Speaker
Description
Marine-seismic airguns are used in oil and gas exploration and reservoir monitoring. High-pressure air is rapidly released from submerged airguns, usually towed a few metres from the sea-surface as part of an array that is designed to concentrate sound transmissions vertically downwards. Although the primary use-case of airgun arrays is probing deep into the seabed, the sound they transmit may travel to large horizontal distances, particularly if they are operated close to seabed slopes such as seamounts and shelf edges. In such circumstances, the sound produced by airguns may become trapped in the ocean’s deep sound-channel where low attenuation and separation from reflection and scattering losses at the sea surface and seabed allow sound to travel thousands of kilometres while still remaining detectable above background noise. The fundamentals of sound generation in airguns are discussed and examples are provided showing how signals may propagate over ranges covering entire ocean basins. Examples of airgun signals in CTBTO hydroacoustic datasets are provided. The impact of airgun sound on the marine life is discussed and possibilities for using CTBTO data to study this impact are outlined. The potential for an 'opportunistic’ use of airgun signals in ocean-acoustic experiments is also considered.
