison of the APD's with two atmospheric noise models, and time domain excision of noise impulses to assess the reduction in noise achievable by nonlinear processing. The analysis of the diurnal variation suggested the existence of a large propagation anisotropy in the nighttime earth‐ionosphere waveguide at a frequency of 3 kHz, with east‐to‐west attenuation significantly lower than north‐south attenuation. Comparison of the APD's with the Field‐Lewenstein model and the Middleton model of atmospheric noise generally showed satisfactory agreement with both models. Processing of the recorded noise by clipping the large atmospheric noise impulses lowered the spectral noise density in Italy by an average of 6.7 dB (winter) and 3.3 dB (summer). A distinct spectral minimum in the vicinity of 3 kHz was always observable in Norway but was frequently not observable in Italy. The statistical distribution of the frequency of the Norway minimum had a peak near 3.6 kHz.