Surveying infrasonic noise on oceanic islands

Abstract

An essential step in the establishment of an international monitoring system (IMS) infrasound station is the site survey. The Provisional Technical Secretariat recommends infrasonic noise be recorded with meteorological data at four separate, promising, locations in the vicinity of the nominal station location to identify a secure site which would give the good signal-to-noise while offering easy access to power and telecommu-nications. A good infrasound station should be sheltered from the prevailing winds by gentle topography, trees, and ground cover and located as far as possible from other natural and cultural noise sources. As the IMS network has been designed to give uniform global coverage, some of the stations will be located on oceanic islands. Noise surveys are being conducted at three locations in the Atlantic: Sao Miguel, Azores; Santiago, Cape Verde; and Ascension Island. These island locations are very important as they provide coverage in a region of great monitoring interest. However, they also offer a range of meteorological, topographical, and habitation conditions which result in few suitable locations to deploy an infrasound array. This paper describes preliminary efforts to characterize infrasonic noise levels on these islands and find locations with the necessary practical requirements.