Diurnal Variability of Ambient Noise in Shallow Tropical Waters, South Western Bay of Bengal

Abstract

Ambient noise recorded at shallow southwestern Bay of Bengal during September 2010 has been analyzed for spectral characteristics in the band 0.1–5.0 kHz. The noise level (NL) exhibits diurnal periodicity in the band 0.5–2.0 kHz, during most of the day. The in situ wind data at the site correlates well with the NL, which also shows a diurnal cycle. Wavelet analysis further carried out establishes of the diurnal periodicity in wind/NL pattern during fair weather conditions under the influence of local wind effects. Wavelet coherence shows wind and noise to be in phase or wind leading noise. Diurnal variation in wind is more frequently observed along the coast in tropical regions due to differential heating of land and sea, and this has attributed to the NL pattern at the site. The period of measurement is also favorable for the formation of such localized circulation since it is the sunny unclouded period prior to the Bay of Bengal cyclone season and the northeast monsoon.